SUMMARY Aphid infestation and incidence of plants with virus yellows in sugar‐beet crops at Broom's Barn Experimental Station from 1964 to 1968 differed greatly with changes in densities of stand ranging from 8,000 to 68,000 plants per acre (0.4047 ha), and with changes in sowing date. The numbers of Myzus persicae (Sulz.) and of Aphis fabae Scop, infesting beet during June and July, the numbers of virus‐itifected plants per unit area, and the percentages of plants with yellows, usually decreased as the plant population increased but usually increased with delay in sowing from mid‐March to early May.
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G. D. Heathcote (1970) studied this question.
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