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

Low levels of host plant resistance can effectively lessen pest pressure by increasing developmental duration and reducing fecundity, and thus favoring population regulation by natural enemies. Commercial potato production in the Midwest U.S. relies on heavy pesticide use beginning in early season for Colorado potato beetle and then potato leafhopper, which effectively eliminates predators and can flare insecticide-resistant green peach aphid populations. We have recently identified several commonly used potato cultivars which differ significantly in their susceptibility to aphids. We conducted field trials to test if moderate host plant resistance to aphids found in current potato cultivars in combination with biological control or insecticide applications was effective in reducing green peach aphid populations, and by doing so, reduced PVY and PLRV spread. Early generation certified seed potatoes, Russet Norkotah (moderately resistant) and Red La Soda (susceptible), were planted in plots 12 rows wide by 60 ft long. Two rows of PVY and PLRV-infected potatoes were planted 15 ft to either side of each 12 row plot with fallow between, to serve as virus sources. Green peach aphid numbers per plot were quantified weekly by counting the number of aphids per 35 leaves. Predators were sampled weekly by sweep net. Early season green peach aphid populations were significantly reduced on Russet Norkotah. However, by late July, populations were not significantly different between the two cultivars. Predators in insecticide-free plots suppressed green peach aphid cumulative insect days (5800) while carbaryl treated plots reached 34,000. Virus testing is ongoing.