Thrips that play dirty: Evaluating biocontrol options for Hercinothrips

Abstract: Hercinothrips femoralis and H. bicinctus are emerging as significant pests of banana in the Canary Islands, due to the limited availability of chemical control options and the demand for residue-free produce. Biological control programs are currently based on preventive releases of Neoseiulus cucumeris sachets, however there is contrasting empirical evidence on their efficacy. Furthermore, predator – prey interactions between Panchaetothripinae and their predators remain poorly studied. To address these gaps, we conducted a series of laboratory and field trials to evaluate preventive and curative biological control strategies using the phytoseiids N. cucumeris and Amblyseius swirskii and other generalist predators. Fruit disc bioassays revealed low predation of both phytoseiids on larvae and eggs of Hercinothrips, compared to other thripids in literature. Nevertheless, whole fruit bioassays with inundative releases of phytoseiids prior to the emergence of H. femoralis larvae, showed much more encouraging results, reducing thrips population by ~ 80 %. Field trials with preventive releases of N. cucumeris and A. swirskii sachets, showed no evidence of control over H. femoralis. In contrast, repeated curative releases of the phytoseiids or Chrysoperla carnea significantly reduced pest levels and fruit damage. In parallel, the naturally occurring predators Franklinothrips megalops and F. vespiformis are being evaluated in laboratory and field settings, to assess their potential and suitability as biocontrol agents in banana. Together, these findings provide new insights
into the biocontrol options against Hercinothrips.