The Use of Malathion to Control the White Clover Seed Weevil, Apion dichroum Bedel (Col., Curculionidae)

Abstract

SUMMARYThe purpose of this study was to investigate the control of the weevil Apion dichroum Bedel in wild white clover grown for seed using a spray of malathion. The experimental area was approximately 12 acres (4 9 ha) and the design was six blocks each of two plots, one being sprayed and the other unsprayed. The changes with time in the density of flower heads vulnerable to weevil attack and of those suitable for harvesting were recorded. The experiment suggested a useful increase in yield‐18 or more Ib per acre (20 or more kg per ha)‐as a result of the treatment, but there was no conclusive evidence of any increase. An increase of 4 Ib per acre (4 5 kg per ha) would cover the cost of spraying. There was no evidence that spraying reduced the activity of bees. Data from two independent sampling methods show that the weevil population in the treated plots was always less than 10 per cent of that in the untreated ones during the whole period in which the crop was vulnerable to weevil attack.