Diagnosing Plant Problems PDF

ID-194 Diagnosing Plant Problems By Kimberly Leonberger, plant pathology Extension associate; Nicole Gauthier, Extension plant pathologist; Richard Durham, con- sumer horticulture Extension specialist and state Master Gardener coordinator; Lee Townsend, Extension entomologist (ret.); Matthew Spring...

ID-194 Diagnosing Plant Problems By Kimberly Leonberger, plant pathology Extension associate; Nicole Gauthier, Extension plant pathologist; Richard Durham, con- sumer horticulture Extension specialist and state Master Gardener coordinator; Lee Townsend, Extension entomologist (ret.); Matthew Springer, Extension wildlife specialist; Adam Leonberger, Jessica Bessin and Erica Wood, Extension horticulture agents; and Stacy White, Extension agriculture and natural resources agent. In this chapter: F or those with a green thumb, growing plants may seem easy. However, when plant problems arise, determining the cause of these issues can be difficult. Developing the skills necessary Data Collection for the Diagnostic Process 01 to determine the cause of a plant problem takes experience and time. The steps involved in the diagnostic process first Considerations and Possible Causes of Plant Problems 04 require analysis of information regarding the history of the Disease 04 symptomatic plant and the surrounding area. Plant symptoms Insects and Mites 10 and signs provide additional evidence to aid in determination of a possible cause. Wildlife  15 There are numerous potential causes for plant problems. Abiotic Causes  17 Living factors such as plant pathogens, insects, and wildlife Diagnostic Assistance 22 can damage plants. In addition, non-living factors including weather, physiological disorders, mechanical damage, nutrition, Summary 22 and chemical injury may also result in plant damage. Critical Appendix 23 thinking is essential to determine which possible causes are the most consistent with the observed damage. While it is not Additional Resources 23 always possible to determine the exact cause of a plant problem, Acknowledgments 23 there are numerous resources available to aid in the process. Photo Credits 24 The steps utilized in the diagnostic process are detailed in this chapter. Data Collection for the Diagnostic Process Diagnosis of a plant problem begins with the collection of information about the plant and its environment, as well as an evaluation of the symptoms present. After information is gathered, it can be used either to diagnose the issue or to rule out possible causes by process of elimination. The following steps detail this process. Plant Identification and History In order to determine whether a problem truly exists, it is important to correctly identify the type of plant. The normal growth of some plants can appear irregular and cause alarm. Time of year should also be considered, as many plants experience alterations in appearance as seasons change. Such is the case with some evergreen trees. For example, pine trees drop older needles in the fall, which can cause distress for those unfamiliar with fall needle drop. However, this process is completely normal for pine trees (Figure 6.1). Variations in growth and appearance can also be the result of different cultivars or varieties. Keeping accurate records of cultivars can help with the identification of normal growth and appearance of the plant. Many new varieties or cultivars Figure 6.1. Some evergreen trees, such as pine, shed older needles have appearances that vary greatly from those more commonly during the fall, giving the tree a brown appearance. CHAPTER 06 Diagnosing Plant Problems 2a 2b Figure 6.2. The ‘Chompers Hybrid’ cultivar produces cucumbers with variegation (2a). However, variegation can also be a symptom of a disease such as cucumber mosaic virus (2b). planted. For example, the cucumber variety ‘Chompers Hybrid’ has a variegated appearance, which may be confused with symptoms from disease or non-living factors (Figure 6.2). As plants grow and adapt to their environment, appearance may change. It is important to consider the history of plants to determine a possible cause of damage. Keep records of planting dates to determine plant age. Additionally, incorrect planting can stress plants and result in an abnormal appearance. A review of plant care activities, such as frequency and duration of watering and application of nutrients, may help determine possible causes of damage. Consider environmental changes that may have occurred in recent months or years. Severe winters or dry summers can affect plants’ appearance and health several months or years after the weather event. Examine the Site Examination of the growing site can provide additional information that aids in the diagnostic process. Since growing requirements vary for different plant types and even for different cultivars, it is important to consider the planting site. Plants have specific environmental conditions in which they thrive. When a plant’s location provides too much or too little light, water, or drainage, plants exhibit symptoms of damage. While it may initially appear that only one plant is affected, surrounding plants should be assessed for similar damage. If multiple different types of plants exhibit similar damage, it is likely that the cause of the damage is a non-living factor, such as chemical, environmental, or mechanical injury. Evaluate the area surrounding the symptomatic plant to identify clues that may establish the cause of a plant problem. Step away from the plant to consider items such as topography (Figure 6.3) and proximity to damage sources, such as wildlife habitats and construction sites. Through an evaluation of the environment surrounding a plant, cause for damage can often be determined. Figure 6.3. Evaluate the area around a problematic plant to deter- mine whether the damage can result from the topography. When plants are installed into low areas where standing water can collect, plant roots suffocate from lack of available oxygen. 6-2  Diagnosing Plant Problems CHAPTER 06 3a 3b Figure 6.4. Dieback is a common symptom exhibited by problematic plants (3a). However, the part of the plant where the problem is occurring in this example is the root system (3b). Inventory of Symptoms and Signs The type of damage that occurs on plants is important for the diagnostic process. Symptoms are the external response of the plant, which may indicate a problem. Symptoms may include leaf spots, holes in leaves, cankers, fruit spots, holes in fruit, irregular growth, root rots, discoloration, wilting, and dieback, as well as numerous other symptoms. Specific symptoms that can result from diseases, insects, wildlife, and abiotic causes are detailed in the following sections. Symptoms should be documented with as much detail as possible. While diagnostics are not based on symptoms alone, this information can assist in eliminating possible causes, and thereby establishing more likely causes for symptoms or problems. It is often necessary to examine the whole plant to clearly identify which part or parts are affected. When spots appear on Figure 6.5. When symptoms such as dieback are evenly distributed leaves or fruit, it is obvious that these are the parts of the plant along the base of several shrubs near the road, the cause is likely abiotic. In this situation, the cause of the damage is de-icing salt. that are affected. However, when symptoms such as wilting or dieback are present, the parts of plants affected are less obvious. These symptoms often indicate a problem at the base of the plant or in the root system (Figure 6.4). Patterns of symptoms can also provide valuable information for the diagnostic process. Take time to assess all plant parts to determine whether damage occurs in uniform or in random patterns. When damage is uniform across all plant parts and/ or entire plantings, it often indicates that the cause is abiotic. For example, dieback at the base of shrubs near a road can be the result of salt damage (Figure 6.5). However, when patterns of damage are inconsistent, the cause is more likely to result from disease, insect, or wildlife. Random symptoms may be present on plant parts, whole plants, or groups of similar plants. Damage that results from insect feeding is inconsistent across the leaves of a plant (Figure 6.6). In contrast, diseases usually begin in lower or inner canopies and create gradient patterns. The timing of symptom appearance and process of change over time can also aid in the diagnosis of plant problems. Damage from wildlife and abiotic factors results in symptoms Figure 6.6. Inconsistent patterns are often the result of disease, that appear suddenly and do not spread to other plants over insect, or wildlife. The damage to this eggplant leaf is the result of flea time. Disease and insect damage appears gradually. Over beetle feeding. 