Limonene for the management of Crape Myrtle Bark Scale (Acanthococcus lagerstroemiae)

Abstract

Crape myrtle bark scale (CMBS, Acanthococcus lagerstroemiae) is an invasive pest of crape myrtles first introduced to the United States less than 20 years ago. CMBS reduce the aesthetic value of these ornamental trees which presents a risk to the crape myrtle industry through additional management and replacement costs. The current recommendation for management is soil applied systemic neonicotinoids which translocate into the pollen of crape myrtle trees at levels that are toxic to pollinators and other beneficial insects. Limonene is a citrus monoterpene previously studied for its pesticidal activity against numerous arthropod pests, fungi, and bacteria. These studies show that weekly limonene at 1% is effective at controlling CMBS with limited toxicity to lady beetle natural enemies. A LC50 for limonene was established at 1.41%. The combination of limonene and yellow panels was not effective for the recruitment of lady beetle natural enemies, but limonene alone (at 1%) was not toxic to lady beetles in the crape myrtle trees. This research provides a new method of chemical control better suited to an environmentally integrated approach for the management of CMBS.