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The presence of thrips in vegetable crops has become an important phytosanitary issue in Mexico. Their direct injuries to plants are the result of the feeding by their immature and adult stages, whereas their indirect injuries are caused by the transmission of various viruses. The objective of this study was to identify the species of thrips associated with 6 vegetable crops in order to determine their population fluctuations and to ascertain the effects of temperature and rainfall on their populations. Samples were collected from zucchini, onion, pepper, cucumber, tomato, and tomatillo in Puebla and Morelos from Feb 2010 to Feb 2011. Three species were identified: Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on all vegetables, Frankliniella fortissima (Priesner) on zucchini and cucumber, and Thrips tabaci (Lindeman) (Thysanoptera: Thripidae) on onion and pepper. The highest population level for thrips coincided with the presence of flowers on the crops, except in the case of o...

Effects of the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) on propoxur pharmacokinetics were examined in the German cockroach, Blattella germanica (L.). Treatment of adult male German cockroaches with the cytochrome P450 monooxygenase inhibitor, PBO, or the esterase inhibitor, DEF, increased propoxur toxicity by 2- and 6.8-fold, respectively, implicating hydrolysis as a major detoxification route of propoxur in the German cockroach. However, significant hydrolytic metabolism could not be demonstrated conclusively in vitro resulting in a conflict between in situ bioassay data and in vitro metabolic studies. In vitro propoxur metabolism with NADPH-fortified microsomes produced at least nine metabolites. Formation of metabolites was NADPH-dependent; no quantifiable metabolism was detected with cytosolic fractions. However, microsomal fractions lacking an NADPH source did produce a low, but detectable, quantity of metabolites (1.6 pmol). PBO inhibited NADPH-dependent propoxur metabolism in a dose-dependent fashion, implicating cytochrome P450 monooxygenases as the enzyme system responsible for the metabolism. Interestingly, DEF also inhibited the NADPH-dependent metabolism of propoxur, albeit to a lower extent. Treatment with PBO or DEF also caused a significant reduction in the cuticular penetration rate of propoxur. The data demonstrate that unanticipated effects are possible with synergists and that caution must be exercised when interpreting synergist results.

Pre- and post-treatment temperature effects on -cyhalothrin toxicity were determined in insecticide-susceptible and resistant German cockroach, Blattella germanica (L.), strains. Acclimation at 19, 26, or 31C for 10 days before insecticide treatment had no effect on l- cyhalothrin toxicity in either strain. No differences were observed in aldrin epoxidase and glutathione S-transferase activities when “Orlando” (susceptible) cockroaches were incubated for 10 days at 19, 26, and 31C. When temperature treatment followed insecticide application, a negative temperature coefficient of toxicity (greater toxicity at lower temperature) toward l- cyhalothrin was observed for the Orlando but not the kdr-type resistant “Village Green” cockroaches. Piperonyl butoxide synergized l- cyhalothrin in “Orlando” cockroaches 3 and 5-fold at 26 and 31C, respectively. Conversely, piperonyl butoxide pre-treatment did not cause a significant reduction in the LD 50 value in the “Village Green” strain regardless of temperature.