PARENT SESSION
Wildlife Toxicology Poster Session.
Wednesday, November 15, 2000
8:00 AM to 12:00 PM
CC West/Center Exhibit Hall

(PWA057) Effects of the mosquito larvicide GB1111 on mallard and bobwhite embryos.

Hoffman, David J.¹, Albers, Peter H.¹, Melancon, Mark J.¹, Miles, Keith², ^{1 2}

ABSTRACT- Golden Bear Oil or GB-1111 is a petroleum distillate that is used throughout the United States as a larvicide for mosquito pupae. The oil forms a barrier at the air-water interface, which suffocates air-breathing insects. There are few published studies on non-target effects of GB- 1111 but the product label warns that "GB-1111 is toxic to fish and other aquatic organisms." Fertile eggs of mallards (Anas platyrhynchos) and bobwhite (Colinus virginianus) were incubated in the laboratory, and treated on days 4 or 11 of incubation with external applications equivalent to either 0, 1/3, 1, 3, or 10 times the maximum rate (5 gal/A) of field application of GB-1111. Hatching success was significantly reduced in mallards treated on day 4 or day 11 at 3 and 10 times the maximum field application, with a calculated approximate LD50 of 1.9 times the maximum field application. Most mortality occurred within a week of treatment. Hatching success of bobwhite was only reduced at the highest level of treatment. Other effects at this level in bobwhite included a significant increase in incidence of abnormal embryos/ hatchlings, lower body and liver weights of hatchlings and a two-fold increase in hepatic microsomal P450-associated monooxygenase activity (EROD) in hatchlings. Recommended rates of field application of GB- 1111 are potentially toxic to mallard embryos, especially under conditions of larvicide drift or spray overlap, but unlikely to impair the survival or development of bobwhite embryos.

Key words: larvicide, embryotoxicity, mallard, bobwhite