It’s all adding up to a BYDV year
Winter barley and winter wheat growers are being warned of a high risk year for Barley Yellow Dwarf Virus (BYDV), linked to the warm climatic conditions this summer, the many early drilled crops plus the early mild autumn weather. This problem requires a programmed approach, starting with a seed treatment and following up with a persistent pyrethroid insecticide such as esfenvalerate, Sumi-Alpha.
"A seed treatment such as clothianidin will give between 6-8 weeks protection against aphids from the time of drilling. This means that growers of early sown winter barley and winter wheat will usually need a post-emergence top up pyrethroid spray to give a further 6 weeks protection," says Dr. David Stormonth, Technical Manager for Interfarm UK Ltd.
David explains that ADAS recommend using the T-sum spray threshold to calculate when the follow-up spray is needed. "This is calculated by taking the daily mean temperature, subtracting 3 from it and then adding the result to the accumulating total until it reaches the threshold level of 170. For crops treated with a seed treatment, this calculation should start six weeks after sowing, but crops without a seed treatment, it starts on the day of crop emergence, when aphids are able to colonise plants. For example, crops emerging in the last week of September this autumn reached a T-sum of 170 by mid-October. Winter sown crops which didn’t received an insecticide seed treatment will need an effective pyrethroid with a quick knockdown and long persistence, such as Sumi-Alpha, sooner rather than later. Those with a seed treatment should be monitored just as carefully," he says.
"To prevent aphids transmitting BYDV, you need an insecticide with rapid initial activity as well as long-lasting effects. 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 gives 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 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. It is also recommended on potatoes, vining peas, edible podded peas, combining peas, field beans, cabbages, Chinese cabbage, kale, Brussels Sprouts, cauliflower, broccoli/calabrese, Kohlrabi, ornamental plants, permanent grassland, rotational grassland and managed amenity turf for the control of aphids, caterpillars, weevils, thrips, midges, leaf rollers, leaf miners, whitefly and bibionid larvae and preventing viruses. Esfenvalerate is available as Sumi-Alpha and Sven.