A Comparison of Vacuum and Whole-Plant Methods for Sampling Predaceous Arthropods on Cotton

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Abstract
A survey of predaceous arthropods in California cotton ( Gossypium hirsutum L.) fields was conducted over a 3-year period as part of an evolving pest management program. The primary objective of the survey was to develop an efficient method for sampling arthropods in relation to larval populations of the bollworm, Heliothis zea (Boddie). Samples were taken with a whole plant extraction method, and at 2 times of day and by 2 methods with the D-VAC® vacuum machine. Vacuum sample data were highly erratic. Data from whole plants had a high man-hours requirement. None of the methods tested is suitable for use in pest management programs. Data from whole plant samples were used to estimate seasonal occurrence of the more abundant predator species. These were the minute pirate bug, Orius tristicolor (White); big-eyed bugs, Geocoris spp. ( G. punctipes (Say) and G. pallens (Stal)); damsel bugs, Nabis spp. mainly americoferus Carayan; green lacewings, Chrysopa spp., mainly carnea Stephens; the notoxus beetle, Notoxus calcaratus Horn; and a complex of spiders. Estimates of their seasonal abundance are given on a per hectare basis. Comparisons were made between the numbers of each predaceous species and numbers of bollworms and cabbage loopers, Trichoplusia ni (Hübner). None of the predaceous species related numerically to bollworms, or to cabbage loopers, the only abundant lepidoptera pest species found in the study areas. The numbers of Geocoris appear to correlate with the abundance of cotton blossoms. The data suggest this species may be feeding principally either on the cotton plant and/or on insect(s) of minor economic importance whose availability as prey depends on the occurrence of a suitable substance in the cotton plant.