Kansas State General Pesticide Application Training Manual PDF

PESTICIDE APPLICATION TRAINING General Manual Kansas State University Agricultural Experiment Station and Cooperative Extension Service Table of Contents Certification Procedures 3 Pests and Pest Control...

PESTICIDE APPLICATION TRAINING General Manual Kansas State University Agricultural Experiment Station and Cooperative Extension Service Table of Contents Certification Procedures 3 Pests and Pest Control 5 Pest Control Methods Insects Plant Disease Agents Weeds Mollusks Wildlife Damage Control Pesticide Formulations 29 Types of Formulations Adjuvants Compatibility Labels and Labeling 36 Parts of the Label Label Terminology Reading the Label Protecting the Environment 59 Potential Hazards Potential Benefits Application Equipment 66 Sprayers Nozzles Tips Dusters and Granular Applicators Calibration 75 Laws and Regulations 85 FIFRA Registration Residues and Tolerances Other Regulations Pesticide Safety 93 Protecting Your Body Handling Pesticides Safely First Aid and Pesticide Poisoning Recognition Other Terms Used in Pest Control 110 Directions for Using this Manual This is a self-teaching manual. At the end of each major section is a list of study questions to check your understanding of the subject matter. By each question in parenthesis is the page number on which the answer to that question can be found. This will help you in checking your answers. These study questions are representative of the type which are on the certification examination. By reading this manual and answering the study questions, you should be able to gain sufficient knowledge to pass the Kansas Commercial Pesti- cide Applicators Certification and Recertification examination. 2  Certification controlling ornamental shrubbery or turf pests on property owned or Procedure rented by the individual and such This manual has been written to property is used as the individual’s assist those persons who are prepar- residence. ing themselves for an examination over the General Standards portion of Commercial certification may not be the commercial pesticide applicator necessary if restricted use pesticides certification exam. State and Fed- are used: eral regulations specify that certain a. within the authority granted standards of competency relating to by a private applicator certifica- both general and specific topics must tion be met by an individual before they b. under the supervision of a are allowed to apply or supervise the certified commercial applicator. application of Restricted Use Pesti- (This does not apply to aerial cides. The General Standards portion applicators or where supervision of the examination must be success- is prohibited by label direction or fully completed by all categories of other legal authority.) applicators. Therefore, this manual c. by veterinarians or physi- may contain information over top- cians, as part of their professional ics that do not directly relate to your services specific categories or types of applica- d. by laboratory personnel in tion work. pest­icide research By law a pesticide is defined as In order to qualify for certification follows: “Pesticide” means, but is you must: not limited to, (1) any substance or a. be at least 18 years old, mixture of substances used to pre- b. submit a completed applica- vent, destroy, control, repel, attract or tion for certification, mitigate any pest (including weeds) c. pass the “General Exam” and (2) any substance or mixture of (cov­ered by this manual) plus an substances intended to be used as a exam in at least one category/ plant regulator, defoliant or desiccant. subcategory of application, Pesticides are classified by the EPA d. Pay the required fees. There as either Restricted Use or General is a separate application fee and Use (not restricted). A certified ap- exam fee. Applicants who fail plicator is required when a restricted a specific category exam may use pesticide is being used. Under take another exam upon paying the Kansas Pesticide Law, a “certified an additional exam fee. No fee commercial applicator” means a certi- is required to take the “General fied applicator, whether or not he/she Exam.” is a private applicator with respect to Upon meeting the qualifications for some uses, who uses or supervises the certification, a certificate and a pocket use of any pesticide which is classi- card will be issued by the Kansas fied for restricted use for any purpose Department of Agriculture. Your cer- or on any property other than that tification will expire on December 31 provided for in the definition of “cer- of the second calendar year following tified private applicator.” A “certified the year it was issued. For example, if private applicator” is one who uses you are issued your certificate on June or supervises restricted use pesticides 1, 1995, it will expire on December 31, for purposes of: (a) Producing any ag- 1997. ricultural commodity, (1) on property Recertification can be obtained by owned or rented by the individual or either of two options: such individual’s employer, or (2) on 1. Passing an examination over the property of another for no com- the general manual and your pensation than trading of personal specific category manual, similar to your initial certification, or services between producers; or (b) 2. Attending a pesticide appli- 3 Certification cator training meeting approved Business License Procedure by the secretary (no examination required). A “Kansas Pesticide Business License” is required before any com- In order to qualify for recertifica- mercial pest control efforts, including tion, you must submit a new applica- advertising, are attempted. Obtaining tion and pay the applicable fees. Note this business license has different pro- that if the required training is not cedures and requirements from those attended during your effective period for becoming a certified commercial of certification, then to be certified pesticide applicator. In brief, there are again you must retake and pass a four requirements to obtain the busi- “current examination.” ness license: Certification in another state does 1. complete the application; not replace the requirement for an 2. pay the fee (calendar year applicator to have Kansas commercial basis); applicator certification. Kansas has 3. furnish proof of financial entered into reciprocal agreements responsibility; and with a few states, whereby commer- 4. have at least one person certi- cial certification in any of those states fied in the categories/subcatego- may be used in lieu of passing Kansas ries of business. commercial certification exams. Additional information on the However, the applicator is required Kansas Pesticide Business License to complete the other requirements can be found in the chapter on Laws for Kansas certification, including and Regulations in this manual. Also, submitting an application and paying for an informational packet, write the fees. Further details on reciprocal cer- Kansas Department of Agriculture, tification are available from the Plant Plant Health Division, Certification Health Division of the Kansas Depart- Record Center, 901 So. Kansas Ave., ment of Agriculture. Topeka, KS 66612–1280, or phone 785/296-2263. 4  Pests and Even though a pest is present, it may not do very much harm. It could Pest Control A pest is anything that: cost more to control the pest than competes with humans, domes- would be lost because of the pest’s tic animals, or crops for food, damage. feed, or water, The three main objectives of pest injures humans, animals, crops, control are: prevention—keeping a pest structures, or possessions, from becoming a problem, spreads disease to humans, suppression—reducing pest domestic animals, or crops, numbers of damage to an ac- annoys humans or domestic ceptable level, animals. eradication—destroying an Pests can be placed in five main entire pest population from a categories: limited defined area. insects (and related animals), plant disease agents, weeds, Pest Control Methods The use of a combination of meth- mollusks, and ods to control pests is basic to all pest vertebrates. control. Successful pest control is As a certified applicator, you must based on the ability to: be familiar with the pests likely to be keep pest damage to a minimum encountered in the area covered by by choosing an appropriate your certification category. To be able combination of control methods, to identify and control the pests, you recognize when direct action, need to know about some aspects of: such as a pesticide application, the common features of pest is necessary, and organisms, endanger the environment as characteristics of