D3209: Pre- and post-digestive cues of the crapemyrtle aphid (Tinocallis kahawaluokalani) relating to anti-nutritive constituents

Herbivorous insects and mites often use pre-digestive cues such as volatile organic compounds in combination with post-digestive cues such as nutritive (sugar and protein) and anti-nutritive (polyphenols and tannins) compounds to make foraging decisions. Plant expression of pre-digestive and post-digestive cues can vary across and within species and cultivars. We wanted to 1) understand pre- digestive cues expressed by various cultivars of crapemyrtle and evaluate the effects the compounds have on the host-selection and 2) understand the developmental behaviors of post-digestive cues of crapemyrtle aphids (CMA: Tinocallis kahawaluokalani). Volatiles and nutritive/anti-nutritive constituents were collected from each cultivar. To evaluate pre-digestive cues, CMA were placed in an olfactometer y-maze and offered combinations of cultivar volatiles in a full-factorial design. To understand consequences of post-digestive cues, CMA were grown on different cultivars of crapemyrtle. Population densities were monitored on each plant, recording the number of aphids in each stage, and the total population density on each cultivar daily. After 1 month, CMA were collected, dried, and evaluated for anti-nutritive compounds that were bioaccumulated. There were strong correlations between specific volatile cues and the associated post-digestive constituents. Specific volatiles may play a role in alate pre-digestive cues and their correlation with post-digestive constituents. CMA grew faster and had greater population densities on cultivars that expressed greater sugar and nitrogen concentrations. More research is needed to understand the relationship between anti-nutritive constituents in plant tissues and their accumulation in CMA.