6-3 CHAPTER 06 Diagnosing Plant Problems time, the organisms that cause these issues multiply and cause by specific pathogen groups. A more extensive list of symptoms additional damage. Thus, symptoms from diseases and insects that can result from each pathogen group can be found in Table worsen over time and move to infect/infest new areas. 5.1 of Chapter 5. This table presents common symptoms of Signs are the physical evidence of causal organisms that are disease, but other combinations are possible. responsible for plant damage. Signs indicate the presence of disease-causing pathogens, insects, or wildlife. Signs can include Fungi and Water Molds fungal fruiting structures or fungal parts, insects or their frass, Fungal and water-mold pathogens are the most common and presence of animals or their scat. More details on the types culprits of disease issues. Fungi and water molds have of signs that can be associated with diseases, insects, and wildlife characteristics that make each group unique, but many are detailed in the following sections. symptoms are similar. Both are capable of producing a wide While abiotic issues do not produce signs, the lack of range of symptoms on different plant tissues. Leaf and fruit observable signs does not necessarily confer that the problem spots are often the first symptoms noticed on symptomatic is the result of an abiotic issue. In many cases, visual observation plants. These spots may be variable in shape, including spots of disease and insect signs requires magnification. Additionally, with dark borders and lighter-colored centers or concentric signs may be limited to specific environmental conditions. rings (bullseye-like appearance) (Figure 6.7). Spots on plant tissue may expand over time. Considerations and Possible Fungi and water molds can also produce stem lesions or Causes of Plant Problems cankers (Figure 6.8). Cankers on branches limit the movement of water and nutrients, which may result in symptoms such as This critical thinking step is the most challenging portion wilting, dieback (Figure 6.9), or flagging. When stems or roots of the diagnostic process. Determining a possible cause first become damaged, aboveground symptoms such as wilting, requires a review of the information that has been collected dieback, or plant death may be observed. Rotted plant tissue in the previous steps. This information is then used to either may appear soft, sunken, discolored, or blackened (Figure 6.10). support or eliminate potential causes of injury or damage. Once information about the plant, site, symptoms, and signs has been gathered, these “clues” may be used to determine a probable cause. Consider all of the known information and possible causes they may indicate. This evidence can also be used to rule out unlikely culprits of the damage. It may be necessary to consult reference materials or additional resources to interpret the collected information. Utilize resources such as university publications, reference books, credible websites, and local county Extension agents. After review of the material and resources, it may be necessary to gather some additional information. A more Figure 6.7. Leaf spots with concentric rings are often the result of thorough inspection of the symptomatic plant may now yield fungal or water-mold diseases. Lesions of early blight of tomato have more symptoms not documented before, or a broader view of this appearance. the site may reveal “clues” not noticed before. This information is then used to continue the process of determining the most likely cause of the plant problem. In order to reach a probable cause for the damage, it may be necessary to repeat this process multiple times. Disease Diseases are the observable symptoms that result from infection by plant pathogens. A detailed description of the plant pathogen groups can be found in Chapter 5, Plant Diseases. These organisms can result in a wide range of symptoms. Signs for many plant pathogens are not visible without the aid of a microscope, which increases the difficulty of diagnosing plant disease problems. The following is a description of common symptoms and signs that may be present as a result of infection Figure 6.8. Cankers may appear as cracks or sunken tissue, such as this anthracnose disease on sycamore. 6-4  Diagnosing Plant Problems CHAPTER 06 While most fungal and water-mold signs are only visible with the aid of a microscope, it may be possible to observe some fungal structures with minimal magnification or the naked eye. A hand lens is often used to view symptomatic plant parts with 10, 20, or 40 times magnification (Figure 6.11). The body of fungi and water molds consists of a mass of threadlike structures (mycelia). These organisms produce sexual and asexual spores, which require magnification to be observed and examined (Figures 6.12 and 6.13). Many fungi produce reproductive structures (fruiting structures such as ascocarps, acervuli, chasmothecia, and pycnidia), which are often visible without magnification. Fruiting structures may appear as small flecks or bumps on infected tissue (Figures 6.14 and 6.15). Overwintering structures that hold numerous spores or fungal Figure 6.9. Dieback often Figure 6.10. Rotted roots may includes slow decline or canopy become brown or black in color, tissue for next season’s infection, such as chasmothecia and thinning and may indicate appear thin, and slough off sclerotia, may also appear as small black specks on plant tissue crown or root disease. Dieback easily. Black root rot is prevalent near the end of the growing season (Figure 6.16). Some of these of this catalpa tree was caused in both herbaceous and woody fungal structures can survive for several years in soil (Figure by Verticillium wilt. plants, including this pansy. 6.17). One group of fungi produces mushrooms, which are large fruiting structures (Figure 6.18). Some fungi generate spores in abundance, making them visible when they are released from their reproductive structures (Figure 6.19). Many fungal fruiting structures are only produced under certain conditions; thus the absence of visible signs does not indicate the absence of fungi. Fruiting structures often require conditions such as the presence of moisture (including humidity) and cool to moderate temperatures. It may be possible to induce the development of identifying structures by placing a portion of the symptomatic plant tissue into an incubation chamber (Figure 6.20). This chamber, usually built with a plastic container or bag and a moist paper towel, mimics the ideal environmental conditions that may result in the development of visible mycelium, fruiting structures, and/or Figure 6.11. A hand lens can be used to magnify plant samples and spores. Structures typically develop in 24 to 48 hours. Note that identify signs. not all fungi will develop visible structures with this process. Figure 6.12. Mycelia can sometimes be observed without the aid Figure 6.13. Magnification can make clusters of spores visible, as with of magnification, as is the case with the white mycelial growth of the brown sporulation of leaf mold on tomato. powdery mildew. 