the damage little as possible. they cause, and The combination of methods you pest development and biology. choose will depend on the kind and You can get identification aids, amount of control you need. publications, and pictures from your Cooperative Extension Service agent Natural Forces or ask other experts for advice. Some natural forces/controls act To solve pest problems, the appli- on pests, causing the populations to cator must: rise and fall. These natural forces act identify the pest, independently of humans and may know what control methods are either help or hinder pest control. available, You usually cannot alter the action evaluate the benefits and risks of of natural forces on a pest popula- each method or combination of tion, but you should be aware of their methods, influence and take advantage of them choose the methods that are whenever possible. Some forces which most effective and will cause affect the pest population include the least harm to people and the climate, natural enemies, topography, environment, and food and water supply. use each method correctly, Climate observe local, state, and federal Weather conditions, especially tem- regulations that apply to the perature, day length, and humidity, situation. affect pests’ activity and their rate of The most important principle of reproduction. Pests may be killed or pest control is this: Use a pesticide supressed by rain, frost, freezing tem- only when necessary and at the low- peratures, drought, or other adverse est labeled rate which will prevent the weather. pest from causing more damage than is reasonable to accept. 5 Pests and Climate also affects pests ­indirectly Host Resistance Pest Control by influencing the growth and develop- Some crops, animals, and struc- ment of their hosts. The population of tures resist pests better than others. plant-eating pests is related to growth Some varieties of crops, wood, and of the host plants. Unusual weather animals are immune to certain pests. conditions can change normal patterns Use of resistant types helps keep pest so that increased or decreased damage populations below harmful levels by results. making the environment less favor- Natural Enemies able for the pests. Host resistance Birds, reptiles, amphibians, fish, works in two main ways: chemicals in the host prevent mammals, and predatory and parasit- ic insects feed on some pests and help the pest from completing its life control their numbers. More than half cycle, the host is more vigorous or of all insect and insect-like species feed on other insects, some of which tolerant than other varieties and are pests. Disease organisms often thus less likely to be seriously suppress pest populations. damaged by pest attacks. Topography Biological Control Features, such as mountains and Biological control involves the use large bodies of water restrict the of naturally occurring enemies—para- spread of many pests. Other features sites, predators, and disease agents of the landscape can have similar (pathogens). It also includes meth- effects. Soil type is a prime factor ods by which the pest is biologically affecting wireworms, grubs, nema- altered, as in the production of sterile todes, and other soil organisms. Some males and the use of pheromones or pests live in heavy, poorly drained juvenile hormones. Most kinds of bio- soil, others in light, sandy soils. Soil logical control agents occur naturally. type also affects the distribution of Releasing more of a pest’s enemies plants (including weeds), which in into the target area can supplement turn affects the population of insects this natural control. and other plant pests. Biological control is never com- plete. The degree of control fluctuates. Food and Water Supply There is always a time lag between Pest populations can thrive only as pest population increase and the cor- long as their food and water supply responding increase in natural con- lasts. Once the food source—plant or trols. But, under proper conditions, animal—is exhausted, the pests die sufficient control can be achieved to or become inactive. The life cycle of eliminate the threat to the crop or many pests depends on the availabil- animal to be protected. Biological con- ity of water. trol can be a low-cost control method Agricultural Forces particularly suited to low-value crops Unfortunately, natural controls/ (pastureland, clover, and hay crops) forces often do not control pests or in areas where some injury can be quickly enough to prevent unaccept- tolerated (golf course fairways, forest able injury or damage—other pest areas). control methods must be initiated. Cultural Control Those available include: Cultural practices are agricultural host resistance, practices used to alter the environ- biological control, ment, the condition of the host, or cultural control, the behavior of the pest to prevent mechanical control, or suppress an infestation. Planting, sanitation, and growing, harvesting, and tillage prac- chemical control. tices sometimes can be manipulated 6  Pests and to reduce pest populations. Other stand its effects. Pests that are not practices such as crop or pasture rota- destroyed may pass along to their Pest Control tion, varying the time of planting, and offspring the trait that allowed them use of trap crops also affect pests. to survive. Mechanical Control When we use one pesticide repeat- Devices and machines used to edly in the same place, against the control pests or alter their environ- same pest, the surviving pest popula- ment are called mechanical controls. tion may show greater resistance to Traps, screens, barriers, radiation, and the pesticide than did the original electricity can sometimes be used to population. Some pests have become prevent the spread of pests or reduce partially immune to poisoning by an infestation. Lights, heat, and re- certain pesticides. frigeration can alter the environment Not every pesticide failure is sufficiently to suppress or eradicate caused by pest resistance, however. some pest populations. Make sure that you have used the cor- rect pesticide and the correct dosage, Sanitation and that you have applied the pes- Sanitation practices help to sup- ticide correctly. Also remember, the press some pests by removing sources pests that are present may be part of a of food and shelter. Other forms of new infestation that occurred after the sanitation which help prevent pest chemical was applied. spread include using pest-free seeds or plants and decontaminating equip­ Factors Affecting ment, livestock, and other possible Pesticide Use Outdoors carriers before allowing them to enter Soil Factors—Organic matter in a pest-free area. soils may “tie up” pesticides, limiting their activity. Soils with high organic Chemical Control matter content may need higher rates Pesticides are chemicals used to of some pesticides for best control. destroy pests, control their activity, or Soil texture also affects the way prevent them from causing damage. pesticides work. Soils with fine par- Some pesticides either attract or repel ticles (silts and clays) have the most pests. Chemicals which regulate plant surface area. They may need higher growth or remove foliage may also be rates for total coverage. Coarser soils classified as pesticides. (sands) have less surface area. Use Pesticides are generally the fast- lower rates on them. est way to control pests. In many Surface Moisture—Pesticides ­instances, they are the only weapon work best with moderate surface available. Choosing the best chemical moisture. Wetness may keep the for the job is important. pesticide from adequately contacting By selecting pesticides wisely and the protected surface. Dryness may applying them correctly, the respon- prevent the pesticide from spreading sible pesticide applicator can use evenly over the surface and contact- these chemicals for the benefit of the ing the target pest. environment. Rain may interfere with pest con- Pest Resistance to Pesticides trol by causing pesticides to run off or The ability of pests to resist poi- to leach down through the soil. Rain soning is called pesticide resistance. during or soon after over-the-top or Consider this when planning pest foliar applications may wash pesti- control programs that rely on the use cides off the plant. However, some of pesticides. protectant fungicides are sometimes Rarely does any pesticide kill all purposely applied just before periods the target pests. Each time a pesticide of expected high humidity and light is used, it selectively kills the most rain. When pre-emergence pesticides susceptible pests. Some pests avoid are applied to the surface, moderate the pesticide. Others