ForestHealthHandbook_complete.pdf

The North Carolina Forest Service Forest Health Handbook 3rd Edition September 2011 Updated August 2013 by Ryan A. Blaedow This publication contains copyrighted material made available und...

The North Carolina Forest Service Forest Health Handbook 3rd Edition September 2011 Updated August 2013 by Ryan A. Blaedow This publication contains copyrighted material made available under a Creative Commons license. For license terms visit Creative Commons at http://creativecommons.org/. This work and images contained within may not be used for commercial purposes unless permission is granted by the copyright owner or photographer. This publication must be distributed free of charge.  Acknowledgment The 3rd edition of the North Carolina Forest Service Forest Health Handbook is a revised version of the original Pest Control Handbook authored by Boe Green in 1952 and the second edition authored by Coleman Doggett, Don Rogers, Thomas Smith, and Jim Smith in 1990. The first two editions have been utilized for more than 60 years, both as a field reference and training manual, and have served as the foundation for the 3rd edition. The contributions of the original authors are deeply appreciated. In addition, we would like to acknowledge the unnumbered scientists and foresters who contributed to the information contained within this handbook. Far too little gratitude is paid to those who devoted their careers to protecting the forests of our state. Contributors Ryan Blaedow Brian Heath Wayne Langston Craig Lawing Jason Moan Rob Trickel Kelly Oten  TABLE OF CONTENTS Page PREFACE..................................................................................................................................................................... 1 INTRODUCTION TO FOREST PROTECTION........................................................................................................ 2 CHAPTER 1 – Forest Entomology Introduction.................................................................................................................................................... 8 Sap-Sucking Insects Scales............................................................................................................................................... 16 Aphids.............................................................................................................................................. 18 Gall-forming Insects....................................................................................................................... 20 Hemlock Woolly Adelgid............................................................................................................... 22 Balsam Woolly Adelgid.................................................................................................................. 24 Defoliating Insects Pine Webworm................................................................................................................................ 26 Pine Sawfly..................................................................................................................................... 28 Eastern Tent Caterpillar.................................................................................................................. 30 Forest Tent Caterpillar.................................................................................................................... 32 Fall Webworm................................................................................................................................. 34 Orangestriped Oakworm................................................................................................................. 36 Pine Colaspis Beetle........................................................................................................................ 38 Bagworm......................................................................................................................................... 40 Cankerworm.................................................................................................................................... 42 Locust Leafminer............................................................................................................................ 44 European Gypsy Moth.................................................................................................................... 46 Japanese Beetle............................................................................................................................... 48 Bark Beetles Southern Pine Beetle....................................................................................................................... 50 Ips Engraver Beetles........................................................................................................................ 52 Black Turpentine Beetle.................................................................................................................. 54 Elm Bark Beetle.............................................................................................................................. 56 Hickory Bark Beetle........................................................................................................................ 58 Wood Borers Pine Sawyer Beetles......................................................................................................................... 60 Ambrosia Beetles............................................................................................................................. 62 Asian Longhorned Beetle................................................................................................................ 64 Emerald Ash Borer......................................................................................................................... 66 Sirex Woodwasp............................................................................................................................. 68  Bud, Twig, and Seedling Pests Pales Weevil.................................................................................................................................... 70 Nantucket Pine Tip Moth................................................................................................................ 72 Twig Pruners and Girdlers.............................................................................................................. 74 CHAPTER 2 – Forest Pathology Introduction.................................................................................................................................................. 78 Foliage Diseases Anthracnose.................................................................................................................................... 86 Brown Spot Needle Blight.............................................................................................................. 88 Pine Needle Cast............................................................................................................................. 90 Dogwood Anthracnose.................................................................................................................... 92 Stem and Branch Diseases Fusiform Rust.................................................................................................................................. 94 Hypoxylon Canker.......................................................................................................................... 96 Pitch Canker.................................................................................................................................... 98 Wetwood / Slimeflux.................................................................................................................... 100 White Pine Blister Rust................................................................................................................. 102 Beech Bark Disease...................................................................................................................... 104 Sudden Oak Death........................................................................................................................ 106 Thousand Cankers Disease........................................................................................................... 108 Vascular Diseases and Declines Fireblight....................................................................................................................................... 110 Bacterial Leaf Scorch.................................................................................................................... 112 Oak Decline................................................................................................................................... 114 Oak Wilt........................................................................................................................................ 116 Dutch Elm Disease........................................................................................................................ 118 Laurel Wilt.................................................................................................................................... 120 Root Diseases Heterobasidion Root Disease / Annosus Root Rot........................................................................ 122 Armillaria Root Rot...................................................................................................................... 124 Littleleaf Disease........................................................................................................................... 126 Phytophthora Root Rot.................................................................................................................. 128 Procera Root Disease.................................................................................................................... 