6-5 CHAPTER 06 Diagnosing Plant Problems Figure 6.14. Fruiting structures such as the small Figure 6.15. Some fruiting structures may appear as slimy masses, such as the salmon- black bumps (pycnidia) (indicated by the white colored sporodochia of Volutella blight. arrow) are visible with or without magnification. Figure 6.16. Chasmothecia are overwintering Figure 6.17. Sclerotia (indicated Figure 6.18. Mushrooms are easily-recognizable structures produced by some powdery mildew by white arrow) are fungal struc- fruiting structures. They are not always present, fungi at the end of the growing season. They can tures that are visible with the even though the fungal body continues to grow be observed with or without magnification. naked eye. below ground. Figure 6.19. When spores are produced in abundance they may be Figure 6.20. When signs are absent, incubation in a bag with a moist visible. Puffball fungi produce fruiting structures above ground and paper towel may induce certain fungal structures. release large numbers of spores in a smoke-like manner. 6-6  Diagnosing Plant Problems CHAPTER 06 Bacteria Diseases that result from bacterial pathogens can exhibit a range of symptoms, several of which are similar to those caused by fungal or water-mold pathogens. Bacterial pathogens can result in leaf and fruit spots. These spots may have a yellow halo (Figure 6.21) or water-soaked appearance (Figure 6.22). Symptoms such as cankers, dieback, and wilting may also result from bacterial infections. As bacteria commonly break apart cells when they infect plants, wet rots of fruit (Figure 6.23) or stems are common. Some bacterial pathogens may result in galls, which are tumor-like growths on plant tissue (Figure 6.24). Due to the small size of bacterial cells, it is uncommon to observe bacterial signs. There are a few bacterial pathogens that accumulate, causing large numbers of cells to ooze from tissue (Figure 6.25). This is considered a sign, even though individual bacterial cells cannot be observed. The lack of visual signs makes the diagnosis of bacterial diseases challenging. Figure 6.21. Leaf spots that result from bacterial pathogens may have a yellow halo around the lesion, such as with bacterial spot on pepper. Figure 6.22. Bacterial leaf spots may appear to be oily or water-soaked Figure 6.24. Galls, or tumor-like growths, can be a symptom of bacte- around the edge of lesions, such as with bacterial blight on beet. rial diseases. Crown gall is prevalent on many different woody plants. Figure 6.23. Bacterial pathogens can damage plant cells, resulting in Figure 6.25. Bacterial ooze can be a sign of bacterial infection. rotting of plant tissues. Bacterial soft rot of cabbage results in decay. Bacterial wilt in cucurbits creates “oozing” signs. 6-7 CHAPTER 06 Diagnosing Plant Problems Viruses Viral diseases result in an extremely wide range of symptoms. Plants infected with viruses may exhibit interruption of a color, known as color breaking (Figure 6.26). Ringspots and line patterns are common symptoms of viral pathogens (Figure 6.27). The leaves and fruit of some plants may display a symptom called mosaic or mottling, in which a lighter green, yellow, or cream color is interspersed with a darker green color. Symptoms such as yellowing of plant tissue (chlorosis), tissue death (necrosis), and dieback may develop as a result of viral pathogens. Some infected plants may exhibit a stunted or distorted appearance, while others may present a prolific amount of growth (witches’ broom) (Figure 6.28). Poor fruit set, flower abortion, and abnormal growth are additional symptoms of viral disease. Many of these symptoms are similar to those that may result from other pathogens or abiotic issues. Viral pathogens are extremely small and are not visible without the aid of an electron microscope. Thus, it is not possible to visually observe signs in the field. Diagnosis of viral diseases relies heavily on symptomology and elimination of other possible causes. Diagnostic laboratories may confirm virus infection with antibody or molecular diagnostic techniques. Figure 6.26. Color breaking is the interruption of the primary color pattern by a virus. Tulip color break virus was responsible for “tulipma- nia” in the 17th century; today color breaking is the result of breeding, not virus infection. Figure 6.27. Viral pathogens can cause a range of ringspots and line Figure 6.28. Witches’ broom is the term used for a prolific amount of patterns. Tobacco rattle virus on peony may exhibit these symptoms. growth, which can occur as a result of viral pathogens. Rose rosette virus develops a classic witches’ broom symptom. 6-8  Diagnosing Plant Problems CHAPTER 06 Other Disease Issues (Nematodes, Phytoplasmas, Parasitic Plants) Nematodes are microscopic, unsegmented worms that infest roots or foliar tissue. When roots become infested, plants commonly appear stunted or lose vigor (Figure 6.29). Nematode feeding on foliar plant parts results in necrosis or leaf blotches (Figure 6.30). Most nematodes are not visible without the aid of a microscope; thus field observation of signs is unlikely. Infection by phytoplasmas can result in a range of symptoms, including yellowing, stunting, witches’ broom, and the production of leaf-like structures in place of flower petals. Plants may also experience virescence, a condition in which chlorophyll (green pigment) develops in tissues where it is normally absent (Figure 6.31). There are no visible signs for phytoplasma pathogens. Parasitic plants utilize host plants to obtain nutrients and water. As a result, parasitized plants may appear less vigorous or exhibit dieback (Figure 6.32). Parasitic plants can be easily observed, which simplifies diagnosis of disease issues of this type. Figure 6.31. Some plants infected by phytoplasmas display vires- cence. Aster yellows is a common disease caused by a phytoplasma. Figure 6.29. Roots infested by nematodes may cause the plant canopy to decline or appear stunted. Root-knot nematode infestation has resulted in the stunted appearance of these squash plants. Figure 6.30. Leaf necrosis or blotches may be a symptom of foliar Figure 6.32. Mistletoe is a common parasitic plant that may result in nematodes. Foliar nematodes can infect a range of leafy plants, dieback of the host plant when populations are high. including ferns. 6-9 CHAPTER 06 Diagnosing Plant Problems Insects and Mites Consider the following when evaluating possible pest damage to plants: Feeding damage is the most common way to identify a Document the range of plant species affected. General feed- potential insect or mite problem. Caterpillars, aphids, and ers, such as Japanese beetles or fall webworms feed on many mites may remain on the foliage for days or weeks after initial plant species; damage by specialist pests is confined to closely infestation. Consequently, infestations can be discovered early related species. by regular examination. However, if pests have completed Determine season or activity period. Some pests have rela- their development and left, only plant damage may remain. tively well-defined activity periods that can help narrow the In addition, mobile or intermittent feeders are often missed list of potential culprits. For example, bagworms begin to feed because they move frequently. Thus, plant damage may be the in early summer. Aphids are cool-season pests, while most only observable clue. mite species are favored by hot, dry weather. Most plant-feeding pests have some type of chewing or Consider type of tissue affected or damaged. Some plant sucking mouthparts. Tissue removal by chewing insects is feeders prefer buds or expanding leaves, while others target obvious, in contrast with the subtle effects of sap feeders. older foliage. Beetles, caterpillars, and tree crickets eat portions of leaves, sometimes leaving distinctive damage patterns. The needle- Chewing Insects like sucking mouth parts of aphids, leafhoppers, and mites remove plant sap, while the saliva of other insects can break Some chewing insects leave characteristic feeding damage. down plant tissues as they feed. Symptoms of insect infestation This damage may help identify the type and age of the insect. may be holes, wilting, discoloration, or spotting. Some sap For example, newly hatched individuals may not be able to chew feeders excrete large volumes of nutrient-rich honeydew. An tough tissue or veins, thus damage is limited to surface “window accumulation of honeydew makes leaves, stems, or branches pane” feeding (Figure 6.33). Older insects can consume tougher shiny and sticky. Black sooty mold may thrive on the deposits. tissue and may leave little behind. Table 6.1 presents examples Finally, thrips tear at flowers and foliage with file-like rasping of common feeding damage patterns by chewing insects. mouthparts that leave fine scratches. Figure 6.33. Some chewing insects may consume only surface tissue, leaving a “window pane” appearance. 