A pesticide is any chemical used to control a pest. Pests may be such organisms as insects, plant-disease agents, weeds, nematodes, and others. Therefore, insecticides, fungicides, and herbicides are all types of pesticides. When used carefully, pesticides can provide great benefits; but since they are designed to be toxic, they also can present risks to users and consumers when used improperly.
Pesticides that are not considered likely to harm humans or the environment when used according to label directions are classified for general use and may be purchased and applied by anyone. However, commercial applicators must obtain a business license from the Maryland Department of Agriculture to apply any pesticide commercially. The U.S. Environmental Protection Agency (EPA) has determined that some pesticides may pose a threat even when used according to label directions; these materials are classified for restricted use. Pesticides may be classified for restricted use if they are highly toxic; they have a history of accidents; they may cause oncogenic effects (tumors), teratogenic effects (birth defects), fetotoxic effects (harm to a developing fetus), or reproductive effects (such as a lowered sperm count); they can leach into ground water; or, they can harm wildlife. To assist you in understanding why a particular pesticide has been classified for restricted use, and to help you understand what precautions you should take to prevent adverse effects, reasons for restriction are identified in the table “Environmental and health effects of pesticides,” which is found at the end of this section. Restricted-use products may be purchased and applied only by a trained, certified pesticide applicator or under the supervision of one. Consult your county Extension agent for information about certification.
Your best guide to the correct and safe use of any pesticide is the product label. Pesticide labels contain such important and pertinent information as the brand or trade name, the amount of active ingredient, directions for use, environmental hazards, what to do in the case of an accident, and storage and disposal directions.
An important feature of pesticide labels is that they are required by law to carry certain signal words that indicate their relative hazard to humans. Highly toxic pesticides must carry the signal word danger along with the word poison and the skull-and-crossbones symbol. The approximate amount of a highly toxic pesticide needed to kill the average person is a taste to a teaspoon. In the case of moderately toxic pesticides, the required signal word on the label is warning with the approximate lethal dose being a teaspoon to an ounce. Those pesticides that are designated to be of low toxicity or comparatively free from danger will carry the signal word caution, and an ounce to more than a pint is the approximate amount needed to kill the average person. Acute toxicity information provided in the table on the following pages is based on animal studies with technical-grade material. Be aware that a formulated product can be either more or less toxic than the technical-grade material. Check the signal word on the label of the product you will be using to be sure.
Risk depends on both toxicity (how poisonous a chemical is) and exposure. Reducing exposure to a minimum reduces risk. The use of protective clothing and equipment is one of the best means to reduce exposure. Maryland Cooperative Extension recommends long pants, a long-sleeved shirt, and socks and shoes as the minimum outfit that a person should wear whenever handling pesticides. If special protective clothing is required, the pesticide label must bear a statement identifying the appropriate gear. However, it is wise to wear extra-protective clothing even if it is not required. A hat will protect your scalp, ears, and eyes (all very absorbent parts of the body) from inadvertent contact with spray drift. Gloves, goggles, face masks, respirators, coveralls, and boots are required when mixing, loading, and applying some pesticides. Gloves or boots should be made of rubber or neoprene, never leather. Leather absorbs chemicals very easily and cannot be decontaminated. Also make sure that belts, hat bands, and other protective gear are not leather.
Organophosphate and carbamate insecticides inhibit cholinesterase, an enzyme in the body that is necessary for proper nerve function. Applicators frequently using these insecticides should have their cholinesterase levels monitored before the spray season begins to establish a baseline reading and continue regular monitoring throughout the season. Organophosphate and carbamate insecticides recommended in this bulletin are identified in the table “Environmental and health effects of pesticides” found at the end of this section. Check with your county Extension agent for information on cholinesterase testing.
On January 1, 1995, the U.S. Environmental Protection Agency (EPA) fully implemented a comprehensive set of standards to protect workers in nurseries, greenhouses, forests, and related structures, as well as on farms. This regulation is called the Worker Protection Standard or WPS. The regulation covers pesticide applicators, mixer/loaders, and workers who perform tasks in treated areas of these operations and, thus, may be exposed to pesticide residues. Owners, leaseholders, and operators of these establishments, and their contractors, supervisors, and workers are subject to enforcement actions.
