Submitted to: International Symposium on Biological Control of Arthropods
Publication Type: Book / chapter
Publication Acceptance Date: 2/2/2009
Publication Date: 3/1/2009
Citation: Naranjo, S.E., Canas, L., Ellsworth, P. 2009. Mortality and Population Dynamics of Bemisia tabaci within a Multi-Crop System. In P.G. Mson, D.R. Gillespie and C.D. Vincent (eds.), Proceedings of the Third International Symposium on Biological Control of Arthropods, Christchurch, New Zealand, USDA Forest Service Publ. FHTET-2008-06 202-207. Interpretive Summary: The sweetpotato whitefly is a pest of worldwide significance on many crops including cotton. It causes direct feeding damage, vectors over 110 plant viruses, induced plant disorders, and reduces yield quality through honeydew excretion. The pest potential of this whitefly is enhanced by its polyphagy (ability to feed on many plants), high reproductive rate, dispersal ability and lack of a resting stage that enables year-round population development on a sequence of host plants in the ecosystem. To better manage the sweetpotato whitefly we need to understand the complex and interacting factors governing its population development in a mosaic of host crops throughout the year. We established “whitefly ecosystems” that consisted on 6 representative crops and other host plants and used life table methods to identify sources and quantify rates of mortality of this insect on these 6 host plants throughout the year in 3 regions of Arizona. We found the highest rates of mortality from predators on most of the host plants during most times of the year. Parasitism occurred at moderate levels on some host plants during summer and fall. The most significant finding was that overall mortality was lowest on spring-planted cantaloupe, a favored host of the whitefly, and that this leads to potential outbreaks of the pest during the summer on cotton. This information will be useful in developing better pest management strategies for all affected crops in the region.
Technical Abstract: The population dynamics of mobile polyphagous pests is governed by a complex set of interacting factors that involve multiple host-plants, seasonality, movement and demography. Bemisia tabaci is a multivoltine insect with no diapause that maintains population continuity by moving from one host to another over the year. To better understand the mechanisms governing population development of this insect within the landscape, whitefly “ecosystems” were established in three geographically and climatically distinct areas in Arizona. These systems consisted of a sequence of six representative hosts (winter broccoli, spring and fall cantaloupes, summer cotton, perennial alfalfa, various annual weeds, and the perennial ornamental, lantana). Source and rates of natural mortality were quantified, in situ, on each host plant by life tables. The quantitative contribution of each mortality factor varied among hosts and time of the year, but was relatively consistent among geographic sites. Predation (sucking insects) and dislodgement from the plant surface (largely chewing predation) were consistently the largest sources of mortality. Median generational mortality was generally > 90% except on spring-planted cantaloupe where median mortality was <70%. Low mortality during the spring on cantaloupe appears to act as a biotic release leading to outbreak populations during summer months. Overall, an understanding of the year round spatio-temporal dynamics of this pest and its associated natural enemies will greatly aid the development of better pest management strategies in all affected crops.