BYDV – assessing the risk now
Sowing winter barely crops during September has now been discounted, almost entirely, by Teagasc. The risks associated with BYDV infections are just too great.
October-sown crops should receive a pyrethroid or sulfoximine now (early November). In the case of November-planted barley, the advice is for growers to walk crops regularly in order to check for the presence of aphids.
BYDV risk depends on time of sowing, location, weather pattern and type of virus present. Aphid flight is inhibited by rain and wind, therefore, risk of BYDV infection is lower when these conditions prevail.
Another important factor when assessing risk is whether a ‘green bridge’ is present or not, as volunteer cereals and grasses are host species for the grain aphid.
According to Teagasc, an insecticide application should always be targeted. When checking if aphids are present in a crop, growers need to look at the headlands because aphids are three-times more likely to land near here than further out the field.
If aphids are present, then apply an insecticide at the two- to three-leaf stage of the crop.
While partial BYDV resistance has been detected among the Ireland’s grain aphid population, pyrethroids will still be effective for the majority of growers.
Insecticides and strains
However, multiple applications of this insecticide should be avoided to prevent the development of full resistance. So growers should alternate to a different insecticide group if a second application is required.
The insecticide Transform contains the active chemical sulfoxaflor. Exisiting stocks can be used up to May 19, 2023.
Teagasc entomologist Dr. Louise McNamara is confirming that 11 strains of the BYDV virus have been found in Ireland.
They can have differing levels of crop impact with yield losses of up to 80% a possibility. However, this would only be in the case of very severe infections. The average loss figure is in the region of 30%.
According to McNamara, BYDV can bring about yield decreases of up to 2t/ha in winter wheat and oats.
“This figure rises to 5t/ha in winter barley crops. The risk will be different in different years and different locations,” she explained.
“On a local scale, there will also be variations in yields between fields.”