Abstract
ABSTRACT This work aimed to evaluate the persistence (duration of harmful activity) of five insecticides used for pest control in peach orchards, on larvae and adults of the predator Chrysoperla externa. The insecticides were sprayed on cv. Bordô vine plants using the maximum dosage recommended for peach orchards. Weekly, at 3, 10, 17, 24 and 31 days after spraying, larvae and adults of the predator were exposed to treated leaves in order to assess the residual effect of insecticides on mortality and possible effects on reproduction. Given the toxicity observed along the weekly bioassays, the insecticides were classified into persistence categories established by the International Organization for Biological and Integrated Control of Noxious Animals and Plants (IOBC). High persistence was obtained for the organophosphorus insecticides (% of active ingredient) phosmet (0.100) and malathion (0.200), and both were considered persistent (> 30 days of harmful activity) to larvae and adults of C. externa. Similarly, the benzoylurea insecticide lufenuron (0.005), which acts exclusively on immature stages of insects, was persistent to larvae. Differences concerning the persistence for both development stages evaluated were observed for the pyrethroid insecticide deltamethrin (0.001), that was persistent to larvae but moderately persistent (16 – 30 days of harmful activity) to adults; and for the organophosphate fenthion (0.050) which was considered moderately persistent to larvae and short-lived (< 5 days of harmful activity) to adults of C. externa.
Highlights
The use of selective pesticides that target pest species, with minimal impact on beneficial organisms, is primordial to sustain biological control in agriculture, mostly on crops like peach, where phytophagous insects constantly occur and insecticide spraying is necessary to ensure satisfactory productivity levels.Chemical control with broad spectrum insecticides like organophosphorus and pyrethroids is one of the most adopted pest management tactics in peach orchards, leading to suppression of natural enemies in orchards and the resurgence of secondary pests that were previously kept under biological control (BOTTON et al, 2011).The green lacewing Chrysoperla externa (Neuroptera: Chrysopidae) is a natural enemy found in many agricultural crops
The lacewing Chrysoperla carnea (Neuroptera: Chrysopidae) is a standard test-species selected by the “International Organization for Biological and Integrated Control of Noxious Animals and Plants” (IOBC) for assessing the effect of pesticides on nontarget organisms, and it is a relevant species considered in regulatory requirements in European Union (VOGT et al, 1998), what justifies the selection of the neotropical species C. externa for studies of pesticides’ side effects
Larval mortality caused by fenthion was significant only at 3, 10 and 17 days after spraying (DAS), while at 24 and 31 DAS mortality was similar to control, being this insecticide considered harmless since 24 DAS
Summary
The use of selective pesticides that target pest species, with minimal impact on beneficial organisms, is primordial to sustain biological control in agriculture, mostly on crops like peach, where phytophagous insects constantly occur and insecticide spraying is necessary to ensure satisfactory productivity levels. The green lacewing Chrysoperla externa (Neuroptera: Chrysopidae) is a natural enemy found in many agricultural crops. This species is a polyphagous predator, and can prey upon soft-bodied arthropods from several orders (SOARES et al, 2003). The lacewing Chrysoperla carnea (Neuroptera: Chrysopidae) is a standard test-species selected by the “International Organization for Biological and Integrated Control of Noxious Animals and Plants” (IOBC) for assessing the effect of pesticides on nontarget organisms, and it is a relevant species considered in regulatory requirements in European Union (VOGT et al, 1998), what justifies the selection of the neotropical species C. externa for studies of pesticides’ side effects
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