are able to with­­- rainfall aids in carrying them down 7 Pests and through the soil to the pests. Rain The challenge lies in our ability to Pest Control may also release pesticide action after control pests so that injury caused by some granular applications. them is held to a minimum, and to Humidity and Temperature—Hu- recognize when direct action, such as midity also affects the way pesticides a pesticide application, is necessary. work. Herbicides often work best when weeds are growing fast—usu- Integrated Pest ally in high humidity and optimum Management (IPM) temperature. However, these same Integrated Pest Management (IPM) conditions may make the protected is the planned manipulation of pest plant more susceptible to pesticide populations in an attempt to achieve injuries. a balance between costs and returns, High temperature and sunlight and between farm production and the will cause some pesticides to break overall environment. Integrated Pest down when they are left exposed on management practices include use top of the soil or on other surfaces. of: cultivation, changes in cropping Low temperatures may slow down or sequence, barriers, pest resistant or stop the activity of some pesticides. tolerant varieties, sanitation, traps, Wind—Wind speed and direction beneficial insects, timely planting can greatly alter the effectiveness of a and harvesting, and judicious use of pesticide application. Excessive wind chemical pesticides. IPM is accom- can blow the pesticide off target and plished by growers who consider all result in inadequate control. Even alternative pest control practices that moderate winds can greatly alter are available on their farms, then use the coverage of Ultra Low Volume one or more cost-effective pest control Concentrate Solutions (ULV) and mist practices that are least harmful to the blower applications. Sometimes the environment. applicator can compensate for minor Use of effective IPM practices winds by applying the pesticides must be based on current informa- at an angle where the winds blow tion about the pest problem, such as the chemical towards the area to be the numbers and kinds of pests in protected. the specific crop or herd. Inadequate knowledge or improper diagnosis of Principles of Pest Control the pest problem results in wasteful We often talk about the “war” use of time and money and disap- against insects, plant diseases, weeds, pointing control of the pest(s). and rats. In a war between countries, Management Tests would a national leader use only the IPM must be practical and tailored Army? Wouldn’t he/she also use to each pest problem on your farm. other tools—Navy, Air Force, and Three tests of practicality are: propaganda? 1. Is it available (to this farm, Yet, in our struggle against pests, when needed)? how often do we use the handiest or 2. Does it fit the entire crop least expensive pesticide? How often or herd management program do we forget to consider other meth- (or can present management be ods or combinations of methods? feasibly changed to accommodate How often do we forget about effects the pest management practice(s) on the environment? It may being considered)? be too often. 3. Cost effectiveness. The “bot- The use of a combination of meth- tom line” when one’s livelihood ods to control pests is basic to all pest is involved must always be: “Will control. Modern pest control uses it pay?” all available methods to keep pests The third factor is the basis of the below economically harmful levels, two concepts, economic injury level and damages the environment as little and economic threshold. Economic as possible in the process. injury level is the lowest number of 8  Pests and pests that will cause an amount of from some insects are made injury equal to the cost of applied into dyes and paints. Silk comes Pest Control control practices. Economic t­ hreshold, from the cocoons of silkworms. sometimes called the “action thresh- destructive insects—Although old” is the pest number or density this is the category which usual- at which remedial control practices ly comes to mind when insects should be taken to prevent the pests are mentioned, it includes the from exceeding the economic injury fewest number of species. These level. The economic threshold is are the insects that feed on, necessarily lower than the economic cause injury to, or transmit dis- injury level to allow time to apply ease to humans, animals, plants, control practices and to permit time food, fiber, and structures. In for those control practices to control this category are, for example, the pests. aphids, beetles, fleas, mosqui- Integrated pest management toes, caterpillars, and termites. consists of selection of specific control practices which work well together Physical Characteristics to best solve a specific set of pest All insects in the adult stage problems under the conditions which have two physical characteristics in prevail at that time and place. common. They have three pairs of jointed legs, and they have three body Insects regions—the head, thorax, and abdo- There are more kinds of insects on men. earth than all other living animals Head combined. They are found in soil, hot The head supports antennae, eyes, Grasshopper springs, water, snow, air, and inside and mouthparts. The antennae vary plants and animals. They eat the in size and shape and can be a help in choicest foods from our table. They identifying some pest insects. Insects can even eat the table. have compound eyes, made up of The large number of insects can be many individual eyes. These com- divided into three categories accord- pound eyes enable insects to discern ing to their importance to man: motion, but probably not clear im- species of minor importance— ages. About 99 percent of all species The four general types of mouth- are in this category. They are parts are: food for birds, fish, mammals, chewing, reptiles, amphibians, and other piercing–sucking, insects. Some have aesthetic sponging, and value. siphoning. beneficial insects—In this small Chewing mouthparts contain but important group are the toothed jaws that bite and tear the predators and parasites that food. Cockroaches, ants, beetles, feed on destructive insects, caterpillars, and grasshoppers are in mites, and weeds. Examples are this group. Piercing–sucking mouth- ladybird beetles, some bugs, parts consist of a long slender tube ground beetles, tachinid flies, which is forced into plant or animal praying mantids, many tiny tissue to suck out fluids or blood. parasitic wasps, and predaceous Insects with these mouthparts are mites. Also in this category are stable flies, sucking lice, bed bugs, the pollinating insects, such as mosquitoes, true bugs, and aphids. bumblebees and honeybees, Sponging mouthparts have a tubular some moths, butterflies, and tongue-like structure with a spongy beetles. Without pollinators, tip to suck up liquids or soluble food. many kinds of plants could not This type of mouthpart is found in the grow. Honey from honeybees flesh flies, blow flies, and house flies. is food for humans. Secretions 9 Pests and Siphoning mouthparts are formed young grows to a point where the Pest Control into a long tube for sucking nectar. skin cannot stretch further; the young Butterflies and moths have this type. molts and new skin is formed. The Thorax number of these stages (called instars) The thorax supports the three pairs varies with different insect species of legs and (if present) the wings. The and, in some cases, may vary with the various sizes, shapes, and textures of temperature, humidity, and availabil- wings and the pattern of the veins can ity and kinds of food. The heaviest be used to identify insect species. feeding generally occurs during the The forewings take many forms. In final two instars. the beetles, they are hard and shell- No Metamorphosis like; in the grasshoppers, they are Some insects do not change except leathery. The forewings of flies are in size between hatching and reach- membranous; those of true bugs are ing the adult stage. The insect grows part membranous and part hard- larger with each successive instar un- ened. Most insects have membranous til it reaches maturity. Examples are hindwings. The wings of moths and silverfish, firebrats, and springtails. butterflies are membranous but are The food and habitats of the young covered with scales. (called nymphs) are similar to those Abdomen of the adult. The abdomen is usually composed Gradual Metamorphosis Insect eggs of 11 segments. Along each side of Insects in this group pass through most of the segments are openings three quite different stages of devel- (called spiracles) through which the