Scientific Research

Management of whitefly populations for the control of watermelon vine decline in Florida

Field studies were designed to confirm that a new ipomovirus, Squash vein yellowing virus (SqVYV), causes watermelon vine decline (WVD) in Florida and is transmitted by the silverleaf whitefly, Bemisia tabaci, (Biotype “B”). Two field studies were conducted in 2006 at SWFREC, Immokalee, FL, in the spring and fall growing seasons. Watermelon plants mechanically inoculated with SqVYV in the field at different growth stages developed WVD symptoms. Watermelon plants exposed to virus-infected squash plants developed symptoms typical of WVD and produced fruit with typical rot symptoms of WVD. Watermelon plants grown in screened cages that prevented whitefly infestation did not develop symptoms of WVD including fruit rot. Plants inside the screenhouse tested virus-free while all the plants outside of the screenhouse exposed to whiteflies tested positive for the virus. This duplicated experiment demonstrates that healthy plants can be grown if whiteflies and the virus are absent. In order to manage the whiteflies, insecticide applications of imidachloprid at transplanting and subsequent foliage applications of pymetrozine did not prevent WVD on treated plants in the spring trial. However, in the fall trial, the rate of spread, how severe the symptoms were of WVD, and the number of whiteflies on plants treated with these insecticides decreased compared to the plants which were not treated with insecticides which demonstrates that that these pesticides may be useful to control whitefly populations and manage vine decline in Florida. Experiments targeting management of WVD by insecticidal control of whiteflies and integrated with cultural methods will continue to be explored.

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