The Brazilian peppertree biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) displays a flexible feeding strategy between foliage and reproductive tissues

Authors: Wheeler, Gregory; Palacios, Jean; DAVID, AARON - Archbold Biological Station; Read, Quentin; Nestle, Rebecca

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2023
Publication Date: 1/18/2023
Citation: Wheeler, G.S., Palacios, J.N., David, A., Read, Q.D., Nestle, R.L. 2023. The Brazilian peppertree biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) displays a flexible feeding strategy between foliage and reproductive tissues. Biological Control. 179. Article 105159. https://doi.org/10.1016/j.biocontrol.2023.105159.
DOI: https://doi.org/10.1016/j.biocontrol.2023.105159

Interpretive Summary: Insects have difficulty adjusting to seasonal changes in plant nutrients. A thrips, Pseudophilothrips ichini, is being released for biological control of Brazilian peppertree, an invasive weed of natural and agricultural areas of California, Florida, Hawaii, and Texas. The thrips larvae and adults feed on flushed leaves and stems that are produced during the vegetative season of the host. However, during the reproductive season from September to December in Florida, few flushing leaves are available as resources are shunted to plant reproduction. As field releases were being implemented, thrips were found feeding and damaging immature fruits and flowers of their host. We hypothesized the thrips used volatile compounds produced by reproductive tissues to locate and feed on these tissues. When examined under laboratory choice tests, individual thrips or groups of either 20 adults or larvae, chose flushing leaves over all reproductive tissues, female flowers, male flowers, and immature fruit. However, to simulate seasons when few flushing leaves were available, additional choice tests were conducted where flushing leaves were omitted, and only reproductive tissues and a filter paper control were included. Individual thrips or groups of either 20 adults or larvae selected all reproductive tissues over controls. When presented with a choice between immature and mature fruit, thrips chose immature fruit. Thrips caused significant damage to live female flowers, male flowers, and immature fruit, and thrips survival rates were similar when fed flush leaves, female flowers, or male flowers. The thrips responses could be tied to VOC production, which significantly varied among tissue types. These results suggest P. ichini has a flexible feeding strategy and exploits Brazilian peppertree reproductive tissues when few flushing tips were available. Further they suggest thrips feeding will have direct impacts on Brazilian peppertree reproduction.

Technical Abstract: A thrips, Pseudophilothrips ichini, is being released for biological control of Brazilian peppertree, Schinus terebinthifolia (Anacardiaceae), an invasive weed of natural and agricultural areas of California, Florida, Hawaii, and Texas (USA). The thrips larvae and adults feed on flushed leaves and stems that are produced during the vegetative season of the host. However, during the reproductive season from September to December in Florida, few flushing leaves are available as resources are shunted to plant reproduction. As field releases were being implemented, thrips were found feeding and damaging immature fruits and flowers of their host. We hypothesized the thrips used volatile organic compounds produced by reproductive tissues to locate and feed on these tissues. When examined under laboratory choice tests, individual thrips or groups of either 20 adults or larvae, chose flushing leaves over all reproductive tissues, female flowers, male flowers, and immature fruit. However, to simulate seasons when few flushing leaves were available, additional choice tests were conducted where flushing leaves were omitted, and only reproductive tissues and a filter paper control were included. Individual thrips or groups of either 20 adults or larvae selected all reproductive tissues over controls. When presented with a choice between immature and mature fruit, thrips chose immature fruit. Thrips caused significant damage to live female flowers, male flowers, and immature fruit, and thrips survival rates were similar when fed flush leaves, female flowers, or male flowers. The thrips responses could be tied to VOC production, which significantly varied among tissue types. Volatile blends from flush leaves that include DMNT, Terpinolene, and d-Elemene may attract P. ichini whereas those that repel them include a-Thujene, a-Pinene, ß-Pinene, Camphene, and ß-Phellandrene. These results suggest P. ichini has a flexible feeding strategy and exploits Brazilian peppertree reproductive tissues when few flushing tips were available. Further they suggest thrips feeding will have direct impacts on Brazilian peppertree reproduction.