Pruning Brazilian peppertrees to augment field populations of the biological control agent Pseudophilothrips ichini

Abstract

Brazilian peppertree, Schinus terebinthifolia (Anacardiaceae) is an invasive weed of natural and agricultural areas of California, Florida, Hawaii, and Texas, USA. A thrips, Pseudophilothrips ichini, is being mass produced and released as an approved agent for biological control of this invasive weed. The P. ichini thrips are flush feeders, especially the larvae, that exploit seasonal new plant growth. Adult P. ichini thrips selected pruned, re-flushing Brazilian peppertree plants, and produced 4-fold more F₁ thrips than those that chose unpruned, non-flushing plants. To determine if pruning increased the abundance of foliar flush production, field populations of Brazilian peppertree in the invaded range were pruned every 3 months for 14 months. The pruned Brazilian peppertree plants produced more flush leaves, that continued to be produced for longer periods, compared with seasonal unpruned plants. Following pruning, re-flushed Brazilian peppertree leaves had greater percent moisture (65.0 % vs 60.0 %) and nitrogen (1.6 % vs 1.3 %) compared with non-flushing leaves. The levels of several terpenoid constituents trended higher in the re-flushed leaves compared with the non-flushing leaves including Germacrene D, Caryophyllene, Bicyclogermacrene, and Sabinene. These results suggest that routine pruning of Brazilian pepper plants at field sites can improve plant quality and may increase the production of thrips. This management approach can be implemented at field nurseries for the mass production of agents.