Aphid (Hemiptera: Aphididae) populations and the incidence of virus yellows on insecticide-free sugarbeet in south-eastern England in 1978-81

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Abstract
The populations of the most common aphid species on sugarbeet, and their principal predators, were monitored on insecticide-free study areas of the crop in south-eastern England in 1978–81. The peak populations of Myzus persicae (Sulzer) varied considerably in size from year to year and were related to the severity of the previous winter. Those of Aphis fabae fabae Scopoli, which occurred slightly later in the season, also varied greatly in size but were not strongly linked to winter temperatures. The sizes of the peak populations of Macrosiphum euphorbiae (Thomas) were similar each year. The annual variation in the level of infection by virus yellows reflected the peak populations of Myzus persicae and not those of the other aphid species. Coccinellids first appeared in the sugarbeet each year in mid-late June, as the aphid populations were developing, and their peak populations did not vary greatly from year to year. Syrphid larvae appeared later in the season than coccinellids, and their numbers seemed closely linked to those of A. f. fabae. Anystid mites were observed on most count dates in all years. The implications of the findings of the study for control of aphids and virus yellows are discussed.