Stephanie Bailey,
Extension Specialist in Entomology
Ricardo Bessin,
Extension Specialist in Entomology
Douglas W. Johnson,
Extension Specialist in Entomology
Lee H. Townsend,
Extension Specialist in Entomology
Donald E. Hershman,
Extension Specialist in Plant Pathology
William Nesmith,
Extension Specialist in Plant Pathology
J. D. Green,
Extension Specialist in Weed Science
This category is for:
Individuals certified in this category not only provide and disseminate information on pest control but also serve as examples for other applicators. Therefore, a broad knowledgeable of pesticide issues and topics is vital.
Laws governing the use and users of pesticides are designed to protect humans and the environment. Early pesticide regulations were of two types:
These early laws were replaced in 1947 by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which was administered by the US Department of Agriculture until 1971. This Act required proper labeling of all pesticides, including herbicides. It did not cover products that were manufactured and sold within only one state.
Restricted Use Pesticides (RUP) are materials that can cause adverse effects on the applicator or the environment, even when used according to label directions. Restricted Use pesticides legally can be purchased and applied only by persons who have had special training as certified applicators, or those who work under their direct supervision.
General Use Pesticides (GUP) are materials that have a low potential to harm the applicator or the environment when used according to label instructions. Persons who purchase and use these products do not need to be certified applicators.
The Pesticide Applicator Training and certification program was established and types of applicators were defined as follows:
A Certified Applicator is anyone who is authorized to use Restricted Use
pesticides. Certified applicators can provide pest control services
but neither sell nor distribute pesticides.
There are two types of
certified applicators:
Kentucky Division of Pesticides
Chapter 217, 217B
Pesticides Use and Application
The main responsibility of the Kentucky Division of Pesticides is to regulate pesticides and their use in the Commonwealth. The Division is the prime pesticide enforcement agency under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA0). FIFRA sets standards of regulation for the marketing and use of pesticides and requires the certification of commercial applicators and dealers. Under FIFRA the pesticide label is law. Therefore, once ground water or any other restrictions are placed on the label of a pesticide, then enforcement from the State Division of Pesticides is required. The Division of Pesticides has the authority to ensure that pesticide applicators follow EPA approved label instructions.
In addition, the Pesticide Use and Application Act Kentucky Revised Statute Chapter 217B empowers the Kentucky Department of Agriculture to regulate and control pesticides to ensure their intended and beneficial use. The Department has the authority to prohibit or restrict the application for a pesticide. Violations of the pesticide use act and regulations are stopped by issuing a written Stop Sales, Use, or Removal on the pesticide, involved in accordance with Kentucky Revised Statute 217.610
Kentucky Pesticide Control - Pesticides Control KRS 217.542 - 217.670 addresses prohibitions relating to the distribution of pesticides and their registration. Pesticides must be registered before they can be sold or used in the state. The regulations require that pesticide product labels are to be registered, provided that such regulations shall not impose any requirements for federally registered labels in addition to, or different from those required pursuant to FIFRA. Also, the department may inspect pesticides wherever found.
It may sample and analyze to determine compliance with the KRS 217.542 - 217.670 and any regulations adopted under those sections. Also any lot of pesticides not in compliance and subject to seizure on complaint by court consent can be condemned and disposed of if found in violation as stated in KRS 217.620
Kentucky Pesticide Use and Application Act - This act regulates the distribution, use, and application of pesticides to pests as defined by KRS Chapter 217B. It recognized the importance of pesticides relative to human health and the environment, including farmlands, from insects, rodents, weeds and other life forms that may be detrimental to farming. However, if these pesticides are used improperly, they present a potential danger to human and animal health and the environment. The purpose of KRS Chapter 217B is to regulate in the public interest the use and application of insecticides, fungicides, and any other pesticides designated by the Department by regulation.
KRS 217B.050 empowers the Kentucky Department of Agriculture to prohibit the use of a pesticide in a given area once certain conditions have been met. It states:
In addition, education and dissemination of information is provided for under KRS 217B.210, and is addressed as follows:
Information and Education - Revision of license examinations, training courses and other materials.
Pesticide Registration
As specified by the amended FIFRA, all pesticides must be registered. Before any registration is issued, however, the manufacturer must submit data to EPA showing that the product, when used as directed:
-- will not injure humans, animals, crops or damage the environment;
-- and will not result in illegal residues on feed and food.
Among the types information required are:
The data submitted to EPA with the application for registration are carefully analyzed. Some of the areas taken into account are: the pesticide's response in the environment including rate and type of decomposition following application; amount of movement and persistence in the soil, air or water; effect of light and rain on the pesti- cide as well as potential effect they (pesticides) will have on man, animal and plant life.
Registration for a single product requires several years and millions of dollars in developmental costs. Only a fraction of the materials investigated by industry actually make it through the process and enter the market place.
Establishing A Legal Residue Tolerance
A residue is the amount of pesticide present following an application. The potentially detrimental health effects of these residues are a major concern. The EPA establishes a tolerance for each pesticide on each food crop before registration for use. The tolerance, usually expressed in parts per million (ppm), is the maximum amount of a pesticide residue that legally can be present on or in feed or foods.
EPA studies and analyzes the manufacturers data in order to set tolerance levels. EPA attempts to determine whether or not the pesticide residues remaining when the product is used as directed will exceed the level that is considered as safe for human consumption.
