Chili thrips have become a significant pest in South Alabama and rival red headed flea beetle for the number one pest in Alabama container nurseries. Heading the pleads of growers, Auburn University researchers Dr. David Held and Dr. Jeremy Pickens put into action a plan to improve upon the current Chili thrips management strategies. In 2017, they were awarded a $25,000 Specialty Crop Block Grant to fund the development of these strategies. One of the issues they plan to tackle is making applications of insecticides more effective through easier monitoring techniques and understanding how to get the most out of a spray application. University of Florida researchers have shown that Chili thrips in ornamental nurseries were more active in flight between 10 A.M. and 4 P.M. Dr. Held thought this may indicate that the effectiveness of an insecticide applications for Chili thrips could be influenced by the time of day. A trial was conducted at a collaborating nursery that included 4 treatments spread out over 1,500 plants. To determine an optimum time range to spray, treatments included: a non-treated control, a morning (before 10 A.M.), midday, and evening (at 4 P.M.) spray. The insecticide used in the trial was spinosad (Entrust® SC, DOW AgroScience). In order to test the efficacy of these treatments, cuttings were taken off individual plants and submerged in alcohol to collect thrips both before and after treatment.
As expected, timing did play an important role in efficacy. The majority of thrips collected were immature (89-90%). That makes sense as many of the adults fly off during collection. Morning treatment reduced total thrips population from pretreatment counts by 83% compared to the water treated control with 50% reduction. No differences were observed between midday (47% reduction) and evening (60% reduction) applications. Applying pesticides at midday had a lower reduction in thrips than the non-treated control. Only one insecticide was tested, but these results suggest that spraying in the morning whenever possible can provide more effective control than sprays later in the day. Morning sprays are not the most convenient in working around REI's but the improvement in efficacy would likely make up for any added hassle.
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Figure 1. Overview of the trial. Figure
sample of how Chili thrips were counted under the microscope.
Jeremy Pickens, Extension Horticullturist, Department of Horticullture, Auburn University
David Held, Department of Horticulture, Auburn University
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