The effects of soil type and moisture on the survival of Pseudophilothrips ichini (Hood)

ABSTRACT Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae) is a classical biological control agent used to control Brazilian peppertree, Schinus terebinthifolia Raddi, in Florida, USA. Brazilian peppertree is an invasive weed that threatens natural and agricultural environments, including sensitive habitats such as mangrove swamps. As P. ichini generally pupates in the soil and its host plant can occur in wet areas, it is important to investigate the effects of soil type, moisture, salinity, and immersion survival time on adult emergence. Five moisture contents (0%, 25%, 50%, 75%, and 100%) were used in factorial combination with three soil types (fine sand, sand, and muck) using fresh or brackish water. To simulate sporadic flooding, we also assessed larval and pupal survival after being immersed in fresh and brackish water for 0, 1, 2, 3, 5, 8, 16, and 32 h. A generalised mixed model logistic regression was used to analyse the data in both experiments. As soil moisture content increased, the proportion of P. ichini emerging as adults decreased across all soil types and water types. The survival of larvae and pupae immersed in either brackish or fresh water declined over time, with no survival at 32 h. There was a significant difference between water types for the survival of pupae and adult emergence of pupae and larvae, with higher survival in brackish water. The outcome of this study contributes to our understanding of P. ichini ecology and the estimation of thrips establishment success in a variety of habitats infested by Brazilian peppertree.