Optimizing mass rearing techniques for Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae), a biological control agent for Brazilian peppertree in Florida

Field release of Pseudophilothrips ichini in Florida for the biological control of the highly invasive Brazilian peppertree, Schinus terebinthifolia, was approved by APHIS in May 2019. Since 2007, P. ichini colonies used for host specificity research were successfully maintained in small cylinders to fit in limited quarantine space. The next phase in the classical biological control process involves the mass production and distribution of the agent. To meet the demand for these beneficial insects, we developed methods that progressed from small colonies to large-scale production. Acrylic cylinders atop 45 cm tall plants in 3.8 L pots were used in quarantine laboratories where 30-50 adult thrips were introduced resulting in an average of 366 F₁ thrips per cylinder per generation. Given the work involved in maintaining many cylinders, we transitioned to fewer, larger enclosures. Screen cages (1.8 x 1.8 x 1.8 m) were set up outdoors in a covered screen house each with six Brazilian peppertrees in 11.4 L pots and 1,500 adult thrips per cage. Yields averaged 15,517 F₁ thrips per cage per generation. Although multiplication rates were comparable to those in cylinders, screen cages produced 42 times more thrips per enclosure with fewer personnel hours. Emerging adults aggregated onto fresh, 1 L “trap” plants and aggregations were taken to the lab for field release preparation. Large screen cages were most efficient, reliably providing tens of thousands of thrips needed each week to meet the demand for field releases as part of the USDA/IPRL technology transfer program.