A No Observable Effect Level (NOEL) is determined through long term feeding studies with laboratory animals. It is the dosage of a pesticide that results in no distinguishable harm. This value, in parts per million (ppm) is then used to set the Acceptable Daily Intake (ADI).
The ADI is defined as the daily exposure level of a pesticide residue which, during the entire life of a person, appears to have an acceptable risk of causing harm. The ADI is usually set 100 times lower, or 1/100th, of the NOEL. A much greater safety factor is required if there is evidence that the pesticide increases the incidence of tumors in test animals.
If label directions are followed, the pesticide residues on a crop should be below the established tolerances. The chances of residues reaching, let alone exceeding, the ADI are very low. Residues usually are reduced even further by washing, peeling, and cooking. Information on pesticide residues in food is available through programs such as the Food and Drug Administration "market-basket" survey.
"In 1990, under regulatory monitoring, a total of 19,962 samples of domestically produced food from all 50 states and Puerto Rico and imported food from 92 countries were analyzed by the FDA for pesticide residues. Of these, 19,146 were surveillance samples, which are collected when there is no suspicion of a pesticide problem. No residues were found in 60% of domestic surveillance samples and in 64% of import surveillance samples. Of the 19,146 surveillance samples, 2.8% were violative (above acceptable limits). Under the incidence/level aspect of monitoring, 172 samples of fish/shellfish, 330 samples of whole milk, and 3502 samples of processed foods including baby foods were analyzed for pesticide residues. Findings from these projects were consistent with the regulatory monitoring data. The findings of the 1990 Total Diet Study are evidence that actual dietary intakes of pesticides are generally well below the standards established by the Food Agriculture Organization/World Health Organization and by the EPA. The 1990 results are similar to those obtained in earlier years and demonstrate the continuing safety of the food supply relative to pesticide residues." (Summary from Residues in Foods 1990, FDA)
State Registration Requirements
Kentucky law requires EPA registered products to be registered also by the state. This state registration regulates the sale or use of a pesticide and is permitted by federal law as long as it does not allow any sale or use prohibited by FIFRA, or impose any requirements for labeling or packaging in addition to or different from those required by FIFRA.
Experimental Use Permits
EPA can grant Experimental Use Permits (EUP) to collect information
needed for initial registration or to add a new use to the current
label. Most EUPs are obtained by the company wishing to register the
pesticide. Those who test unregistered pesticides generally do so
under the experimental use permit of the company producing the pesticide.
Pesticide Labels and Labeling
Pesticide labels and labeling are among the most important documents that pesticide applicators have. The label refers to any information printed on the product container. Labeling refers to any information that is attached to or accompanying the product at the time of purchase. The pesticide user is legally responsible to follow all label directions. Under the "Directions for Use" section of the label there usually is a statement that says: "It is a violation of Federal Law to use this product on a manner inconsistent with its labeling." The user is personally liable if a pesticide application results in damage.
While "the label is the law", some allowances are permitted. Under Section 2ee of amended FIFRA it is legal to:
Registration for Minor or Specialty Crop Uses
The lack of registered pesticides for use on small acreage crops has become a frustrating problem. Many specialty crops cannot be produced economically or with the quality that markets demand without some use of pesticides. However, the registration process is costly. Gathering the additional data needed for registration increases the time required for developing a new product and obtaining the necessary information on tolerances and residues.
The relatively low financial return in proportion to effort and cost usually results in companies seeking registration of the pesticide only for large acreage crops (corn or soybeans), or crops that receive several applications each year (cotton or some fruits).
Before 1972, many minor or specialty crop uses of pesticides were taken care of by state registration of products from small companies that sold only within the state. Changes in FIFRA resulted in the loss of many minor or specialty crop uses. In addition, pesticides that were registered before 1972 now are going through a reregistration process that requires expensive data to keep old labels in effect. Many companies faced with the reregistration process have eliminated many low acreage or minor crops from their labels.
There are a few methods that have been established to help aid the minor or specialty crop use problems. Interregional Research Project No. 4) (IR-4) is a cooperative effort among the USDA, EPA, State Experiment Stations, and the pesticide industry to accumulate the data necessary to obtain minor use labels for currently registered pesticides. This may involve the addition of a new crop to the label or to allow changes in rate, timing, or application method.
For food or feed crops, the major task of the IR-4 project is to obtain a residue tolerance. This can only be done if there is at least one existing tolerance for the pesticide in question. The UK Agricultural Experiment Station cooperates with IR-4 projects. to obtain pesticide minor uses for Kentucky growers.
State Local Needs (Section 24-c Labels)
Section 24 (c) of FIFRA permits the Kentucky Department of Agriculture to register federally registered pesticides for some uses that are not on the existing label. These 24-c or State Labels, are valid only in the state of issue. The applicator must possess a copy of the state label when the pesticide is applied. In Kentucky, 24-c labels must be renewed annually.
When there is an existing or expected local or minor pest problem, the Kentucky Department of Agriculture will be permitted to register one or more pesticide products if:
States cannot register:
Special local needs registrations may be sought by commodity groups, university, industry or others. The pesticide manufacturer or formulator must, however, be willing to support the effort and to prepare the documentation needed to justify the request. The registration is not effective for more than 90 days if disapproved by the EPA Administrator within that time.
