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What is the BYDV risk with late drilled spring barley?

Agronomy Issues
06.04.2021

Spring barley drilling this season has been a drawn-out affair, with some crops going into the ground in December and many towards the end of March and into April.  Late drilled spring barley has different risks associated with it than early drilled crops, one of these is BYDV. 

Unlike autumn drilled barley, it is the later drilled spring barley crops that will suffer more from BYDV.  This year, a later aphid flight is predicted compared to 2020.  The map below shows the 10-year average predicted aphid flights in green and the predicted date for 2021. 

For crops drilled before mid-March and away from winter cereal inoculum, the BYDV risk is relatively low.  However, for some, the drilling window for spring barley has been pushed to late March and early April, and so the risk of BYDV for these crops is still present. 

BYDV infection is more serious in spring barley that has not yet reached GS31. After this growth stage the impact of BYDV on yield is not as significant. Later drilled crops are more likely to be smaller at the time of aphid flight, and therefore yield losses can be significant. 

Crops drilled from late March to April, have a much shorter growing season, and have less time to tiller before the crop reaches stem extension.  This may result in less ears overall and therefore lower numbers of grains produced.  If the season turns dry, tiller losses to drought can have a large impact on yield compounding any yield loss caused by BYDV. 

Early nitrogen can help to feed and strengthen tillers, improving tiller survival, which will be especially important in low tillering crops.  For a crop drilled after March, the RB209 advice is to apply 100% nitrogen in the seedbed or a 2-way split for quantities over 70 kg N/ha.  This will also help crops grow away from the impact of the virus, lessening symptoms and reducing yield losses.

Apart from early drilling, the other major cultural control is increasing plant populations, this allows the crop to better compensation for BYDV.  As well as increasing seed rate, VIBRANCE Duo seed treatment has been shown to increase establishment numbers and rooting, helping to build a crop with more resilience to BYDV. VIBRANCE Duo now has BBPA approval for malting barley and can be used for any spring barley crop going into the quality market.  (For more info on VIBRANCE Duo click here)

There is not a definitive threshold for primary infection in spring cereals, it is down to local knowledge on pressure as well as growth stage of the crop.  In spring cereals only one insecticide is needed at initial aphid invasion to gain control of primary infections, so monitoring late drilled spring barley crops regularly for aphids is important to get the timing right.  Aphid flights start at ~11oC, and you can use the AHDB website for predictions on aphid flights in your area to help understand when aphid flight risks might occur. 

If aphids are found in a high-risk site, use HALLMARK Zeon at 50 mls/ha for aphid control. Syngenta trials have shown up to 0.8 t/ha loss with a second application. Due to secondary infection not being the target of these applications, BYDV Assist App Should NOT be used for spring cereals.