Host Plant Preferences of Frankliniella occidentalis and Thrips tabaci (Thysanoptera: Thripidae) for Onions and Associated Weeds on the Southern High Plains

Thrips species composition and host preference for onions and eight common weed species were determined in onion fields on the Southern High Plains in Texas. Eleven thrips species were collected, and Frankliniella occidentalis (Pergande) was the most abundant in both 1989 (57.1%) and 1990 (99.5%). Thrips tabaci Lindeman was abundant (40.4%) in 1989; however, only two specimens were collected in 1990. T. tabaci exhibited a strong preference for Allium cepa L. F. occidentalis did not exhibit a preference for A. cepa but rather, in 1989, exhibited preference for Salvia sp., Amaranthus palmeri Wats, and Kochia scoparia (L.) Schard., in descending order of preference, and in 1990 exhibited a preference for K. scoparia in only one field. Immature thrips occurred predominantly on A. cepa in 1989 and on the weed species in 1990. These associations indicate that the immatures collected in 1989 were probably T. tabaci, whereas those collected in 1990 were probably F. occidentalis because they followed similar patterns of association as the respective adults. In addition, a modified aromatic Berlese funnel for rapid plant sampling and thrips extraction in the field is described. Percentage extraction efficiency was dependent on plant species and ranged from 81 to 98.3 for adult thrips and 72.2 to 100 for immatures.