Emergency Registration of Pesticides
(Section 18 Labels)
"The Administrator of the EPA may, at is discretion, exempt any Federal or State agency from any provision of FIFRA, if he determines that emergency conditions exeis which would require such exemption. The Administrator, in determining whether or not such emergency conditions exist,shall consult with the Secretary of Agriculture and the Governor of any state concerned if they request such determination" (FIFRA)
It is illegal to apply a pesticide unless it has the appropriate label for the use or purpose. Situations can occur for which there are no registered pesticides. For example, a serious outbreak of a new or previously minor pest may occur on a crop for which no registered pesticide is available. If it is a food crop and no tolerance exists for it, a state 24(c) label cannot be granted. FIFRA provides for the emergency use of pesticides in these situations.
A state may obtain permission to use an unregistered pesticide in an emergency situation when:
FIFRA provides for three types of exemptions:
If a pest outbreak has occurred or is about to occur and no effective pesticides are registered for that use or purpose, the Kentucky Department of Agriculture may ask for an exemption to use a specific pesticide. Information including the nature, scope, and the frequency of the problem, the pest involved, which pesticide or pesticides will be used and in what amounts, the economic benefits anticipated, and an analysis of possible adverse effects must be supplied to the EPA, wihch grants the exemptions. Reports must be filed when the treatment is over. A specific exemption is only good for a specified amount of time and for a designated area.
Quarantine or Public Health Exemption
This exemption may be granted to prevent the introduction or spread of a foreign pest into or throughout the US or to prevent a public health problem. No pesticide that has been suspended by EPA may be used.
Crisis Exemption
A crisis exemption may be used if a registered pesticide is not readily available to control or eradicate the pest and if there is not time to obtain a specific exemption. No pesticide that has been suspended or canceled may be used. The Administrator of EPA must be notified within 36 hours. Within 10 days of the use, the state must file information similar to that required for the specific exemption.
The EPA can issue a notice of intent to cancel or reclassify (as general or restricted use), or can hold hearings on the proposed changes if:
Suspension
If the Administrator of EPA decides that action is necessary to prevent an imminent hazard during the time required for the cancellation issue to be settled, he may suspend the registrations of the pesticide immediately. A suspension order cannot be issued unless an intent to cancel the pesticide registration is filed at the same time or has been filed previously.
Benefits and Risks Assessment
A benefits and risks assessment is a process which deals with pesticide registration, and/or classification. Extension specialists and Experiment Station researchers have been asked to assist in providing information and data to support the continued registration of pesticides that are going through the review process. If a pesticide shows potentially dangerous characteristics, it is subjected to intensive scientific review and public comment. Then, a decision is made on whether or not to allow continued use or begin the process of cancellation or suspension.
The criteria that trigger a review are: if the pesticide is highly toxic and may pose the threat of immediate poisoning to people or wildlife, if it may cause serious long-term health problems such as tumor formation or mutations in people or "non-target" animals, if the pesticide lacks an emergency first-aid treatment, occurs as excess residues on feeds or food products, or poses a major threat to the environment.
Demonstrations
Demonstrations can be used to show the effectiveness of proven or new practices or products. There are two basic types.
Result demonstrations may be large plots, sometimes in the form of strips across a field. Use of a whole field for a treatment is not a good demonstration because you have nothing to compare it with and do not know what would have happened had other treatments been used. Yield data is seldom required but the farmer cooperator may obtain gross yield comparisons. Observations should be maintained through the season and notes taken, particularly on unexpected developments.
Experiments are conducted to develop reliable information. The information sought may be new, or needed to solve practical problems. Experiments may be set up to determine if new information applies to the practical problems in your area, or to check recommendations. Regardless of the purpose, experiments must be carefully planned to be successful.
Setting Up An Experiment
Before conducting a field experiment, it is best to prepare a statement that answers the following questions:
The last question is very important The intended use of the data collected in the experiment will greatly affect your answers to the other questions. You should be familiar with these terms in setting up experimental or demonstration pest control work.
Block is a group of experimental units or plots in which each treatment occurs the same number of times. They are grouped because they are very similar before treatments are applied.
Border rows are used around test plots or between treatments when one treatment may affect the results in adjacent plots, such as through spray drift. Field margins may have different fertility, weed pressure, sunlight and moisture availability so normally they are not used
Check or control plots are experimental units to which treatments are not applied, or to which a standard treatment is applied for comparison to other treatments.
Experimental error refers to the inherent variability among experimental units or plots against which differences among treatments Willie tested.
Plot - The experimental unit.
Randomization is a random assignment of treatments to experimental units by purely objective methods (e.g. drawing numbers from a hat or using a random numbers table).
Replication - When each treatment appears two or more times in an experiment.
Sample - Representative unit(s) taken from an experimental unit or plot (e.g. the number of infected plants, percentage ground covered by weeds, or numbers of corn borers in each plot).
Treatment - The factor being tested in an experiment (e.g. type of herbicide or fungicide).
Experimental Design
Designing an experiment is an extremely important step because errors made in the design can invalidate the results of the entire experiment. The most able statistician cannot assist you in reaching valid conclusions from an improperly designed experiment. It is generally best to avoid complex experiments which involve elaborate designs unless you check with a statistician. If you have trouble with a design or are in doubt about its validity, seek assistance before initiating the research.
Many factors, such as soil type, drainage, compaction, erosion, pest infestation, temperature variation, can affect the outcome of experimental field work. These factors may change with time and with location in a field. You must be constantly alert in selecting plots in order to avoid selecting ones that may differ from others. These sources of bias may be minimized by randomization.
