Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2000
Publication Date: June 20, 2000
Citation: Miliczky, E.R., Calkins, C.O., Horton, D.R. 2000. Spider abundance and diversity in apple orchards under three insect pest management programs in Washington state. Agricultural and Forest Meteorology. 2:203-215. Interpretive Summary: Scientists at the USDA-ARS Laboratory in Wapato, WA are cooperating with apple growers in implementing a technology known as mating disruption to control codling moth, the major insect pest of apples in central WA. Mating disruption allows reduced use of man-made, broadly toxic insecticides to control codling moth. One benefit may be higher spider populations and a greater spider contribution to pest control since spiders are primarily predators of insects. This research compared spiders in 3 conventional orchards (high use of man-made insecticides), 3 mating disruption orchards (reduced insecticide use), and 3 organic orchards (no man-made insecticides used). Spiders were most abundant in organic orchards and least abundant in conventional orchards. Numbers in 2 mating disruption orchards were slightly higher than in conventional orchards and substantially higher in the third. The kinds of spiders in mating disruption orchards were more similar to those in conventional than in organic orchards. Most spiders in WA reproduce only once a year and may be susceptible to even reduced insecticide use.
Technical Abstract: Spider densities were compared among conventional, mating disruption, and organic orchards where use of synthetic, broad-spectrum insecticides was high, reduced, and absent, respectively. Arboreal spider densities were significantly higher in organic compared to combined mating disruption and conventional orchards but differences between mating disruption and conventional blocks were not, during the 2 year study. Understory spider densities were higher in organic orchards than combined mating disruption and conventional orchards 1 out of 2 years. Arboreal, visually oriented, hunting spiders were significantly more abundant in organic compared to mating disruption and conventional orchards both years and more abundant in mating disruption compared to conventional 1 of 2 years. Understory, visual hunters were more abundant in organic orchards 1 of 2 years. Many species occurred in both the trees and the understory vegetation. Species of ground surface dwelling spiders, however, were distinct from the arboreal and understory species. Densities of ground surface spiders were as high in conventional as in mating disruption orchards and highest in an organic orchard.