Insecticidal action of five allyl esters on eggs and larvae of three tortricid fruit pests: Laboratory tests

Several substances containing the allyl ester group in their structure have shown insecticidal properties. In the search for new insecticide molecules, five allyl esters from aromatic and heterocyclic acids (allyl 1-naphthoate, allyl 2-thiophenecarboxylate, allyl 2-furoate, allyl salicylate, and allyl cinnamate) were synthesized. Their toxicity on Cydia pomonella (L.), Grapholita molesta (Busck) and Lobesia botrana (Denis et Schiffermuller) (Lepidoptera Tortricidae) eggs of different age, by topical application, and on neonate larvae, by exposition to topically treated diet, has been assessed. When applied to less than 24-h old eggs, the most active compounds on the three species were allyl cinnamate, allyl 1-naphtoate, and allyl 2-thiophenecarboxylate (LC₅₀ range: 2.4 - 7.9 mg/mL), while allyl salicylate was the least active one (LC₅₀ range: 13.4 - 17.5 mg/mL). The most active ones killed the eggs in the earlier phases of development (white egg and red ring). In contrast to the action of allyl esters of fatty acids, none of the tested allyl esters affected the duration of the development of treated eggs. The mortality and the duration of development of surviving larvae were not affected. Allyl cinnamate was also the most active compound on neonate larvae (LC₅₀ range: 3.1 - 6.1 mg/mL) of three species. As conclusion, allyl cinnamate is suggested to be the best insecticide candidate of this series of compounds.