University of Kentucky College of Agriculture, ENT-70 Food and Environment Cooperative Extension Service Pesticides and Pesticide Safety Kentucky Master Gardener Manual Chapter 10 By Lee Townsend, extension entomologist, University of Kentucky. est is not a biological term for an organism’s environmental In this chapter: role as are the words plant, herbivore, predator, and scavenger. It is a term for an organism that is either causing damage or is Types of Pesticides ............................................140 Psomewhere where it’s not wanted. Pests can include plants, insects The Pesticide Label ...........................................142 and their relatives, and microorganisms that cause plant diseases. Often, pests are a problem because we use cultural practices or cre- Exceptions to Label Instructions ..................143 ate conditions favoring organisms that they feed on, compete with, Pesticide Formulations ....................................143 or infect the desirable species. Application Equipment ...................................144 Key pests are present and often cause enough damage to require regular control (for example, Japanese beetles on roses). Occasional Calibrating Sprayers .........................................144 pests require control during some years because of favorable Safety .....................................................................146 weather conditions (such as fireblight on crabapples). Sporadic pests do not require control most years but may be very damag- Other Safety Issues ...........................................147 ing in certain circumstances (such as periodical cicadas on newly Integrated Pest Management ......................148 established trees). Credits ...................................................................148 Some natural forces act on all organisms, causing their numbers to rise and fall from year to year. You may not be able to alter the effect of natural forces on a pest population, but you can be aware of their influence and take advantage of them whenever possible. These natural forces include climate, natural enemies, geographic barriers, food and water supply, and shelter. Unfortunately, natural controls may not act quickly or com- pletely enough to prevent unacceptable injury or damage. That is when other control measures must be used. Those measures include host resistance, biological control, cultural control, mechan- ical control, sanitation, and chemical control, or pesticides. The active ingredient in a pesticide product is a chemical that, when used according to label directions, can reduce or control a pest problem. A pesticide application should be thought of as tem- porary solution to a pest problem, not the way to solve it. Ideally, a pesticide helps to reduce losses or damage until the conditions lead- ing to the outbreak change or those conditions can be corrected. Cooperative Extension Service | Agriculture and Natural Resources | Family and Consumer Sciences | 4-H Youth Development | Community and Economic Development 140 • Pesticides and Pesticide Safety CHAPTER 10 Accurate identification is the first step To inhibit germination or seedling in an effective pest management program. growth, use pre-emergent herbicides. To (See Chapter 8, Insects, in this manual for control weed seedlings, these herbicides more information.) Identification is the key must be applied to the soil before the seed- to all kinds of information about the pest, lings break through the soil surface. In order including its life cycle, behavior, and recom- to come into close contact with germinat- mendations for effective management. ing weed seeds, these products require Incorrect pest identification is a leading rainfall or incorporation into the soil. Some cause of pest control failures and improper products do not move within the plant, so use of pesticides. injury symptoms occur only at the site of Your county office of the Cooperative uptake. In contrast, systemic herbicides Extension Service can help with pest iden- enter through the roots and move up. Their tification and control recommendations. effects are most obvious where the product Diagnostic labs in plant disease, insect, tends to accumulate. and weed identification are also available, Postemergent herbicides are applied to along with help in how to take useful pest the foliage of growing weeds. Those that samples. Most of these diagnostic services become active upon contact kill the plant are free. by destroying leaf and stem tissues. They require thorough spray coverage. In con- trast, systemic postemergents move within Types of Pesticides leaves and other green parts to growing Herbicides points, where they act. These products vary in their ability to move within a plant. Herbicides are pesticides that kill plants. Factors that affect how well these herbi- Selective herbicides are used in lawns, land- cides work include characteristics of plant scapes, and gardens to control unwanted leaf surface, plant size and age, water stress, plants without damaging desirable plants. air temperature, humidity, and herbicide Nonselective herbicides are used to kill all additives. Differences in the amount of her- plants in an area. Selective (and in some bicide uptake within the plant often explain cases nonselective) products are used as the year-to-year variation in herbicide spot treatments to control weeds in turf and effectiveness. ornamental landscapes to remove undesir- Plants that can rapidly degrade or able species growing near desirable plants. deactivate a herbicide can escape its toxic A herbicide’s mode of action is the way effect. However, plants under stress (such it affects a plant. Some herbicides damage as hot or cold temperatures, high humid- leaf cells, causing them to dry up; others ity, or physical injury) may be affected by reduce the nutrient uptake. A few interfere herbicides that they normally tolerate. Also, with the plant’s ability to grow normally or misapplication, especially at excessive rates, to conduct photosynthesis. The mode of can overwhelm the ability of the plant to action often dictates when and how a her- degrade or deactivate the chemical and bicide is used. Herbicides must adequately result in plant injury. make contact with and enter the plant. Then, a sufficient amount of the herbicide must move to the site of action to produce the desired effect. CHAPTER 10 Pesticides and Pesticide Safety • 141 Fungicides Stomach poisons kill insects with chew- ing mouthparts after they feed on treated Fungicides are pesticides that destroy plant tissue, while contact insecticides must or inhibit the growth of fungi. Contact be absorbed into the body to kill the target. fungicides, sometimes called protectant Contact insecticides often are used against fungicides, remain on plant surfaces after sap-feeding pests that do not eat plant application and do not enter plant tissue. tissue and require thorough spray cover- In order to be effective, contact fungicides age. An insecticide may work as a stomach must be on the plant’s surfaces before infec- poison against caterpillars or beetles and tion begins. as a contact insecticide against aphids or Systemic fungicides are absorbed into scale crawlers. These products are broken the plant and moved up within the water- down by moisture, sunlight, or microor- conducting tissue (xylem); downward ganisms, so their residual effect is limited. mobility is limited. Systemic fungicides Consequently, correct timing of applica- sometimes can suppress the fungus after it tions is important. has infected the plant. Systemic insecticides are absorbed into Fungicide labels usually provide a plants through the roots or foliage. They can range of application rates and intervals. be particularly effective against sap-feeding Fungicides can be used as a preventive (usu- insects such as aphids and may provide con- ally at low rates and/or with long intervals trol of some borers and leaf miners. Uptake between applications) when a disease of a systemic insecticide by the roots and outbreak has not yet occurred but when movement to the pest -feeding site may take weather favorable for disease is expected. several weeks, so this type of insecticide Fungicides may also be used, often at higher may have to be applied several weeks before rates and/or at short intervals, after an the pests are active. Systemic insecticides outbreak has occurred and disease pressure can remain in the plant at effective levels is high. Such applications cannot cause sick for a long period of time and may have an tissue (yellow or brown leaves, rotted roots) impact on beneficial insects. to become healthy again, but they can While many insecticides affect the protect uninfected tissue and new growth. insect’s nervous system, products with These applications are only effective if the different modes of action are being used— turf is actively growing. those that target muscles, insect develop- ment and metamorphosis, or parts of Insecticides the nervous system that are distinctive to Insecticides can be classified as either insects. broad-spectrum insecticides, which can The active ingredients in organic insec- kill a variety of insects (caterpillars, beetles, ticides typically come from plant extracts aphids, etc.) or as selective insecticides, (pyrethrins, neem), products from soil which affect a limited range of species (for microorganisms (Bt, spinosyn), or plant example, caterpillars only) and can help to fatty acids (insecticidal soaps). The spec- preserve