Manipulating feeding stimulation to protect crops against insect pests?

Enhancing natural mechanisms of plant defense against herbivores is one of the possible strategies to protect cultivated species against insect pests. Host plant feeding stimulation, which results from phagostimulant and phagodeterrent effects of both primary and secondary metabolites, could play a key role in levels of damage caused to crop plants. We tested this hypothesis by comparing the feeding intensity of the pollen beetle Meligethes aeneus on six oilseed rape (Brassica napus) genotypes in a feeding experiment, and by assessing the content of possible phagostimulant and phagodeterrent compounds in tissues targeted by the insect (flower buds). For this purpose, several dozens of primary and secondary metabolites were quantified by a set of chromatographic techniques. Intergenotypic variability was found both in the feeding experiment and in the metabolic profile of plant tissues. Biochemical composition of the perianth was in particular highly correlated with insect damage. Only a few compounds explained this correlation, among which was sucrose, known to be highly phagostimulating. Further testing is needed to validate the suggested impact of the specific compounds we have identified. Nevertheless, our results open the way for a crop protection strategy based on artificial selection of key determinants of insect feeding stimulation.