Evaluating synthetic plant volatiles to augment lady beetle population for the conservation biocontrol of Acanthococcus lagerstroemia (Hemiptera: Eriococcidae)

Lady beetles are voracious predators of insect pests such as aphids and scale insects. Recently, they have been identified as a potential biocontrol agent for the crape myrtle bark scale (CMBS) - an exotic scale insect that feeds on the sap of crape myrtle (CM) trees. Lady beetles employ visual and semiochemical cues in locating their prey. Several studies have reported lady beetle attraction to herbivore-induced plant volatiles (HIPV’s) such as methyl salicylate and limonene. Augmenting populations of lady beetles and exploiting their service to manage CMBS population is therefore desired. In our study, we investigated synthetic HIPV’s for their potential in attracting ladybeetles. We sampled and recorded the abundance of lady beetles on HIPV-treated CMBS infested trees compared with CMBS infested trees with no HIPV (control trees) at 1 week, 1 month, and 2 months after treatment. Treatments included methyl salicylate (M), limonene (L), and a combination of methyl salicylate and limonene (M+L). From our results, no treatment significantly increased the abundance of lady beetles on CMBS infested trees relative to control. In fact, significantly higher numbers of lady beetles were recorded on control trees. We suggest that our lures may have interfered with the right blend of volatiles emitted by the infested trees to recruit lady beetles. Our study highlights the need for a better investigation and evaluation of the right blend of HIPV’s required to attract lady beetles and achieve effective biocontrol on CMBS infested trees in the landscape.