Most of the known enzyme systems involved in the degradation of insecticides, other xenobiotics, and hormones of insects, appear to be inducible by various dietary chemicals, both plant-based and man-made. Although the understanding of the mechanism of this phenomenon comes almost entirely from studies of higher animals, there are good reasons to believe that the insect system is similar in most respects. If so, it involves a recognition system wherein exogenous chemicals in the insect's environment can stimulate the production of the enzymes that degrade them. Evidence is presented that some plant species and some plant allelochemicals are capable of such enhancement and that this is sufficient to increase the tolerance of an insect to various insecticides. It is also suggested that induction by plant chemicals may be involved in the insect's adaptation to its plant diet. Further understanding of the phenomenon, especially in regard to the cyclic nature of the process in plants and insects, may be of value in organizing pest management programs.

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Colorimetric and radiometric analyses have been used to study the persistence of carbaryl in estuarine water and mud in laboratory aquaria held at two temperatures. In the absence of mud, the carbaryl concentration decreased approximately 50% in 38 days at 80 C. Most of this decrease was accounted for by the production of 1-naphthol.At 20°C. after 17 days, the carbaryl had almost completely disappeared, with 43 % converting to 1-naphthol. When mud was present, both carbaryl and 1-naphthol declined to less than 10% in the sea water in 10 days. Both compounds were adsorbed by the mud, where decomposition continued at a slower rate. Radioactive carbon dioxide was produced in the aquaria containing 14C carbonyl-labeled and 14C ring-labeled carbaryl, indicating decomposition by hydrolysis of the carbamate and oxidation of the naphthyl ring. The total recovery of the 14C activity was only 40%. It is postulated that much of the remainder was evolved as methane. In a preliminary field experiment in which a portion of a mud flat was treated with carbaryl at rates similar to those used in the control of pests of oyster beds, carbaryl could be detected in the mud for 42 days. 1-Naphthol persisted in significant quantities for only one day.

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