Evaluation of Neoseiulus cucumeris and Amblyseius swirskii (Acari: Phytoseiidae) as biological control agents of chilli thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae) on pepper

The invasive chilli thrips, Scirtothrips dorsalis Hood poses a significant risk to many food and ornamental crops in the Caribbean, Florida and Texas. We evaluated two species of phytoseiid mites as predators of S. dorsalis. In leaf disc assays, gravid females of Neoseiulus cucumeris and Amblyseius swirskii both fed on S. dorsalis at statistically similar rates. Larvae were the preferred prey for both species, consuming on average 2.7/day, compared with 1.1–1.7 adults/day in no choice tests. Adult thrips were rarely consumed in subsequent choice tests when larvae were also present. Mite fecundity was statistically similar for both species feeding on thrips larvae (≈1.3 eggs/day) but significantly less for A. swirskii restricted to a diet of adult thrips (0.5 eggs/day). In greenhouse tests with infested pepper plants, both mite species established and reduced thrips numbers significantly over 28 days following a single release (30 mites/plant). However, A. swirskii was the more effective predator, consistently maintaining thrips below 1 per terminal leaf, compared with up to 36 for N. cucumeris and 70 in control treatments. Similar results were obtained for plants maintained outside in the landscape, where A. swirskii continued to reproduce and control thrips up to 63 days post release.