Growers face an elevated risk of barley yellow dwarf virus (BYDV) this autumn due to warmer soils and earlier drilled crops.
Some of the earliest drilled crops were at 2/3 leaf stage by the end of September, says Neil Watson, technical support manager for Hutchinsons. If aphids colonise these plants early, it is imperative to time insecticides to the earliest emerged parts of the field.
Warm air temperatures have been conducive to early aphid flight, says Mr Watson. It remains to be seen whether that continues. But trap data shows that aphids were already in flight last month.
“With the loss of Deter to cover the early infection period, we are now solely reliant on the pyrethroids. Also remember that without Deter we have the lost the additional early protection from slug hollowing it afforded us.”
Mr Watson explains that there are also many fields that have not been treated to kill the green bridge, be it volunteers or grass weeds. He recommends a glyphosate treatment prior to drilling or mixed in with the pre-emergence treatment.
To prevent in-crop transmission, growers should start counting from the 170 day degree spray threshold once aphids have been seen in the crop. The exception to this is if large numbers are seen feeding on a crop. They should be sprayed immediately.
“It’s important not to rely solely on variety tolerance in barley – it might mitigate some of the impact of any BYDV that gets into the crop – but it shouldn’t impact on spraying decisions.”
Mr Watson points out that with regards to the genetic resistance for the wheat variety Wolverine, it offers a really useful addition in combating BYDV. But he cautions that resistance does not mean complete control.