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Title: PARTIAL LIFE TABLE STUDIES OF BEMISIA IN COTTON FIELDS SUBJECT TO DIFFERENT MANAGEMENT STRATEGIES

Author
item Naranjo, Steven
item ELLSWORTH, PETER - UNIV. OF AZ MAC
item DIEHL, JONATHAN - UNIV. OF AZ. MAC

Submitted to: Silverleaf Whitefly: 1997 Supplement to the Five Year National Research and
Publication Type: Proceedings
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: As part of a large-scale experimental study initiated in 1996, comparative partial life table studies were conducted in plots treated with either conventional insecticides or one of two insect growth regulators. Cohorts of eggs and settled 1st instar nymphs were established from natural populations in late July and again in mid August. The fate of each individual was then tracked by visual observation every 3-4 days. During both observational periods populations of Bemisia were relatively low. In general, natural enemies appeared to be a greater source of mortality in fields treated with IGRs, however, life table studies were not conducted in replicated plots and robust statistical inferences cannot be presently made. Predation of nymphs ranged from 38-48% in the first trial and 21-35% in the second trial. Predation of eggs ranged from 20-32% in trial 1 and 11-25% in trial 2. Parasitism of nymphs was very low (< 5%) in the first trial and increased slightly in the second. Insecticides killed from 9-25% of nymphs in trial 1 and were a greater source of nymphal mortality in trial 2 (11-52%). Based on this limited data set it is not possible to generalize about the impact of various mortality factors on the population dynamics of Bemisia. Additional observations will be needed, particularly in fields supporting higher population densities of the pest. We plan to continue these studies in 1997 in large replicated plots.