Evaluation of foliar applications of an experimental biopesticide and commonly used insecticides for control of sweet potato whitefly on zucchini, 2023

Bemisia tabaci is a serious pest of several crops and causes a characteristic “silverleafing” on squash leaves which can cause a reduced yield and fruit quality. For this trial to evaluate its management using foliar sprays of insecticides, 3 raised beds 32 inches wide on 6-ft centers were prepared at the Southwest Florida Research and Education Center in Immokalee, FL. Beds were covered with white-on-black polyethylene. Plants were directly seeded by hand at 24-inch spacing on 26 September. Plots were assigned in an RCB design with 4 replications consisting of treatments and an untreated check plot with 15 plants in each single row plot and 5 plants between each plot acting as a spray buffer and pest reservoir. Foliar treatments were applied (Table 1) with a high clearance sprayer operating at 180 psi and 2.3 mph with delivery through 2 vertical booms, each equipped with 2 yellow Albuz hollow cone nozzles applying at a total volume of 40 gpa. Adult whitefly were counted weekly from 20 October to 17 November by carefully turning over 2 leaves on each of the 5 plants per plot. Whitefly nymphs were sampled on the same dates by collecting 1 lower leaf from each of the 5 plants per plot to count nymphs in the laboratory. Eight 0.5-inch² discs were removed from each leaf using a cork borer and nymphs were counted on each under a stereoscopic microscope. Data were subjected to 1-way ANOVA and means separated using LSD (P = 0.05).

All treatments significantly reduced the number of adult whitefly observed per leaf when compared to the untreated on all sample dates except for the PQZ rotation and Barrett30 at 1% on 20 October and the Barrett30 at 0.5% on 17 November (Table 2). Significant reduction in the number of whitefly eggs in all treatments compared to untreated checks was observed on 27 October and 9 November (Table 3). All treatments showed a reduction in egg numbers on those sample dates and without a significant difference between treatments. All treatments significantly reduced the number of nymphs counted on all sample dates compared to the untreated check with no significant differences observed among the treatments (Table 4). No phytotoxicity was observed.

Acknowledgment

This research was supported by industry gifts of pesticide and funds.

Funding

None declared.

Conflicts of interest. None declared.