130 CHAPTER 3 – Disorders and Abiotic Stress Agents Wind.............................................................................................................................................. 134 Snow / Ice...................................................................................................................................... 134 Rain............................................................................................................................................... 135 Lightning....................................................................................................................................... 135  Hail................................................................................................................................................ 136 Storms........................................................................................................................................... 136 Flooding........................................................................................................................................ 137 Drought......................................................................................................................................... 137 Salt Damage.................................................................................................................................. 138 Frost / Freeze Damage.................................................................................................................. 138 Heat............................................................................................................................................... 139 Air Pollution.................................................................................................................................. 139 Fire................................................................................................................................................ 140 Mechanical Damage...................................................................................................................... 140 Root Injury.................................................................................................................................... 141 Herbicide Damage......................................................................................................................... 141 Nutrient Imbalance........................................................................................................................ 142 Frost Crack.................................................................................................................................... 142 Sun Scald....................................................................................................................................... 143 Soil Compaction............................................................................................................................ 143 Soil Grade Changes....................................................................................................................... 144 Improper Pruning.......................................................................................................................... 144 Deep Planting................................................................................................................................ 145 Improper Mulching....................................................................................................................... 145 Included Bark................................................................................................................................ 146 Girdling Roots............................................................................................................................... 146 Genetic Disorders.......................................................................................................................... 147 Appendices Appendix A: Diagnosing Disorders of Trees................................................................................ 149 Appendix B: Pest Management..................................................................................................... 153 Appendix C: Non-Native Invasive Species................................................................................... 155 Appendix D: Diagnostic and Laboratory Services........................................................................ 157 Appendix E: Sample Collection Guidelines.................................................................................. 159 Appendix F: Photographing Tree Disorders................................................................................. 163 Appendix G: Diagnostic Tools of the Trade................................................................................. 165 Appendix H: Additional Resources and Selected References...................................................... 160 Appendix I: Image Citations........................................................................................................ 169 Appendix J: Glossary................................................................................................................... 179 Appendix K: Forest Health Branch Contact Information............................................................. 185  Introduction Forest Health Handbook, 3rd Edition The North Carolina Forest Service Forest Health Handbook describes some of the most important and/or common forest insects and diseases that damage trees in North Carolina. The main purpose of this manual is to provide basic information on threats to forest health, guidance in diagnosing tree disorders, and pest management recommendations. It is not intended as a final reference when dealing with any of the pests described. Rather, it should serve as a training aid and introductory text for those unfamiliar with the forest entomology and pathology fields, and as a quick reference guide for specific insect and diseases problems. The information provided is specific to North Carolina. The 3rd Edition of the Forest Health Handbook provides much of the same information as its predecessors. Insects and diseases are divided into sections based on the type of damage caused. For each specific stress agent, a brief overview is provided followed by information on the causal agent, hosts, symptoms and signs, life cycle or disease cycle, importance, management recommendations, seasonal timelines, and distribution information. This edition also features color photographs to supplement descriptions of symptoms/signs, to assist with diagnoses in the field, and to illustrate concepts or examples. Introductory material on forest protection, forest health, pathology, and entomology are provided to introduce readers to the terms and concepts used in these forestry sub-disciplines. Finally, a set of appendices is provided at the end of the manual with additional information on tree physiology and anatomy, non-native invasive organisms, diagnosing tree disorders, sample collection and submission guidelines, plant disease/insect management, additional resources and references, and Forest Health Branch contact information. Time-sensitive information was excluded from this handbook (when possible) to prolong its relevance and usefulness. Therefore, information on the distribution of non-native invasives, laws and regulations, and pesticide use information may be found lacking or over-generalized in this manual. Readers are encouraged to consult the list of additional resources at the end of the handbook for current, time-sensitive information on these topics. An effort was made to utilize (to the greatest extent possible) images from ForestryImages.org, an online source for forest health, natural resources, and silviculture-related images. This was done so that the reader can access original, high-quality images from the manual online for the purposes of study or diagnosis. Commercial use of these images has not been authorized. Image citations are provided at the end of the handbook; images from Forestry Images are available at: http://www.forestryimages.org/. 1  Introduction to Forest Protection Forest protection is the scientific branch of forestry concerned with the study and control of biotic (living) and abiotic (non-living) stress agents that affect the health and/or integrity of trees, forest communities, and wood products. Stress agents are destructive and their effects must be limited to protect and conserve our forest resources, maintain tree health, and provide forest products for current and future generations. Historically, forest protection has primarily been concerned with fire science and fire control. Biotic stress agents have been the focus of two major branches of forest protection: forest entomology (the study of insects) and forest pathology (the study of pathogens and disease). The study and control of other abiotic stress agents has traditionally been shared by forest protection and silviculture. This book will focus primarily on the biotic forest stress agents (primarily insects and diseases), though brief consideration will be given to abiotic stress agents with the notable exception of fire. The reason for this exclusion is two- fold. First, the science of fire and fire control are sufficiently different from other aspects of forest protection; consideration of fire and fire control is provided elsewhere in far more detail than can be provided here. Second, while fire is a major concern because of its destructive potential and threat to human safety, its negative impact on forest health is relatively minor in comparison to the other stress agents. For instance, in one of the few studies of its kind, the U.S. Forest Service estimated that in 1952, losses in forest productivity (tree mortality and reduced tree growth) due to forest stress agents in the U.S. equaled