Temporal optimisation of abamectin use on Schinus terebinthifolia used to rear the biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae)

Abstract

ABSTRACT Mass rearing herbivorous insects used as biological control agents requires a steady supply of optimal host plant material. This often necessitates the use of pesticides to minimise infestations and damage from generalist herbivores. Knowing the efficacy persistence of the pesticide is critical to prevent non-target effects on reared agent populations. We determined the amount of time for an abamectin foliar spray to degrade such that there were minimal impacts on the mass rearing of Pseudophilothrips ichini (Hood), a biological control agent for Brazilian peppertree (Schinus terebinthifolia Raddi) in Florida. Abamectin was applied to plants at the label concentration (0.31 ml/L) for controlling mites. Groups of three plants were brought into our quarantine facility 1, 3, 7, 10, and 14 d after application and were then each infested with 40 founding adult thrips. Founding adult survival was not impacted by the delay, i.e. interval between application and thrips infestation, with at least 75% recovered alive regardless of the delay. However, delaying infestation had a significant effect on the number of offspring produced, with, on average, only 50 produced when waiting 1 d, between 250 and 364 for the intermediate wait times, and 688 produced when waiting 14 d. Waiting 14 d after treatment before infesting new plants would achieve optimal colony yields but waiting as little as 7 d may still be a reasonable balance between timely production operations and colony yields. Those developing insect mass rearing programmes should consider all variables specific to their procedures that may impact pesticide persistence.