Contribution of cereal aphids to PVY incidence in southern Idaho

Potato Virus Y (PVY) is a concern for potato production in the U.S. Many aphid species transmit PVY in a non-persistent manner. Although green peach aphid (GPA), Myzus persicae, is the most efficient PVY vector, it is less abundant in the potato growing areas of Idaho than are many cereal aphids. A field study was initiated during 2012 with the hypothesis that cereal aphids disperse to nearby fields as cereal crops dry down before harvest. Even though these aphids may transmit PVY less efficiently than GPA, they may contribute to spread of PVY in adjacent potato fields due to their abundance. Aphid fauna in four different commercial potato fields in south-central and south-eastern Idaho were sampled weekly using yellow sticky traps and yellow pan traps. Potato fields were chosen with an adjacent cereal field such that the prevailing wind would facilitate aphid dispersal from cereal fields to potato. In 2012, 40 sticky traps per field were arranged in four rows 15 m apart and 10 traps spaced 15 m within each row. Row placement of sticky traps was as follows: edge of the cereal field, edge of the adjacent potato field, and 15 and 30 m from the edge of the potato field. Additionally, 12 yellow pan traps charged with 35% propylene glycol were arranged in three rows 15 m apart and four traps spaced 30 m within each row; placed on the cereal field edge, the potato field edge, and 15 m inside the potato field. In 2013, all the sticky traps were replaced with pan traps, and all the pan traps with sticky traps. Aphids from the pan traps were identified and placed in 95% ethanol for later virus analysis. The most abundant aphid species from pan trap samples (2012) were: Metopolophium dirhodum, Rhopalosiphum padi, Sipha elegans, Diuraphis noxia, and Sitobion avenae; GPA abundance was relatively low. Aphid abundance peaked in mid to late July in south-central fields and late July to early August in south-eastern fields. Field PVY occurrence, confirmed via DAS-ELISA on potato leaves sampled three times per season (840 samples/date/field), increased in all the locations following mid-summer increases in aphid abundance in both years. Overall aphid abundance and PVY incidence were greater in 2013 than 2012.