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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Publications at this Location » Publication #121837
Title: SPIDERS (ARANEAE) AS POTENTIAL PREDATORS OF LEAFROLLER LARVAE AND EGG MASSES (LEPIDOPTERA: TORTRICIDAE) IN CENTRAL WASHINGTON APPLE AND PEAR ORCHARDS

Author
item Miliczky, Eugene
item Calkins, Carrol

Submitted to: Pan Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2002
Publication Date: 4/1/2002
Citation: Miliczky, E.R., Calkins, C.O. Spiders (Araneae) as potential predators of leafroller larvae and egg masses (Lepidoptera: Tortricidae) in central Washington apple and pear orchards. Pan Pacific Entomology. 78:140-150.

Interpretive Summary: Future insect control in orchards will rely more heavily on natural enemies and less on insecticides. Spiders are abundant and important predators of insects. In orchards where insecticides have been eliminated or greatly reduced spiders are abundant, but know we little about their feeding habits. Leafrolling caterpillars are pests in Washington orchards, feeding on foliage and fruit from within rolled leaves held together with silk. Female moths, lay their eggs on leaves in groups of several hundred. We tested hunting spiders (those that do not make webs) found in local orchards, for ability to prey upon leafroller caterpillars and eggs. Eleven species of spiders ate at least a few of the available caterpillars. However, a nighttime active sac spider consumed at least 65% of available caterpillars. Thirty-five of 37 sac spiders ate caterpillars; one female ate at least 14. The sac spider was also the only one of 12 species that frequently fed on eggs as 26 of 57 individuals did so; two spiders consumed three egg masses each. Thus in orchards where spider numbers are high and insecticide use is low, spiders may contribute substantially to leafroller control.

Technical Abstract: Eleven species of arboreal, hunting spiders, common in central Washington apple and pear orchards, were evaluated as potential predators of the tortricid leafrollers, Pandemis pyrusana Kearfott and Choristoneura rosaceana (Harris), pests in Pacific Northwest orchards. All species fed on leafroller larvae in small cage tests. Cheiracanthium mildei L. Koch (Clubionidae) was the most effective predator in small cage tests, consuming 65% of available larvae. Tests conducted with six species using caged apple trees also showed that C. mildei was the most effective predator. Twelve species were tested as predators of C. rosaceana egg masses. C. mildei was the most effective as 46% of tested individuals consumed part or all of an egg mass. Two C. mildei completely consumed three egg masses apiece. In addition, Oxyopes scalaris Hentz and Cheiracanthium inclusum (Hentz) exhibited limited feeding on eggs.