approximately 90% of the sawtimber volume cut in the same year. Of this staggering loss, 45% was due to disease, 20% due to insects, 18% due to abiotic factors such as weather, and only 17% due to fire. Forest protection is a scientific discipline that requires an understanding and utilization of the principles and practices of not only forest pathology and forest entomology, but also forest ecology, forest management, silviculture, tree physiology, tree anatomy, soil science, physics, chemistry, and general biology. Likewise, forest protection is a critical component of silviculture which is the science of forest establishment, growth, and composition. In addition, stress agents (particularly insects and microorganisms) play a critical role in determining the health and diversity of forest communities; therefore, an understanding of forest protection is necessary for proper forest management and the science of forest ecology. Forestry as we know it would not be possible without an understanding and appreciation for the principles and practices of forest protection and its inter-related disciplines. The ultimate goal of forest protection is to minimize tree mortality and growth loss due to forest stress agents, and thereby protect and preserve healthy forest communities. But what exactly is a healthy forest? Forest Health Forests are tree-dominated communities of plants, animals, and microorganisms that interact with each other and the forest’s abiotic components including soil, water, landform, and climate. A simplified example of a forest community would be a typical food web which includes producers, consumers, and decomposers: each organism in the food web is eaten by or eats other organisms. The totality of these interactions forms a network (or web) with connections present between all members of the community. In reality, the interactions and connections in a forest community are vast and complex, although the basic idea holds true: each component of the forest has an effect on and is affected by the others. Trees affect which plants and animals reside in the forest, protect soil from erosion, reduce runoff, improve water quality, and clean and cool the air. Likewise, the forest’s abiotic components and organisms determine what tree species are found in a forest. Humans, for better or worse, are also an important constituent of forest communities because of our influence and reliance upon them. We rely upon our forests for a wide variety of resources, we value them for a range of social and cultural reasons, and they are an essential component of a healthy planet. Many forests are managed or protected to meet the goals and objectives of those who utilize and rely upon them; or are altered in ways that are damaging to the forest community. A healthy forest is a forest that possesses the ability to sustain the unique species, interactions, and processes that exist within it and that can meet the present and future needs of people for a variety of values, products, and services. There are many types of forests found in North Carolina, each with a unique set of species, interactions, and processes. The health of our forests must be maintained to ensure the survival of plant and animal species that make the forest their home and to protect those processes that sustain a healthy environment. A healthy forest can have unhealthy trees, just as an unhealthy forest can have healthy trees. Forest health can be determined on a variety of scales ranging from an entire forest ecosystem to an individual shade tree. A single dead tree in a large forested tract can provide wildlife habitat, may be an essential component of natural stand thinning or succession, or may create a gap in the canopy for a diversity of other plant species. However, a single dead tree in an 2  Introduction urban forest might mean the loss of a high-value and prized shade tree, could represent years of lost revenue from a fruit tree that has taken years to bring to maturity, or may pose a hazard to people or structures nearby. Alternatively, the loss of many trees in a forest may not significantly impact forest health if other individuals of the same or similar species are able to support the community. But complete eradication of a single tree species by an insect or disease could have catastrophic consequences for a forest ecosystem. Defoliating insects and cosmetic diseases that are of little concern in forested situations may be intolerable afflictions to shade trees or ornamentals in a home owner’s front yard. Annual growth losses due to poor soil conditions or drought may be of little concern in a park or on a tree-lined street, but could mean the loss of profitability over the course of a thirty year rotation in a pine plantation. The determination of forest health must be made relative to the species, processes, or resources of interest, and the stress agents present in the forest community. Stress Agents Tree health is threatened by stress agents that cause a sustained disruption of the normal physiological processes or structural functioning of a tree. Physiological processes include photosynthesis, respiration, transpiration, translocation of photosynthetic products and nutrients, growth, reproduction, mychorrizal associations, compartmentalization, and defensive responses. Structural functioning of the tree is dependent on anatomical features such as the roots and root hairs, root crown, stem, branches, buds, flowers, seeds, leaves, bark, and the vascular system. If a disruption in physiology or structure is sustained over a long enough period of time, or if it is severe enough, a tree can be harmed or killed. Primary stress agents are capable of attacking and injuring or killing otherwise healthy trees. A secondary stress agent can only attack a tree that has been weakened by primary stress agents or predisposing factors. Predisposing factors, such as drought, extreme temperatures, nutrient deficiency, and fire, are most often abiotic stress agents. Physiological or structural damage to trees due to non-living entities or abiotic stress agents are not considered to be diseases (diseases are caused by pathogens), but are more commonly referred to as abiotic disorders or abiotic injuries. Examples of abiotic stress agents include nutrient imbalances, improper soil pH, soil compaction, grade changes, hardpan, drought, flood, saltwater intrusion, lightning, frost, heat scorch, hail, sun scald, storm damage, mechanical injuries, herbicide damage, and air pollutants. Abiotic disorders are generally not species specific, meaning that most tree species are susceptible to most abiotic stress agents. Some tree species are more tolerant of abiotic stress agents or may have slightly different environmental preferences, but in general, an abiotic stress agent will affect most or all tree species to some degree. This can be particularly destructive when the stress agent is severe and widespread; entire forest communities can be severely damaged by a hurricane, drought, or environmental pollutants for instance. However, most abiotic disorders are relatively localized and they cannot spread from tree to tree. Management of acute injuries (e.g. mechanical damage and fire) emphasizes prevention prior to being damaged and possible treatments after the damage has occurred. Chronic disorders (e.g. drought and nutrient deficiencies) are less likely to be preventable, but may be treatable. Biotic stress agents are living organisms including plants, animals, and disease-causing microorganisms such as fungi, bacteria, viruses, and nematodes. Most biotic stress agents are known as pests because they interfere with the intended use of a forest, a tree, or wood products. Some pests only inflict mechanical damage (e.g. a deer rubbing its antlers on the stem and damaging the bark) while others damage forest productivity through competition (e.g. weeds). The most important biotic stress agents are either predators or parasites; both attack trees to feed on or within them to obtain nutrients. Predators (in this case known as herbivores) are free-living organisms that usually feed on more than one individual host to reach maturity. Parasites on the other hand, live on or within a tree (usually one individual tree is sufficient to reach maturity) to obtain nutrients, and in the process they cause injury (see insects) or disease (see pathogens). Biotic stress agents, specifically insects and pathogens, are transmissible; meaning that they can spread from one host tree to another. Although this may at first seem obvious, it is an important distinction for several reasons. First, the transmissibility of pests means that the disease or injury caused by them can also spread. When managing biotic stress agents that can spread, one needs to take into consideration movement of the pests across the landscape and through time. Simply controlling the pest at the site where damage or disease is occurring may not be adequate. Secondly, insect and pathogen populations have the potential to grow exponentially over time as they spread. This can result in outbreaks (insects) or epidemics (pathogens) capable of severe and widespread impacts on forest health. Third, biotic stress agents can only be transmitted to suitable hosts. Therefore, when monitoring, diagnosing, and managing biotic stress agents, one needs to take into consideration only the suitable host species. 