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Aphids in Sugar Beet Seed Crops 91 recovered were on the flower stalks, a third were on the old leaves, and the rest were on the mature leaves. In another crop looked at in May 1961 there were twice as many leaves as flowering heads, and about 60 per cent of the aphids in a 100-plant sample were on the flowering heads.In the 1961 work samples of the upper 6 in. of flower spike, together with one middle and one basal leaf, were taken from each of 100 plants along two or three parallel traverses near the centre of each crop. The samples were bulked in polythene bags, and the aphids subsequently washed off, identified, and counted, in the laboratory. Numbers of M. persicae per acre were then estimated by multiplying half the sample count by the average number of flower heads per plant, and by one-hundredth of the plant population, and the other half by a factor based on the estimated number of leaves, and by one-hundredth of the plant population.The results in the table show the wide variation in numbers of M. persicae per acre, and in the percentage of immature alates. In the unsprayed crops the average infestations ('000 per acre) were: Essex, 405; Bedfordshire, 344; and Lincoln, 991. Maximum populations were of the same order in all three areas, and there was appreciable variation in population between crops within relatively circumscribed areas of country. In all three areas it is clear that many of the seed crops were heavily infested with M. persicae.On the farm at Guilden Morden where a crop was surveyed in both years, the infestation in 1961 was only a tenth of that found in 1960, suggesting that the populations recorded in the 1961 survey were not unusualfy high. Populations in the root crop in June/July 1961, were much lower: the maximum recorded was about 375,000 per acre over a large part of one field, and there were less than 50,000 per acre in most of 86 fields looked at in East Anglia at this time.Nearly 3,000 acres of sugar beet and mangold seed crops are grown each year, mostly in East Anglia. If the aphid population, anyhow of Ihe former, averaged 580,000 per acre in June/July, as this work suggests, the annual production of potential virus yellows vectors would be of the order of 1,700 million from seed crop sources. I wish to thank those British Sugar Corporation Fieldmen who assisted in estimating the plant populations of many of the surveyed crops. REEERENCE WATSON, M. A. (1942). Sugar-beet yellows virus. A preliminary account of experiments and observations on its effect in the field. Ann. appl. Biol., 29, A CONTROL measure for the strawberry seed beetle, Harpalus ruftpes Deg., which can be used during fruiting is sometimes required, as attacks are often unexpected. Infestations may recur for several years in the same crop, but not necessarily, and when or where attacks will take place cannot yet be predicted. In June 1955, baits based on meat and bone meal, bran and minced currants, and porridge oats, with 1 per cent BHC (as 50 per cent wettable powder) as

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S U hl M A R Y I n a Iaboratory trial, the previous diet of strawberry-seed beetles influenced their choice of food. T h e beetles generally preferred crushed oats to chicken pellets or bran though they fed more often on ripe strawberries than on the other foods. Baits of crushed oats containing malathion and fenitrothion (each at 0 . 1 5 % active ingredient) and 0.1 yo a.i. of aldrin were eaten when strawberries were also available. I n field trials, beetle mortality ranged from about 30% in small enclosed plots to about 90% in large field plots. Malathion bait remained effective for 5-7 days under wet conditions and 10-12 days under dry. Fenitrothion and aldrin baits were effective for 2-3 weeks. Observations made after using fenitrothion baits suggest that they are not a danger to wild life. In a survey of forty-seven commercial crops linnet damage was found in thirty-five crops and seed-beetle damage in three crops. Linnet damage was most severe in unstrawed maiden crops.