Chilli thrips (Scirtothrips dorsalis) has been documented in Florida since 1991. This pest has a history of impacting ornamentals, some vegetables, grapes and berry crops. Most recently, chilli thrips has affected citrus, but only in nurseries and in citrus under protective screens (CUPS).
Feeding damage includes death of young flush (Figure 1), leaf damage on expanded flush that results in curled mature leaves with unknown impacts on photosynthesis (Figure 2) and scarring of fruit (Figure 3). Studies in other cropping systems have documented development time, natural enemies and the impacts of a suite of chemical controls. However, there is little information regarding the interactions of this pest in Florida citrus.
Beginning February 2022, the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) has been documenting the seasonal population patterns and the infestation in space over time within CUPS. In 2022, there was an influx of adult chilli thrips in the month of March, concurrent with heavy flush in CUPS, with a second peak in September. The September peak occurred immediately following a peak in the juvenile population.
In 2023, there was a similar increase in adult chilli thrips capture in the spring. However, with a summer of extreme temperatures, there was no subsequent peak in juveniles or adults. These data suggest that adult chilli thrips migrate into CUPS in the spring, likely attracted to the flush. If conditions are good for development, the pest remains to reproduce on citrus inside the structures.
To better understand these population patterns, in 2023 researchers set a sampling grid to determine how thrips are distributed in space within CUPS. These data are still being analyzed, but patterns are emerging that align with the thrips population patterns. In late March through mid-April 2023, chilli thrips infestation began in the edge trees of CUPS (Figure 4) and spread to the interior of the field by late summer (Figure 5).
These data suggest that infestation and damage may be reduced by monitoring for early-season activity and focusing management on outer rows of trees. Additionally, weeds can serve as reproductive hosts for this pest. Weed management should be part of chilli thrips management plans in CUPS.
Lauren Diepenbrock is an assistant professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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