Repellency of essential oils to Frankliniella occidentalis (Thysanoptera: Thripidae) as affected by type of oil and polymer release.

Eight essential oils [0.125-1.0% (vol:vol) in acetone] were separately deposited on leaf disks to evaluate their potential to repel western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), adult females. Two of the best-performing essential oils were incorporated into polymer matrices of methyl cellulose or alginate [0.5 or 1% (wt:vol)] to verify the potential of the polymer to extend repellency of oils over time (24-120 h). Results showed that at a concentration of 0.5%, Thymus vulgaris L. (common thyme) and Satureja montana L. (winter savory) were the most repellent essential oils. For these two treatments, no western flower thrips were counted on treated leaf disks 60 min after the start of the test. T. serpyllum and O. compactum also showed repellency values > or = 90% at this concentration. With both the alginate and methyl cellulose polymers, the incorporation of polymers into treatment solutions containing 0.5% concentrations of S. montana and T. serpyllum resulted in higher repellency compared with treatment solutions lacking these polymers for a minimum of 3 d. For the alginate polymer, differences associated with polymer concentrations were most dramatic. High repellency was maintained for 4 d when a 0.5% concentration of the alginate was used in combination with a 0.5% concentration of S. montana. The use of repellent oils with polymers that extend their repellency may prove useful for both pre- and postharvest applications in flower crops.