opment before reaching maturity: insect breathes. In some insects, the egg, nymph, and adult. The nymphs tip end of the abdomen carries tail- resemble the adult in form, eat the like appendages. same food, and live in the same envi- ronment. The change of the body is Insect Development gradual, and the wings (when pres- Most insect reproduction results ent) become fully developed only in from the males fertilizing the females. the adult stage. Examples are cock- The females of some aphids and roaches, lice, termites, aphids, and parasitic wasps produce eggs with- scales. out mating. In some of these insect species, males are unknown. A few in- Incomplete Metamorphosis sects give birth to living young; how- The insects with incomplete meta- Gradual Metamorphosis ever, life for most insects begins as an morphosis also pass through three egg. Temperature, humidity, and light stages of development: egg, naiad, are some of the major factors influenc- and adult. The adult is similar to the ing the time of hatching. Eggs come in young, but the naiads are aquatic. various sizes and shapes—elongate, Examples: dragonflies, mayflies, and round, oval, and flat. Eggs of cock- stoneflies. roaches, grasshoppers, and praying Complete Metamorphosis mantids are laid in capsules. Eggs The insects with complete meta- may be deposited singly or in masses morphosis pass through four stages on or near the host—in soil or on of development: egg, larva, pupa, plants, animals, or structures. and adult. The young, which may be Metamorphosis called larvae, caterpillars, maggots, or The series of changes through grubs, are entirely different from the which an insect passes in its adults. They usually live in different growth from egg to adult is called situations and in many cases feed on ­metamorphosis. different foods than adults. Examples When the young first hatches from are beetles, butterflies, flies, mosqui- Complete Metamorphosis an egg, it is either a larva, nymph, or toes, fleas, bees, and ants. naiad. After feeding for a time, the Larvae hatch from the egg. They grow larger by molting and passing 10  Pests and through one to several instars. Moth ment bears two pairs of legs. The and butterfly larvae are called cater- antennae are short and mouthparts Pest Control pillars; some beetle larvae are called are comblike. Millipedes feed on grubs; most fly larvae are called decaying organic matter, seeds, bulbs, maggots. Caterpillars often have legs; and roots. maggots are legless. Weevil grubs are There is no metamorphosis; centi- legless; other kinds of beetle larvae pedes and millipedes do not change usually have three pairs of legs. except in size between hatching and The pupa is a resting stage during reaching the adult stage. which the larva changes into an adult with legs, wings, antennae, and func- Controlling Insects tional reproductive organs. Control of insects and their rela- tives may involve any of the three Insect-Like Pests basic pest control objectives. Control Mites, ticks, spiders, sowbugs, is usually aimed at suppression of pillbugs, centipedes, and millipedes pests to a point where the presence or resemble insects in size, shape, life damage level is acceptable. Preven- cycle, and habits. Pest species usually tion and eradication are useful only in can be controlled with the same tech- relatively small, confined areas such niques and materials used to control as indoors or in programs designed to Arachnid insects. keep foreign pests out of a new area. Arachnids The key to successful control of Ticks, scorpions, spiders, and insect and insect-like pests is knowl- mites have eight legs and only two edge of the stage(s) of their life cycle body regions. They are wingless and in which they are most vulnerable. It lack antennae. The metamorphosis is generally difficult to control insects is gradual and includes both larval in either the egg or pupal stage, nymphal stages. Eggs hatch into because these stages are inactive: not larvae (six legs) which become nymphs feeding, immobile, and often in inac- (eight legs) and then adults. Ticks and cessible areas such as underground, mites have modified piercing–sucking in cocoons or cases, and in cracks or mouthparts: spiders and scorpions crevices. Crustacean have chewing mouthparts. Controlling insects in the late instar and adult stages is moderately Crustaceans successful. The insects, because of Sowbugs and pillbugs, water fleas, their size, are most visible in these and wood lice have 14 legs. They stages and usually are causing the are wingless and contain only one most destruction. Therefore, control segmented body region. They have attempts are often begun at these two pairs of antennae and chewing times. However, the larger insects are mouthparts. Sowbugs and pillbugs often more resistant to pesticides, and have a hard, protective shell-like adults already may have laid eggs for covering and are related to the aquatic another generation. lobsters, crabs, and crayfish. The The best control usually is achieved Centipede metamorphosis is gradual, and there during the early larval or nymphal may be up to 20 instars before adult- stages when the insects are small and hood is reached. vulnerable. Control during these stag- Centipedes and Millipedes es requires careful monitoring of pest Centipedes are made up of populations and thorough knowledge 30 seg­ments, each containing one pair of the pest’s life cycle, habitats, and of legs. They have chewing mouth- feeding patterns. parts. Some species can inflict painful Environmental conditions, such as bites on humans. humidity, temperature, and availabili- Millipedes contain 30 segments ty of food, can alter the rate of growth and are cylindrical like an earthworm. of insects and thus affect the length of Millipede The body is wingless and each seg- the life cycle. Optimum environments 11 Pests and (usually warm and humid) can de- control program for Japanese beetles. Pest Control crease the time of development from Japanese beetles are subject to attack egg to adult. by two naturally occurring species of bacteria which cause the fatal milky Insect Control Strategy disease. Preparations containing Control methods used for insects spores of the contagious bacteria are include: host resistance, biological produced commercially and released control, cultural control, mechani- in infested areas. Another example cal control, sanitation, and chemical is Bacillus thuringiensis or Bt, used to control. control European cornborer, cabbage Host Resistance looper and many other caterpillars. Some crops, animals, and struc- Sterile Males—Males of some tures resist insects and their relatives pest insect species may be reared and better than others. Some varieties of sterilized in laboratories and released crops and wood are nearly immune to in large numbers into infested areas certain insects. Use of resistant types to mate with native females. These helps keep pest populations below matings produce infertile eggs or harmful levels by making the envi- sterile offspring and help reduce the ronment less favorable for the pests. pest population. This technique has Biological Control been used successfully in only a few Biological control of insects in- species and is still being developed. cludes: The screw worm, which attacks cattle, predators and parasites, is one insect on which this technique pathogens, has been effective. sterile males, Pheromones—Some insects (and pheromones, and insect-like organisms) produce natu- juvenile hormones. ral chemicals, called pheromones, Predators and Parasites— which cause responses in other ­Organisms known to attack insect insects of the same or very closely (and insect-like) pests in their native related species. Once a particular in- environment can be imported or sect pheromone is identified and the reared in laboratories and released in chemical is synthetically produced, it infested areas. This is done only after can be used to disrupt the behavior of the parasites or predators are deter- that insect species. Synthetic phero- mined to be harmless to man, animals, mones may be used to disrupt normal plants, and other beneficial organ- reproduction, or they may be used to isms. For example, several kinds of attract the pests into a trap. parasites and predators of the alfalfa Because each pheromone affects weevil have been imported from only one specific group of insects, Europe and Asia and released in the their use poses no risk of harm to infested areas in this country. Several other organisms, including man. species have become established and Unfortunately, only a few have been are helping to reduce pest numbers. discovered and produced