The activity of a selected extract of <Emphasis Type="Italic">Drimys winteri</Emphasis> bark and polygodial on settling and probing behavior of the lettuce aphid <Emphasis Type="Italic">Nasonovia ribisnigri</Emphasis>

An n-hexane extract and the sesquiterpene polygodial isolated from the bark of Drimys winteri J.R. Forster & G. Forster (Winteraceae) were tested to assess their ability to inhibit settling of the aphid Nasonovia ribisnigri Mosley on lettuce leaves; assessments were made using a choice and no-choice leaf-disk assay. The n-hexane extract and the polygodial both significantly inhibited settling in the choice and no-choice tests, but their application on lettuce leaves did not result in any aphid mortality. Probing behavior of N. ribisnigri on polygodial-treated plants was assessed by means of the electrical penetration graph technique. Polygodial interfered with aphid probing behavior by reducing the total probing time, the number of probes, and the number of intracellular punctures. Aphids did not reach the sieve elements of polygodial-treated plants during the 2-h access period. Both tested compounds have the potential to be used in the development of lettuce aphid control agents to reduce the risk of virus transmission.