SPATIAL-DISTRIBUTION AND SAMPLING PROCEDURES FOR FRANKLINIELLA SPP (THYSANOPTERA, THRIPIDAE) IN STAKED TOMATO

Phytophagous thrips were sampled in commercial tomato, Lycopersicum es culentum L., fields in western North Carolina during a 3-yr period for m 1990 to 1992. Tomato flowers were collected to sample thrips and eva luate 3 different sampling units (2,5, and 10 flowers) for their relat ive net precision. Flower thrips, Frankliniella tritici (Fitch), and w estern flower thrips, Frankliniella occidentalis (Pergande), were the dominant species collected, accounting for 96% of all specimens. Relat ive net precision values indicated that a 10-flower unit was more prec ise and cost-efficient than either the 2-or 5-flower unit. Frequency d ata collected from the 10-flower unit were described by the negative b inomial distribution. Both F.occidentalis and F. tritici exhibited an aggregated distribution in tomato fields. Taylor power law did not dif fer among thrips species or total thrips. A fixed-precision-level sequ ential sampling plan was developed using the parameters of Taylor powe r law generated from total number of thrips in a 10-flower sampling un it. The resulting sampling plan was tested with sequential sampling bo otstrap simulations (n=500) using 11 independent data sets for the val idation. Bootstrap simulation over a range of densities demonstrated t hat actual D-0 values at D-0 = 0.30 averaged < 0.26 in every case.