SUMMARY Counts of Aphis fabae Scop, eggs in winter and of the active stages in May on the spindle bush, Euonymus europaeus L., are used to predict the need for chemical control of the black bean aphid on spring‐sown field beans, Vicia faba L. For the purposes of forecasting, most of England south of the Humber is divided into 18 areas for which separate forecasts are made. A level of 5 per cent of plants colonized on the SW. headlands of fields in early to mid‐June is used as an economic threshold above which control measures are justified. From 1970 to 1975, area forecasts of the probability of attack were successful. According to the sampled fields there was considerable annual variation in the size of infestations, ranging from widespread, potentially damaging populations in 1973 and 1974 to very small populations in 1975. There was also considerable variation between areas: for example, in East Anglia and the East Midlands treatment was justified only in 1973 and 1974, whereas in Hampshire and Worcestershire/Herefordshire treatment was justified in all years except 1975. It was estimated that, from 1970 to 1975, control based on forecasting would have led to a gain of £11·4/ha over no treatment, and £3·8/ha over correctly timed routine preventive treatment applied annually irrespective of the aphid situation.

On behalf of the 'Closed' Conference of Advisory Entomologists) SUMMARY The control of leatherjackets in grassland by insecticides which were potential alternatives to DDT was tested in four series of field trials between 1968/69 and 1975/76 at sites throughout England and Wales. Satisfactory control was obtained with sprays of chlorpyrifos or triazophos, both of which gave results similar to spraying with DDT. Fenitrothion sprays gave good control at sites in high rainfall areas. Gamma-HCH as a spray was effective only at a high rate of application; in bran bait or bait pellets it did not give consistently good results. Parathion granules or methiocarb spray also failed to give good control.

SUMMARY This further series of field trials in 1972–75 at sites in England and Wales confirmed that a useful, but not wholly adequate, degree of control of slugs in maincrop potatoes could be achieved with one application to the growing crop of 5–6 kg/ha of methiocarb pellets from mid‐July. Increasing the rate of application to 11–2 kg/ha improved control marginally, as did the addition of a second application of 5–6 kg/ha later in the season. Measurement of rainfall and slug activity did not provide a basis for improving control by more appropriate timing of applications, although bait‐trapping slugs gave some indication of the level of crop damage to be expected.

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