05-22-1998 Council Packet - Laserfiche WebLink

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I. What Ara Lawn Cara Chamicals and Haw Ara Thay Uaad? Chemicals used on lawns are pesticides ar\6 fertilizers. Lawn care pesticides are substances used by man to control pests, primarily destructive insects, fungi and weeds, while fertilizers are plant nutrients to help the grass—and any other plants present—to grow. Most lawn care pesticides are “general use" products^- the federal Environmental Protection Agency (ERA) con siders them safe for use by anyone who follows label directions. However, some types of lawn products are "restricted use" substances. They are only sold to and used by "certified applicators.” persons who satisfy ERA and state training requirements. For "restricted use" pesticides the label instructions alone are nor consid* ered adequate to assure safe and proper use. Herbicides are used to kill weeds and are the class of pesticides most often applied to lawns. Weeds are “plants growing out of place ”—where they are not wanted. Bluegrass growing in a bentgrass golf green would oe considered a weed. Conversely, bentgrass in a bluegrass lawn is a most objectionable weed. Yet each grass is excellent for its particular purpose. Herbicides can be selective, killing one type of plant but not injuring another. The widely used lawn herbicide 2.4-0 controls broadteaf weeds like dandelion and plan tain but does not harm most established perennial grasses. Nonselective herbicides like glyphosate kill all plants in a lawn, so they can be used before reseeding lawn areas that nave been overrun by undesirable per ennial grasses. Phenoxy herbicides are plant hormones that control broadleaf weeds by disrupting the plants' normal growth processes. Spraying, if done properly, usually provides better v^eed control than spreading dry herbi cide. so spraying is often tl le method preferred by com mercial lawn care companies. Insecticides control nuisance insects which damage turfgrass or otherwise disrupt a lawn. Grubs are the larvae of beetles such as Japanese beetles. May bee tles (June bugs), chafers, and billbugs that damage lawns by feeding on grass roots. The damage is most evident m the spring and fall when grub-infested turf can easily be pulled up because the roots have been cut by the chewing insects. Unlike the common herbicides, some insecticide formu lations (generally the higher concentrations) are classi fied for restricted use only by certified applicators. Because humans and insects share certain biological similarities, chemicals lethal to insects can also be injuri ous to humans if the latter are exposed to sufficient amounts.' Fungicides are used to control fungus diseases of turf. II. Are Lawn Care Chemicals Safe*? Fertilizers are not pesticides and they generally are not considered toxic substances. This appraisal is probably accurate, but users of fertilizers should still use care in handling them, for instance, to avoid eye exposure and to prevent access by children. Clearly, fertilizers are not entirely risk-free substances. Nevertheless, recent con cerns have been raised about pesticides, not fertilizers, so the remainder of this booklet will focus on these materials. Unlike most other substances used by man. pesticides are designed to kill pests and must be toxic to the pests in order to work. A few lawn care pesticides are toxic to nearly all animal and plant life, such as fumigants used to eliminate nematodes prior to replanting grass in an infested area. Most lawn care pesticides, however, are relatively specific because their primary toxic effects are directed only to target species. For example, under nor mal conditions of use. phenoxy herbicides kill most broadteaf plants but do not adversely affect grasses, insects, or rodents. Toxicity to animals, plants, or humans can be acute or chronic. Acute toxicity refers to the damage a sub stance can do as a result of a sing/e exposure to rela tively large amounts of the material. Chronic toxicity describes the ability of a substance to cause damage as a result of many repeafedexposures during a pro- longed period of time to relatively /ow levels of the mater nal. Toxicity can result from dermal (skin) contact, inges tion (oral), or inhalation. Table 1 presents the four categories used to describe the acute toxicity of pesti cides. Eye exposure to some chemicals may be poten tially hazardous, but eye damage is usually due to the local irritant properties of the substance rather than its systemic toxicity. Acute toxicity of any given pesticide depends upon the inherent toxicity of the substance as well as the amount (dose) and the test organism receiving it. The oral or oeimal dose of a substance capable of causing death (lethal dosej in fifty percent (50%) of a group of labora tory animals is called the LD^. For inhalation toxicity, lethal dose measurements are given in units of air con centration such as milligrams per liter (mg.'l) leading to the designation LCu. Although the L0« and LC^ are crude measures of acute toxicity and different species of animals may have different susceptibilities to a sub stance. they provide a scale by which the acute human toxicity of a substance can be roughly estimated. The LOw is usually expressed as an amount of substance administered divided by the weight of the animal (usu ally rat. mouse or rabbit) tested: for example, milligrams of substance per kilogram of body weight (mg/kg). The /owerthe LD„ or LC» value, the more toxic the material is to the test organism. When they are diluted with water tor application according to label directions and applied to turf, most lawn care pesticides would fall in the least toxic category IV and pose virtually no hazard. Chronic toxicity arises from long term or repeated expo sure 10 a substance and ngam depends on the amount and lest organism, but it also depends on the duration of exposure to the toxic agent. Chronic effects can range from relatively mild irritation to serious, life-threat- ening disease 0^