3 4 Alternate Hosts Viroids Competitors Phytoplasmas Parasites Grade Change Viruses Compaction Myxomycetes Plants Saltwater Intrusion Bacteria Drought pH Slope Nutrient Excess Oomycetes Nematodes Flooding Meristem Feeders Nutrient Deficiency Fungi Micronutrients Defoliators Mammals Texture Microorganisms Macronutrients Borers Hard Pan Allelopathic Compounds Phloem Feeders Insects Soil Pesticides Air Pollution Birds Radiation Girdling Roots Heavy Metals Animals Genetic Disorders Toxins Natural Gas Misc. Toxins Deep Planting Root Damage Storm Damage Pruning Sun Scald Disorders Injury Fire Mechanical Damage Girdling Included Bark Frost Cracks Snow Hail Heat Weak Wood Wetwood Weather Ice Frost Lightning Rain Rubbing Branches Wind Biot ic Abiot ic Tr ee St r ess Agent s  Introduction Hosts A tree attacked by an insect or pathogen is called a host. Most parasites have only one or a few tree species that act as suitable hosts, but a few parasites have a wider host range. This is because pests and trees have co-evolved over millions of years together and are engaged in an eternal “arms race” for superiority. Trees have evolved very powerful defensive responses to ward off attacks by potential parasites. Some of these defense responses are quite obvious (e.g. toxic chemicals, thick bark, leaf shedding, resin production, etc.) while others occur at a microscopic, chemical, or genetic level. In response, parasites have had to develop an arsenal of weapons (e.g. modified mouthparts, specialized digestive systems, toxins, enzymes, and even chemicals that shut off host defense responses) to survive. Because there are hundreds of thousands of plant species, insects and pathogens have evolved over time to “battle” just one or a few tree species; they could not possibly overcome the wide variety of defense adaptations found in all plant species. This means that most parasites are very host specific (i.e. they are very picky eaters). Some insects or pathogens can only complete their life cycle on a single tree species, or even on a single tree cultivar. The fact that most parasites are so extremely host specific has given rise to the saying: “resistance is the rule, susceptibility is the exception.” In general, a tree species is said to be resistant if it is capable of preventing or overcoming an attack by a specific parasite, but is said to be susceptible if that parasite can successfully attack, obtain nutrients, and disease or injury results. A tree can be resistant to one parasite, but susceptible to another. Resistance can be complete, meaning that the tree is not a host and can completely prevent a parasite from causing injury or disease; or it can be incomplete, meaning that the tree is susceptible to attack, but the severity of disease or injury is less than what would be observed in a less resistant (or more susceptible) species. 5 6  Forest Entomology Forest Insects 7  Forest Entomology Insects kill more trees in the U.S. each year than any mechanisms against these insects, and predators adapted other forest stress agent. In addition, they can cause to feed on these exotic species are often lacking, exotic significant growth loss, degrade lumber, make trees insect populations have the potential to increase rapidly vulnerable to attack by secondary insects and diseases, and cause serious damage to the forest ecosystem. The spread tree pathogens, and can be a serious nuisance. first serious exotic forest insect to arrive in the U.S. was However, most insects that feed on trees do not cause the gypsy moth (Lymantria dispar). Since its serious harm. For instance, many of our native moths introduction in Massachusetts in the late 1860’s, the and butterflies feed on tree foliage in their larval stage. gypsy moth has defoliated and killed millions of acres of Trees have evolved along with these insects and under normal circumstances are tolerant of such activity. Gypsy moth egg masses laid on a cargo Many insects play important roles in the forest container shipped from Asia. ecosystem including pollination, nutrient cycling, eliminating sick or weakened trees from the forest, and are even an important food source for many animals, especially birds. Many insects found in our forests are predatory and feed on some of our more serious forest insect pests and keep their populations in check. hardwood trees. Since that time, other insects such as the European elm bark beetle, hemlock woolly adelgid, beech scale, balsam woolly adelgid, Asian longhorned beetle, emerald ash borer, and the redbay ambrosia beetle, along with many others, have done serious and irreparable damage to our nation’s forests. Exotic Predatory insects such as the clerid beetle insects are now some of the biggest and most serious keep forest pest populations suppressed threats to our forest ecosystems. Entomology is the study of insects, and forest Under normal circumstances, insect populations are entomology is the study of forest insects, particularly highly suppressed by predators and disease. In addition, those insects which feed on or do damage to trees or trees have evolved effective defense mechanisms against lumber. Forest entomologists study insect biology, life insect pests, and therefore serious or widespread damage cycles, classification, interactions with their host plants or mortality caused by insects is rare. However, when and other organisms, and control/management strategies. trees become stressed or when predators fail to keep The first insects appeared around 340 million years insect populations under control, the tremendous ago. Since that time, they have spread across our planet reproductive potential of insects can lead to large to occupy virtually every habitat imaginable. Their outbreaks and serious infestations resulting in tree adaptations and modifications are nearly endless and damage or death. When outbreaks occur, they are often often bizarre. The smallest insects are some species of difficult or impossible to control. Therefore proper parasitic wasps that are less than 1/16 inch long; the forest management, early detection of infestations, and largest include moths with 12 inch wingspans, giant practices that promote predatory populations are key walkingsticks almost a foot and a half long, and goliath components of minimizing the impact of serious forest beetles that are 3 inches wide! Scientists predict that insect pests. there are at least 10 million different species of insects During the last few decades, there have been dozens worldwide, of which only about 1 million are currently of introductions of exotic insects from other countries. known to science. Insects are so plentiful, in fact, that Because our tree species have not adapted defense they represent approximately 85% of all known animal 8  Forest Entomology Coleoptera……. …………. Beetles Diptera……….................... Flies Hymenoptera…………….. Ants, Bees, Wasps Lepidoptera………………. Moths and Butterflies Orthoptera………………… Grasshoppers, Katydids, Crickets Phasmida……………..….. Walkingsticks Isoptera…………………… Termites Hemiptera………………… Cicadas, Leafhoppers, The eastern Hercules beetle is the largest Aphids, Scales beetle found in North Carolina All adult insects (with only a few exceptions) have species on the planet. In the U.S. there are about 92,000 the following characteristics: 1) a hardened external described insect species and an estimated 73,000 yet to skeleton; 2) three distinct body regions (head, thorax, be described. World-wide, there are more beetles than and abdomen); 3) one pair of segmented antennae; 4) any other insect. one pair of compound eyes; 5) three pairs of segmented Insects are in the phylum Arthropoda which includes legs; and 6) one or two pairs of wings. Immature insects all animals with exoskeletons and segmented bodies. may resemble miniature adults or may have a completely Entomology typically encompasses the study of two different body shape and appearance. Arachnids differ classes of arthropods: Class Insecta which are of course from insects in that they have only two body segments the insects; and Class Arachnida which includes the and eight legs. spiders, mites, scorpions, and ticks. There are The head is the hardened region of the insect body approximately 30 insect orders, however not all orders that bears sensory organs such as eyes and antennae, and include forest pests. The most common insect orders the mouthparts used for feeding. The large eyes that encountered in forest entomology include: occur in most adult insects are called compound eyes Thorax Abdomen Ocellus Pronotum Mesonotum Metanotum Terga Antenna Cercus Compound Eye Head Mandible Ovipositor Spiracles Maxilla Labium Plural Suture Episternum Epimeron Prothorax Metathorax Mesothorax 9 because they are made up of many individual light siphoning, etc. In chewing insects, the mandibles may sensing units (up to several thousand per eye). Most be stout, curved, and toothed with special adaptations for adult insects also have three ocelli (simple eyes) located cutting, crushing, or grinding. The labium and labrum on the top of the head. Antennae are long, segmented are used to guide food into the mouth, and the maxillae sensory appendages that can be used to detect odors and have antenna-like appendages that touch and taste the sounds and to touch and taste objects. The function and food. In piercing-sucking insects, the mandibles and/or appearance of the antennae varies with the insect species maxillae are modified into long, needle-like appendages; and can be useful for identification purposes. the labium/labrum may be somewhat flattened and The mouthparts are among the most varied of insect elongated to surround, guide, and protect the body parts and are specially adapted to accommodate mandibles/maxillae. In piercing-sucking insects, the their diverse diets. Therefore, mouthparts are often elongated mouthparts are also known as the beak or critical to classifying insect species. Mouthparts consist proboscis. of an upper lip called a labrum, a pair of jaw-like The thorax is the second body segment (located mandibles, sometimes a tongue-like organ called a between the head and abdomen) and is made up of three hypopharynx, and a lower lip or labium. In addition, individual segments known as the prothorax, the mouthparts contain a pair of elongated organs called mesothorax, and metathorax. The segments of the maxillae that serve as sensory organs or are modified for thorax often contain grooves and ridges, and in addition piercing/sucking purposes. In general, insect mouthparts to the arrangement of hardened