syntheti- However, they do not always prevent cally, and the use of pheromones is serious outbreaks and the resultant still in the experimental stages. It is damage. very costly to discover, produce, and Pathogens—Parasitic bacteria, market a chemical which will be use­- viruses, and fungi may be introduced ful in controlling only one pest species. into an infested area to control insects Juvenile Hormones—Another by subjecting them to disease. These type of species-specific chemical is disease agents, like predators, are of- also being developed. Juvenile hor- ten found in the pest’s native environ- mones interrupt the metamorphosis ment. They can be imported or they of insects (and insect-like organisms). can be reared in laboratories. These chemicals prevent reproduction For example, the use of patho- by keeping immature insects from gens is an important part of the pest maturing into adults. Each chemical 12  Pests and acts against a single pest species and Mechanical Control has the same advantages and disad- Mechanical controls used on insects Pest Control vantages as pheromones. The few are: juvenile hormones available are usually screens and other barriers, applied as a broadcast spray to reach traps, as many target pests as possible. light, heat and cold, and Cultural Control radiation and electrocution. Cultural control methods for insects include: Screens and Other Barriers—A crop rotation, major aspect of insect control indoors trap crops, is the use of screens and other barri- delay of planting, and ers to keep insects out. Flying insects, harvest timing. such as mosquitoes, wasps, and flies, Crop Rotation—Taking infested are kept outside by blocking any fields out of production and leaving openings with screening. The effec- them fallow or planting an alternate tive mesh size depends on the size of crop may deprive pests of host plants the smallest flying insect pests in that on which to feed and reproduce. environment. Crawling insects are Rotations are most effective against also kept outside by screens or other insects which have long life cycles barriers, such as tightly sealed doors and infest the crop during all stages and windows. Barriers made of sticky of growth. Many of the traditional substances sometimes can stop crawl- rotational schemes were developed ing insects from entering an area. to reduce pest problems such as corn Traps—Traps are sometimes used rootworm. to control the target pest. More often, Trap Crops—Other crops attractive however, they are used to survey for to the pests may be planted early or the presence of insect pests and to de- nearby to draw pests away from the termine when the pest population has main crop. Destruction of such crops increased to the point where control is at the proper time breaks the repro- needed. ductive cycle of the pest before the Light—Many insect pests may be desired crops are infested. To control attracted to artificial light at night. the pickle worm in cucumbers, for However, since not all the pests are example, the grower might also plant killed, the light attractant may actu- yellow squash, to which the pest is ally help create infestations around more attracted. The squash crop can swimming pools and other limited be sprayed or destroyed before the size areas. pest can complete its development. Heat and Cold—It is sometimes Delay of Planting—Delaying possible to expose insect pests to the the date of planting may reduce the killing effects of the heat of summer popu­lation of certain pests by elimi- or cold of winter. Insects that feed on nating the host plant needed for food stored grain and flour, for example, and reproduction when the pest can sometimes be controlled by venti- population is at its peak. For example, lating grain elevators in winter. prevention of Hessian fly damage in Radiation and Electrocution—Ra- wheat can be avoided by delaying diation and electrocution are some- planting until fly reproduction has times used to kill pests in a limited ended for the year. area. The electric screens in such Harvest Timing—Crops should places as outdoor restaurants and not be left in the field after maturity if amusement parks are used to attract they are susceptible to pest attack. For and electrocute a variety of noctur- example, wireworm damage to mature nal insect pests. Ionizing radiation is potatoes causes a serious quality re- used to sterilize pests by destroying duction. Damage increases if the crop reproductive tissues, and ultrasonic is left in the ground even for a very radiation is used to kill pests in some short time after maturity. products. 13 Pests and Sanitation A few insecticides interfere mech­ Pest Control Cultivation, moldboard plowing, anically with the insect’s functions. and burning of crop residues soon For example, mineral oils suffocate after harvest greatly aid in the control insects; silica dusts destroy their body of some insect pests on agricultural water balance by damaging their crops. Pink bollworm infestations in protective wax covering. cotton, for example, can be greatly Outdoors—With few exceptions, reduced by plowing the field immedi- insecticides labeled for outdoor use ately after harvest. are designed to be used for full cover- Removing litter from around build- age of an area. The objective is to cover ings helps control pests which use it the entire surface to be protected with for breeding or shelter. Ants, termites, a residue of active insecticide. Insects and some other indoor pests may be which then eat or otherwise contact suppressed by using this technique. the treated surface are killed. Sanitation is important in the con- Thorough knowledge of the target trol of animal parasites and filth flies. insects helps determine the frequency Fly control in and around barns and of application and the choice of livestock pens, for example, is greatly chemicals. One well-timed applica- aided by proper manure manage- tion of an effective pesticide may pro- ment. A major aspect of fly control in vide the desired control. Sometimes residential areas and cities is weekly repeated insecticide applications will or biweekly garbage removal. This be necessary as the insect infesta- scheduling prevents fly eggs and tion continues and pesticide residues maggots in the garbage from reaching break down. adult fly stage, since the fly’s life cycle The pesticide label, Cooperative is 10 to 14 days, even in very warm Extension Service recommendations, weather. and other sources usually indicate Indoors, sanitation is a major meth- a range of treatment intervals and od of preventing insect pest problems. dosages. By carefully observing the Keeping surfaces in rest-rooms and pest problem and applying chemi- food preparation areas immaculately cals when the pests are most vulner- clean and dry is an important factor able, you often will be able to use in suppressing or eliminating ant, fly, lower doses of pesticides and apply and cockroach infestations. them less often. Over a long growing Chemical Control period, this can mean considerable Chemicals used to control insects savings in time, money, and total and insect-like pests include insecti- pesticide chemicals applied. cides, miticides, and acaricides. Most Most control strategies take advan- chemicals used to control insects act tage of the natural controls provided in one of two ways: by the pest’s natural enemies. When repellents—These products you choose a pesticide, consider what keep pests away from an area affect it will have on these beneficial or from a specific host. Products organisms. Ask your pesticide dealer, designed to keep mosquitoes, your agricultural Extension agent, or chiggers, and ticks off humans other experts for advice. are an example. Indoors—Most indoor insect direct poisons—Common insec- control is aimed at prevention or ticides include chemicals that eradication of the pest problem while poison one or more life systems minimizing the exposure of humans in the pest. Some will poison an and animals to chemicals. The most insect if they are eaten (stomach common application techniques are poisons); others require only crack and crevice treatments, spot contact with the insect’s body treatments, and fumigation of entire (contact poisons). structures, commodities, or individual pieces of equipment. 