Up to 40 per cent of leaves were damaged and growers incurred financial loss from additional pesticide applications, crop rejections and increased packhouse costs.
In AHDB Horticulture project FV 376, crop covers were shown to be effective. Two experimental products and spinosad (Tracer) were identified as effective controls in leaf dip laboratory tests in project FV 408 and project FV 408a, led by Gemma Hough of ADAS, aimed to identify insecticides that are effective against S. flava.
In FV 408a adult Scaptomyza spp. were collected from a commercial crop, which made it impossible to confirm that each adult was S. flava. The work was therefore carried out on "Scaptomyza spp.". First, the pests' survival on pesticide-treated rocket leaves was assessed in the lab. There were 11 treatments including approved and coded products. Tracer, HDCI 060, HDCI 045 and HDCI 047 were the best performers. Next, the pests' survival and leaf puncturing damage on whole rocket plants sprayed with the four treatments was determined.
All treatments significantly reduced numbers of live adults, leaf punctures and leaf mines per plant compared with the untreated control. The last trial was on a commercial baby-leaf cruciferous crop. Treatments included the four best pesticides, an untreated control and a fleeced treatment.
All significantly reduced the mean number of leaf punctures per plant compared to the control. Fleece was the most effective treatment, followed by HDCI 060 and HDCI 045. But all, including the least effective, were as good as Tracer. Discussions to obtain extensions of authorisation for minor use (EAMUs) for the best-performing products is ongoing.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk
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