Monocrotophos and dicrotophos residues in birds as a result of misuse of organophosphates in Matagorda county Texas USA

Abstract

About 1100 birds of 12 spp. [Red-winged blackbird ( Agelaius phoeniceus ), great-tailed grackle ( Quiscalus mexicanus ), brown-headed cowbird ( Molothrus ater ), mourning dove ( Zenaida macrours ), Eastern meadowlark ( Sturnella magna ), vesper sparrow ( Pooecetes gramineus ), common snipe ( Gallinago gallinago ), blue-winged teal ( Anas discors ), mottled duck ( Anas fulvigula ), common moorhen ( Gallinula chloropus ), redhead ( Aythya americana ) and ruddy turnstone ( Arenaria interpres )] died from organophosphate poisoning in Matagorda County on the Texas Gulf Coast in March and May 1982. Birds died from feeding on rice seed that was illegally treated with dicrotophos or monocrotophos and placed near rice fields as bait to attract and kill birds. Brain acetylcholinesterase inhibition of affected birds averaged 87% (range 82-89%), and contents of gastrointestinal tracts contained residues of dicrotophos (5.6-14 ppm) or monocrotophos (2.1-13 ppm). Rice seed collected at mortality sites contained 210 ppm dicrotophos or 950 ppm monocrotophos. Mortality from dicrotophos poisoning continued for almost 3 wk. The practice of illegally treating rice seed with either of the 2 organophosphates appears to be infrequent but widespread at present.