14  Pests and Plant Disease Agents on dead host tissue so they are called facultative saprophytes. Pathogens Pest Control Importance of Plant Diseases that cannot live as facultative sapro- All plants are subject to plant phytes are called obligate parasites. diseases. Diseases have plagued Since pathogens are able to spread agricultural plants since the dawn of from plant to plant, they are consid- history. The Romans were particularly ered infectious. troubled by cereal rusts and went so All pathogens except viruses have far as to invent a festival to appease standardized Latin scientific names Robigo, the god of rust. The famous consisting of a genus and species Irish potato famine of name (for example, Fusarium gra- 1845 and 1846 was caused by a dis- minearum). The purpose of scientific ease called late blight. It resulted in names is to allow scientists to specify the starvation of hundreds of thou- exactly the name of a pathogen to sands of people and the emigration avoid confusion. Unfortunately, these of more than 1.5 million to the United scientific names are often difficult to States. Today, plant diseases remain remember and are sometimes subject a major limiting factor in the produc- to revision as we learn more about the tion of agricultural and horticultural organisms. For most practical purpos- crops and the maintenance of land- es, the common name of the disease is scapes. used rather than the scientific name of What Is a Plant Disease? the pathogen. A plant disease is any harmful Particular pathogens can infect condition that makes a plant different only certain species or varieties of from a normal plant in its structure plants. This group of plants is called (appearance) or function (ability to the host range of the pathogen. Some grow and yield). The study of plant pathogens have a broad host range, diseases is called plant pathology. while others have a very narrow Plant diseases are usually manifested host range. When a plant cannot be by visible symptoms. Yellowing, leaf para­-sitized by a pathogen, it is called spots, root rot, mottling or mosaics, resistant. If it is easily parasitized, it galls, wilting, or stunting are examples is fully susceptible. Some plants are of plant disease symptoms. parasitized to a lesser extent and are called moderately susceptible. Causes of Plant Disease In order for a biotic disease to Plant diseases can be divided into develop, there must be three compo- two main groups based on their cause. nents present: (1) a pathogen, (2) a Abiotic (nonliving) causal agents susceptible host, and (3) a favorable include temperature extremes, mois- environment. Certain pathogens, ture extremes, air pollutants, nutrient such as viruses that require a vector deficiencies, mineral toxicities, pesti- (carrier) have a fourth component. cide toxicity, etc. Abiotic causal agents If any of the components is missing, cannot spread from plant to plant and disease will not occur. The initial so are nonparasitic and noninfectious. population of the pathogen is called Biotic (living) causal agents include the inoculum. Many control strategies fungi, bacteria, mycoplasma-like aim to destroy or reduce the inoculum organisms (MLO’s), viruses, and so that disease will be prevented or nematodes. Biotic causal agents are delayed. Crop susceptibility may be also called pathogens. Some plant affected by temperature, fertility, and pathologists also include parasitic stage of crop growth. Important envi- plants like dodder or mistletoe as ronmental factors for disease devel- pathogens. Pathogens gain nutrients opment include temperature, rainfall at the expense of the living host plant duration and frequency, wind speed, so they are generally parasitic. Some humidity, and soil moisture. also have the ability (faculty) of living 15 Pests and Major Groups of Pathogens of plants in the absence of disease Pest Control Fungi symptoms. Bacteria can be identified by their ability to grow on different The fungi are the most important types of agar media or with serologi- group of plant pathogens. However, cal techniques. Fire­blight of apple, fungi also include many important or- halo blight of beans, alfalfa bacterial ganisms that are used in the making of wilt, potato soft rot, and bacterial leaf bread, some cheeses, or beer. They are spot of peaches are caused by bacteria. also critical in the decay and cycling of organic debris. Fungi are usually Mycoplasma-Like Organisms composed of multi-celled, thread-like (MLO’s) filaments called hyphae. Hyphae ab- MLO’s are actually a type of bacte- sorb the water and nutrients needed ria which lack a cell wall. They have for growth of the fungus. Most fungi become highly specialized obligate are microscopic, but some, such as parasites that inhabit the food con- mushrooms may become quite large. ducting vessels (phloem) of the plant Most fungi reproduce by spores circulatory system. They are trans- which function like tiny seeds. Spores ferred from plant to plant by leafhop- of different species vary greatly in pers or by grafting. MLO diseases color, size, and shape. Some types of often involve yellowing, stunting, or Fungi spores remain viable for years, and excessive proliferation shoots. These others last only hours. Spores may symptoms are similar to those caused be borne on the hyphae or within by some viruses. However, unlike specialized structures called fruiting viruses, MLO’s are sensitive to antibi- bodies. Fruiting bodies are usually otics, particularly tetracycline. Aster barely visible with the naked eye and yellows and elm phloem necrosis are vary from flask-shaped structures to two examples of MLO diseases. disk-shaped or cushion-shaped struc- Viruses tures. Plant pathologists can usually Viruses are much smaller than identify a fungus by careful examina- bacteria and are composed simply of tion of the spores and fruiting bodies. some genetic material (DNA or RNA) Fungi may attack the fruits, flowers, in a protein coat. Since viruses lack leaves, stems, or roots of a plant. They the ability to live freely, they must may be airborne, soilborne, waterborne, take over a host cell and direct it to seedborne, or insect­borne. Water or reproduce the virus. Viruses come in high humidity is nearly always essen- a variety of shapes and sizes, but they Bacteria reproducing by division tial for spore germination and growth can only be seen with a high-powered of hyphae. Most pathogenic fungi can electron microscope. complete a generation in a week or Characteristic symptoms are often less. Fungus diseases include apple used for preliminary virus identifi- scab, corn smut, powdery mildew of cation. Confirmation of identity is blue­-grass, rose black spot, wheat leaf usually done with a technique called rust, and corn ear rot. ELISA (Enzyme Linked Immunosorbent Bacteria Assay) that uses specific antibodies. Bacteria are single-celled organ- Many viruses that cause plant disease isms which are much smaller than are carried by insects or mites. Aphids fungi. They usually reproduce by and leafhoppers are the two most simply dividing in half. Each half common vectors (carriers). becomes a fully developed bacterium. Viruses may also be transmitted Different kinds of viruses Bacteria can build up fast under ideal on contaminated shears, on hands, conditions. Some can divide every 30 by grafting, in infected bulbs or cut- minutes. As with fungi, most bac- tings, and in seeds. A few viruses are teria are favored by water and high trans-mitted by pollen, nematodes, or humidity. Plant path­ogenic bacteria soilborne fungi. Wheat streak mosaic, are facultative saprophytes and some tomato spotted wilt, and maize dwarf are commonly found on the surface mosaic are examples of virus diseases. 16  Pests and Nematodes history of the field? Have there been Nematodes are small (usu- any chemicals sprayed? What is the Pest Control ally microscopic), colorless, slender variety? roundworms. Most nematodes are Often an examination for symptoms harmless, but some are parasites of will reveal the pathogen itself. When animals and others have adapted to the pathogen is large enough to see feeding on plants. Plant pathogenic without the aid of a microscope, it nematodes have a specialized hol- is called a sign. This is in contrast low feeding spear that they use like to a symptom which is a change in a straw to suck the contents from the structure or function of the host. plant cells. Nematodes may attack the Finding a sign often leads to a prompt aboveground portion of the plant but diagnosis. normally feed on roots. They feed on Be aware of the major diseases in the outside of a root or enter inside your area. When you arrive at a tenta- and feed within the root cortex. Root tive diagnosis, make sure it is consis- lesions, galls, or stubby roots are tent with all the facts. Often diagnosis all possible symptoms of nematode is challenging and may require the feeding. Feeding causes stunting of help of your county Extension agent. the root system which often leads Help is also available from the KSU to symptoms