Host Recognition by the Blackmargined Aphid (Homoptera: Aphididae) on Pecan

Leaf discs from pecan, Carya illinoensis (Wangenh.) K. Koch, pea, Pisum sativum L., peach, Prunus persica (L.) Batsch, and fig, Fiscus benjamina L. were presented to nymph and adult blackmargined aphids, Monellia caryella (Fitch) in no-choice and choice bioassays. Nymph longevity and developmental rates, and adult longevity and reproductive rates were significantly greater when aphids were placed on pecan than on pea, peach or fig. In no-choice bioassays, both nymph and adult aphids preferred to settle-on pecan, while they preferred to wander- or settle-off of pea, peach and fig. In choice bioassays, both nymph and adult aphids preferred to settle-on pecan than to settle-on pea, peach and fig. Analysis of pecan, pea, peach and fig leaf cuticular chemistry showed that n-alkane distribution patterns and the major cuticular components, specifically triterpenes and their oxidation products, differed among the four plant species. This study provides the first evidence within the pecan/aphid interactive system which suggests that the distinct foliar cuticular chemistry of pecan may have an influence on the host recognition behavior of M. caryella.