Insecticidal and repellent action of allyl esters against Acyrthosiphon pisum (Hemiptera: Aphididae) and Tribolium castaneum (Coleoptera: Tenebrionidae)

In this project, three allyl esters from middle-chain fatty acids (allyl octanoate, allyl heptanoate and allyl hexanoate) and two from aromatic acids (allyl cinnamate and allyl 2-furoate) were investigated against two differential pests. Lethal and sublethal repellent effects by topical and ingestion exposure were tested against the pea aphid Acyrthosiphon pisum (Harris) and the red flour beetle Tribolium castaneum (Herbst) as these represent two insect pest orders of Hemiptera and Coleoptera each with a specific feeding behavior using piercing-sucking and biting-chewing mouthparts, respectively.Significant mortalities against aphid nymphs were produced when fed via diet containing allyl cinnamate, allyl 2-furoate and allyl heptanoate at 0.1mgmL^-1, and in dose-response tests allyl cinnamate was the most active with an LC₅₀ of 0.03 (0.02-0.05) mgmL^-1. Although topical application on aphids was only effective at doses of 0.1mg aphid^-1 for allyl cinnamte, beetles of T. castaneum adults were sensitive to all allyl esters assessed with LC₅₀'s ranging between 0.1 and 0.2mg insect^-1.In binary choice bioassays, none of the allyl esters produced repellent effects on A. pisum aphids, neither by ingestion (0.1mgmL^-1 in the diet) nor by contact (100μgcm^-2 on filter paper). In contrast, all allyl esters, except allyl hexanoate, showed high to moderate repellence effects on T. castaneum beetles at 10μgcm^-2. Interestingly, the repellent activity of allyl cinnamate was equal to the commercial insect repellent N,N-diethyl-m-toluamide (DEET). The data obtained suggest a possible role of allyl esters in insect pest control.