Monitor/Pyrethroid Combinations for Management of the Sweetpotato Whitefly on Fresh Market Tomatoes in West-Central Florida, Spring, 1990

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Abstract On 20 Mar, transplants were set 18 inches apart on raised beds of EauGallie fine sand covered with black polyethylene mulch. Plots consisted of three, 20-ft-long rows on 5 ft centers and were irrigated by a seepage subirrigation system. Treatments were replicated 4 times in a randomized complete block design. Pyrethroid and Monitor/Pyrethroid treatments were alternated weekly with Thiodan 3 EC at 0.94 lb (AI)/acre. Beginning with Thiodan, treatments were applied with a high clearance, self-propelled sprayer on 20, 26 Apr, 4, 11, 16, 23, 30 May, 5 - 6, and 18 Jun. The sprayer was operated at 200 psi and 3.4 mph and used hollow cone nozzles fitted with D-3 disks and #25 cores. The number of nozzles per row were increased from 4 to 8 to increase gallonage as the plants grew. Thus, 50 gal/acre were applied the first three sprays, 75 gal/acre the fourth spray and 100 gal/acre for the remaining sprays. The terminal leaflet was collected from the 7th or 8th leaf (counting from the top) of each of ten stems from the middle row of each plot on 16 May, 11, and 27 Jun. The numbers of eggs, crawlers, sessile nymphs, and pupae of the sweetpotato whitefly were counted. All fruit of marketable size were harvested on 14 and 27 Jun and the fruit were counted and weighed. Samples of 50 fruit from each plot were held at room temperature in paper bags. As the fruit ripened, each was rated 1 to 4 for increasing severity of external symptoms of irregular ripening (IRR). This disorder is associated with high populations of the sweetpotato whitefly and is characterized by incomplete ripening of longitudinal sections of fruit. The percent of unmarketable fruit was calculated in which fruit rated 3 or 4 were considered unmarketable. Whitefly data were transformed to the square root of the number plus 0.5 prior to analyses and percentage data were transformed to arcsine of the square root of the proportion prior to analyses. All data are presented in the original scale.