Randomization is the process of determining which experimental plots or units are to receive a given treatment by a purely random fashion. This may be done by tossing a coin, drawing cards or numbers, or using a table of random numbers. When randomizing plots, avoid systematic arrangements such as regularly alternating two treatments or repeating several treatments in the same order. This is a common mistake. Often a treatment can affect nearby treatments and lead to incorrect conclusions.
Avoid selecting a group of numbers that "look as though they ought to be random.
The Completely Randomized Design (Figure 1.) is simple and flexible. Treatments are assigned at random to a previously determined set of plots. Any number of treatments may be tested in this design. It is best to assign the same number of plots to each treatment but it is not essential. This design may be better for livestock tests than for field crop work. It is appropriate when plots are very similar before the treatments are applied.
A B A A C ck
C C B C ck ck
Figure 1. Completely randomized design with three herbicides --A, B, C, and, untreated (ck) plots replicated three times.
When the plots are laid out within a field, the number of plots is determined by multiplying the number of treatments by the number of replications of each treatment; (e.g., 3 herbicide treatments plus untreated control= 4 plots x 3 replicates) = 12 plots.
The Randomized Complete Block Design (Figure V is used to keep variability among plots in a block as small as possible. In this design, the treatments are assigned at random to a group of plots called a block Because adjacent plots usually yield more alike or have similar disease or pest infestations than those separated by some distance, the block is kept as compact as possible. This is accomplished by placing the plots, usually long and narrow in shape, dose together. It is desirable to obtain a compact block. Thus, treatments should be as few as possible.
Plots can be laid out as strips through a field. This design will provide highly reliable data but will become cumbersome with a large number of treatments -- usually more than five to six. Note that each treatment occurs once in each block.
A C ck B Block I
ck B C A Block II
C A B ck Block III
Figure 2. Randomized complete block design with three herbicides - A, B, C, and untreated plots (ck).
Control or Check Plots
The experimental units or plots to which the treatment is not given are called the control or check. Inclusion of control plots is recommended in all statistically sound experimental field work. The selection of check plots or units should be made with the same objectivity as that of other plot selection. The same variable factors that may affect treatment plots will affect control plots. Control plots should not be arbitrarily located near a fence row, lane, gate, or simply in the middle or side of the field.
Calibration
Correct calibration and accurate measuring and mixing of pesticides are extremely important in research and demonstration pest control work. Although the hazards of application may be reduced and the chances of nontarget pollution minimized in small plot work, the chances of misapplying the correct rate of pesticide arc generally increased. Small errors in measuring the candidate material, for example, may cause over- or under-dosing, of the treatment plot.
Small errors in calculations are greatly magnified in small plot research The addition of two extra fluid ounces of a candidate herbicide in a 1(J0 gallon tank of water during mixing for general field application may not necessarily be significant. This small amount, however, added to two quarts of water in small plot research can result in highly inaccurate results. Measuring amounts for small plot work may mean using metric units (grams or milliliters) rather than ounces, pints or pounds.
Liquid measurements should be made with graduated cylinders or pipettes. Safety pipette fillers or propipettes should be used with pipettes in order to avoid the inadvertent introduction of the pesticide into the mouth Never use your mouth to suck material into a pipette. Dry materials should be measured on properly adjusted scales that provide measurements in milligrams, grams, or ounces.
Keep detailed records on pesticide applications- including date and specific location of application site; pesticide, formulation, amount applied, area of land or site treated, crop or site; name of applicator, purpose of application; and source of pesticide.
Suppose you have a small plot sprayer with a 12' swath width. With the throttle set at 2800 rpm, the sprayer speeds were timed as follows:
| Gear | Seconds/100' |
| 2 | 35 |
| 3 | 20 |
| 4 | 15 |
Spray output from the boom when equipped with Type 101 flat fan nozzles was measured at 12 quarts per minute.
The gallon per acre output with the 101 nozzles installed and the sprayer operating in 4th gear can be calculated as follows (note- underlined limits cancel out leaving final units):
Area covered- 12' swath times 100' travel= 1,200 sq ft covered / 43,560 sq ft per acre= 0.027 acre. 43,560 sq ft per acre divided by 1,200 sq ft = 363 units per acre (an acre can be divided into 36.3 units of 1,200 sq ft).
Sprayer output- 12 quarts divided by 60 sec per minute = 0.2 quarts per second times 15 sec (time for sprayer to cover 1,200 sq ft) = 3 quarts per 1,200 sq ft or per 0.027 acres. 3 quarts x 363 = 108.9 quarts per acre. 108.9 quarts per acre divided by 4 quarts per gal = 27.2 gal per acre.
You want to apply three different formulations of the same herbicide to plots at the rate of 0.5 lb of (a)ctive (i)ngredient per acre. Calculate the amount of each formulation needed per 0.01 acre plot.
Formulation A-4 pound per gallon EC - 0.5 lb a.i. per acre divided 4 lb a.i./gal EC= 0.125 gal EC per acre times 3785 ml per gal= 473. ml EC per acre; 473 ml EC per acre times 0.01 acre = 4.73 ml EC per plot.
Formulation B- 75% Dry Flowable- 0.5 lb a.i. per acre divided .75 lb a.i./lb DF= 0.66 lb DF per acre times 16 oz per lb= 10.7 oz DF per acre; 10.7 oz per acre times 0.01 acres = 0.107 oz per plot. With this small amount, it is best to use grams for accuracy. There are about 28.4 gm/oz. So, 28.4 times 0.107= about 3 grams of formulation per plot.