6-10  Diagnosing Plant Problems CHAPTER 06 Table 6.1. Characteristic damage by common chewing insects. Type of Insect Illustration of Damage Many flea beetles chew scattered, rounded “shotholes” in leaves. Other 34a chewing insects such as tree crickets and katydids, chew similar but larger holes. (Figure 34a) Some insects feed on soft plant tissue but do not chew through veins. 34b This “skeletonizing" is characteristic of Japanese beetles. Some newly hatched caterpillars (bagworms) and sawfly larvae produce this pattern of injury. Slugs feed on low foliage in shaded, humid areas. They rasp tissue, causing similar damage. Look for their slime trails on foliage and surrounding soil. (Figure 34b) Many beetles and larger caterpillars may consume most of the leaf, 34c leaving only the midrib or large veins. (Figure 34c) Grasshoppers and some caterpillars hang on to the edges of leaves 34d and feed from the side. Others may feed evenly around the perimeter so the leaf becomes gradually smaller but keeps its general shape. (Figure 34d) Weevils chew uneven notches in the sides of leaves as they feed. 34e (Figure 34e) 6-11 CHAPTER 06 Diagnosing Plant Problems Continued from previous page. Table 6.1. Characteristic damage by common chewing insects. Type of Insect Illustration of Damage Leafcutter bees remove smooth, rounded sections. (Figure 34f ) 34f Blotch and serpentine leafminers feed on tissue inside the leaf, creating 34g hollow areas that may be swollen or discolored. Insects or accumulated waste may be visible by holding damaged leaves up to the light. Leaf miners commonly infest holly and boxwood. Heavily mined leaves may drop prematurely. (Figure 34g) Fall webworms (FWW) build tents on the ends of branches, whereas 34h Eastern tent caterpillars (ETC) build tents in the crotches of tree branches. ETC and FWW use silk to create communal nests. ETC feed on wild cherry and related species from March through April. Two genera- tions of FWW spin tents on the ends of branches of many tree species in June and August. (Figure 34h) Bagworms spin silk coverings with pieces of host plant foliage 34i attached. The structure provides protection from desiccation and pred- ators. Skeletonized feeding damage by this small caterpillar is visible on the leaf surface. The camouflaged bagworms are often undetected until damage becomes severe. (Figure 34i) Leaftier and leaf roller caterpillars use silk to fold or roll leaves and cre- 34j ate individual shelters on foliage in which they feed. (Figure 34j) 6-12  Diagnosing Plant Problems CHAPTER 06 Sap Feeders undersides of leaves, so they are easily overlooked. Often, the effects are subtle and symptoms are slow to develop. Table 6.2 General decline of an entire plant or plant part can appear presents examples of common damage that may result from as yellowed or wilted foliage, general loss of vigor, or dieback. sap feeders. These general symptoms can indicate many problems, including sap-feeding insects. Many sap feeders are small and feed on the Table 6.2. Characteristic damage by common sap-feeding insects. Type of Insect Illustration of Damage Saliva injected during feeding by some insects can cause distorted growth or discolor- 35a ation. Injury may be mistaken for chemical injury or disease. Examine the undersides of the leaves for presence of insects. Normal new growth may indicate that the injury occurred some time ago. (Figure 35a) Fine spotting (stippling) on leaves may be caused by leafhoppers, plant bugs, lace bugs, 35b or mites. Saliva injected during feeding destroys chlorophyll at the feeding site, but the toxins do not diffuse throughout the leaf. Continued feeding by increasing numbers of pests can cause the entire leaf to lose color and drop prematurely. If stippling symp- toms are present on the newest growth, then the infestation may still be active. Look for pests on undersides of leaves. (Figure 35b) Thrips tear at leaf tissue to puncture cells and feed on their contents. Injury appears as 35c thin scratches or flecking of the leaves. Thrips can produce distorted growth by feeding in buds or along veins in developing foliage. Black varnish-like spots of waste accumu- late on the lower leaf surface where these insects feed. (Figure 35c) Scale insects are destructive pests of landscape trees and shrubs. They resemble 35d growths on plant leaves or bark, but they can be scraped off with a fingernail. Armored scales live under crusty, waxy coverings that resemble rough spots on bark. They spend their lives on woody tissue. Soft scales resemble larger bumps, so they are much easier to detect. In addition, they produce large amounts of nutritious excre- ment called “honeydew.” Over time, buildup of honeydew supports the growth of the dark sooty mold fungus. Sap removal by scale insects gives heavily infested plants the appearance of drought stress. (Figure 35d) 6-13 CHAPTER 06 Diagnosing Plant Problems Gall Makers Significant damage can occur after brood emergence in an area. Many borers produce exit holes. These insects usually attack Galls are abnormal growths that may be found on most plant trees that are injured, dying, or suffering from transplant shock. parts, from catkins to leaves (Figure 6.36). Most are caused by However, some can infest healthy trees. Multiple exit holes tiny wasps, aphids, flies, or mites. Unlike scale insects, they are typical of the adult stage of an insect leaving the tree after cannot be easily scraped off. completing its development. Several beetle families produce Many gall makers attack woody plant species, resulting in small holes while entering the tree to lay eggs. Exit holes of galls on twigs or branches (Figure 6.37). However, most insect roundheaded borers are typically one-eighth to three-eighths galls do not affect plant health. The number of galls on a plant of an inch wide and scattered randomly on branches or trunks. can fluctuate naturally from season to season. Scattered small holes are emergence sites of shothole borers or bark beetles, while D-shaped emergence holes, such as those Borers and Girdlers made by the emerald ash borer, are characteristic of flatheaded Plant decline or foliar wilt along a single branch can mean borers (Figure 6.39). Tunneling insect larvae such as the petiole infestation by borers or girdling insects. borer can cause sudden, premature leaf drop. Petioles generally Borers tunnel into woody tissues, often disrupting plants’ turn black, and a small, white worm can be found in the ability to move water and nutrients. Damage produced by borers leaf stem. varies with the type of insect. Borer damage is often apparent as Girdlers are beetles that chew around a twig so that it breaks holes or splits on the outside of woody tissue. Longitudinal slits easily (Figure 6.40). The beetle’s eggs are laid in the portion of with splintered margins that form along finger-sized branches the twig that falls to the ground. This damage increases stress are typical of periodical cicada egg-laying damage (Figure 6.38). to the tree and creates sites for potential disease development. Figure 6.36. Some insects can cause gall Figure 6.37.The horned oak gall represents Figure 6.38. Longitudinal slits along finger- formation on leaves. an example of insect galls on woody tissue. sized diameter branches are typical of periodical cicada egg-laying damage. Figure 6.39. D-shaped emergence holes are Figure 6.40. Girdling insects chew around twigs or branches and increase the likelihood characteristic of flatheaded borers. of breakage. 