Abstract
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.
Highlights
Western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), is one of the most harmful pests on many horticultural and agricultural crops worldwide (Kirk & Terry, 2003)
The feeding and oviposition deterrent effect on F. occidentalis of the pure compounds methyl jasmonate, cis-jasmone, and allylanisole as well as their 1:1 blends methyl jasmonate/cis-jasmone, methyl jasmonate/allylanisole, and cis-jasmone/ allylanisole (Figure 1) applied to leaf discs was dosedependent: increasing concentrations resulted in reduced feeding damage and reduced oviposition rate
The application of cis-jasmone at about 0.66% reduced the feeding damage by 50% on the treated leaf disc compared to the control disc, methyl jasmonate applied at about 0.77% was required to deter thrips feeding by 50%, and allylanisole at about 0.94% reduced feeding damage by 50% (Table 1)
Summary
Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), is one of the most harmful pests on many horticultural and agricultural crops worldwide (Kirk & Terry, 2003). Adults and immature stages both feed on plant tissue by penetrating plant cells and sucking out the cell sap (Childers, 1997). In addition to the direct feeding damage, plants are damaged indirectly because F. occidentalis is a potent vector of plant virus diseases (Wijkamp et al, 1995). Management of F. occidentalis is problematic due to their minute size and their thigmotactic behaviour (Lewis, 1997). Control strategies relying on repeated application of chemical insecticides have resulted in widespread development of resistance in F. occidentalis (e.g., Jensen, 2000).
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