Formulation C- 20% granule- 0.5 Lb a.i. divided by .20 (concentration of a.i. in G) = 2.5 Lb of granules needed for an acre. 2.5 lb times 16 oz per lb = 40 oz per acre times 0.01 acres = 0.4 grams per plot. 0.4 timcs 28.4 = 11.4 gm of 20% G per plot.
Application Techniques
A well-designed experiment can lose its value through careless techniques of treatment application and data sampling or collection.
Sampling
Even though the experiment has been properly designed, quality data can be obtained only through the use of an intelligently planned and uniform sampling method. If the sample taken, whether pest numbers or tissue for pesticide residues, is not representative the results will be neither valid nor useful. The data may give rise to erroneous and misleading conclusions.
The collection of a representative sample is infuenced by a number of variables that must be taken into account before the sampling procedures can be planned. These include the source of the sample, the size and part of the commodity to be sampled, the method of application, and the purpose of the sampling.
For practical reasons, there is frequently a limit to the number of samples which can be taken from a particular plot. Therefore, certain fundamental sampling methods must be followed. In general, the sample should represent the situation in the plot.
Do not take samples near plot borders. Have one person take all samples if possible. If more than one individual is involved, make sure that the sampling procedure is clear. Do not allow one person to sample all replications of one treatment. If possible, sample at the same time-- hour, day --and do not pool or bulk samples initially.
The way a pesticide destroys or controls a target organism is known as its mode of action. An understanding of the modes of action makes it easier to select the right pesticide and to predict which pesticides will work best in a particular situation. If pests develop resistance to one pesticide then selection of one with a different mode of action will often achieve control.
In general, pesticides within a chemical class have the same mode of action on specific types of pests. They also may have similar characteristics such as chemical structure, persistence in the environment and types of formulations possible.
Herbicides
The mode of action of some herbicides is to destroy weeds by damaging leaf cells and causing them to dry up. Others alter the uptake of nutrients or interfere with the plant's ability to grow normally or to conduct photosynthesis. The mode of action often dictates when and how a herbicide is used. Herbicides must 1) adequately contact plants, 2) be absorbed into the plants, 3) move to the site of action in the plant without being deactivated, and 4) reach toxic levels at the site of action.
Those that inhibit germination or seedling growth are used as preemergent herbicides; they are applied to the soil to control weed seedlings before they break through the soil surface. They rely on rainfall or are incorporated into the soil to place the herbicide in close contact with the germinating weed seed. Some products (e.g. trifluralin) do not move within the plant so injury symptoms are confined to site of uptake. Others (e g. atrazine) are systemic and enter through the roots and move upward. In general, symptoms will be most obvious where the product tends to accumulate.
Other types are used as post emergent herbicides and are applied to the foliage of emerged weeds. Some post emergents have contact activity, meaning they kill the plant by destroying leaf and stem tissues. Other post emergents are translocated (moved within the tissues of the plant) from leaves and other green parts to growing points.
Chemical and physical relationships between the leaf surface and herbicide often determine the rate and amount of uptake. Uptake also can be affected by plant size and age, water stress, air temperature, humidity, and herbicide additives. Differences in the amount of herbicide uptake within the plant often explain the year-to-year variation in herbicide effectiveness.
Like soil-applied herbicides, postemergence herbicides differ in their ability to move within a plant. Nonmobile (contact) postemergence herbicides must thoroughly cover a plant for good control. Mobile herbicides move within the plant to the site of action.
Plants that can rapidly degrade or deactivate a herbicide can escape the toxic effect. The ability of some plants to rapidly degrade a herbicide is the basis whereby plants are differentially susceptible to some herbicides. However, plants under stress (hot or cold temperatures, high humidity, or physical injury) may be affected by herbicides to which they normally are tolerant. Misapplication, especially excessive rates, can overwhelm the ability of the plant to degrade or deactivate the chemical and result in plant injury.
Insecticides
Insecticides may act as nerve poisons, stomach poisons, muscle poisons, desiccants, growth regulators, and/or sterilants. The mode of action of organophosphate, carbamate, and synthetic pyrethroid insecticides is to interfere with the normal function of the nervous system. Some insecticides, such as dormant oils, have a purely physical effect by clogging air passages.
Organophosphate, carbamate, and synthetic pyrethroid insecticides are widely used today to control insects, ticks, and mites. Organophosphate and carbamate insecticides have very similar modes of action, while synthetic pyrethroids work at a different site.
Organophosphate and carbamate insecticides work at the synapse gap of the nervous system. Normally, acetyldholine (ACh) carries nerve impulses across the gap. After the nerve impulse has passed, the Ach molecule is broken down by the enzyme acetylcholinesterase (AChE)and the synapse gap is returned to the normal state, ready to carry another impulse.
The AChE enzyme functions to prevent persistent "activation" of the nerve junction. Certain chemicals including organophosphorus and many carbamate pesticides block the action of the enzyme AChE and acetylcholine accumulates causing an over-stimulation of the nerves or nerve junctions.
Symptoms of this poisoning are (1) contraction of the pupil of the eye, (2) tightness of the chest, (3) increased bronchial (respiratory tract) secretions, (4) sweating, (5) tearing of eyes, (6) rapid pulse rate initially followed by a decrease in the pulse rate, (7) nausea, vomiting, abdominal pain and diarrhea, (8) involuntary urination, (9) muscle twitching, (10) cramps and (11) increased salivation.
