Abundance of Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) and other thrips in commercial snap bean fields in the Homestead Agricultural Area (HAA)

Abstract

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae), an economically important pest of leguminous crops, is native to the Asian tropics. M. usitatus was recorded for the first time in 2020 in southern Florida (USA), where it has significantly impacted production of snap bean (Phaseolus vulgaris L.; Fabaceae). Surveys were conducted in five fields between October 2021 and April 2022 to determine the abundance of M. usitatus in relation to other thrips species. From crop establishment until harvest, whole plant samples were collected from each field at weekly intervals. During each phenological stage (vegetative, flowering, fruiting), plant parts present at the time of sampling (foliage, flowers, pods) were partitioned and processed separately to determine the relative abundance of thrips species as affected by phenological stages and plant parts. To analyze the effect of plant part, only the fruiting stage, when all plant parts were present, was used. Thrips palmi Karny, the primary pest of snap bean prior to the establishment of M. usitatus, was the most abundant thrips species. M. usitatus was the second most abundant thrips species, and mostly found in flowers during the fruiting stage. Frankliniella occidentalis (Pergande), not previously reported as a pest of snap bean in south Florida, was the third most abundant, followed by Frankliniella bispinosa Morgan and Frankliniella insularis (Franklin). Overall abundance of thrips species was the lowest during the vegetative stage when only foliage was present and highest during the fruiting stage when all plant parts were present and most abundant in flowers. Sex ratios were female-biased for each species. Contrary to our hypothesis, the study did not produce evidence that M. usitatus establishes earlier in commercial snap bean fields or reaches higher levels of abundance than T. palmi.