Research Product

In a review of one of the newer insecticides, diflubenzuron (Dimilin, TH-6040, [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl) urea]), MARX (1977) emphasized that its ability to impair chitin synthesis, leading to toxicity in insects, is useful for controlling several insect pests. Diflubenzuron, one of many chitin inhibitors, is registered for use against the gypsy moth, a pest destructive to forests. Applications are pending for registration by the U.S. Environmental Protection Agency for additional uses, including protection of cotton and soybean crops and as a mosquito larvicide (possibly in coastal waters). Additional advantages of diflubenzuron cited by MARX (1977) were: (i) low application rates to achieve control of target species; (ii) inability to move through the food chain, thereby averting concentration in higher carnivores; and (iii) degradation in the environment unlike some organochlorine pesticides. Recent reports, however, indicated that diflubenzuron reduced populations of mayflies and cladocerans in field tests and killed cladocerans, clam shrimps, and tadpole shrimps at concentrations below 0.01 µg/l or less in 24 to 48 h in laboratory toxicity tests. Reproduction also declined among brine shrimp, Artemia salina, exposed to 2.0 µg/L (Cunningham 1976). Therefore, we believed it imperative to test effects of diflubenzuron on a marine crustacean, a vital link between primary producers and consumers in estuarine and marine food webs. Our tests showed that diflubenzuron is acutely and chronically toxic to a small, estuarine crustacean, Mysidopsis bahia.