scale-like plates that can be classified by their function: either chewing, cover the thorax, can be useful for identification piercing-sucking, or some other variation of these two purposes. Each of the three segments of the thorax has a categories including rasping-sucking, sponging, pair of segmented legs that may be specially adapted for Chewing Piercing – Sucking Mouthparts Mouthparts Antenna Ocellus Compound Eye Labrum Maxilla Mandible Labrum Maxillary Pulpus Labium Labium Labial Pulpus 10  Forest Entomology Maxiallary Pulpus Labrum Mandible Compound Eye Labial Pulpus Front Leg Antenna Head Prothorax Thorax Elytra Middle Leg Femur Hind Leg Abdomen Hind Wing Tibia Tarsus running, jumping, grasping, swimming, etc., depending laying, digging, sawing, piercing, or stinging. The on the insect. Each leg is made up of six segments, the abdomen of larvae may contain prolegs or last of which is a pair of claws. Insect larvae such as ornamentations (that may be hairy, spiked, colorful, or caterpillars may have additional pairs of fleshy legs on even toxic) to deter predators. the abdomen known as prolegs, but these legs do not Insects undergo dramatic changes in appearance and have six segments and disappear in the adult stage of the behavior during the course of their lives. Immature insect. Most adult insects also have one or two pairs of forms may differ so significantly from adults that they wings that reside on the thorax, although some insects may not even be recognized as the same species. During lack wings altogether. The wings vary in shape, color, their development, insects undergo a drastic change in size, thickness, texture, and even function. Beetles for form known as metamorphosis. There are two basic instance, have two pairs of wings: one pair is elongated, types of metamorphosis: incomplete and complete. thin, transparent, and often used for flight; the other pair Incomplete metamorphosis is characterized by known as elytra are thicker and hardened, and serve as immature insects that resemble adults and change mostly protective covers for the underwings. in size and the development of wings and genitalia. The last body segment, which tends to be softer and Immature life-stages typically have compound eyes and more flexible than the head and thorax, is the abdomen. mouthparts; they generally have the same feeding habits The abdomen contains most of the insect’s internal as adults. Insects that undergo complete metamorphosis organs, and usually consists of eleven distinct segments. have immature life stages that do not resemble the Most adult insects lack any appendages on the abdomen, adults, are generally worm like, have simple eyes, no but exceptions include some male genitalia and the visible wings, short antennae, and mouthparts that often female ovipositor which can be specially adapted for egg differ greatly from the adult stage. 11  1st Instar Eggs Adult Pupa Egg Incomplete 2nd Instar Complete Metamorphosis Metamorphosis Adult 1st Instar Larva 3rd Instar 3rd Instar Larva 4th Instar 2nd Instar Larva All insects begin their life as an egg. Immature stage is followed by an additional life stage known as the insects which hatch from eggs are known as nymphs pupa. The pupa does not feed nor move, and is usually (incomplete metamorphosis) or larvae (complete covered in a protective coating that may be silken, hairy, metamorphosis). All immature insects grow in size by a or hardened. During pupation, the structure of the insect process known as molting, which is periodic shedding of completely changes from the larval form to the adult. In the skin and expansion of tissues before the new the pupal stage, the insect’s tissues are broken down, underlying skin hardens. The number of times an reorganized, grow, and differentiate into their adult immature insect molts before becoming an adult ranges form. New mouthparts, digestive systems, reproductive from four to eight and varies with species and even organs, wings, compound eyes, and other dramatic gender. Between molts, the immatures are known as additions and changes take place. instars. Insect development is often monitored by knowing what stage or instar the insect is currently in. Management recommendations such as pesticide applications are often timed to target certain instar stages (e.g. an insecticide must be sprayed before the 3rd instar). The Cecropia moth caterpillar has bright ornamentations to deter predators The adult Cecropia moth bears no resemblance to its caterpillar after emerging from its cocoon The pupal stage may last for days, weeks, or even months. When the fully formed adult is ready, it emerges from the pupal skin and its new body begins to quickly dry, harden, and develop pigmentation. Some adults feed on completely different hosts or host tissues Following the final instar stage, insects that undergo than their larvae; others do not feed at all and may only incomplete metamorphosis become adults. For insects live for a few hours or days: just long enough to mate that undergo complete metamorphosis, the final instar and lay eggs. 12  Forest Entomology Many insects feed on and breed within trees and after year. Most other defoliating insects do not have other forest plants. Forest insects cannot attack any such destructive potential. For instance, many of our plant species; instead, insects tend to be host-specific. A native moth and butterfly larvae feed on tree leaves. host is a plant that can be utilized for an insect to Because only a few larvae feed on any given tree, little complete its life cycle. Most insects have only one or a or no damage occurs. Any time a tree is partially or few suitable host species; however some insects can completely defoliated during the growing season there is attack a wide range of host plants. The mechanisms that a general decline in the health of that tree. This decline determine which insects can attack which plants are very can cause the tree to grow slower, make the tree more complicated and result from complex interactions and susceptible to secondary pests, and can even cause tree signals between the two organisms. mortality in some cases. If a tree is defoliated early in Trees have evolved structural and chemical defenses the growing season, it may refoliate, but this such as thick bark, waxy leaf coatings, root secretions, dramatically decreases the tree’s energy reserves. and even toxins that prevent or deter insect attacks. A Defoliation that occurs later in the growing season plant that possesses the ability to prevent attack is typically does less harm to the tree because the tree has completely resistant to that insect. Some plants may be already had ample time to build up energy reserves attacked by insects, but because of defensive adaptations before the onset of winter. they are able to limit damage and are considered to be Bark beetles are a highly destructive group of forest resistant compared to more susceptible plants. pests. The southern pine beetle, the most destructive Susceptible plants are vulnerable to insect attacks that forest insect in the South, falls into this group, as do the result in severe damage or death. Resistance and Ips engraver beetles. Adult bark beetles bore into the susceptibility form a continuum that ranges from inner bark of susceptible host trees to lay eggs in long completely resistant to highly susceptible. A plant can tunnels known as egg galleries. When larvae hatch from be resistant to one insect, but susceptible to another: these eggs, they begin to bore through the inner bark and each interaction is unique. Forest insect pests are generally grouped by the type of damage they cause to their hosts. These insects fall Galleries formed by southern pine beetle adults into one of five categories: defoliators, bark beetles, and larvae girdle a tree’s vascular system wood borers, sapsucking insects, and meristem feeders. Defoliating insects feed on the foliage of trees, which are the main tissues responsible for photosynthesis. Although most defoliating insects are harmless or tend to be merely a nuisance, when outbreaks occur they can become highly destructive. For example, the gypsy moth is a highly damaging defoliator because its populations can grow rapidly, each larva can eat over a square foot of leaf surface per year, and a heavily infested tree can be completely defoliated year Eastern tent caterpillars feed on the foliage of a variety of hardwoods during the spring 13 feed on the nutrient-rich cambium and phloem tissues, Sap-sucking insects are those insects that possess and even the outer sapwood. The tunnels created by piercing-sucking mouthparts and are able to penetrate feeding larvae are known as larval galleries. If a tree is the nutrient conducting tissues to feed on the plant’s sap. heavily infested by bark beetles, the cumulative effect of Most sap-sucking insects are only able to feed on soft, the galleries is girdling, which occurs when the nutrient succulent tissues where the vascular system is close to conducting tissues of the phloem are completely severed the plant surface; others possess mouthparts which can and destroyed. In addition, if the outer sapwood is penetrate tree bark. Though most are not, piercing- damaged, the tree may be unable to transport water and sucking insects can be highly damaging to trees. For will wilt. Healthy trees resist attack by bark beetles by instance, the hemlock woolly adelgid is a sap- producing sap or pitch to push adult beetles out of entrance holes. When trees are in a weakened state or Aphids are sap-sucking insects that are commonly are attacked by large populations of beetles, they may be found on both conifers and hardwoods unable to generate enough sap to prevent beetles from entering. Therefore, when bark beetles do gain entrance to a tree, the most common result is tree mortality. Many of the bark beetles carry fungi, such as blue stain fungi, that can degrade wood quality and plug the tree’s vascular tissue accelerating the