Insect species which, in natural systems are regulated at low densities by natural enemies, are often at high densities in commercial apple orchards because insecticides decimate natural enemies and/or commercial orchards provide a rich and abundant resource for herbivores. In addition to the detrimental impacts of insecticides on natural enemies, it was also thought that the orchard habitat, due to its relatively low diversity, was less than optimal for many natural enemies. The Obliquebanded leafroller (OBLR) is a native North American lepidopteran pest of apples that to date, has not been a candidate for biological control. Recent experiments conducted in unsprayed habitats of gray dogwood and in apple plantings not treated with insecticides indicated that orchards are quite adequate habitats for many natural enemies of this important pest. To determine the potential for OBLR biological control in commercial apple orchards, studies were conducted to assess parasitism of OBLR in orchards treated with conventional insecticides and with newer, more selective compounds. To eliminate the potentially lethal effects of insecticides and to insure that uniform host populations were available to monitor parasitism, trees were artificially infested with sentinel OBLR larvae reared from laboratory colonies. Larvae were exposed to natural enemies for 48 hours, recollected, and reared in the laboratory on diet. Emerging parasitoids were identified. Appropriate statistical methods were used to compare natural enemy levels and species diversity in the two insecticide regimes.
Species 1: Lepidoptera Tortricidae Choristoneura rosaceana (obliquebanded leafroller)
Keywords: Hymenoptera, habitat
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