Delayed insecticide application is useful in managing Scirtothrips dorsalis (Thysanoptera: Thripidae) in Florida strawberry

Scirtothrips dorsalis Hood is an invasive and early season pest of strawberry in Florida which causes foliage injury leading to stunted plant growth and yield loss. Spinetoram, an effective insecticide of thrips pests with limited applications per season, are applied repeatedly during early season to manage S. dorsalis, providing fewer options for thrips pests later in the season. New strategies are needed to effectively manage S. dorsalis such as using fewer overall applications of insecticides by delaying the first application because young strawberry plants can compensate for slight feeding injury without compromising strawberry yield. A study conducted in strawberry field plots in Balm, Florida during 2018 and 2019, showed that delaying spinetoram application @740 ml ha^-1, for 14 days after an initial infestation of zero, five, 10, or 20 S. dorsalis per plant did not reduce the plant vigor and yield, compared to when spinetoram was applied four days after the infestation. The compensation and yield were determined by measuring the plant biomass and canopy area, and marketable and injured fruit yield, respectively. Plant injury did not exceed levels from which plants could not recover at a density between one to two S. dorsalis per trifoliate (nominal action threshold) which was associated with a 10-30% feeding injury on leaves. Delaying the first insecticide application will reduce the overall input costs of strawberry production and make Florida strawberry growers profitable in the competitive market with Mexican and South Californian strawberries and still provide protection against S. dorsalis.