The elements of these safety standards include requirements for training handlers and workers, notification of pesticide applications, the use of specific protective equipment, establishment of specific reentry periods, requirements for decontamination procedures, and assignment of emergency duties. More information on WPS is available from your county Extension office. Know and follow all requirements under the standard.
Besides posing risks to the applicator, pesticides also can harm the environment when misused or when used without properly considering the site of application or storage. Be aware of sensitive organisms (fish, birds, and other wildlife) and areas (streams, wells, bare ground areas, and adjacent land uses) in making your decisions about the safest chemical to choose for a particular job. The table “Environmental and health effects of pesticides,” found at the end of this section, includes notes on specific chemicals’ toxicity to wildlife, ground water contamination potential, phytotoxicity (ability to cause plant injury), and other factors to consider. The pesticide label also provides such information.
Although degradation of pesticide residues in and on the plant occurs with time, small amounts of pesticide will often remain at harvest. The EPA determines safe levels of residues that can remain at harvest and establishes a tolerance or legally allowable level for each pesticide on each commodity for which it is registered. The tolerance is usually in the range of 0.1 to 10 parts of the pesticide per million parts (ppm) of the crop. You must check the pesticide label for the required waiting period between application and harvest, which is identified on the label and in this bulletin as days to harvest or the preharvest interval (PHI). You also must make sure that the proper dose is applied at the correct time. Using a higher dose than the label states could result in illegal and possibly harmful levels of residue at harvest.
In addition to and in conjunction with information provided on the pesticide label, we offer the following suggestions to assist you in carrying out an effective and spray-saving operation:
Improper storage of pesticides can lead to accidental poisonings, contamination of the environment, and deterioration of the chemicals themselves. The storage building should be fireproof, with good lighting and ventilation, and an exhaust fan. The building must be posted with appropriate warning signs and should be kept locked at all times. The storage area must be separate from living, working, and eating areas. Shelves should be sturdy. Metal shelves are easiest to clean if there is a spill; wooden shelves should be lined with absorbent paper. All pesticides should be stored in their original containers. If the label becomes damaged or unreadable, contact your dealer for a copy to attach to the container. Store herbicides separately from other pesticides, fertilizers, and other materials to prevent cross-contamination, which could lead to plant injury. To delay chemical breakdown, keep pesticides out of direct sunlight and do not allow them to freeze. Most pesticides have a storage life of about 2 years under good conditions. Have first aid and spill cleanup materials handy.
There are few environmentally safe ways to dispose of leftover or unwanted pesticides. The safest and least expensive way is to use them according to label directions. Empty containers still contain small amounts of pesticides and must be disposed of properly to avoid accidents or environmental contamination. When using liquid pesticides, fill the container one-quarter full with diluent, replace the closure or plug, rotate the container, and add the rinsate to the spray tank. Repeat this procedure two more times, then puncture the top and bottom of the container to prevent reuse. When using dry formulations, carefully empty the contents of the container into the tank, then cut both ends to help remove any remaining pesticide and to prevent reuse. Containers of both liquid and dry formulations can be deposited in a licensed sanitary landfill only after following these procedures.
Federal and state laws require keeping records of pesticide use. This is a recordkeeping requirement, not a record reporting requirement. Access to records will be granted only through the U.S. Secretary of Agriculture, the state agency responsible for reinforcing pesticide laws, or a health professional. The laws vary and the requirements differ for private and commercial certified applicators in the states covered by these recommendations. However, all applicators in these states will fulfill the various legal requirements by keeping the information listed below. Fill in a standard form similar to the following one to be sure you get all the necessary data for each application. In addition to meeting the requirements, keeping records of pesticide use is a wise precaution. Records can establish proof of proper pesticide use in damage suits, provide information to trace residue or damage problems, and allow you to compare the results obtained from different pesticides. The more information on record, the more useful the records will be to you. More information on recordkeeping is available from your county Extension office.
