SPATIAL DISTRIBUTION OF SYMPIESIS MARYLANDENSIS GIRAULT (HYMENOPTERA: EULOPHIDAE) IN APPLE ORCHARDS INFESTED BY ITS HOST, THE APPLE BLOTCH LEAFMINER, PHYLLONORYCTER CRATAEGELLA (CLEMENS) (LEPIDOPTERA: GRACILLARIIDAE)

Abstract

AbstractThe spatial distribution of the eulophid Sympiesis marylandensis Girault was examined in Connecticut in October 1988 and 1989 by vacuum-sampling apple trees in three zones of two apple orchards infested by its gracillariid host, the apple blotch leafminer, Phyllonorycter crataegella (Clemens). The abundance of females of S. marylandensis decreased with increasing distance of the zone or the sampled apple tree from the forest. The abundance of males in different regions of the orchard was similar. In two of three samples, the density of mines of leafminers was significantly higher near the edge than in the center of orchards. Parasitization of leafminers of the second generation and the number of female parasitoids vacuum-sampled during the third generation did not have a similar distributional pattern. We suggest that the amount of parasitism by S. marylandensis would be affected negatively by spraying trees at the border of orchards to kill immigrating pests.