Control of Aphids and Whiteflies on Watermelon, 1995

Abstract

Abstract Watermelon was direct-seeded on 30 Mar at the Central Florida Research and Education Center, Leesburg, FL. Each plot consisted of four 35-ft rows, 7 ft apart with plants spaced 2.5 ft apart. Treatments were replicated four times in an RCB design. Fungicide (mancozeb or chlorothalonil) was applied weekly, usually 2 d after insecticides. All materials were applied with a 2-row tractor-mounted boom sprayer with 18 Albuz (lilac) ceramic hollow cone nozzles, spaced 8 inches apart, delivering 178 gpa at 400 psi or 133 gpa at 200 psi (CGA-215944 and Thiodan only). Silwet (0.02% or 0.03%, vohvol) was tank-mixed with Mycotrol. CGA-215944 was tested for aphid control only and was applied when the number of aphids exceeded five per leaf (high rate on 24 May only, low rate on 24 May and 7 Jun). All other treatments were applied on 24 May, 1,7, 13, and 20 Jun except Thiodan which was not applied on 24 May. Small whitefly nymphs (first and second instars) and large nymphs (third and fourth instars, pupae) were counted and summed on three 0.6-inch diam leaf disks cut from each of 20 leaves per plot for 5 weeks, beginning on 29 May and ending on 26 Jun. Aphids were counted on whole leaves. A square root transformation was used to stabilize the variance of counts for analysis. A two-way ANOVA and a mean separation test (Waller-Duncan k-ratio) were used to determine differences among treatments.