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Title: MOVEMENT AND MORTALITY OF BEMISIA TABACI CRAWLERS ON COTTON

Author
item Naranjo, Steven
item Burke, Rebecca

Submitted to: Sweetpotato Whitefly Progress Review Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2002
Publication Date: 6/1/2002
Citation: N/A

Interpretive Summary:

Technical Abstract: Greenhouse studies were conducted to examine movement and estimate rates of mortality of crawler stage Bemisia tabaci on cotton. Five female whiteflies were allowed to oviposit for 24 h in clip cages on the lower surface of a single leaf (generally the 2nd to 3rd leaf from the terminal) of cotton plants that had 6-8 expanded leaves. After removal of adults, plants were then placed in organdy cages to prevent further oviposition. One to two weeks after oviposition plants were destructively sampled, and the location (leaf node, upper or lower leaf surface) and number of settled nymphs were recorded. The petiole lengths of all leaves and internode distances were measured and recorded. The number of hatched and unhatched eggs on the oviposition leaf also were recorded. The experiment was replicated 20 times in still air and 20 times with plants exposed to a table-top fan blowing air at a velocity of approximately 2.2 meters/second. This latter condition was used to simulate the effects of a moderate breeze on crawler movement and mortality. The survival of crawlers did not differ statistically between still-air and wind treatments and averaged 85.5% overall. Survival ranged from 50 to 100% on individual plants. Over 99% of all surviving crawlers settled on the lower surface of leaves and 99.9% settled on the leaf where eggs were oviposited. Over both treatments only 3 individuals (out of 2700 surviving nymphs) moved from the leaf of origin and they all moved to leaves lower on the plant. Assuming that these individuals crawled rather than fell, the mean distance moved was 200 mm. These results suggest that crawlers move very little and that survival is high on young cotton plants in the absence of other natural factors such as natural enemies. Further study is needed in the field over a wider range of conditions to evaluate natural levels of mortality for life table analyses.