Establishing Diorhabda carinulata: Impact of Release Disturbances on Pheromone Emission and Influence of Pheromone Lures on Establishment

Authors: Gaffke, Alexander; SING, SHARLENE - Forest Service (FS); DUDLEY, TOM - University Of California; BEAN, DANIEL - Colorado Department Of Agriculture; RUSSAK, JUSTIN - University Of California; MAFRA-NETO, AGENOR - Isca Technologies, Inc; PETERSON, ROBERT - Montana State University; WEAVER, DAVID - Montana State University

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2020
Publication Date: 4/2/2020
Citation: Gaffke, A.M., Sing, S.E., Dudley, T.L., Bean, D.W., Russak, J.A., Mafra-Neto, A., Peterson, R.K., Weaver, D.K. 2020. Establishing Diorhabda carinulata: Impact of Release Disturbances on Pheromone Emission and Influence of Pheromone Lures on Establishment. Journal of Chemical Ecology. 46:378-386. https://doi.org/10.1007/s10886-020-01176-4.
DOI: https://doi.org/10.1007/s10886-020-01176-4

Interpretive Summary: When transporting weed biological control insects to field release locations, the insects are commonly packaged into small paper containers, kept in the dark, and chilled with ice packs. This practice is used to minimize stress to the insects while they are being transported. While packaging insects for transport is generally regarded as beneficial, there may be unintended consequences. A USDA-ARS scientist with the Chemistry Research Unit in Gainesville, FL in collaboration with Montana State University, University of California, Colorado Department of Agriculture, U.S. Forest Service, and ISCA Technologies investigated potential negative impacts of keeping insects at high densities in small, dark, and chilled paper containers. It was discovered that the packaging of the weed biocontrol agent Diorhabda carinulata, also called the northern tamarisk beetle, greatly reduced the beetle’s ability to produce its aggregation pheromone. It is much harder to establish these beetles in the field when they are not producing their pheromone. Subsequent experiments determined that the negative effects of packaging could be negated simply by deploying lures with the pheromone at the field release locations. This will allow land managers to keep the benefits of packaging biocontrol insects, while also correcting for the negative impacts to pheromone production.

Technical Abstract: Before weed biocontrol insects are transported and released in a new area, insects are commonly collected into small paper containers, chilled, and kept under dark conditions. This process can be termed the pre-release protocol. The influence a pre-release protocol can have on establishment success of a gregarious biological control agent was assessed using the northern tamarisk beetle Diorhabda carinulata (Desbrochers) and its exotic, invasive host plant saltcedar (Tamarix spp.). Pre-release protocol impacts on aggregation pheromone production by D. carinulata were characterized under controlled conditions. Additional experiments were undertaken to determine if deployment of species-specific aggregation pheromone lures might enhance the agent’s persistence on new release sites. Adults that experienced the pre-release protocol produced significantly less aggregation pheromone compared to undisturbed adults. Olfactometer bioassays indicated a cohort of adults subjected to the pre-release protocol were less attractive to other adults than a control cohort. Efficacy of aggregation pheromone-based lures for increasing retention of adults on new release sites was evaluated by comparing capture numbers of adult beetles at paired treatment and control release sites 10-14 days after the release of 300, 500, or 1000 individuals. A greater number of adult D. carinulata was captured where the pheromone lures had been deployed. Application of aggregation pheromone when a new release of D. carinulata is planned may allow biological control practitioners to limit negative outcomes due to Allee effects.