Vertical distribution of pear thrips (Thysanoptera: Thripidae) in forest soils
1992
Skinner, M. | Parker, B.L.
Between July and December, pits (30 cm deep) were excavated in sugar maple forests to determine the vertical distribution of pear thrips, Taeniothrips inconsequens (Uzel). In well-drained, fine sandy loam, 67.3% of the larvae occurred in the upper 10 em and < 10% were below 18 cm. The highest percentages of thrips were found at 4-6 and 6-8 cm. In the litter, 0.01% of the thrips were found. Pear thrips distribution in clay and gravelly, sandy, and shallow, poorly, and well-drained fine sandy loam soils differed significantly (P = 0.0001). However, the percentage of thrips to 10 cm was not significantly different among soil types. The hand-held bulb planter (barrel 10 cm long) was suitable for large-scale sampling, giving a volume of soil that could be processed quickly to extract thrips. About 67% of the pear thrips soil population was captured using this tool during the inactive phase of the thrips. Vertical distribution of thrips changed during periods of adult emergence from and reentry into the soil. In May during emergence, > 40% of the thrips were located in the upper 4 cm, whereas during dormancy, only 21% of the thrips were found that deep. In early June, when larvae reenter the soil, thrips were commonly found in the litter, but by mid-June, vertical distribution had stabilized, suggesting that downward movement of thrips into the soil had ceased.
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