Aphid attraction by aroma: The chemical ecology of crapemyrtle (Lagerstroemia spp.) and crapemyrtle aphid (Tinocallis kahawaluokalani)

Crapemyrtle aphid (Tinocallis kahawaluokalani) are a major economical pest to the crapemyrtle (Lagerstroemia spp.) industry. The damage left by CMA on the crapemyrtle has led to an increased concern in specialty crop pest management. Volatile organic compounds (VOCs) of seven crapemyrtle cultivars were extracted and offered to alate and non-winged adult aphids to understand preferences of the respective aphids. The behavioral analyses were run by placing 1 ul drop of the extracted VOCs on a filter paper disc. Only two discs containing extractions from two cultivars were offered at a time and placed, 3 cm apart. A CMA was placed in the middle of the two discs at 1.5 cm. The behavioral assay was done in a full factorial design with 10 female and 10 male replicates of both alates and wingless adults. We then analyzed the chemical composition of the five cultivars using gas chromatography mass spectrophotometry to identify the principal VOCs. We have found D-limonene and benzeneacetylaldehyde to be among the most differential in identifying CMA preference, with several other possible monoterpene identifiers. CMA were attracted to VOCs of cultivars with more benzeneacetylaldehyde and were less interested in VOCs of cultivars with D-limonene. We then analyzed the nutritional composition (phenolics and tannins) of the five cultivars and found that there were correlations between principal VOCs and nutritional constituents. Our findings offer possible mechanisms for determining crapemyrtle susceptibility to CMA, with possible implications for cultivating new varieties.