of drought or nutrient Plant Diagnostic Clinic. stress. The life cycle of nematodes i­ ncludes Principles of Plant Disease an egg, four larval stages, and an Management adult. Most larvae look like adults, For some plant diseases, it is pos- but are smaller. Many nematodes mi- sible to achieve complete control. Nematode with feeding spear extended grate from root to root. The females of An example would be wheat Karnal some, such as the root knot and cyst bunt. It is completely controlled in the nematodes, become fixed in the plant USA by quarantine regulations that tissue. The root knot nema­tode de- prevent its introduction. However, posits its eggs in a mass outside of its for many diseases, complete control is body. The cyst nematode keeps part impossible or too expensive. Disease of its eggs inside its body after death. management attempts to maximize They may survive there for many profits by reducing disease severity to years. Root knot, soybean cyst, pine the economic thres­hold. The economic wilt, and stubby root are examples of threshold is the point where the cost nematode ­diseases. of disease management and the eco- nomic bene-fits of disease reduction Diagnosis of Plant Diseases are balanced. Attempting to control plant dis- Plant disease management attempts eases without sufficient information to alter one of the three components usually results in failure. For maxi- necessary for disease development. mum effectiveness, it is important to Control measures may be directed at: diagnose the problem correctly. The (1) reducing or eliminating the patho- first step is to evaluate the visible gen, (2) reducing susceptibility of the symptoms. Look at the whole plant, host plant, or (3) reducing the favor­ including the roots. What plant parts ability of the environment for disease are affected? Is the symptom a wilt, development. The ease of control of a leaf spot, gall, root rot, etc.? Is it disease often depends on the stage in worse on the upper or lower leaves? the life cycle of the pathogen. Disease Is the stem vascular tissue discolored? control measures are usually directed When did symptoms first appear? at the most vulnerable stage of the Is the disease pattern related to soil pathogen life cycle. The principles of type, topography or edges of the disease control include the following. field? Are healthy and diseased plants Genetic Resistance interspersed? Additional information Plant breeders attempt to improve is often useful. What is the cropping the yield and quality of important 17 Pests and plants by incorporating high levels practical control measure. In addi- Pest Control of genetic disease resistance. tion, resistance is usually long-lasting. Exclusion There are some notable exceptions, Exclusion is the prevention of however. For example, wheat leaf rust establishment of a pathogen in a pre­­- resistance can be short-lived if the leaf viously uninvaded area. Many plant rust fungus mutates and adapts to the pathogens are controlled by quaran- host resistance. tines which regulate the move­ment of There are different levels of genetic plants into this country. The principle resistance ranging from highly suscep- of exclusion can also be applied to tible, moderately susceptible, mod- greenhouse crops where it is impor- erately resistant, to highly resistant. tant to prevent the introduction of Plants which get diseased, yet still infected stock plants. manage to yield well are called toler- ant to infection. Protection Protection involves some type Crop Rotation of barrier between the host and the Many pathogens survive between path-ogen. Nonsystemic chemical crops in the soil or on crop debris. fungicides are considered protec- However, the majority of pathogens tants because they form a chemical do not cross over between different barrier over the surface of the plant crop species. Therefore, crop rotation that protects against fungal invasion. can break the life cycle of the patho- Protectant fungicides must be ­applied gens and reduce the inoculum. prior to infection in order to prevent Sanitation invasion since they have no effect on Since many pathogens survive on established infections. crop debris, destruction or removal Eradication of debris can be an effective control Eradication is the practice of measure. Removal of infected volun- removing or destroying a pathogen teer plants, destruction of weed hosts, after it has become established in an fumigating or steaming of soil, and area. rogueing of diseased plants are all examples of sanitation. Avoidance Avoidance is the practice of growing Planting Date plants in places or at times when the Planting date can have a large ef- pathogen is inactive, rare or absent. fect on many pests including diseases, insects, and weeds. Therapy Therapy is the curing of disease or Field Selection lessening of disease severity of a plant Certain plant disease are more that is already infected. Systemic prevalent in certain types of fields. fungicides can be used for therapy be- For example, Phytophthora root rot cause they can stop the development of alfalfa is more common in poorly of fungi that have already infected. drained bottomland fields. It is often Another example is heat therapy of best to avoid putting susceptible crops infected wheat seed to rid it of inter- in fields that are predisposed to cer- nal loose smut infections. Therapy is tain disease problems. often impractical or more costly than Disease-free Seed or other control measures. Propagation Materials Many diseases are carried in the Methods of Plant Disease seed or in infected stock. Certified, Management clean seed should be free of most Disease Resistant Varieties seedborne pathogens. Many horti- Plant disease resistant varieties are cultural crops are subject to diseases one of the most effective and economi- that are spread by propagation. New cal ways to control plant diseases. For plants should be carefully inspected many diseases, resistance is the only for symptoms of disease. Suspicious 18  Pests and shipments should be refused or held cal control options. Pesticide use is in isolation while being checked for regulated by the EPA. Always consult Pest Control pathogens. Diagnostic tests may be pesticide labels for directions and necessary to verify that stock is disease- restrictions on use. free. These are available through the Chemical control is most likely Cooperative Extension Service. to be used when: (1) the crop has a Changing the Environment to be high value, (2) resistant varieties are Less Favorable not available, (3) there is a lack of Certain horticultural practices tend ­adequate cultural control practices, or to favor diseases by making the envi- (4) when crop quality is paramount ronment more conducive. For example, (as with apples). watering plants in the greenhouse in the evening can result in long periods Weeds Any plant can be considered a of leaf wetness compared to water- weed when it is growing where it ing in the morning. Good greenhouse is not wanted. Weeds are a problem ventilation can reduce humidity because they reduce crop yields, in- levels and suppress many diseases. crease costs of production, and reduce Growing plants above or below their the quality of crop and live­-stock optimum temperature can cause products. In addition, some weeds stress and make plants more suscep- cause skin irritation and hay fever, tible to root rots. and some are poisonous to man and For field crops, excessive overhead livestock. Weeds also can spoil the irrigation can promote foliar diseases. beauty of turf and landscape plants. High nitrogen fertilization can promote Weeds interfere with crop produc- overly lush foliage which creates a tion by: humid microenvironment which fa- competing for water, nutrients, vors diseases like powdery mildew. light, and space, Quarantines contaminating the product at The transport of important patho- harvest, gens to new locations can sometimes harboring pest insects, mites, be prevented by quarantine regula- vertebrates, or plant disease tions. Quarantines tend to be costly to agents, and enforce. releasing toxins in the soil which Chemical Control inhibit growth of desirable Fungicides, bactericides, and plants. nematicides have been developed for Weeds may become pests in water plant disease control. There are no by: chemicals to control viruses. Fungi- hindering fish growth and re- cides can be divided into nonsystemic, production, protectant types, and systemic types. promoting mosquito production, Protectant fungicides must be ap- hindering boating, fishing, and plied before infection, while systemic swimming, and fung-icides can sometimes be applied clogging irrigation