Location: Pest Management and Biocontrol ResearchTitle: Relative influence of plant quality and natural enemies on the seasonal dynamics of bemisia tabaci (Hemiptera: Aleyrodidae) in cotton Author
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2013
Publication Date: 6/1/2013
Publication URL: http://handle.nal.usda.gov/10113/56907
Citation: Asiimwe, P., S.E. Naranjo & P.C. Ellsworth. 2013. Relative influence of plant quality and natural enemies on the seasonal dynamics of bemisia tabaci (Hemiptera: Aleyrodidae) in cotton. Journal of Economic Entomology. 106:1260-1273. Interpretive Summary: Sweetpotato whitefly, Bemisia tabaci is a key pest of cotton and other field and vegetable crops in the arid southwestern U.S. and better knowledge of the factors affecting population dynamics of this pest are critical to improving pest management systems. Plant quality and natural enemies are two important drivers of insect population dynamics in general but their influence can vary depending on the nature of the plant-insect interaction. In a three year field study, we investigated the comparative influence of plant quality and natural enemies on the seasonal dynamics of sweetpotato whitefly. We used varying irrigation regimes to manipulate plant quality, while natural enemy densities were manipulated using broad spectrum insecticides. We consistently found higher densities of whitefly when we reduced natural enemies. Populations often increased up to six fold compared to when natural enemy densities were unaltered. In contrast, plant quality effects were weak and inconsistent. Natural enemy population densities were also generally not affected by plant quality. This study demonstrates the crucial role of natural enemies in the seasonal dynamics of whiteflies in cotton and indicates the need for producers to practice management methods that will encourage natural enemies and allow conservation biological control for this pest.
Technical Abstract: The abundance and distribution of insect herbivores is determined by, among other things, plant quality and natural enemies. These two factors vary temporally and spatially, subsequently affecting seasonal population dynamics. The relative influence of plant quality and natural enemies on the seasonal dynamics of Bemisia tabaci (Gennadius) was investigated in a three-year field study in cotton. Plant quality was manipulated through varying irrigation regimes: irrigations done at 20%, 40% and 60% soil water depletions; and natural enemy densities were manipulated using broad spectrum insecticide applications that reduced their densities compared to unsprayed controls. In each year, densities of B. tabaci eggs, large nymphs and adults were consistently higher when natural enemy densities were reduced compared with when they were left unaltered, regardless of irrigation regime. In contrast, effects of plant quality on densities of all whitefly stages were weak and inconsistent. In addition, natural enemy densities and predator:prey ratios also were not generally affected by plant quality. Interactions between natural enemies and plant quality on whitefly dynamics were rare. In general, whitefly densities were elevated 2/3rd of the time and increased 2-6 fold when natural enemy densities were reduced compared with plant quality effects which influenced whitefly densities about 1/3rd of the time and were expressed inconsistently over the years. This indicates that natural enemies exert a comparatively greater influence on seasonal dynamics of B. tabaci in cotton than plant quality, as manipulated by differential irrigation.