The population dynamics of the thrips species assemblage in French bean, lettuce, tomato and zucchini agro-ecosystems

Management of insect pests is one of the most important aspects of crop agronomy in the agricultural industry. This has become increasingly sophisticated as new approaches based on a greater understanding of individual pests and their biology are developed and used in Integrated Pest Management (IPM) programs to target pest populations at critical development periods to reduce potential injury to the crop. Our understanding of Thysanoptera biology and ecology in vegetables is restricted to a few key pest species, and very little attention has been given to other thrips species that dwell within these systems. This has produced a large gap in our understanding of the population dynamics of pest and non-pest species in vegetable agro-ecosystems. This deficit restricts the capacity to develop IPM strategies for the important pest thrips species. To contribute to our understanding of the Thysanoptera and the relationship of this insect order with the vegetable agro-ecosystem, this study determined the thrips species assemblage in French bean (Phaseolus vulgaris, var. ‘Labrador’), lettuce (Lactucta sativa, var. ‘Rador’), tomato (Solanum lycopersicum, indeterminate trial variety courtesy of Syngenta©) and zucchini (Cucurbita pepo, var. ‘Amanda’) agro-ecosystems, and further investigated: the temporal distribution of thrips populations on a crop phenological scale; the variability of the spatial distribution of thrips clusters; the effect of weather on thrips relative abundance; and the reproductive host association between thrips and the four crops. Investigations undertaken in this three-year study (27th December 2011 to 3rd June 2012; 24th December 2012 to 4th June 2013; 27th December 2013 to 17th June 2014) determined that four thrips species assemblages exist in each of the four agro-ecosystems. These comprised of key thrips species including Frankliniella occidentalis (Pergande) and Megalurothrips usitatus (Bagnall) in French bean, Desmothrips tenuicornis (Bagnall), F. occidentalis and F. schultzei (Trybom) in lettuce, F. occidentalis, F. schultzei and Pseudanaphothrips achaetus (Bagnall) in tomato and F. occidentalis, F. schultzei and Tenothrips frici (Uzel) in zucchini. French bean and zucchini supported the greatest diversity and abundance of thrips, whilst tomato supported the least within the assemblage. This study represents the first published description of thrips species assemblages in these important vegetable crops.