Economic damage levels and treatment thresholds for leafminer insects in Solanum tuberosum crops

Abstract

Integrated Pest Management (IPM) can only result in reduced insecticide use when treatments are applied when infestations reach economic thresholds (ET) determined from economic injury levels (EIL). The objective of this study was to determine the EIL and ET for Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) and Liriomyza huidobrensis (Burgess) (Diptera: Agromyzidae) in 8 and 11 fields of the potato cultivar 'Ágata', respectively. The EILs were calculated based on control costs, production values, control efficacy and injuries of each insect and the ETs were calculated by subtracting 20% from the EIL value, given that control measures must be undertaken before the pest populations reach the former level. The EIL for L. huidobrensis at 50 and 70 days after planting (DAP) ranged from 0.07 to 0.24 and from 0.09 to 0.32 mines per plant, respectively, and those of P. operculella at 50 DAP ranged from 0.07 to 0.24 mines per plant. The ET for L. huidobrensis at 50 and 70 DAP were 0.05–0.19 mines per plant, respectively, and those of P. operculella, 0.05 to 0.19 mines per plant at 50 DAP. These results suggest that management of these pests in potato crops should use the ET of 0.07 and 0.05 mines per plant for control decisions regarding L. huidobrensis and P. operculella, respectively.