Olfactory responses of western flower thrips (Frankliniella occidentalis) populations to a non-pheromone lure

Abstract

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of horticultural crops worldwide. The search for alternative pest management techniques has resulted in increasing interest in the use of kairomones and other behaviour-modifying chemicals to mitigate the impact of this pest. In this study, we determined whether the origin of populations, feeding history, and/or genotype influence the response of WFT to the thrips kairomone lure methyl isonicotinate (MI) in a Y-tube olfactometer study. Four New Zealand thrips populations were tested: (1) from a commercial glasshouse capsicum crop, (2) from a long-established laboratory colony (>222 generations) kept on chrysanthemums, (3) from a laboratory colony (6–9 generations) kept on French dwarf beans, and (4) thought to be a separate cryptic non-pest species from outdoor yellow tree lupins, Lupinus arboreus Sims (Fabaceae). In the laboratory tests, significantly more WFT from all four populations chose the MI-laden arm of a Y-tube olfactometer when it contained 1 μl methyl isonicotinate (61.3–73.2%) compared with the blank no-odour arm. No differences in response to MI were found between the two laboratory and the one glasshouse WFT populations. Both laboratory populations and the greenhouse population belonged to the ‘glasshouse pest’ genotype of WFT. However, the cryptic non-pest WFT genotype responded more strongly to MI than any of the other populations, although the response was only significantly stronger than that of the long-established laboratory population. Significant differences were also found among populations in the average time taken for thrips to make a choice to enter either arm of the Y-tube olfactometer, with the cryptic non-pest lupin genotype taking the shortest time, followed by thrips from the capsicum glasshouse. The results are discussed with respect to the variability in olfactory perception and olfactory behaviour within a species and the relevance to the use of such a kairomone lure in pest management programmes.