Western Flower Thrips In Cotton: Pest or a Beneficial Natural Enemy?

Omnivory by Western Flower Thrips (WFT) involves consumption of various types of plant material in addition to eggs of spider mites (Tetranychus urticae).  Thus, depending on the amount of plant vs. prey material consumed, WFT could be considered a pest or a beneficial natural enemy.  Additionally, previously published studies suggest a compensatory interaction between plant and prey consumption where a decrease in plant feeding is accompanied by an increase in prey consumption and visa versa.  We investigated omnivory by WFT on each of six varieties of cotton, (Gossypium hirsutum and G. barbadense), with mite-eggs present.  Plant consumption by adult female thrips was nearly twice that of immatures whereas the consumption of mite-eggs was similar between life-history stages.  This indicates both life-history stages are equally beneficial but adult female thrips cause a greater risk to cotton growers than immatures.  Plants feeding by immature and adult female thrips were significantly and similarly influenced by genotype, yet there was no significant inverse relationship between prey and plant consumption. Interestingly, prey consumption by immature thrips was also significantly influenced by genotype.  Our results are important for devising IPM programs to manage WFT in two ways: 1) adult female thrips should be targeted over immatures, 2) variation in plant feeding among varieties and having been similarly expressed on both life-history stages supports the potential for plant breeding programs to introgress resistance into elite cultivars.