6-14  Diagnosing Plant Problems CHAPTER 06 Wildlife Medium-sized mammals: This group includes species like raccoons, skunks, opossums, armadillos, foxes, coyotes, Determining what wildlife species is causing a problem can and groundhogs. These species can range in size from several be difficult. Wildlife species can cause a wide range of damage pounds up to the size of a medium-sized dog. (Coyotes can to plants, through feeding or other activities. Wildlife damage reach about 40 pounds.) Unfortunately, this is the most wide- can be broken into two broad categories: aboveground damage ranging group in terms of the damage they can cause to plants from feeding, trampling, or antler rubbing and belowground or landscaping. Fruit-bearing trees, gardens, or landscapes issues. The following sections discuss various types of wildlife may all be affected. Damage to plants may result when these damage. Use any and all observations including plant damage mammals dig holes in the ground when searching for food or and the types of habitat located around the damaged plant to establishing dens. Some species may directly remove seeds, help determine the species responsible. bulbs, fruits, or vegetables. Large mammals: Deer, elk, black bears, cattle, and horses Damage Type may tear and cut branches, leaves, or the whole plants of sprouting fruits and vegetables. Livestock culprits aren’t actually Aboveground Damage from Feeding considered wildlife but can cause damage similar to deer and Each group of wildlife species referenced in this section is elk. Large mammals are usually easier to identify because of divided by feeding behaviors and resulting damage. their size and the amount of “evidence” they leave in the area. Small mammals (rodents): Chewed bark and cambium Tracks and/or scat are often present within the area, as well as tissue on small trees and shrubs are most frequently caused by extensive damage to plants that occurs in a very short period mice, rabbits, squirrels, muskrats, or beavers. Look for teeth of time. Deer and elk are capable of consuming large quantities marks. These will be clean cuts, and plant tissue will not appear. of hundreds of species of plants year-round. Damage will torn (Figures 6.41 and 6.42). Frequently, teeth marks will be occur more frequently on plants or sections of plants where left in the plant material. These teeth marks can help gauge new growth is occurring. Bud damage occurs most frequently the size of the animal that caused the damage. Water sources during winter months by both deer and elk, which can cause close by may indicate issues from muskrats or beavers. Beaver severe damage and potential death for the plants. damage is unique and easily identifiable due to their ability to chew into large trees and cause extensive damage to plants near ponds or streams. Other damage common from this group includes damage and removal of berries, fruits, or vegetables. Teeth marks left in berries or vegetables may help to gauge the size of the culprit, when there are no tracks or scat to aid in identification. Figure 6.41. Clean cuts from a larger mammal, the beaver. Figure 6.42. Clean cuts on a pine seedling caused by a rabbit. 6-15 CHAPTER 06 Diagnosing Plant Problems Birds: Birds can cause damage to plants by either tissue Belowground Issues removal or pecking damage. The removal of edible plant Damage to plants can be directly or indirectly caused by material such as fruits is the most common (Figure 6.43). wildlife. This is especially true when damage occurs below the Berries may have tears or damage from pecking. Tooth marks soil surface. These issues are harder to diagnose as they are often will not be present in this type of damage. Other types of out of sight. Roots of trees and bushes may be girdled by vole birds, such as woodpeckers, may damage plants by pecking feeding during winter, when vegetative material is scarce. This bark material. Sapsuckers, often confused with woodpeckers, belowground damage often goes unnoticed until the following create horizontal lines of holes in tree bark (Figure 6.44). These spring, when plants show decline or poor vigor. In order to birds remove sap from holes to use as a food source during determine whether voles are active in the area during winter, winter months. monitor vole burrows. Turtles: Damage from turtles is uncommon, but box turtles Mole tunnels may disturb plant roots, but tunneling is usually can feed in vegetable gardens. Look for damage close to the only aesthetic and is not directly harmful to plants. Moles can ground, with torn pieces of plant material or dime-sized or be beneficial by managing grubs in lawns and increasing soil larger chunks missing out of vegetables. aeration. Checking for tunnels or soil mounds will indicate whether there are moles present within the area. Expect any plant damage to occur within close proximity to these tunnels. Tools for Identifying the Cause of the Problem Tracks and Scat One of the easiest ways to determine potential species causing plant damage is to look for tracks or scat near the damage. This will help narrow down the possibilities of what may be causing the damage, but presence of tracks or scat does not mean the animal that left them is causing the damage. It is just a tool to help determine what species are in the area, and this information is added to the list of other “clues” to help narrow down the potential list of causative species. When trying to determine the species that left a track, pay close attention to the size of the track, the number and position of fingers and toes, whether claws are visible, and, if there are multiple sets of tracks, the spacing between prints (Figure 6.45). Apply this information to a mammal or bird field guide, which will have a section on tracks. Alternatively, there are several good resources for track identification online including the Internet Center for Wildlife Damage (refer to Additional Figure 6.43. Berry damage from birds (indicated by the white arrow). Resources section for link). Figure 6.44. Sapsuckers damage trees by making lines of holes. Figure 6.45. Example of tracks that may be left as evidence. 6-16  Diagnosing Plant Problems CHAPTER 06 Scat is the fecal matter or droppings of wild animals and is a reliable sign that wildlife has been present in the area. When Abiotic Causes examining scat, avoid touching or wear rubber gloves to Abiotic plant injury may be caused by environmental protect against potential diseases. Take note of scat size, width, or physical conditions. These problems are noninfectious, and shape (Figure 6.46). Characteristics, such as a tubular or meaning they are not caused by living organisms. In many rounded shape, flat or pointed ends, and singular or multiple cases, vigorous plants are healthier than those under stress. droppings, will help guide the identification of the species. See Thus, it is important to consider the age-old horticulture “Scat Identify Key” resource in the Additional Resources section recommendation of “the right plant for the right place.” For to help identify scat. plants to thrive, they must have light, water, and nutrients in the proper amounts and temperatures within a range that Trail Cameras supports growth. Plants grown in a location similar to their Trail cameras offer an affordable and easily implemented native habitat, especially in areas with minimal disruptions, will option to determine causes of wildlife damage. Cost of cameras generally suffer less abiotic injury than those introduced from can be as little as $25 depending on features and brand. In most more exotic