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Predatory insect may help control whitefly

Scientists at the University of Florida have found an insect predator that may help greenhouse tomato growers manage populations of the sweetpotato whitefly when used as a piece of an integrated pest management system.

Bemisia tabaci, also known as the sweetpotato whitefly or silverleaf whitefly, attacks a range of plants, including sweetpotato, squash, tomato and poinsettia. The biotype B species has been established in the United States since the late 1980s. It transmits Tomato yellow leaf curl virus. Young tomato plants infected with tomato yellow leaf curl virus are stunted and unproductive.

University of Florida scientist Hugh Smith used a $28,417 IPM Enhancement Grant to observe the feeding habits of the whitefly predator Dicyphus hesperus to see how effective it would be at controlling whitefly in the greenhouse. He also evaluated its activity in conjunction with biopesticides commonly used on whitefly in greenhouse tomato.

Greenhouse tomato growers often try to grow as sustainably as possible to compete in a crowded tomato market. Avoiding synthetic insecticides often gives their crop an edge over field-grown tomatoes, so many growers turn first to biological control. In addition, producers of greenhouse tomato in Florida rely on hives of commercial pollinators that can be harmed by many insecticides.

Unlike most commercially-available biological control agents, which avoid tomato because of the sticky substance on the leaves, Dicyphus hesperus is adapted to sticky plants. D. hesperus is a predatory true bug that feeds on both eggs and larvae of several pest species, including whitefly, spider mites and caterpillars.

Because D. hesperus is used primarily in Canada and northern states, Smith wanted to know how it would fare in the warm, humid climates of the Southeast and the tropics. He also wanted to see if it would produce large enough populations to control B. tabaci.

Unlike in Canada, where its populations explode on mullein plants, D. hesperus populations grew much more slowly in Florida. Even so, it still had an impact on whitefly populations. During a greenhouse trial where 12 predators per plant per week were released for 3 weeks, only 7 whitefly eggs per leaf remained in the containers with the predator, versus 151 on untreated plants; and 14 nymphs per leaf remained in containers with the predator, versus 229 nymphs in the control.

Although the predator reduced whitefly populations, only one whitefly is needed to infect a plant with Tomato yellow leaf curl virus. Virus-resistant varieties are available for field tomatoes, but not for greenhouse tomatoes. Smith says that developing those varieties is the next step toward protecting greenhouse tomatoes from the virus.



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