Winter barley and winter wheat growers should be expecting a high risk season for BYDV, linked to the warm climatic conditions this summer, the many early drilled crops plus the current mild autumn weather. The solution to this problem is a programmed approach, starting with a seed treatment and followed up with a long-lasting pyrethroid insecticide such as esfenvalerate, Sumi-Alpha.
"June was a good month for insect pests when populations built up to very high levels. This build up can mean a high risk of aphids and hence Barley Yellow Dwarf Virus (BYDV) in early-sown autumn cereals. As cereals emerge, aphids will make a bee-line to any green foliage. Even if a seed treatment such as clothianidin has been used to give 6-8 weeks protection from drilling, growers of early sown winter barley and winter wheat will need a post-emergence top up spray to give at least a further 6 weeks protection. The count down of persistence for the insecticidal treatment starts at drilling, irrespective of when the crop emerges. So in crops already treated with a seed treatment, I would advise growers to apply a pyrethroid with a quick knockdown plus long persistence, such as Sumi-Alpha, in October and November," says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.
David continues that for winter sown crops which haven’t received an insecticide seed treatment, an application of Sumi-Alpha will be needed sooner rather than later, starting in September for some crops. ADAS recommend using a spray threshold of 170 day degrees above the aphid development temperature of 3°C starting from crop emergence.
"Sumi-Alpha offers the best persistence of all pyrethroids as well as having strong repellancy activity on aphids. It has flexible dose rates according to the persistence required. The full rate of 165 mls per hectare is used in high risk situations where 6 weeks protection is required. High risk situations include early drilled crops, crops grown after grass or grassy stubbles, crops in the South and West, crops in sheltered fields close to hedges and coastal areas. For medium risk situations, a dose rate of 125 mls/ha would give 4 weeks of protection and for low risk BYDV situations 100 mls/ha would give similar persistence to cypermethrin. Growers should ask their distributor for the right dose rate to suit the individual farm and field situations," explains Dr. Stormonth.
He mentions that Sumi-Alpha is fully compatible with many post-emergence herbicides including FMX (flumioxazin) as Digital, Guillotine and SumiMax and is highly rainfast.
Developed by Sumitomo Chemical Company of which Interfarm is an affiliate, Sumi-Alpha contains 25 gms ai/litre esfenvalerate formulated as an emulsifiable concentrate and is packed in a 1 litre pack. Recommended on all varieties of winter wheat, winter barley and spring wheat, it is recommended for the prevention of BYDV by controlling aphids at a maximum dose rate of 165 mls/ha, with a maximum of 2 applications per crop. It can be applied up until the 31st March of the year of harvest. Esfenvalerate is available as Sumi-Alpha and Sven.
For further comment and information, please contact Dr. David Stormonth, Technical Manager, Interfarm UK Ltd. on 01354 741414 or 07818 036506 (mobile) or via e-mail david.stormonth@interfarm.co.uk