locations or those planted in areas with human- situations, the cheaper versions are capable of taking the quality impacted habitats. While plants differ greatly with regard to pictures needed to identify wildlife culprits. Set the camera optimal environmental conditions, the injuries observed when up in a manner that maximizes the chances of the nuisance conditions are not met also vary greatly. Besides natural causes, wildlife triggering the device. Place a camera in the area that plants sometimes suffer injury from chemicals or constraints is experiencing the issue, preferably close to the plant(s) being humans bring into their growing space, such as herbicides, damaged. Cameras should be placed at an appropriate height deicing salts, and synthetic materials around stems and roots. for the size of animal thought to be causing the problem. For All of these noninfectious factors may contribute to plant injury. example, if squirrels or rabbits are suspected, direct the camera to focus closer to the ground. With deer or elk, cameras should Weather be placed about hip height. Even though a certain species is captured in a picture, this may not be the species that is causing Several aspects of weather may affect plant growth, including the problem. Use pictures to help narrow down the potential temperature, sunlight, and rainfall. Damage that results list of causative species. from weather conditions may be exhibited as a wide range of symptoms. Resources and Reference Material Late-summer fertilization (especially nitrogen) and References can be helpful when attempting to identify abundant soil moisture encourage perennials to continue to wildlife species and damage. These resources include field grow well into autumn and delay cold acclimation. Plants that guides and internet sources like the Internet Center for fail to adjust to cooler temperatures may exhibit winter damage Wildlife Damage. to buds or stems. This damage appears as partial dieback to stems as growth resumes in spring or as lack of vegetative and/ or flower bud growth. Figure 6.46. Raccoon scat is dark and tubular. Figure 6.47. Broad-leaf evergreens such as magnolia may exhibit leaf burn as a result of winter injury. 6-17 CHAPTER 06 Diagnosing Plant Problems Broad-leaf evergreens (such as holly, magnolia, cherry laurel, and boxwood) may exhibit another type of winter damage called leaf burn or leaf scorch (Figure 6.47). On sunny days, these plants photosynthesize with open stomata. Cold, winter winds, combined with low water availability due to frozen soils, cause desiccation of leaves via rapid loss of water through stomata. In severe cases, this leaf burn may affect a large portion of the plant’s canopy, causing deformity or even death. Fleshy stems with little bark coverage may also be affected. Milder cases of leaf burn may be expressed only on the leaf margins and may only cause temporary unsightly brown leaves that are replaced in spring with new growth. It is important to keep evergreens well-watered in late fall and winter as long as soils are thawed. A layer of mulch helps retain soil moisture. Frost damage is another type of cold-temperature problem that can occur in spring as plants begin regrowth or as temperature-sensitive annuals are planted. Frost may occur when temperatures drop a few degrees or more below freezing. Sensitive plants exposed to frost may display blackening of young growing tips, leaves, flowers, or buds. Annual plants whose growing tips are damaged may be completely lost. Figure 6.48. High temperatures can result in drought stress, which Perennial plants usually regrow, but sensitive flower buds may may be observed as leaf scorching. be damaged, resulting in reduced flower and fruit production. Plants may be protected from frost by covering with light cotton or synthetic fabric material to catch warmth from the ground and hold it close to the plant. It is important that such material not only cover the plant, but also stretch down to the ground. Sometimes small plants are covered with solid objects such as flower pots or buckets; these objects should be removed to allow ventilation as temperatures warm. Coverings offer protection from light frost but are not effective when temperatures drop below 25°F. Another aspect of cold-temperature damage may occur on tropical houseplants or certain vegetables. These plants are accustomed to growing under warm conditions, and as a result, low, non-freezing temperatures (40°F-50°F) may cause damage. Common houseplants such as peace lily, philodendron, and certain orchids, exhibit wilting and even death with prolonged exposure to low, non-freezing temperatures. Cold damage occurs with certain vegetables after prolonged storage under refrigerated conditions. Cucumbers, tomatoes, peppers, and watermelon may exhibit water-soaked tissue when refrigerated for long periods. Hot temperatures, usually coupled with bright sunlight, may also cause damage to plants. For example, hot temperatures increase water demand in plants, causing them to release more water through their stomata than can be supplied by the root system. This results in temporary wilting, but plants usually recover overnight if there is sufficient soil moisture. Nevertheless, some scorching of leaves may result (Figure 6.48). Plants are naturally adapted to certain light conditions (sun, part-sun, or shade). For example, shade-adapted plants will show symptoms such as yellowing, scorch, burn, or death when Figure 6.49. Plants subjected to high soil moisture or flooding may exhibit a variety of symptoms, including yellowing of new growth grown under sunny conditions. Plants germinated and grown and defoliation. 6-18  Diagnosing Plant Problems CHAPTER 06 in one environment (greenhouse, house windowsill, nursery lower-light conditions. Conversely, plants that are grown in holding area) and then transplanted outdoors may scorch or high-light conditions and then moved to shade usually exhibit burn when suddenly exposed to brighter light. It is important stunted growth and defoliation. New leaves produced in shade to gradually expose these plants to higher light conditions conditions are larger and thinner, and plants generally produce (called hardening off ) before permanently planting them in a fewer flowers than similar plants growing in sun. brighter location. Even houseplants abruptly moved to a bright Extremes in rainfall may also result in abiotic damage to window may exhibit some damage to leaves accustomed to plants. Severe low-moisture conditions or drought may cause symptoms such as wilting, yellowing, marginal leaf burn, and premature fall coloration of leaves. Insufficient rainfall is best remedied by irrigation. However, spotty or shallow irrigation may fail to meet plants’ needs. A weekly, relatively deep irrigation equivalent to one inch of rain (wetting the soil to six to eight inches deep) is usually more beneficial to plants that frequent shallow irrigation. Newly transplanted plants with limited root systems may benefit from frequent shallow irrigation until roots are established. Too much rainfall or irrigation may also cause damage to plants. Plants under high soil-moisture or flooded conditions may exhibit wilting, yellowing of new growth, and defoliation due to damage to roots caused by low oxygen (Figure 6.49). Ensure that soils are well drained and aerated by incorporating organic matter; elevate soil in mounds or raised beds in areas of poor drainage. Physiological Disorders Physiological disorders are often characterized by gradual decline over time. Symptoms of decline include reduced growth, premature leaf coloration, winter injury, whole-plant dieback, water sprout production on woody plants, and increased susceptibility to insects and disease. Decline may be caused by a number of abiotic issues (Figure 6.50). Soils may lose structure and become compacted due to traffic, which impacts root health and subsequently foliage health. Packaging material, such as synthetic burlap or galvanized wire baskets, often