Submitted to: Plant Disease Management Reports
Publication Type: Research Notes
Publication Acceptance Date: 6/24/2008
Publication Date: 8/5/2008
Citation: Kousik, C.S., Adkins, S.T., Turechek, W., Roberts, P.D. 2008. Use of Reflective Plastic Mulch and Insecticide Sprays to Manage Viral Watermelon Vine Decline in Florida, 2007. Plant Disease Management Reports. 2:V169. Interpretive Summary:
Technical Abstract: Watermelon vine decline (WVD) caused by squash vein yellowing virus (SqVYV) is a new and emerging disease in southwest and west central Florida. The virus is transmitted by the silver-leaf whitefly (Bemisia tabaci). Experiments were conducted during the fall of 2007 in Immokalee, FL, to determine the effects of combining reflective plastic mulch and insecticide sprays in managing WVD. Four-week old plants of the seeded watermelon cultivar ‘Crimson Sweet’ grown in 50-cell Jiffy trays were transplanted onto raised beds covered with either reflective (silver) or non-reflective (white) plastic mulch. The experiment was arranged as a split plot design with four replications. A 4-wk old squash plant inoculated with SqVYV was planted at the ends of each plot to serve as the source of initial inoculum. Soon after transplanting, Admire Pro (imidacloprid) was applied (8 fl oz/A) as a soil drench on plants in the insecticide treated sub plots for managing whiteflies. Whitefly management was continued only on the Admire treated plots with two sprays of Oberon 2SC (spiromesifen, 7 fl oz/A) during the season. Plants were monitored for WVD symptom appearance on a regular basis. Plants were rated on a 1-9 scale for percent of plant foliage affected and severity of symptoms. Four disease ratings recorded during the season were used to calculate area under the disease progress curve (AUDPC). Data on watermelon fruits with internal greasy or necrotic rinds and rotting flesh, which are symptoms of SqVYV infection, were recorded. Symptoms were first observed on the leaf petioles about a month after transplanting. The initial appearance of symptoms was on the plants closest to the squash inoculum plants. Insecticide treated plots had significantly lower AUDPC (P=0.0038) compared to the untreated plots, and plots with reflective mulch had significantly (P=0.0214) lower AUDPC compared to the plots with non-reflective mulch. Similarly the percentage of fruits with WVD symptoms were significantly less (P=0.0124) in insecticide treated plots compared to untreated plots. No significant interaction (P=0.4611) between insecticide treatment and mulch was observed for disease development (AUDPC) on the plants or the fruits. Adult whitefly counts recorded about one month after transplanting were lower in treated plots compared to untreated plots (P=0.0417). The combination of reflective mulch and insecticidal treatment to manage whiteflies significantly lowered development of WVD symptoms on plants and fruit compared to non-reflective untreated plots. Use of these disease management tools should be considered as part of an overall strategy for managing whitefly transmitted viral WVD in Florida.