host’s decline. Wood borers differ slightly from bark beetles in that their activity is not strictly confined to the cambium and phloem tissues of the inner bark. Wood borers will also bore into and feed on the sapwood. Damage from wood borers includes girdling of the water and nutrient sucking insect that feeds at the base of hemlock needles conducting tissues of the vascular system, and usually and is responsible for nearly wiping out both eastern and results in death. Many devastating non-native invasive Carolina hemlocks in North Carolina. The balsam insects, such as the emerald ash borer, redbay ambrosia woolly adelgid, which created the ghost forests of high beetle, and Asian longhorned beetle belong to this group. elevation Fraser fir in North Carolina, also are highly Many secondary insect pests also fall into this group, destructive. Piercing-sucking pests include scales, including the twolined chestnut borer and the southern aphids, adelgids, pysillids, leafhoppers, and related pine sawyer. Wood borers that feed on dead or dying species such as mites. Under the right conditions, trees require sufficient wood moisture; trees that have piercing-sucking insects can cause serious damage been dead for a prolonged period of time (e.g. when the resulting in tree decline or mortality. Some of these bark falls off) are no longer suitable for wood borer insects, such as aphids, can also cause a distortion of activity. However, as long as wood moisture remains plant parts and unsightly galls. sufficient, wood is susceptible to attack. Therefore, many wood boring insects are a significant threat to freshly cut trees or lumber. Wood borers can tunnel deep into the xylem and The balsam woolly adelgid has eliminated most of significantly degrade the value of wood the mature Fraser fir found in North Carolina 14  Forest Entomology Meristem-feeding insects feed on those tissues of a plant known as meristems, which are responsible for plant growth. Meristems include shoot tips (which account for increases in tree height and branch length) and the cambium (which accounts for increasing tree diameter). An example of a meristem feeder would be the Nantucket pine tip moth which lays its eggs on the shoots of young pines. Upon hatching, larvae bore into the young, rapidly growing shoots to eat the nutrient rich tissue. When populations are high enough, meristem feeders can kill trees (especially seedlings and young trees), but more often they only disfigure trees or cause reduced growth. Feeding by these insects can cause the terminal shoots to die, resulting in increased lateral branch growth that gives rise to trees with poor form and multiple stems. Damage from these insects also reduces tree growth and vigor, and may make them more susceptible to secondary pests. The Pales weevil feeds on the secondary meristem tissue (cambium) of young pine seedlings The Nantucket pine tip moth feeds on the primary meristem tissue (growing shoots) of young pines 15 Scale Insects Overview: Scale insects are some of the most destructive pests of shade trees and ornamentals, but few are serious forest pests. All scale insects pierce plant tissues and obtain nutrients by the ingestion of large amounts of plant sap. Localized injury may occur around feeding sites and serious damage or death may occur in heavily infested trees. All adult scales produce a waxy or shell-like covering. Many scale insects are often very inconspicuous (some scale coverings act as camouflage) making diagnosis of an infestation difficult (Fig 5). Others may produce an obvious waxy coating that is easily visible. There are hundreds of species of scale insects that feed on North Carolina trees and shrubs. However, each scale species usually infests only one (or a few) host species. Therefore, many scales are named for the specific host species on which they feed. Causal Agent: Scale insects: Order Hemiptera, Suborder Sternorryncha, Superfamily Coccoidea Hosts: Many species of conifers and hardwoods. Scale insects are usually very host specific. Symptoms / Signs: Symptoms vary widely with the scale species, host, and host tissue attacked. The most common symptoms observed may include foliage spotting, speckling, chlorosis, curling, and/or wilting; as well as galls, distorted growth patterns, bark swelling, twig dieback, branch dieback, decline, and mortality. Adult females are sedentary, wingless, and may lack distinctive divisions between the head, thorax, and abdomen. They are covered with a hard scale or waxy secretion, and can range from 1/50 inch to ¼ inch long. Scale coverings can be flattened and shield-like (Fig. 3), spherical (Fig. 8), or anywhere in between. Wax coatings (frequently white) (Fig. 6) may simply be a thin transparent film (Fig. 7), but some species produce powdery bloom-like secretions. Adult males usually have wings, lack mouthparts, and are very active flying insects but are rarely observed. Nymphs are nearly microscopic and only mobile for a few days to a couple of weeks. After their first molt, they lose their legs, become sedentary, and begin to form a scale or wax covering. The best way to detect crawlers is to hold a white sheet of paper under an infested branch. Shaking the branch will cause the crawlers to fall onto the paper, where they may be visible as small moving dark specks. In addition, like many other sap-sucking insects, some scales produce large amounts of honeydew (waste and excess plant sap that could not be processed by the digestive system) that drips down onto lower surfaces. Specialized fungi known as “sooty molds” grow on the honeydew, turning those surfaces dark gray or black (Fig. 2). Other insects, such as ants and wasps, may also invade the area to feed on fresh honeydew. Life Cycle: Life cycles vary by scale species. Usually there are 1-4 generations per year in North Carolina. Most scales overwinter as late-stage nymphs. In the spring after maturation is complete, the eggs inside the adult female’s body mature within one to several weeks after fertilization. When the eggs hatch, the first stage nymphs (known as “crawlers”) search for feeding sites, or may spread to neighboring trees on the wind or by animal vectors such as birds and small mammals. Once a feeding site is located, the crawlers molt and become sedentary. Their long piercing-sucking mouthparts may penetrate deep into the plant to reach nutrient-rich sap. Feeding sites may be leaves, buds, twigs, or main stems depending on the scale species. It may take 2-8 weeks for nymphs to transform into fully mature adults. Populations can grow exponentially, resulting in heavy infestations in short periods of time, and are frequently cyclical. Importance: Moderate. Most scales pose no serious threats to tree health. However, scales can be a serious nuisance on landscape trees and ornamentals. Gloomy scale can cause serious dieback or even death in many maple species. The tuliptree scale (Fig. 1) is a serious pest of yellow poplar that can cause branch dieback or death. The beech bark scale releases a potent toxin and carries a pathogen that threatens the survival of American beech. Lecanium scales are a very common pest of hardwoods, but rarely require control measures (Fig. 4). Management: Chemical control options are available for high-value trees. Treatments are usually ineffective against adults. Therefore, applications of insecticides or horticultural oils must target crawlers when they are active. Close monitoring of crawler activity and repeated chemical applications are usually necessary for successful control. Timeline: Species dependent. Life stages may overlap significantly. Crawlers are most active in the spring and fall. Range: Statewide. 16  Sap-Sucking Insects Fig. 1 Tuliptree scales Fig. 2 Pine tortoise scales Fig. 3 Obscure scale Fig. 4 Lecanium scales Fig. 5 Black scale Fig. 6 Wax scales Fig. 7 Green scales Fig. 8 Soft scale 17 Aphids Overview: Aphids are usually minor pests of hardwoods and conifers, however, a few can cause serious harm to landscape trees and ornamentals, while others can be serious pests in seedling nurseries. Some aphids act as vectors for viral or bacterial diseases, and most have the potential to become persistent and troublesome pests. All aphids pierce plant tissues and obtain nutrients by the ingestion of large amounts of plant sap. Localized injury may occur around feeding sites, and serious damage or death may occur in seedlings or young trees. Usually natural predators keep aphid populations under control, therefore, serious infestations are often observed following insecticide applications that adversely affect predatory insects. Aphids can feed on almost any plant tissue, but are most common on foliage and new growth. Aphids produce large amounts of honeydew resulting in sooty mold that can damage or degrade the beauty of ornamentals. Some aphids produce a woolly or waxy material that covers their body; others induce gall formation at the feeding site. There are hundreds of species of aphids, most of which are named for their host plants. Causal Agent: Scale insects: Order Hemiptera, Suborder Sternorryncha, Superfamily Aphidoidea Hosts: Conifers and hardwoods. Aphids are usually host specific; almost all plant species are attacked by one or more species of aphid. Symptoms / Signs: Aphids weaken a plant by feeding on sap, or may transmit plant pathogens. Symptoms vary widely with the aphid species, host, and host tissue attacked. The most common symptoms observed may include foliage spotting, speckling, chlorosis, curling, and/or wilting; as well as distorted growth patterns (Fig. 6), galls (Fig. 7), bark swelling, twig dieback, branch dieback, decline, and mortality. Aphids are small (1/64 - 1/4 inch long) pear-shaped insects (Fig. 1) that live in colonies (Fig. 2 & 5) on the leaves and new growth. They may be winged (Fig. 3 & 4) or wingless and vary widely in color, shape, and size. Some aphids produce alarm pheromones when threatened or disturbed, stimulating