A lethal dose of a cholinesterase inhibiting organophosphorus compound is reported to produce death due to respiratory failure (asphyxia). Symptoms of carbamate poisoning are essentially the same as those produced by the organophosphate compounds.
Synthetic pyrethroid insecticides do not work at the synapse gap. Instead, they work on the membrane that surrounds nerve fibers. These insecticides affect the movement of some vital chemicals into and out of the nerve fibers and interfere with the ability of the nerve to carry an impulse. Since both work on the nervous system, the symptoms that they produce are similar. In terms of insecticide resistance, the mode of action is different. For example, horn flies in some parts of Kentucky have become resistant to some pyrethroid insecticides. They are susceptible to organophosphates and these need to be used where resistance has shown up.
Fungicides
Strictly speaking, fungicides are chemicals used to kill or to halt the development of fungi. It is also, as used here, a general term for chemicals used to control both fungi and bacteria. Some fungicides are used as eradicants because they are capable of destroying fungi that have already invaded and begun to invade plant tissues. Their mode of action is to inhibit the metabolic processes of the growing fungal organisms. Most act as protectants to prevent infection, however. Modes of action range from preventing fungal spore germination and penetration of tissues to interference with fundamental cellular activities such as respiration.
Pesticide Resistance
Most pests are susceptible to pesticides and are effectively controlled by them. Some pests become tolerant to one or more pesticides that once were effective against them. These pests are considered to be resistant. Resistance may show a step-by-step progression. For example, after several applications of a particular pesticide, higher rates are needed to get the same degree of control that used to be achieved with a lower rate. Finally, the pesticide has no effect, regardless of the rate used. Switching to a pesticide from a different chemical class (and different mode of action) may help. However, sometimes resistance to one pesticide group also provides cross-resistance to other types of chemistry.
Resistance involves a change in the genetics of the pest and is inherited from one generation to the next. Usually, a pest population has a few individuals that are able to breakdown or chemically modify a pesticide. They can survive an application. Their offspring are resistant, also.
Resistance develops fastest when control is based entirely on one pesticide or a group of closely related pesticides. Resistance management uses as many different control options as possible.
Toxicity is a measure of the ability of a material to cause harmful effects. Toxicity of a pesticide depends upon:
Pesticides can cause three types of harmful effects: 1) immediate or acute effects, 2) chronic or delayed effects, and 3) allergic effects. Acute effects are illnesses or injuries that may appear immediately after exposure (usually within 24 hours) to a pesticide. This may be through mouth, skin, or inhalation exposure. Delayed effects, also called chronic effects, do not appear until at least 24 hours after exposure. They may be due to repeated exposure over days, months or years, or to a single exposure that does not show a harmful reaction until much later. Allergic effects are harmful reactions that some people develop in response to substances that do not cause the same reaction in most other people. The first exposure to a substance may cause a sensitization that will lead to allergic responses with subsequent exposure.
One method of measuring acute toxicity is to determine the chemical dosage that will kill one-half (50%) of the group. Thus, the figure LD50 (lethal dose 50 percent) can be applied by mouth (oral) or skin (dermal) exposure. The LD50 value is usually expressed on a weight to weight basis, i.e., milligrams of chemical per kilogram of body weight for a given test animal. Other information generally specified in reporting LD50 values includes species, strain, age and sex of the experimental animal administration route, concentration of test material and vehicle used to administer the chemical.
LD50 values have become the universally accepted means of expressing toxicity. Acute oral LD50 values provide a means of comparing one chemical to another and thus a means of evaluating the relative toxicity of chemicals when administered orally. Many are and will be tempted to use the values in an absolute sense, i.e., direct extrapolation of LD50 to humans even to the point of calculating the LD50 dose for man. The relevance of these animal values to man is questionable. Further assumption could lead to serious consequences. One should assume in the absence of information to the contrary, that the chemical is at least as toxic to humans as it is to the most sensitive test animal.
Toxicity vs. Hazard
A hazard of using a chemical is the danger it presents or possibility or probability that injury may result from using a substance. Hazard can be expressed as toxicity of a product times time of exposure. Relatively short exposures from just a few seconds to minutes, to very toxic materials can produce symptoms and cause serious injury. This hazard is recognized by most people. However, health problems can result from long term exposure (days, weeks, and years) to products that are not acutely toxic. Occupational exposure should be minimized through the use of appropriate protective equipment and personal hygiene (washing, laundering clothing, etc.).
Pesticides may enter the body through the mouth, skin, eyes, or lungs. Dermal or skin exposure is usually the most common means, about 80% of work related cases of pesticide poisoning. Reportedly, over 97 percent of the pesticide to which the body is subjected during most exposure situations and especially to applicators of liquid sprays, is deposited on the skin.
Not all pesticides are absorbed equally into the body. The list below gives an idea of the variation.
| thiourea | 1 |
| 2,4-D | 6 |
| malathion | 7 |
| parathion | 9 |
| lindane | 9 |
| carbaryl (Sevin) | 75 |
Also, pesticides may be more readily absorbed through the skin on certain parts of the body.
| forearm | 9 |
| palm of hand | 12 |
| abdomen | 19 |
| back of hand | 21 |
| back of ear | 34 |
| forehead | 36 |
| armpit | 64 |
| groin | 100 |
Studies have shown that absorption of the insecticide parathion varies depending on the where it occurs on the body. Absorption through the skin of the head and neck area was found to be greater than other sites tested with the exception of the skin of the armpit, the ear canal and the scrotum. Absorption through cuts, abrasions or other disruptions of the skin may be as much as eight times that through intact skin.
