Control of Sweetpotato Whitefly With Foliar Insecticides on Staked Tomatoes, Fall 2013 *

SWF biotype B continues to be a destructive tomato pest in Florida, mostly due to its role as a vector of tomato yellow leaf curl virus. Affected plants yield little or no fruit when infected young. For this trial, two sets of three beds 420 ft in length were prepared on 15 Aug at the Southwest Florida Research and Education Center in Immokalee, FL. Dry fertilizer (10-2-10 NPK) was incorporated at a rate of 1,000 lb/acre, beds were fumigated with PicClor 60 EC at 240 lbs/acre, and each bed received two drip tapes with 8-inch emitter spacing and was covered with black polyethylene film mulch. Seedlings of ‘Soraya’ obtained from a commercial greenhouse were transplanted 18 inches apart on 6 Sep. Fertilizer was injected during the course of the growing season as liquid 7-2-7 through the drip, and Actigard (0.33–0.50 oz/acre), Koicide (1.5 lbs/acre), and Manzate Pro Stick (1.5 lbs) were applied as needed for suppression of fungal and bacterial disease. Xentari DF at 1.5 lbs was applied on 11, 17, 24, and 31 Oct and 18 Nov for control of lepidopteran pests.

The center row in each three-bed section was left untreated to serve as a buffer and refuge for pests. The four remaining rows were used to accommodate 12 treatments in an RCB design with four replicates each divided into plots consisting of 20 plants each with four plants left between plots as buffers. Soil drenches of Admire Pro and Verimark were made on 11 Sep by delivering a 100 ml suspension per plant using an EZ-Dose® sprayer operating at a pressure of 45 psi ( Table 1 ). Foliar sprays ( Table 1 ) were applied with a high-clearance sprayer set up for single row operation at 180 psi and 2.3 mph. The sprayer was fitted with two vertical booms equipped with yellow Albuz® hollow cone nozzles, each delivering 10 gpa. Total spray volume increased from 40 to 80 gpa as nozzles were added to accommodate plant growth ( Table 1 ). Whitefly adults were evaluated weekly from 9 Oct to 18 Nov on five leaflets from one mid-canopy level true leaf taken from five plants per subplot. Eight 0.5-inch ² leaf discs were cut from each of three leaflets of one terminal seventh node trifoliate sampled on 9, 16, 23, and 30 Oct and 6 and 18 Nov from five plants per plot, and immature stages were counted under a stereoscopic microscope. Fruit of marketable size were harvested from six plants in each plot on 3 and 19 Dec and culled for defects due to insect damage, uneven ripening, bacterial spot, and surface deformities such as shoulder cracking and zippering. Number, size, and weight of marketable fruit were recorded. Data were subjected to ANOVA and means separated using LSD ( P  = 0.05).

All treatment programs provided a significant decrease in the number of whitefly adults observed on all sample dates when compared with the check ( Table 2 ). No significant difference was observed between the Admire or Verimark treatments, the Venom and Exirel programs, or 32 oz of Portal compared with 21 oz of Torac on any sample date.

All treatment programs except for the GF2860 at 3.75 oz on 16 Oct provided a significant decrease in the number of whitefly nymphs observed on all sample dates when compared with the check ( Table 3 ). No significant difference was observed between the Admire or Verimark treatments nor Portal and Torac on any sample date. The Venom and Exirel programs were only significantly different on one sample date with the Exeril having significantly fewer nymphs on 23 Oct. The 5.25 oz rate of GF2860 had significantly fewer nymphs than the 3.75 oz rate on 9, 16, and 23 Oct and 6 Nov.

No significant differences in yield were observed; the average over all treatments was 146.3 ± 10.5 fruit and 62.2 ± 4.1 lbs per six-plant plot.

No phytotoxicity was observed for any treatment.

Author notes