Survival and movement of Bemisia tabaci (Homoptera: aleyrodidae) crawlers on cotton

Greenhouse and field studies were conducted to estimate survival rates of crawler stage Bemisia tabaci (Gennadius) Biotype B (=B. argentifolii Perring & Bellows) on cotton (Gossypium hirsutum L.) plants to enable more accurate life tables to be constructed for this important insect pest. The survival of crawlers did not differ significantly between still-air and artificial wind treatments in the greenhouse and averaged 90%. Overall, 99.5% of the crawlers settled on the abaxial surface of leaves, and 99.9% settled on the leaf where eggs were oviposited. Out of 4,125 nymphs, only five settled on leaves other than 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 at least 200 mm. Using a combination of cohort-based life table studies to measure egg mortality and recruitment studies to measure egg to settled first instar mortality in the field, crawler survival was estimated to average 89.2% over three study sites in Phoenix and Maricopa, AZ. Overall results suggest that crawlers move very little on cotton and that survival of the crawler stage is relatively high under both greenhouse and field conditions. Generational mortality rates estimated from previous life table studies in the field that excluded crawler mortality would increase by only 0.8% with the addition of this minor mortality component.