constricts root systems, leading to decline. Improper planting techniques may also result in decline or death of a plant. Prior to planting, all potentially girdling roots should be removed, so they do not wrap around the base of the plant. Plants should be installed at an appropriate depth and then maintained correctly. Improper maintenance, such as excess mulch or exposed roots, can lead to increased plant stress and an increased risk of decline. Symptoms of improper planting practices may appear within the first few years after planting. However, other symptoms may take five or more years to become visible. Inappropriate temperature, rainfall, or sunlight may also result in decline, particularly if these conditions are mild or otherwise not extreme. This situation results in delayed symptom development but compromises plant health over time. Decline is best managed by good cultural practices. Proper fertilization, irrigation during drought, mulching, and proper pruning may help to slow or reverse decline. It is important to Figure 6.50. Decline refers to a decrease in plant vigor and can result closely monitor pest situations on stressed plants, as they often from numerous abiotic issues. develop compromised natural pest resistance. 6-19 CHAPTER 06 Diagnosing Plant Problems Mechanical Damage Another cause of decline is damage to the lower trunk by string trimmers or landscape equipment. Plants’ phloem vessels Plants often suffer physical damage from devices used in are located just under the bark and can be easily damaged, managing the landscape. Synthetic material left on plant roots especially on young trees. If damage occurs, photosynthates may eventually constrict the root system. Synthetic burlap or from the leaves fail to be transported to the root system. A twine should be completely removed from the root system weakened root system results in decline, and in severe cases, before planting. It is common to stake trees after planting to plants may fail to leaf out in spring. While it may seem logical prevent them from blowing over during strong winds. Trees to cover the base of the trunk with protective material, this staked too tightly are slower to establish new root systems than practice also presents problems. Protective covers or wraps may those that are allowed to sway slightly. The material used to retain moisture and invite decay. The best practice is to maintain secure the tree to the stake may also be problematic. Bare wires a wide layer of mulch around the tree, making it unnecessary to or twine tightly secured to the trunk or branches may be quickly trim or mow close to the trunk. However, mulch itself can be overgrown by the plant, making it difficult to remove later and damaging when it is applied too deeply or too closely around eventually causing constriction and girdling of the branch or the trunk. trunk (Figure 6.51). Covering the section of twine or wire that touches the tree with flexible garden water hose or coarse fabric will delay growth around the fastener. In most instances, staking Nutrition material should be removed after one growing season. There are 16 nutrients that are necessary for plant growth. Mechanical damage may also be caused by wind, ice, or snow Deficiencies or excess of any of these nutrients may cause load. For woody plants, proper pruning, especially when plants symptoms such as discoloration (Figure 6.52), stunting, are young, helps to develop strong trunks and branch angles distortion, or burning. Sometimes, nutrients are present in that are better able to withstand weight and force. A discussion adequate amounts but soil pH, when too acidic or too alkaline, of proper pruning techniques is provided in Chapter 17, Care limits the availability of nutrients to plants. Plant roots that of Woody Plants. are compromised by poor drainage, compacted soils, low soil moisture, or pest issues may also result in nutrient deficiencies due to the plant’s inability to uptake nutrients. Symptoms of nutrient deficiency or toxicity are characterized in Chapter 1, Basic Botany. When nutritional issues are suspected, the first step is to complete a soil test (see Chapter 4, Soils and Fertility). Testing the soil will determine the level of important nutrients in the soil, as well as the soil pH. Recommendations from a soil test may help remedy the nutritional issue or, in rare cases, suggest the need for further analysis. Figure 6.51. Wires or other materials used to secure plants should be Figure 6.52. Nutritional deficiencies may result in a wide range of removed at the appropriate time to avoid constriction and girdling of symptoms, including discoloration of plant tissue. the plant. 6-20  Diagnosing Plant Problems CHAPTER 06 Figure 6.53. Chemical damage may be observed as chlorotic or necrotic spotting on leaf surfaces. Chemical Damage as reduced growth, wilting, or chlorosis may be observed. In severe cases, wilting can occur even when the soil is wet. Lower Patterns of chemical injury on individual plants differ, leaves generally wilt first, followed by the drying of leaf margins depending primarily on whether a chemical causes damage (leaf scorch). Herbicides that inhibit root growth include the directly on contact or whether it is absorbed and moved agricultural herbicides dinitroanilines, DCPA (Dacthal), and throughout the plant. Direct-contact damage can occur on diphenamid. Excess nitrogen fertilizer can have the same foliage, stems, and roots. Symptoms from shoot-contact results. Keep in mind that many other factors also injure chemicals occur over the general plant canopy. The injury does roots or inhibit their growth, including nematodes, disease- not spread with time or move to previously undamaged plants. causing pathogens, soil compaction, cold weather, salinity, and Injury is characterized by chlorotic or necrotic spotting (Figure nutritional deficiencies or excesses. 6.53). Spots are usually uniform in size and evenly distributed Some chemicals can move throughout a plant after being over all or most plant surfaces, with a distinct margin between absorbed. The effects of these mobile chemicals depend upon affected and healthy tissue. whether they are transported in the xylem or the phloem. If a chemical is applied directly to aboveground parts, the Toxic chemicals transported in the xylem primarily cause application pattern may be observed. For example, the pattern of symptoms in older plant foliage as they move upward from spray droplets may be visible, or areas where spray accumulated the crown. Examples of xylem-transported chemicals include along leaf edges may show the most damage. In the case of a urea fertilizer and the agricultural herbicides triazine, alachlor, toxic gas (volatile chemical), areas between leaf veins and along and metolachlor. Chemicals transported through the phloem leaf margins, where water concentration in lowest, develop may move in many directions from the point of absorption; damage first. Examples of shoot/foliage contact chemicals are for example, it may move from the shoots to the roots or vice foliar-applied fertilizers; the agricultural herbicides paraquat, versa. Symptoms caused by phloem-transported chemicals acifluorfen, and dinoseb; and herbicidal oils. (Very few, if any, occur primarily in the plant’s new growth and meristematic contact herbicides are available to home gardeners.) regions. Affected young tissue is discolored or deformed, and Toxic contact chemicals in the root zone, including excess injury may persist for several sets of new leaves. Examples of fertilizer, can result in damaged roots or poor root development. phloem-transported chemicals include the common garden Roots can be injured and root tips may be killed. Damaged roots herbicides 2,4D, dicamba, and glyphosate. are unable to obtain water; thus aboveground symptoms such 6-21 CHAPTER 06 Diagnosing Plant Problems Diagnostic Assistance Insect Sample Submissions: When insects have been determined to be the issue, plants with suspected insect In many cases, it