defensive responses (e.g. dropping to the ground, shaking aggressively) in their neighbors. Other aphids have wax glands in their abdomen that produce a woolly or waxy coating that may cover their entire body (Fig. 9). Like many other sap-sucking insects, aphids produce honeydew (waste and excess plant sap that could not be processed by the digestive system) that drips down onto lower surfaces. Fungi known as “sooty molds” grow on the honeydew, turning those surfaces dark gray or black. Other insects such as ants and wasps may also invade the area to feed on fresh honeydew, and some ant species “farm” aphids for honeydew (Fig. 8). Life Cycle: Life cycles vary considerably in different aphid species. Usually, aphids overwinter in the egg stage and hatch in early spring as plant growth resumes. Only wingless females are produced at first, which feed and reproduce without mating, resulting in a growing population of more wingless females. When the colony gets big enough, winged females are produced that fly to an alternate host plant species to feed and continue to reproduce without mating. Late in the season, winged forms return to the original host plant species where a generation of both males and females is produced; they mate and lay eggs before the onset of winter. Numerous overlapping life-stages can be found throughout the growing season. Importance: Moderate. Most aphids cause little or no serious harm to host plants; however, large infestations can cause damage. Generally, aphids are a serious nuisance that degrade the appearance of landscape trees and ornamentals. Management: Chemical control options are available and infested plants must be thoroughly treated. Contact insecticides and horticultural oils are usually ineffective against aphids with waxy protective coatings; systemic insecticides are sometimes effective in these cases. Aphids are notoriously difficult to control and nearly impossible to eradicate completely. An integrated pest management approach is usually the most effective. Predatory/parasitic insect populations usually keep aphid populations in check; insecticide applications that kill beneficial insects may result in aphid outbreaks. Timeline: Species dependent. Life stages may overlap significantly. Active throughout the growing season. Range: Statewide. 18  Sap-Sucking Insects Fig. 1 Tobacco aphid Fig. 2 Aphid colony Fig. 3 Green peach aphid Fig. 4 Giant bark aphid Fig. 5 Black cherry aphid Fig. 6 Leaf curl ash aphid Fig. 7 Woolly apple gall aphid Fig. 8 Ant feeding on honeydew Fig. 9 Woolly alder aphid 19 Gall-forming Insects Overview: Many insects induce hypertrophies (a condition of abnormal rapid cell division and cell enlargement) in host tissues during feeding or to complete their life cycle. These hypertrophies are generally referred to as galls, and are caused by a wide variety of insects. Gall-forming insects release plant growth-regulating chemicals that alter normal plant growth and development. Most gall-forming insects are host species-specific and are often named for their host. Galls can be formed on virtually any host tissue including leaves, buds, flowers, cones, shoots, twigs, branches, and main stems. There are hundreds of gall-forming insects, most of which cause little if any serious harm to their host plants. However, because galls may be large and conspicuous, they often cause concern. Causal Agent: Gall-forming insects include a number of insect and arachnid orders and families including aphids, phylloxerans, midges, adelgids, mites, psyillids, beetles, moths, sawflies, and wasps. Most often it is the immature stage of the insect that is responsible for gall production. Galls formed by gall wasps are among the most common galls observed. Hosts: Most common in hardwoods. Most hardwood species serve as hosts to one or more gall-forming insects; galls are particularly common in oaks. Some conifers including pines, fir, spruce, and baldcypress (Fig. 9) are hosts to gall-forming midges and adelgids. Symptoms / Signs: The causal agents of galls are usually not observed; larvae inside of galls are difficult to identify. Diagnosis is usually based on the gall symptoms and host species. Galls vary widely in size, shape, color, texture, and longevity and are determined by the host species, host tissue, and the causal agent. In general, galls are tissue swellings caused by rapid cell division and enlargement (gall midges in conifers also cause resin accumulation at their feeding sites, which contribute to gall swelling). Galls can be small leaf spots or bumps (e.g. eyespot galls on maple, dogwood, and yellow poplar (Fig. 1)), soft and fruit-like (e.g. oak apple galls (Fig. 2)), carpet- like (e.g. eriophyid galls (Fig. 4)), woody (e.g. many oak galls), ornamented (e.g. horned oak galls (Fig. 3)), spiny rose galls), fuzzy (e.g. hedgehog gall, woolly rose gall (Fig. 5)), cone-like (e.g. eastern spruce gall (Fig. 6)), well defined (e.g. nipple galls (Fig. 7)), deformed (e.g. many psyllid galls), or abnormal clusters of buds, shoots, or leaves (e.g. witches brooms (Fig. 8)). The variations are nearly endless. Life Cycle: Life cycles vary considerably. Galls are produced by plant growth-regulating compounds (sometimes called plant hormones) released by larvae, but a few galls are caused by adult life stages (e.g. sawfly-induced galls). Additional resources should be consulted for specific information on gall-forming insects. The life cycle of a typical oak gall caused by a gall wasp is given below as an example. Each gall-making wasp species utilizes only one or a few closely related tree species as a host; each gall maker creates a distinctive gall on its host. An interesting characteristic of many gall wasps is that they are heterogamous: the offspring differ significantly from their parents, but are identical to their grandparents. This is also referred to as alternating generations. The galls formed by alternating generations may be formed on different host tissues and look completely unlike those caused by the parent (Fig. 10 & 11). In fact, the offspring and their galls may look so unlike their parents that in many cases, entomologists have unknowingly described them as separate species. Many gall wasps overwinter as mature adults inside their galls. In the spring they emerge and lay eggs in suitable host tissue. Larvae rapidly develop; the plant growth-inducing chemicals they release cause rapid multiplication and growth of nutrient-rich cells surrounding the larval chamber on which they feed. Adults of the second generation emerge and lay eggs on the same host (but often different tissue). Larvae formed during this generation mature during the summer and fall but will not emerge until the following spring. Importance: Low. Galls usually cause little if any serious harm to their hosts. Management: Usually not required. Timeline: Species dependent; active throughout the growing season. Range: Statewide. 20  Sap-Sucking Insects Fig. 1 Eyespot galls Fig. 2 Oak apple galls Fig. 3 Horned oak gall Fig. 4 Eriophyid mite gall Fig. 5 Mossyrose gall Fig. 6 Eastern spruce gall Fig. 7 Nipple galls Fig. 8 Witches brooms Fig. 9 Cypress gall Fig. 10 Cynipid gall wasp (Generation 1) Fig. 11 Cynipid gall wasp (Generation 2) 21 Hemlock Woolly Adelgid Overview: The hemlock woolly adelgid was first introduced to the eastern United States in the early 1950’s from Asia. Since that time, it has spread throughout much of the natural range of our native hemlocks and threatens to eradicate virtually all hemlocks from our forests. The hemlock woolly adelgid is an aphid-like insect that feeds on nutrient-rich sap; large populations of the insect that heavily infest trees cause decline and eventually death over a period of three to seven years. There are many potentially disastrous consequences of losing mature hemlocks from our forests as they are critical for water and soil quality preservation, and are depended upon by many plant and wildlife species. Causal Agent: Hemlock woolly adelgid (Adelges tsugae) Hosts: Eastern and Carolina hemlocks; also hundreds of ornamental hemlock cultivars. Symptoms / Signs: Symptoms develop gradually over a period of several years. The foliage on infested branches will begin to pale in color, often turning from dark green to grayish-green or gray. Needles will dry out and may fall off the tree within a few months. A new flush of needles may occur on some infested trees, but this is not necessarily an indicator of improving tree health. Infested trees put on little if any new shoot growth. Crowns will appear thin and individual branches may be killed starting in the bottom of the crown and spreading upwards (Fig. 3). Trees will usually die within 3-7 years of becoming heavily infested. In areas where the adelgid front has already passed through, large numbers of pale-gray snags line watersheds (Fig. 7). Sedentary adult adelgids will be located on the undersides of branches (Fig. 1). Adults (< 1/16 inches long) (Fig. 8) are covered by a white woolly coating and are usually attached at the base of needles (Fig. 4). Heavily infested branches will look as if they have been sprinkled with snow (Fig. 2). The juvenile crawlers are nearly microscopic, but can be seen (when present) by shaking an infested branch over a white piece of paper; crawlers will appear as small black dots moving on the paper surface. Life Cycle: The hemlock woolly adelgid has a complex life cycle that involves a number of life stages and an alternate host (spruce) in Asia. The life-cycle here in the U.S. is not as complex because our native spruce species are not suitable for the production/survival of certain life-stages of the insect. In spring, two life stages are produced at the same time: winged sexuparae and non-winged progrediens. Note: Sexuparae do not survive or reproduce in North America. Progrediens hatch as crawlers from late March through early May. Crawlers are mobile for several weeks and can be dispersed to new trees by wind, people, and