Spring Movement of Cereal Aphids1 into South Dakota1

Four species of aphids commonly colonize cereal crops in South Dakota: greenbug, Schizaphis graminum (Ron dani); English grain aphid (EGA), Macrosiphum avenae (F.); corn leaf aphid (CLA), Rhopalosiphum maidis (Fitch); and R. padi (L). However, none of these aphids seem capable of overwintering in South Dakota, though anholocyclic populations may persist until mid-December on winter grains. No sexuales of any of these species have been found in samples of populations from the field, and no sexuparae of R. padi have been taken in surveys of aphids on Prunus (Kieckhefer and Gustin 1967). The reappearance of aphids in cereal crops in South Dakota each April or May has been abrupt; initial populations consist exclusively of alate viviparae with no fundatrices or nymphs present. Appearance of alate populations on spouting grains in spring has frequently been so early as to preclude development from eggs because of insufficient time and unfavorable environment for development. Populations of alate viviparae of these species of aphids undoubtedly migrate from the south and become reestablished in South Dakota each spring. Surveys in Texas, Oklahoma, and Kansas in March and April have shown that greenbugs, EGA, and R. padi survive the winter in portions of some or all of these states and that numbers increase early in spring (Cartier 1957, Plant Pest Control Division 1965, Wallin and Loonan 1971). Jensen and Wallin (1965) and Taylor (1965) suggested low-level jets as a vehicle for long-distance transport of aphids into the North Central states and Berry and Taylor (1968) took greenbugs and EGA in collections from an airplane in low-level jet winds (3,000 ft) over Kansas. Arrival of greenbugs and EGA in Iowa has been associated with low-level jet winds (Wallin et al. 1967, Wallin and Loonan 1971). The objective of our study was to determine the dates cereal aphids reach South Dakota in spring and to analyze weather patterns that were associated with this arrival.