Resistance to green peach aphid,Myzus persicae (Sulzer), and potato aphid,Macrosiphum euphorbiae (Thomas), in potato cultivars

Previous research suggests that extant potato cultivars offer little promise as sources of useful aphid resistance. However, few prior studies have critically measured the effects of host cultivar on aphid age-dependent life table statistics or related these measures to field performance. Therefore, a comprehensive field and greenhouse study was undertaken to assess 49 commercial potato cultivars, primarily of North American origin, for resistance to green peach aphid,Myzus persicae (Sulzer), and potato aphid,Macrosiphum euphorbiae (Thomas). Cultivars were found to show considerable differences in resistances to each aphid species, but these resistances were not significantly correlated (R2=0.032). In greenhouse life table studies, the intrinsic rate of increase (rm) of green peach aphid was lowest (0.167) on cv Russet Norkotah and highest (0.350) on cv Red La Soda. Potato aphidrm was lowest (0.122) on cv Aracy and highest (0.229) on cv Irish Cobbler. Among cultivars, year of release, maturity class and yield potential did not significantly influence number of progeny per female per day for either green peach aphid or potato aphid (P=0.987 and 0.954, respectively). In field trials (2004 and 2005), yield potential was significantly correlated with green peach aphid counts, (P=0.006 and <0.0001, respectively). Aphid/predator population models using aK value of 15.2 predicted that following colonization green peach aphid populations would remain stable for 20 days on Russet Norkotah (resistant), whereas on Red La Soda (susceptible) populations would reach over 54,000. With non-persistent foliar insecticides as the only control, population models indicated that three applications would be necessary to maintain green peach aphid below the Minnesota recommended action threshold on Red La Soda for 21 days, while just one application would be needed for green peach aphid on Russet Norkotah. In combination with biological control or insecticide use, this resistance could provide substantial control while reducing the reliance on pesticides.