RESUMO
Pesticides can be toxic to nontarget organisms including the natural enemies of agricultural pests, thus reducing the biodiversity of agroecosystems. The lethal and sublethal effects of four insecticides with different modes of action-pyriproxyfen, teflubenzuron, acetamiprid, and cypermethrin-were evaluated on pupae and adults of Eriopis connexa, an effective predator in horticultural crops. Pupal survival was reduced by pyriproxyfen (26 %) and cypermethrin (41 %). Malformations in adults emerged from treated pupae were observed after acetamiprid (82.7 and 100 % for 100 and 200 mg a.i./l, respectively), pyriproxyfen (48.6 %), and cypermethrin (13.3 %) treatments. A longer mean oviposition time was also observed in adults emerged from pupae treated with cypermethrin. Moreover, the latter insecticide as well as teflubenzuron did not reduce reproductive parameters, whereas females emerged from pyriproxyfen-treated pupae were not be able to lay eggs even when females showed large abdomens. Upon exposure of adults, survival was reduced to approximately 90 % by acetamiprid, but no reduction occurred with pyriproxyfen, teflubenzuron, or cypermethrin though the fecundity at fifth oviposition time of the female survivors was reduced. Pyriproxyfen decreased the hatching at all the oviposition times tested, whereas fertility was reduced in the fourth and fifth ovipositions by teflubenzuron and in the first and third ovipositions by cypermethrin. In conclusion, all four insecticides tested exhibited lethal or sublethal effects, or both, on E. connexa. The neurotoxic insecticides were more harmful than the insect-growth regulators, and pupae were more susceptible than adults. The toxicity of insecticides on the conservation of predators in agroecosystems of the Neotropical Region is discussed.
Assuntos
Besouros/efeitos dos fármacos , Inseticidas/toxicidade , Pupa/efeitos dos fármacos , Animais , Feminino , Oviposição/efeitos dos fármacos , Clima TropicalRESUMO
This work investigated the susceptibility of the predatory stinkbug Podisus nigrispinus (Dallas) to lufenuron using different insecticide concentrations and exposure methods. In laboratory, 5th-instar nymphs and adults were exposed to 0, 25, 50, 100, 150 and 200 mg a.i./l of lufenuron by topical exposure and by ingestion exposure through treated drinking water. In open-sided greenhouse, 5th-instar nymphs and adults were caged on cotton plants treated with lufenuron at the lowest and the highest recommended doses (10 and 50 g a.i./ha). Ingestion exposure was set up by providing the predator during five days a cotton leafworm caterpillar Alabama argillacea (Hübner), previously fed on treated cotton leaves. Ingestion and topical exposure caused severe mortality to nymphs at concentration over 50 and 150 mg a.i./l, respectively. In general, adults of the predator were not susceptible to the lufenuron. On the other hand, egg viability was significantly reduced at concentrations over 100 mg a.i./l. Nymphs caged on treated plants and fed on treated caterpillars did not reach adult stage, while nymphs exposed to residual contact were not affected. Three-day old females exposed to residual contact and to residual contact ingestion of lufenuron through contaminated caterpillars (10 g a.i./ha) restored their egg viability between the 3rd- and 4th-week of adult lifetime, while, females fed with treated caterpillars (50 g a.i./ha) showed egg viability lower than 10 percent during lifetime. These results show the importance of using lufenuron at the lowest recommended dose, as a conservation strategy for P. nigrispinus.
Este trabalho investigou a suscetibilidade do percevejo predador Podisus nigrispinus (Dallas) ao lufenurom usando diferentes concentrações e métodos de exposição. Em laboratório, ninfas de 5° ínstar e adultos foram expostos a 0, 25, 50, 100, 150 e 200 mg i.a./l de lufenurom via tratamento tópico e ingestão de solução inseticida. Em casa telada, ninfas de 5° ínstar e adultos do predador foram confinados em plantas pulverizadas com as doses (10 e 50 g i.a./ha) recomendadas do lufenurom. A contaminação do predador por ingestão foi obtida fornecendo, durante cinco dias, uma lagarta do curuquerê-do-algodoeiro Alabama argillacea (Hübner) alimentada previamente com folhas pulverizadas. Ambas vias de contaminação, por ingestão e tópica, foram tóxicas para ninfas nas concentrações acima de 50 e 150 mg de i.a./l, respectivamente. Em geral, os adultos não foram suscetíveis ao lufenurom. Por outro lado, a viabilidade dos ovos foi reduzida a partir da concentração 100 mg i.a./l. Ninfas confinadas em plantas pulverizadas e alimentadas com lagartas tratadas não atingiram o estágio adulto, enquanto aquelas expostas apenas ao resíduo nas folhas não foram afetadas. Fêmeas expostas aos três dias de idade via contato residual e residual mais ingestão de lagartas tratadas (10 g i.a./ha) restauraram a viabilidade de ovos entre a 3ªe a 4ª semana da fase adulta, enquanto aquelas alimentando-se de lagartas tratadas (50 g i.a./ha) mantiveram a viabilidade dos ovos abaixo de 10 por cento durante toda a vida. Estes resultados mostram a importância do uso da menor dose recomendada de lufenurom para a preservação de P. nigrispinus.