Pesticide is the generic term that describes chemicals used to kill pests. Pesticides include fungicides to kill fungus and diseases in soil and plants; herbicides to kill weeds and other undesirable plants, and insecticides to kill bugs.

The federal government estimates there are more than 35,000 pesticides manufactured from 800 different chemical components. Some pesticides popular in the chemical lawn care industry follow, with a summary of their health effects, if available, and their estimated use rates in two Maryland counties and statewide. INSECTICIDES

* Dursban (common name), Chloropyrifos (chemical name), of the chemical family organophosphates. It can affect the central nervous system. Overexposure through skin absorption, inhalation or ingestion results in sweating, nausea, blurred vision, lack of muscle coordination and chest tightness. It affects reproduction in laboratory animals. Long-term health effects of Dursban and other organophosphates are unknown.

Use rate (1982 estimates) -- Montgomery, 18,466 lbs.; Prince George's, 3,116 lbs.; Maryland, 66,038 lbs.

* Diazinon (chemical name), numerous common names, also an organophosphate with same health effects as Dursban.

Use rate (1982 estimates) -- Montgomery, 14,754 lbs.; Prince George's, 15,004 lbs.; Maryland 66,038 lbs. HERBICIDES

* 2,4-D is one of two chemical components of the Vietnam defoliant Agent Orange, and use is restricted though not banned by the National Park Service. It kills plants by causing them to grow too quickly. Health studies are inconclusive in part because 2,4-D is usually mixed with other pesticides. Overexposure can result in numbness of extremities, blurred vision, headaches, nausea. Recent data shows increased risk for cancer related to 2,4-D's chemical family, phenoxyacetic acids.

Use rate (1982 estimates) -- Montgomery, 8,738 lbs.; Prince George's, 4,566 lbs.; Maryland, 106,461 lbs.

* Dicamba (chemical name Banvel) is a convulsant poison. Symptoms of overexposure include vomiting, tremors and convulsions. Testing for long-term health effects is incomplete.

Use rate (1982 estimates) -- Montgomery, 16,289 lbs.; Prince George's, 471 lbs., Maryland 17,749 lbs. FUNGICIDES

* Benomyl is a mild skin irritant with low acute and chronic toxicity. Effects on reproduction observed in laboratory animals led to new precautions ordered by the EPA in 1982.

Use rate (1982 estimates) -- Montgomery, 791 lbs.; Prince George's, 198 lbs.; Maryland, 1,728 lbs.

* Daconil has caused cancer in laboratory rats, but not in mice. Selected in January 1984 by EPA for general toxicological review. Can be inhaled or absorbed through the skin and eyes, causing respiratory, gastrointestinal and skin irritation and skin sensitivity.

Use rate (1982 estimates) -- Montgomery, 3,905 lbs.; Prince George's, 4,454 lbs.; Maryland, 10,779 lbs.

Chemical and health information according to Hazardline, Occupational Health Services Inc. and Dr. Max Eisenberg, director, Maryland Department of Health and Mental Hygiene Office of Environmental Programs, Scientific and Health Advisory Group.

Estimated Maryland use figures from a Maryland Department of Agriculture survey of 771 businesses and 172 public agencies, of which 58 percent responded. County amounts based on location of businesses and agencies.