Effect of second-stage IPM practices on parasitism of apple blotch leafminer (Lepidoptera: Gracillariidae) larvae in Massachusetts apple orchards.
1994
Van Driesche R.G. | Prokopy R.J. | Christie M.
In 1989 and 1990, parasitism of the apple blotch leafminer, Phyllonorycter crataegella (Clemens), was assessed in 17 and 16 apple orchards, respectively, in Massachusetts to determine the effect of integrated pest management (IPM) practices that reduced pesticide use between early June and late August. In test blocks on each farm, broadcast pesticide applications for control of the apple maggot, Rhagoletis pomonella (Walsh), were replaced by use of either red spherical sticky traps on perimeter apple trees to intercept immigrating apple maggot flies or by applications of pesticides to perimeter apple trees. In either case, no insecticides or miticides were applied to the interior of test blocks after early June. Use of these methods was designed as second-stage IPM, and apple blotch leafminer parasitism under such management was compared with an adjacent block in each orchard using conventional pesticide tactics. Average parasitism of tissue-feeding apple blotch leafminer larvae across all orchards was slightly greater in the second and third host generations in blocks in which second-stage IPM practices were used than in conventionally managed blocks on the same farms. Most enhancement of apple blotch leafminer parasitism occurred in orchards in which traps were used to control apple maggot flies. Orchards in which perimeter-pesticide applications were made showed little or no difference in parasitism levels from those of full spray blocks. None of six orchard or insect variables examined (block size, ratio of interior trees to edge trees, nature of surrounding vegetation, number of pesticide applications per leafminer generation, density of tissue-feeding stage apple blotch leafminer mines, or percentage parasitism in the previous apple blotch leafminer generation) explained a significant proportion of the variation in parasitism seen among orchards and blocks in correlation analyses.
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