animals (particularly birds). Crawlers quickly settle down and attach themselves to a feeding site at the base of a needle where they remain attached for the rest of their life. The adelgids have a long stylet (3 times the length of the insect) that penetrates deep into plant tissues and obtains nutrients from cells that store and deliver nutrient-rich sap to the rest of the tree. By June or July, the progrediens have developed into mature sedentary adults, and produce white cottony sacs of eggs that cover their bodies (Fig. 5). Another life-stage called sistens hatch from these progredien eggs in mid-summer. Sisten crawlers attach themselves to needle feeding sites within a few days of hatching. Sistens remain attached throughout the fall and winter; in February they produce white sacs of eggs that hatch into progrediens and sexuparae a few months later. Importance: High. The hemlock woolly adelgid is a serious threat to our native hemlock species and ornamental varieties. There may be catastrophic consequences for ecosystems that depend on this important late-successional species. Management: Chemical control options are available for high-value trees in early stages of decline. Insecticidal soaps and oils can be sprayed onto small trees, but coverage must be thorough and timed accordingly to target susceptible crawlers and nymphs. Systemic insecticides, which can be injected into the tree or applied as a soil drench, are effective for up to three years. Research to use predatory beetles introduced from Asia and the Pacific Northwest as biological control agents is currently underway. Timeline: White and woolly adult adelgids first become visible in early spring. Crawlers are active in late spring and again for a short period during mid-summer. White woolly residue is usually visible year-round. Range: Throughout the native range of hemlock in the state. (Fig. 6). 22 Sap-Sucking Insects 23 Balsam Woolly Adelgid Overview: The balsam woolly adelgid was first introduced to the northeastern United States in the early 1900’s from central Europe. In the 1950’s, the insect was introduced to the southeast, and now all natural fir stands in North Carolina are thought to be infested (Fig. 6). The balsam wooly adelgid is considered to be a serious threat to Fraser firs in forests, Christmas tree plantations, and seedling nurseries. The insects attach themselves to the bark of stems and twigs to feed; abnormal cell growth and swelling follow and prevent water conduction in the sapwood. Trees decline and die within 2-3 years of being attacked. The long-term ecological consequences of this pest in fir-dominated ecosystems are unknown. Causal Agent: Balsam woolly adelgid (Adelges piceae) Hosts: All North American true firs; eastern U.S. species include balsam and Fraser fir. Symptoms / Signs: The most common symptom of trees attacked by the balsam woolly adelgid is abnormal swelling of infested tissues. This swelling is called “gouting” and is most common around buds, branch nodes, and on stunted shoots (Fig. 3 & 4). Gouting is most severe in trees that are only lightly infested for a prolonged period of time; the tops of these trees are usually killed first, and will often curl over. In more severe cases, adelgids will infest the main stem of the tree (Fig. 1); abnormal swellings resembling severely roughened bark may be present at feeding sites. When adelgids attack the main stem, trees are sometimes weakened to such a degree that gouting does not appear on other tissues. Foliage may become chlorotic, needles may fall off, and trees usually die within 2-3 years. Adult adelgids are very small (< 1/32 inch long) and are covered by a thick mass of white, woolly, and waxy coating that protects both the adult and its eggs. The adults are easiest to find where they gather in high densities around buds, branch and twig nodes, and on the main stem especially where bark is roughened. Juvenile crawlers are nearly microscopic, but can be seen (when present) by shaking an infested branch over a white piece of paper; crawlers will appear as small black dots moving on the paper surface. After crawlers attach and begin to feed, they become flattened and wax-fringed. Life Cycle: The balsam woolly adelgid has 2 ½ - 3 generations per year in North Carolina. Only female adelgids are present in North America, and they can reproduce without mating. Life stages widely overlap. Eggs hatch in spring and crawlers are mobile for several weeks; they are easily spread by wind and birds. Crawlers settle down and attach at feeding sites, such as bark lenticels and other natural openings. After the crawler’s mouthparts pierce the bark and it begins to feed, the insect transforms (without molting) into an immature resting stage called a neosisten. Neosistens generally develop into adult sistens by the end of June, and for the next several weeks eggs are laid by the sedentary female adults. Eggs (Fig. 2) hatch within a few days, crawlers quickly attach to feeding sites, and transform from neosistens to adults in September and October. In warmer parts of the state, a partial third generation will develop. Neosistens are the only over-wintering stage. Importance: High. The balsam woolly adelgid is a serious threat to our native firs. The long term consequences of balsam woolly adelgid-caused mortality are unknown. When the insect first colonizes a new stand, populations grow exponentially and high rates of tree mortality are observed. Natural regeneration follows, however, successive cycles of regeneration and mortality may cause significantly declining populations of firs over time (Fig. 6). Management: Chemical control options are available for high-value trees (Fig. 5). Contact insecticides are most effective against the crawler stage in May-June or September-October. Insecticidal soaps and oils may be effective against wax-covered adults, but coverage must be thorough and timed to avoid burning the foliage. Chemical applications can reduce adelgid populations enough to allow natural tree defenses to overcome the remaining infestation. Many treated trees may remain free of adelgids for several years. Timeline: Crawlers are active in late spring and again for a short period during mid to late summer. Life stages overlap significantly, and evidence of white woolly adults can usually be seen year-round. Range: High elevations in western North Carolina. 24  Sap-Sucking Insects Fig. 1 Infested stem Fig. 2 Eggs laid around a bud Fig. 3 Twig gouting Fig. 4 Branch gouting Fig. 6 Mortality and regeneration Fig. 5 Chemical treatment Fig. 7 Distribution 25 Pine Webworm Overview: The pine webworm is considered to be a minor pest of southern pines. The pine webworm larvae primarily feed on young seedlings, but may attack larger saplings or even mature trees. Severe defoliation is uncommon; even heavy infestations of the pine webworm are not usually severe enough to kill the host, but heavily defoliated seedlings may have reduced growth and vigor. There are many species of web-spinning sawflies and pine false webworms similar in appearance and behavior; generally, the information provided below applies to all of these species. Causal Agent: Pine webworm (Tetralopha rubestella). Hosts: Southern pines including loblolly, longleaf, pitch, shortleaf, slash, Virginia, white pine, and others. Symptoms / Signs: Symptoms include defoliation; early larval instars mine the needles whereas later instars clip and feed on the entire needle. Browning of mined/clipped needles may be observed. Growth reduction is possible when defoliation is severe. Pine webworm infestations are unmistakable, but usually go unnoticed until after the larvae have disappeared and feeding is complete. Needle mining by early instars is difficult to detect. Larger larvae will form colonies within a silken web nest. As the larvae feed and mature, the nest becomes filled with small brown fecal pellets and clipped needles. The result is an unmistakable mass of frass and webbing wrapped around branches or clustered at branch crotches (Fig. 1 & 2). Nests range from less than 2 inches to more than 5 inches in diameter. The larvae when fully grown are approximately ¾ inches long, tan to yellow-brown or brown, with dark-brown longitudinal stripes (Fig. 3). Adult moths are rarely observed, but are drab or dark gray with darker forewings; wingspan is approximately 1 inch (Fig. 4). Life Cycle: There are two generations per year in North Carolina. Pine webworms overwinter as pupae in the soil. The emergence of adult moths begins in May and continues throughout the summer. Adults mate and the females lay eggs in longitudinal rows on the needles of a suitable host; up to 20 eggs may be laid on a single needle. When larvae hatch, they spin a silken strand behind them, eventually entangling many needles. Young larvae mine the needles from within, but as they grow, they devour entire needles. Larger larvae will form colonies within a single silken nest; colonies may contain anywhere from two to more than 80 individuals. The feeding larvae fill the nest with frass and clipped needles. In September, the second generation of larvae drop to the ground and burrow into the soil to pupate. Importance: Low. Pine webworms usually cause little if any significant damage. When severe infestations occur, young seedlings can be killed but usually growth reduction is the only result (Fig. 5). Management: Usually not required. Pine webworm larvae are a preferred food of natural predators such as birds and rodents. There are also several species of parasitic wasps and flies that keep pine webworm populations in check. Timeline: Emergence of first generation adults occurs in May. The first webs (from the current growing season) may be visible as early as June. Nest formation and feeding occurs throughout the summer. Pupation of the second generation occurs mid to late September. Nests from the previous growing season are persistent and may be visible year-round. Range: Statewide. 26