Oral exposure to pesticides during ordinary spraying has not been measured. Respiratory exposure can be very significant when spraying in dosed areas with very small particulate spray such as a mist spray, dusts and materials that vaporize rapidly under normal conditions such as fumigants.
Material Safety Data Sheets (MSDS) provide information about the chemicals within a product, first aid measures, and safe handling information and procedures for emergency response to accidental spills or releases. Unlike the pesticide label there is no required format and the amount and quality of information on them varies.
The manufacturer prepares the MSDS and provides it to distributors with the first product shipment and with the next shipment after an update. Distributors must supply copies to their customers if requested to do so.
The major sections of a typical MSDS include:
Material identification- Brand name, chemical name and family, and manufacturer.
Hazardous ingredients- Hazardous components of the material, their percentages by weight, known health hazard rating, and permissible exposure limit for an 8 hour work day.
Physical data- Tell what the material is like and how it behaves. This information aids in designing ventilation systems and providing adequate fire and spill equipment and procedures.
Fire and explosion data- This includes flash point, lowest autoignition temperature (at which it will ignite without a spark or flame).
Human health data- Gives potential routes of exposure during normal use or during an emergency. Indicates carcinogenic potential if applicable, as well as, acute and chronic health hazards. This section includes signs and symptoms of exposure and medical conditions that can be aggravated by exposure.
Employee protection- States the personal protective equipment needed, ventilation, and special precautions.
Reactivity data- Describes the conditions to avoid to prevent an unwanted reaction and the toxic substances that can be produced by fire, etc.
Spill and leak procedures- Gives methods for proper handling of spills and leaks, disposal information and significant environmental hazards.
Special precautions and storage data- Special precautions described.
Shipping data- usually optional and one of the last sections on the sheet.
Animal toxicity data- Toxicity values for laboratory animals and other species such as birds and fish.
FATE OF PESTICIDES
IN THE ENVIRONMENT
Once a pesticide has been released into the environment, either by application or a spill, various processes determine its fate. These are:
· T~ANSFER or movement of the pesticide from one place to another
· DEGRADATION or breakdown of the pesticide
Adsorption
This is similar to iron filings (pesticide particles) sticking to a magnet (soil particles). Fine textured clay soils and soils with high organic matter content are much more adsorptive than coarse, sandy soils. Since water molecules compete with pesticides for soil binding sites, wet soils tend to adsorb pesticides less than do dry soils. Other factors, including soil pH and chemical properties of the pesticide, also have an effect.
The types of problems caused by adsorption are:
· reduced pest control because pesticide is tied up in soil
· plant injury from "carry over" of pesticides that are released
in sufficient amounts to injure a rotational crop. This also can
lead to illegal residues in food or feed crops.
· pesticides bound to soil particles can be washed away by rain or
blown by wind.
Transfer
Pesticides can be transferred in the environment through volatilization, runoff, leaching, uptake, or crop removal.
· Volatilization is the conversion of a liquid or solid to a gas
that then moves off into the air. Volatilization is affected by
tendency of the pesticide to become a gas. It increases in high
air temperatures, wind speed, and lower humidity. Volatilization
can mean injury to nontarget plants due to drift. Pest control
may be reduced because less pesticide remains at the application
site. Incorporation or use of less volatile products or
formulations can reduce potential problems.
· Runoff occurs when water moves over a sloping surface; it can
carry pesticides that are mixed in it or bound to eroding soil.
Slope or grade of the treated area as well as texture and moisture
content of the soil rate of rainfall tillage practices and amount
of surface residue determine runoff rate.
Runoff can lead to injury of nontarget plants, harm to nontarget animals such as fish and other aquatic life. Pesticide runoff into streams and other surface waters can injure crops, livestock, humans, and may contaminate surface and groundwater. Incorporation of the pesticide can reduce runoff. Reduced tillage cropping systems, contour planting, or buffer strips can slow the movement of runoff water and keep it out of sensitive areas.
· Leaching, the third transfer process, moves pesticides in water
within the soil. Leaching potential is determined to a great
extent by the chemical properties of individual pesticides.
Pesticides are more likely to leach in the soil if they.
Soil characteristics that favor leaching are: coarse, sandy texture; low organic matter content; or fast draining soils.
The most significant leaching often occurs when a heavy or long rain follows an application. This movement can reduce pesticide level in the soil enough to cause poor control of the pest. Most important, leaching can contaminate the groundwater. Careful attention to developing weather systems can play a major role in preventing leaching.
Uptake is the movement of pesticides into plants or animals. Once inside, the pesticide may be broken down or remain until the crop is harvested or the plant decays.
Crop removal or harvest removes the pesticide from the treatment site. Washing and processing can remove or degrade the residue.
Degradation
Degradation of pesticides in the environment can occur by the action of microbes, chemical degradation or light degradation. Microbial degradation occurs as fungi, bacteria, and other microorganisms use pesticides, or other chemicals in the environment, as energy sources. This occurs most often in the soil Repeated use of the same pesticide can allow the buildup of microorganisms that can degrade it. Premature breakdown of the pesticide can result in poor control.
