The influence of orchard ground cover and introduced green lacewings on spring populations of western flower thrips in apple orchards
Bare soil, grass and weedy ground covers were compared for their influence on population densities of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera:Thripidae), within a blossoming British Columbian apple orchard. Weedy ground cover harbored the thrips before and during their movement into the apple blossoms and more western flower thrips were found in the trees in weedy ground plots than in bare soil plots during the first week of bloom. These early season differences in thrips counts did not persist through thc season, and were not consistently reflected in the percent of apples damaged by the thrips. The F1 generation of western flower thrips in cluster samples were lower in trees where nymphs of the common green lacewing Chrysopa carnea (Stephens) (Neuroptera: Chrysopidae) were introduced at bloom. The introduced lacewings did not reduce thrips damage to the apples.
Key words: Frankliniella occidentalis; thrips; apples; ground cover
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