Seasonal and Diurnal Dynamics of Spiders (Araneae) in West Virginia Orchards and the Effect of Orchard Management on Spider Communities

Abstract

Four West Virginia apple orchards under different management (unmanaged; horticultural management only; horticultural management with apple, peach, and cherry trees interplanted; and standard commercial management) were sampled for spider abundance. Sampling was done with limb jarring at four times during the season; samples were taken hourly over a 24-h period. A total of 1,926 spiders from 15 families was collected, and 44% of all spiders were Salticidae. More spiders were collected in August (37%) than earlier months, but the highest diversity of spider families was in July. Older, unsprayed apple trees had the greatest diversity of spiders. The family Oxyopidae was most abundant in the commercially managed orchard. Spiders in the families Anyphaenidae, Philodromidae, and Thomisidae were significantly more abundant during night samples than during the day. Philodromids were also significantly more abundant on peach and cherry trees than on apple, possibly being attracted to extrafloral nectaries. Comparisons with other published data sets found that regional differences were more important determinants of spider community structure in apple than insecticide use. Northwest European, sprayed Quebec, and sprayed Washington apple orchards were found to be dominated by web-building spiders; the other North American and Israeli orchards were dominated by hunting spiders. Abundance and diversity of the spider community in orchards suggests that spiders could be major contributors to biological control of many insect pests.