| Aphids increase whilst predators lag behind |
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Following the cold winter relatively few aphids were seen in arable crops in early summer. However, recent trap results suggest that numbers are building and could pose a serious risk to autumn sowings. The numbers of aphids flying in recent weeks are at similar levels to this time last year. The Broom’s Barn aphid traps also record the number of ladybirds and these have not built up; at the moment they are at 25% of the level in 2009. This could mean that the risk of turnip yellows (TuYV) in rape and BYDV in cereals this autumn might be higher than last year. “This is particularly worrying as our and other surveys for TuYV in the current crop show that levels are high in many areas. Growers will need to use a good seed treatment to control TuYV and BYDV, “ advises Adrian Cottey, Seed Treatment Manager for Bayer CropScience. “Clothianidin is a new generation neonicotinoid treatment that gives good control of establishment pests but, importantly, it also prevents aphids spreading these viruses. As Modesto in oilseed rape it is the only treatment with label approval for TuYV. As Redigo Deter it will control BYDV in cereals.” Recent work by Broom’s Barn shows that TuYV is present in all plant parts, including the roots of infected rape. “This is worrying as aphids feeding on regrowth in stubbles could pick up the virus and pass on to newly emerged rape this autumn. Obviously numbers of volunteers can be reduced by good stubble cultivations, but the risk of virus transfer from other sources including weeds and field margins, suggest that investment in clothianidin seed treatments will be well worthwhile this season,” advises Mr Cottey.
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