Chemical degradation results from breakdown that does not involve microorganisms. One of the most common reactions is hydrolysis- a result of the pesticide reacting with water.
The final process, photodegradation, is a breakdown as the pesticide is exposed to sunlight. Sunlight can cause the breakdown of pesticides on foliage and on the soil surface.
Groundwater is the source of water for wells and springs. Most is found in saturated zones of rock sand or gravel called aquifers. Rain, melting snow, and surface water such as streams raise the water table, which is the upper level of the aquifer. Over 85% of the Kentuckians living in rural areas depend on groundwater.
Geology controls the occurrence and movement of groundwater and therefore has an important effect on groundwater quality. Different types of rocks have different permeabilities (measure of how fast water can move through them). The physiographic regions of Kentucky are based primarily on the types of rocks that lie beneath them.
The Ohio River Valley and Jackson Puchase are composed of loose sediments ranging from gravel to sand, silt and clay. The underlying groundwater recharges rapidly after rains or irrigation. The limestone and dolomite that underlie the Mississippian and Bluegrass regions tends to dissolve along fractures and weak areas. Development of sinkholes at the surface, connected by open solution channels beneath the surface, is called a karst system. Surface water is free to move directly through sinkholes and rapidly through underground solution channels. Pollutants can easily contaminate the ground water in karst systems.
The potential for groundwater pollution also is affected by its distance from the surface and the number of faults, fractures, and sinkholes that pollutants can move through from the surface.
INTEGRATED PEST MANAGEMENT (IPM)
Sustainable production of adequate food and fiber for a rapidly expanding population while maintaining a healthy environment and safe water supply has become a top priority in recent years. The use of pesticides as the only means of controlling pest problems has some serious disadvantages:
1) Pests may become resistant to one or several pesticide classes.
2) Pests that previously were insignificant can become major problems.
3) Pesticide residues are more likely to exceed acceptable levels.
4) Destruction of beneficial organisms and natural enemies can lead to greater pest problems.
5) Environmental damage or groundwater contamination can be serious.
6) Long term control or management strategies are ignored.
7) Excessive control costs.
Pest management involves the integration of the most effective chemical and non-chemical methods with those of the ecosystem to lower and regulate pest populations. Success depends on the degree to which the integration of actions is guided by an understanding of the population dynamics of the pest and the general principles of ecology.
The philosophy of pest management is to "manage" a pest population rather than to "eradicate" it. The objective is to maintain pest populations below the economic threshold established for that pest on a certain crop. The general steps include correct identification of the pests or suspected pests as well as an assessment of potential for economic loss.
A pest is a plant or animal present in great enough numbers at a time when it can cause economic losses, or affect health or comfort. The numbers necessary to be a pest vary with the pest itself and the nature of the injury that it can cause.
The economic threshold is the number or density of a pest at which damage can no longer be tolerated It is the level at which a control measure should be initiated to keep the pest from causing economic losses. Economic thresholds are available for some key pests. In some cases, there may be "suggested treatment guidelines" or other rule-of-thumb" estimates that can be used to aid in making control decisions. Use of these tools will reduce the chances of making unneeded pesticide applications and increase the potential of gaining a return of the investment of treatment cost.
The information needed to use economic thresholds is generally obtained through systematic field examination or scouting. Correct identification of insects, weeds and diseases is essential to implementing pest management. The appropriate scouting procedure must be followed so that the information collected is useful. Economic thresholds for some soybean insect pests are based on percentage defoliation of the plants while others use numbers per 4 foot of row. Information in IPM is available through your County Cooperative Extension office.
Methods of Pest Control
Natural Control- is any condition that reduces the survival or slows down reproduction and growth of a pest organism and cannot be altered at will by man. The weather, especially temperature and moisture, is the major natural control force. It can encourage or discourage insect or plant disease outbreaks.
Cultural Control- is any manipulation of the environment that makes it less favorable for the pest. Crop rotation and sanitation are often recommended to reduce disease problems that can develop as a result of growing the same or closely related crops in the same field for several consecutive years. Host plant resistance is another major cultural control method, utilizing plant characteristics that discourage or tolerate pest infestations.
Mechanical Control- involves the measures that destroy the pest outright, such as using a swatter to kill a fly or cultivation to control weeds. Screens may be used as a barriers to prevent pests from entering an area.
Regulatory Control- uses quarantine and inspection procedures to prevent the entry and establishment of foreign plant and animal pests in a country or area. A trapping program to detect gypsy moth infestations in Kentucky is part of a regulatory control program. If possible, infestations are eradicated, suppressed or contained
Biological Control- involves the use of natural enemies, such as parasites, predators, or pathogens to keep pests below economically damaging levels. Small parasitic wasps have been released in Kentucky to aid in the management of alfalfa weevils.
Chemical Control- is the use of pesticides to control pest problems. We normally think of chemical control as the use of herbicides, insecticides, or fungicides but it may involve repellents, attractants, hormones, antibiotics, fumigants, or growth regulators.
Pheromone trap to detect insect activity
Congress passed the Endangered Species Act which protects and conserves animals, plants, and their habitats that are threatened or in danger of becoming extinct throughout all or a significant part of their range. The law requires that critical habitats the species need to survive must be protected. Labels and bulletins will be developed to identify these areas and to indicate any precautions that must be taken with specific pesticides used in the areas. The publication ID-103, Kentucky's Endangered and Threatened Species, is available through your county extension office.
