Pelleting the seed of iceberg lettuce (Lactuca sativa L.) and butterhead lettuce (Lactuca sativa L. var. capitata L.) with imidacloprid to control aphids

An evaluation was done of the aphid control by pelleting the seeds of iceberg lettuce (Lactuca sativa L.) and butterhead lettuce (Lactuca sativa. L. var. capitata L.) with imidacloprid which was conducted in fields during 1994 and 1995. Plants raised in peat blocks according to the standard practice of commercial plant raisers in The Netherlands were subsequently planted out in the fields. Imidacloprid was administered to pelleted lettuce seeds in a dose of 800 g kg(-1) of raw seed in iceberg and in doses of 200, 400, 600 and 800 g kg(-1) of raw seed on butterhead lettuce. In 1994 the dose of 800 g kg(-1) raw seed provided iceberg lettuce with a good protection for more than seven weeks after drilling. In butterhead lettuce a treatment of 600 g in 1995 controlled aphids until the harvest which was over eight weeks after serving. Supplementary crop treatments were started seven weeks after drilling and continually until one week before harvest The iceberg lettuce crop was sprayed weekly with. pirimicarb (0.25 litre ha(-1)). Finally an application of heptenophos (0.275 litre ha(-1)) was carried out four days before harvest. The combination of seed and crop treatment gave complete aphid central until the harvest.