Persistence of nanoemulsions of bioactive volatiles and their impact on aphid feeding behaviour

Myzus persicae and Aphis gossypii (Hemiptera: Aphididae) are two of the most significant aphid species acting as vectors for plant viruses in vegetable crops worldwide. This work provides new knowledge relating the persistence (including population growth and survival) and impact on aphid probing and feeding behaviour of plant essential oil-derived products. Modifications in M. persicae behaviour (EPG results) were noted in plants treated with 0.2% nanoemulsions of distilled lemon oil: (1) the non-probing activity lasted longer, (2) both non-phloematic probing and phloem ingestion activities of aphids were shorter, and (3) xylem ingestion activity and the time taken to achieve sustained phloem ingestion appear to be longer. Finally, a slight increase was also observed in the mean duration of the non-probing activity of M. persicae on plants treated with 0.2% nanoemulsions of farnesol. When pepper plants were sprayed with a 0.2% nanoemulsion of farnesol with Tween 80^® (1:2), the population growth of M. persicae colonies on treated plants was slower (40 aphids/plant) than on controls (60 aphids/plant) up to the day seven. The slope of the aphid population growth line corresponding to the formulated mixture of bioactive volatiles was lower (2.26 b) and statistically significant in comparison with the control (7.09 a), probably due to a controlled-release effect up to day 14. No systemic effects were obtained for the bioactive volatiles tested.