Abstract
ABSTRACT The selectivity of five insecticides, regularly used in peach farming, was assessed for larvae of the predator Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) by means of bioassay in semi-field conditions. The bioassay was based on the counting of captured larvae after release in peach trees treated with the insecticides (% of active ingredient in spray liquid): deltamethrin (0.001), fenthion (0.050), phosmet (0.100), lufenuron (0.005) and malathion (0.200). Bait-cards with eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) were used to capture larvae from treated plants; five of them were fixed in plant canopy and five others left on the soil around stem. A protective barrier made up of galvanized steel sheet was used for each plant to avoid loss of larvae. The number of larvae feeding on the bait-cards was measured for four days. According to the number of captured larvae, each insecticide effect was estimated and classified into toxicity categories as stated by the International Organization for Biological and Integrated Control of Noxious Animals and Plants (IOBC). Based on observations, the insect growth regulator lufenuron was harmless, while the neurotoxins deltamethrin and malathion were slightly harmful; and lastly, fenthion and phosmet were moderately harmful to C. externa larvae in semi-field conditions. Thus, lufenuron should be recommended for integrated pest management, since it would preserve this predator species in peach orchards.
Highlights
Among the damaging factors in peach yields in Brazil, it is noteworthy mention the infestations of pest-insects such as fruit flies Anastrepha fraterculus (Wied.) and Ceratitis capitata (Wied.) (Diptera: Tephritidae), as well as oriental fruit moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae) and secondary pests like aphids, mites and mealybugs (NAVA et al, 2014)
Predatory insects from the family Chrysopidae naturally occur in various agricultural ecosystems, including peach orchards (SCHUBER et al, 2008)
The use of selective pesticides or with low impact on this predator is of upmost importance
Summary
Among the damaging factors in peach yields in Brazil, it is noteworthy mention the infestations of pest-insects such as fruit flies Anastrepha fraterculus (Wied.) and Ceratitis capitata (Wied.) (Diptera: Tephritidae), as well as oriental fruit moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae) and secondary pests like aphids, mites and mealybugs (NAVA et al, 2014). Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) is the most abundant and has been widely studied in the Neotropics due to its high potential for use in biological control programs (ALBUQUERQUE; TAUBER; TAUBER, 1994). This predator is notable for regulating populations of several phytophagous insects in peach crop areas, feeding on eggs and small larvae of lepidopterans, mites, aphids and mealybugs (FREITAS, 2002; DE BORTOLI et al, 2006). The maintenance of C. externa populations in peach orchards should be consistently considered To this end, the use of selective pesticides or with low impact on this predator is of upmost importance. It becomes necessary further surveys on insecticide selectivity to this species
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