ditches, after infection as a therapeutic agent. drainage ditches, and channels. Protectant fungicides tend to have Weeds can harm grazing animals by: very broad activity against many poisoning, and fungi. Certain systemic fungicides causing an “off-flavor” in milk have fairly narrow activity. and meat. Chemical control efficacy is vari- Weeds are undesirable in rights-of- able. It is most effective on fungal way because they: diseases of aboveground plant parts. obscure vision, signs, guideposts, Chemical control tends to be expen- crossroads, etc., sive and sometimes multiple appli- increase mowing costs, cations are required. Unfortunately, hinder travel, many diseases have no labelled chemi- provide cover for rodents and 19 Pests and other pest animals, and mature, produce seed, and die. Ex- Pest Control clog drainage areas. amples: mullein, burdock, and The type of weed problems en- bull thistle. countered depends on: Perennials current crop or vegetation, Plants which live more than two cropping history, years and may live indefinitely are tillage practices, perennials. Perennial plants may frequency of mowing, mature and reproduce in the first herbicide used, and year and then repeat the vegetative, management practices. seed production, and maturity stages Development Stages for several following years. In other All plants have four stages of de- perennials, the seed maturity and velopment: production stages may be delayed for seedling—young plant recently several years. Some perennial plants established from a germinating die back each winter; others, such seed. as trees, may lose their leaves, but vegetative—rapid growth; do not die back to the ground. Most production of stems, roots, and perennials grow from seed; many foliage. also produce tubers, bulbs, rhizomes seed production—energy direct- (below-ground root-like stems), or ed toward production of seed. stolons (above-ground stems that pro- Uptake of water and nutrients duce roots). Examples of peren­nials Annuals is slow and is directed mainly are johnsongrass, field bindweed, to flower, fruit, and seed struc- dandelion, and plantain. tures. Simple perennials normally repro- maturity—little or no energy duce by seeds. However, root pieces production or movement of which may be left by cultivation can water and nutrients. produce new plants. Examples: dandeli- ons, plantain, trees, and shrubs. Life Cycles of Plants Bulbous perennials may repro- Annuals duce by seed, bulblets, or bulbs. Wild Plants with a one-year life cycle garlic, for example, produces seed are annuals. They grow from seed, and bulblets above ground and bulbs mature, and produce seed for the next below ground. generation in one year or less. They Creeping perennials produce seeds include grasses and broadleaf plants. but also produce rhizomes (below- There are two types: ground stems), or stolons (above- Summer annuals are plants that ground stems that produce roots). Biennials grow from seeds which sprout in the Examples: johnsongrass, field bind- spring. They grow, mature, produce weed, and Bermudagrass. seed, and die before winter. Examples: crabgrass, foxtail, cocklebur, pigweed, Weed Classification and lambsquarters. Land Plants Winter annuals are plants that Most pest plants on land are grow from seeds which sprout in grasses, sedges, or broadleaves. the fall. They grow, mature, produce Grasses seed, and die before summer. Examples: Grass seedlings have only one downy brome, cheat, henbit, mus- leaf as they emerge from the seed. tards and pennycress. Their leaves are generally narrow Biennials and upright with parallel veins. Most Plants with a two-year life cycle are grasses have fibrous root systems. The biennials. They grow from seed and growing point on seedling grasses is develop a large tap root and compact sheathed and located below the soil cluster of leaves (called a rosette) the surface. Some grass species are annu- Perennials first year. In the second year, they als; others are perennials. 20  Pests and Sedges submergent (submersed)—all Pest Control Sedges are similar to grasses except of the plant grows beneath the that they have triangular stems and water surface. Example are three rows of leaves. They are often watermilfoil, elodea, naiads, listed under grasses on the pesticide pondweeds (Potamogeton), and label. Most sedges are found in wet coontails. places, but principal pest species are Emergent and floating plants, like found in fertile, well-drained soils. some land plants, have a thick outer Yellow and purple nutsedge are pe- layer on their leaves and stems which rennial weed species which produce hinders herbicide absorption. Submer­- rhizomes and tubers. gent plants have a very thin outer Broadleaves layer on their leaves and stems and Broadleaf seedlings have two are very susceptible to herbicide injury. “seed leaves” as they emerge from the Algae cotyledons or soil. Their leaves are Algae are aquatic plants without generally broad with netlike veins. true stems, leaves, or vascular systems. Broadleaves usually have a taproot For control purposes, they may be and a relatively coarse root system. classified as: All actively growing broadleaf plants plankton algae—microscopic have exposed growing points at the plants floating in the water. They end of each stem and in each leaf axil. sometimes multiply very rapidly Perennial broadleaf plants may also and cause “blooms” in which have growing points on roots and the surface water appears soupy stems above and below the surface of green, brown, or reddish brown, the soil. Broadleaves contain species depending on the algal type. with annual, biennial, and perennial fila­mentous algae—long, thin Grasses life cycles. strands of plant growth which Aquatic Plants form floating mats or long strings extending from rocks, Vascular Plants bottom sediment, or other un- Many aquatic plants are similar to derwater surfaces. Examples are land plants and have stems, leaves, cladophora and spirogyra. flowers, and roots. Most act as peren- macroscopic freshwater al- nial plants—dying back and becom- gae—these larger algae look like ing dormant in the fall and beginning vascular aquatic plants. The two new growth in the spring. They are should not be confused, because classified as: their control is different. Many emergent (emersed)—plants are attached to the bottom and rooted in the bottom and pro- grow up to 2 feet tall; however, duce most of their leaves and they have no true roots, stems, flowers at or above the water or leaves. Examples are chara surface. Examples are watersh- and nitella. ield arrowhead and water prim- rose. Parasitic Seed Plants floating—all or part of the plant Dodder and witchweed are impor- floats on the surface. Examples tant weeds on some agricultural, or- are waterlilies, duckweeds, wa- namental, and forest plants. They live ter meal and American lotus. on and get their food from the host plants. They can severely stunt and Sedges marginal—emersed weeds that can and frequently do grow on even kill the host plants by using the saturated soil above the water host plant’s water, food, and miner- surface. Examples are sedge, als. These plants reproduce by seeds. bulrush, rush, cattails and Some can also spread from plant to smartweeds. plant in close stands by vining and twining. 21 Pests and Controlling Weeds Cultural Control Pest Control Weed control is nearly always Tillage—This is an effective and designed to suppress a weed infesta- often-used method to kill or control tion. Prevention and eradication are weeds in row crops, nurseries, and usually only attempted in regulatory forest plantings. However, tillage weed programs. may bring buried seeds to the surface To control weeds which are grow- where they can either germinate and ing among or close to desirable compete with the newly planted crop plants, you must take advantage of or be spread to nearby fields. Tillage the differences between the weeds also may increase soil erosion and and the desired species. Be sure that may help to spread established the plants you are trying to protect plant diseases to uninfected areas are not susceptible to the weed control of the field. method that you choose. Generally, Time of Planting—Crops can the more similar the desirable plant be planted early to give the crops and the weed species are to one an- a competitive advantage over later other, the more difficult weed control emerging weeds, or the planting date becomes. For example, broad­-leaf can be delayed until after weeds have weeds are most difficult to control in germinated and been destroyed by broadleaved crops, and grass weeds cultivation or herbicides. are often difficult to control