may not be possible to determine the cause injury, photos, or vials containing an insect sample can be of a plant problem without additional assistance. Numerous submitted directly to the University of Kentucky Department resources are available to aid in this process. County-based of Entomology. Specialists review these samples and provide Extension agents are local resources that can be utilized to correct identification and management information. assist homeowners with identification of the cause of a plant Weed Identification: Extension weed specialists at the problem, as well as to provide recommendations regarding University of Kentucky Department of Plant and Soil Sciences management of problems. In Kentucky, at least one agriculture are able to provide species identification, as well as weed man- and natural resources and/or horticulture agent is located agement information. When herbicide injury is suspected, spe- in each of the 120 counties. Agents possess a broad range of cialists in this program review samples to determine whether knowledge on a variety of agricultural and horticultural topics. the problem is consistent with herbicide contact. However, These individuals may provide various services to diagnose the University of Kentucky does not provide herbicide residue plant problems, including consultation, sample assessment, testing. and/or site visits. Contact the local Cooperative Extension Plant Identification: The Herbarium at the University of office for more information on services provided. To locate a Kentucky Department of Forestry can provide identification local Extension office, visit https://extension.ca.uky.edu/county. of woody plants and wildflowers. Diagnosis of a specific plant problem may require a Soil Tests: The University of Kentucky Division of Regulatory specialist to assist in the identification process. The University Services provides soil testing for a minimal fee. Soil samples can of Kentucky and Kentucky State University both employ be submitted through a county Extension office. Once soil is specialists that focus on specific areas of plant health. Specialists analyzed, a report is provided that includes recommendations in the departments of plant pathology (diseases), entomology to improve soil health. (insects), forestry (wildlife), and horticulture (abiotic) partner Plant Tissue Analysis for Nutrients: Several private labo- with Extension agents to provide homeowners and commercial ratories can provide an analysis of the nutrient composition of growers with diagnoses and management recommendations for plant tissue for a fee. A county Extension agent can determine the wide array of plant problems. These specialists are accessible if this service is needed and provide additional information on through local county Extension agents. submitting a sample. A wide range of diagnostic services are available to assist residents of Kentucky in determining the causes of plant problems and growing healthy plants. A county Extension agent Summary can assist in determining which, if any, of these services are The process of diagnosing plant problems can be a needed. Homeowners should work with the county Extension challenging exercise in critical thinking. Information about the agent to submit samples. This ensures that appropriate samples problematic plant is collected by considering the identity of the are provided, improving response time and reducing the risk plant and its history. Examination of the site may also provide of an insufficient sample submission. additional information that may aid in the process. A thorough Plant Disease Diagnostic Laboratory: When a plant analysis of symptoms and signs is important for the diagnostic problem has been determined to be the result of disease, a process. After collection, this information is used to determine sample of the affected tissue may be sent to one of the two whether the problem is the result of a living factor (disease, University of Kentucky Plant Disease Diagnostic Laboratories. insect, or wildlife) or a non-living cause. It may be necessary Diagnosticians review samples using microscopy, culturing, to consult a variety of resources in order to draw conclusions and/or molecular methods. Diagnosticians provide identifica- from the information collected. If a probable cause cannot tion and management information. The University of Kentucky be determined after a review of the information collected, plant pathology fact sheet Submitting Plant Specimens for numerous services are available to assist in the diagnosis of a Disease Diagnosis (PPFS-GEN-09) provides helpful information plant problem. for collecting appropriate samples. 6-22  Diagnosing Plant Problems CHAPTER 06 Appendix Acknowledgments Appendix A: Considerations for Diagnosis of Ornamentals The authors would like to acknowledge and thank Mary in the Landscape Harper, Barren County Kentucky Extension Master Gardener, and the following University of Kentucky reviewers: Emily Pfeufer, Extension plant pathologist; Julie Beale and Brenda Additional Resources Kennedy, plant disease diagnosticians; and Cheryl Kaiser, University of Kentucky Department of Plant Pathology Extension staff associate, for editorial and compositions Publications https://plantpathology.ca.uky.edu/extension/ contributions. Portions of the abiotic section were adapted or publications revised from the original text by James L. Green, former Oregon University of Kentucky Department of Entomology Publications State University Extension horticulture specialist. https://entomology.ca.uky.edu/entfacts/ University of Kentucky Department of Forestry Wildlife Publications https://forestry.ca.uky.edu/wildlife-pubs University of Kentucky Wildlife Damage Website https://forestry.ca.uky.edu/wildlifedamage Internet Center for Wildlife Damage http://icwdm.org/ Scat ID Key https://icwdm.org/identification/feces/scat-id/ University of Kentucky Department of Horticulture Residential Publications http://www.uky.edu/hort/home-horticulture University of Kentucky Cooperative Extension Service https://extension.ca.uky.edu/ Kentucky State University Cooperative Extension Service https://www.kysu.edu/academics/college-acs/school-of- ace/co-op/index.php Considerations for Diagnosis of Ornamentals in the Landscape https://plantpathology.ca.uky.edu/files/ppfs-gen-15.pdf Kentucky Cooperative Extension Service County Office Information http://extension.ca.uky.edu/county Submitting Plant Specimens for D ise a se D iag nosis https://plantpathology.ca.uky.edu/files/ppfs-gen-09.pdf 6-23 CHAPTER 06 Diagnosing Plant Problems Photo Credits University of Kentucky Paul Bachi—6.23, 6.31, 6.36 Auburn University Julie Beale—6.3 Lacy L. Hyche, Bugwood.org—6.40 Ric Bessin—6.6, 6.34d Bugwood.org William Fountain—6.35d, 6.37, 6.49 William Brown Jr.—6.2b, 6.4b Nicole W. Gauthier—6.5, 6.28, 6.48 John Ghent—6.41 John Hartman—6.8, 6.9, 6.25, 6.30, 6.32, 6.51 H.J. Larsen—6.4a Cheryl Kaiser—6.10, 6.18, 6.47 Burpee.com—6.2a Brenda Kennedy—6.17, 6.38, 6.52, 6.53 California Polytechnic State University at San Luis Obispo Adam Leonberger—6.15 Gerald Holmes, Bugwood.org—6.29 Kim Leonberger—6.7, 6.11, 6.13, 6.14, 6.16, 6.20 Colorado State University Kenny Seebold—6.21 Whitney Cranshaw, Bugwood.org—6.35c Matt Springer—6.42, 6.43, 6.45, 6.46 Howard F. Schwartz, Bugwood.org—6.22 Lee Townsend—6.34a, 6.34b, 6.34c, 6.34f, 6.34g, 6.34h, Creativecommons.org 6.34i, 6.35b, 6.39 Kalyanvarma—6.19 University of Tennessee Forest Research Institute, Slovakia Alan Windham—6.44 Milan Zubrik, Bugwood.org—6.34j USDA Forest Service North Carolina State University Steven Katovich, Bugwood.org—6.1, 6.35a Jim Baker, Bugwood.org—6.34e Vitalitree R.K. Jones, Bugwood.org—6.26 Jason Sharman, Bugwood.org—6.50 University of Delaware Wisconsin Department of Agriculture, Brian Kunkel, Bugwood.org—6.33 Trade and Consumer Protection University of Georgia Anette Phibbs, Bugwood.org—6.27 University of Georgia Plant Pathology, Bugwood.org—6.24 Unaffiliated Sheryl Pirone—6.12 Revised 01-2024