Pesticide Profile - Ethoprop

Quick Facts:

• Chemical name: O-ethyl S, S-dipropylphosphorodithioate

• Trade name(s): Mocap, Ethoprophos, Prophos, Rovokil

• Pesticide type: nematicide, soil insecticide

• Class: organophosphate, cholinesterase inhibitor

• Routes of exposure: ethoprop is a contact insecticide/nematicide.

• Use: registered for a variety of row crops, sugarcane (28%), potatoes (35%), tobacco (14%), and corn (6%). The remaining 15% is accounted for mainly by golf course and industrial lawn applications, pineapples, beans, and cucumbers.

• Approximately 700,000 pounds are used in the U.S. annually on about 200,000 acres, mainly in the Northwest (potatoes) and the South (sugarcane; use in Florida accounts for 52% of total).

• Ethoprop is persistent in water and does not degrade for extended periods. It is resistant to photodegradation and hydrolysis.

• Ethoprop has caused many incidents of fish mortality in association with use according to label instructions.

Chemical Structure

Background

Ethoprop is a nematicide and soil insecticide that was first marketed in the 1960's. It is used to combat wireworm and fleabeetle larva infestations in potatoes, root borer in bananas and plantains, and soil insect pests of sugarcane. It is also used at high rates in pineapple fields in Hawaii and Puerto Rico. Use is increasing in the Northwest on potato farms due to the cancellation of another organophospate, fonofos. Growers estimate that 40% of the potato crop grown in the Northwest will soon be treated with ethoprop.

The environmental risks posed by ethoprop are related to its acute toxicity in conjunction with its extreme persistence in the environment, especially in aquatic systems. In soil, the half-life of ethoprop ranges from 10 to 40 days in field dissipation studies. In the laboratory, an aerobic soil metabolism study established a 100 day half-life for ethoprop. In water, ethoprop is stable, resistant to hydrolysis and photodegradation, for long periods of time (a year or more). Leaching studies have shown ethoprop to be highly mobile in soils, and thus, poses a risk for surface and groundwater contamination. Ethoprop has been detected in wild rivers systems: Cuyahoga, Sandusky, Maumee, and Raison River of the Lake Erie river system. Ethoprop has also been detected in groundwater in New York.

Environmental Effects

Fate

• Persistence: In soil, 25 days average half-life with a range from 3 to 56 days from various studies. In water, stable to photodegradation and hydrolysis at pH 7 and below.

• Bioaccumulation: measured bioaccumulation factors in bluegill sunfish were 230x for viscera and 86x for fillets, indicating the potential for bioaccumulation in animal tissues.

• Solubility: slightly soluble in water, readily soluble in most organic solvents.

Ecotoxicity 

• Ethoprop and its metabolites are highly toxic to mammals on an acute oral and acute dermal basis. Reproductive effects are observed at 30 ppm, which is lower than the expected environmental concentrations after one application of ethoprop to grass at 1 pound per acre.

• Slightly to highly toxic to freshwater fish. Fish life cycle studies have shown ethoprop to effect the growth rate of young fish and also to increase the rate of mortality in chronic toxicity tests.

• Very highly toxic to birds in an acute oral basis.

  European starling                        LD 50                   7.5 mg/kg
  Red-winged blackbird                LD 50                   4.21 mg/kg
  Domestic chicken                       LD 50                   5.62 mg/kg

  Ethoprop is very highly toxic to birds on a chronic dietary basis, as well, which may be the more relevant measurement given the environmental persistence of ethoprop. Chronic effects include reduction in the number of viable embryos, reduction of clutch size, and reduction of female body weight.

Incidents

Most of the reported incidents have involved fish kills, oftentimes in association with golf course applications. The U.S. Fish and Wildlife Service have concluded that ethoprop use endangers Attwaters Prairie Chicken, Aleutian Canada goose, and theYuma clapper rail.

• Louisiana. Two hundred shad died when Mocap (ethoprop) was applied according to label instructions to a golf course.

• South Carolina. Numerous bass, mullet, and eels were killed after ethoprop application to a golf course.

• North Carolina. Over 400 bream, crappie, and bass were found dead after treatment of a tobacco field with ethoprop.

• Georgia. Nine Canada geese were found dead after turf application of ethoprop to a golfcourse. While laboratory derived LD 50'd indicate that waterfowl may are more tolerant of ethoprop than passerines, this incident shows that grazing waterfowl are susceptible in the field.