Microarthropods Associated with Insecticide-Treated and Untreated Artichoke Fields in California

Samples of microarthropods from artichoke leaves, flower heads, and soil debris were taken from fields where growing conditions were similar except for insecticide treatment; fields were treated in Castroville and untreated in Carmel Valley, Calif. Methyl parathion and methidathion were applied every 2 wk for the control of the artichoke plume moth, Platyptilia carduidactyla (Riley), the major pest of artichoke. Pesticide-treated fields had eight fewer predatory and phytophagous microarthropod species. Anystis sp. Was absent; numbers of Parasitus bituberosus Karg and Pergamasus quisquiliarum Canestrini were reduced in treated fields. These mites are important predators of artichoke pests including first-and second-instar artichoke plume moth, thrips, aphids, and mites. A secondary outbreak of Tetranychus urticae Koch was observed in methyl parathion-treated fields. These factors should be considered in an IPM program for artichoke.