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Much of the debate around drilling date centres on black-grass control. But following the withdrawal of neonicotinoid seed treatments, Barley Yellow Dwarf Virus (BYDV) also poses a danger to early crops.

Autumn 2019 was the first year without the seed treatments. But exceptionally wet conditions meant farmers and agronomists didn’t get an idea of the danger posed by aphids spreading BYDV in a ‘typical’ autumn.

With some farmers considering drilling earlier in response to last autumn and a likely  increase in cereal area to compensate for a drop in oilseed rape, BYDV may pose more of a threat.

Oxfordshire agronomist Luke Cotton doesn’t expect a huge change in drilling plans this autumn but is concerned about BYDB. “Without neonicotinoid seed treatments, wheat and barley crops are far more vulnerable. Even after autumn 2019, I did see some BYDV in untreated crops, so the danger is there if we get the right conditions for aphids.”

Delayed drilling manages the risk of aphids transmitting BYDV. The second generation of aphids which spread the disease take longer to emerge in cooler weather. The T-sum calculation for pyrethroid sprays is targeted at controlling the second generation, Mr Cotton thinks that the AHDB T-Sum tool is a good starting point for understanding risk in season.

“If you drill in September, it could mean two or three pyrethroid sprays which is a problem practically, it’s not simply a case of getting it on. There are also the resistance and sustainability issues around repeated sprays. The threat of aphids and grass weeds combined make it very difficult to drill wheat early without huge risks to the crop.”


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