Dietary yeast affects preference and performance in Drosophila suzukii.

Yeasts play an important role in nutrition physiology and host attraction of many Drosophila species, and associations with various yeast species are documented for several drosophilid flies. The pest Drosophila suzukii (Matsumura) has a predominant association with the yeast Hanseniaspora uvarum. However, research has not been conducted on the nutritional physiology of the yeasts associated with D. suzukii (spotted wing drosophila). Therefore, in this study, we determined whether dietary yeast was nutritionally relevant and whether yeast species closely associated with D. suzukii positively affected life-history traits. Our results confirm a crucial role of dietary yeast in the larval development and survival of D. suzukii. Furthermore, we found specific effects of the closely associated yeast species H. uvarum and Candida sp. on larval survival. Observations of the egg-laying behaviour of D. suzukii on cherry fruits artificially colonised with different yeast species revealed that the number of eggs laid increased on fruits colonised with Candida sp. and Saccharomyces cerevisiae.

Continuous exposure to the deterrents cis-jasmone and methyl jasmonate does not alter the behavioural responses of Frankliniella occidentalis.

Behavioural responses of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), a generalist, cell sap-feeding insect species with piercing-sucking mouthparts, after continuous exposure to two deterrent secondary plant compounds are investigated. We compared in choice assays on bean leaf discs, the settling, feeding, and oviposition preferences of F. occidentalis females that had no experience with the two fatty acid derivatives methyl jasmonate and cis-jasmone before testing (naïve thrips) vs. females that had been exposed to the deterrent compounds before testing (experienced thrips). The thrips were exposed to the deterrents at low or high concentrations for varied time periods and subsequently tested on bean leaf discs treated with the respective deterrent at either a low or a high concentration. Frankliniella occidentalis females avoided settling on the deterrent-treated bean leaf discs for an observation period of 6 h, independent of their previous experience. Our results demonstrate that feeding and oviposition deterrence of the jasmonates to the thrips were not altered by continuous exposure of the thrips to the jasmonates. Habituation was not induced, neither by exposure to the low concentration of the deterrents nor by exposure to the high concentration. These results indicate that the risk of habituation to two volatile deterrent compounds after repeated exposure is not evident in F. occidentalis. This makes the two compounds potential candidates to be integrated in pest management strategies.

Habituation in Frankliniella occidentalis to deterrent plant compounds and their blends.

Feeding and oviposition deterrence of three secondary plant compounds and their 1:1 blends to adult female Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) and the potential for habituation of the thrips to the pure compounds and the 1:1 blends at various concentrations were investigated. In choice assays, we tested dose-dependent feeding and oviposition deterrence of the two fatty acid derivatives methyl jasmonate and cis-jasmone, the phenylpropanoid allylanisole, and their blends when directly applied to bean leaf discs. The concentration required to reduce the feeding damage by 50% relative to the control treatment (FDC50) was lowest for cis-jasmone and highest for allylanisole. The feeding deterrent effect of both jasmonates was increased when blended with allylanisole. Feeding deterrence and oviposition deterrence were strongly correlated. In no-choice assays conducted over four consecutive days, we discovered that dilutions at low concentrations (FDC15) applied to bean leaves resulted in habituation to the deterrents, whereas no habituation occurred at higher concentrations (FDC50). We observed a tendency that the 1:1 blends reduce the probability that thrips habituate to the deterrent compounds. Our results may be useful in the development of integrated crop protection strategies with the implementation of allelochemicals as pest behaviour-modifying agents.