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.”
Barley yellow dwarf virus (BYDV) is a nasty virus of cereal crops that can kill patches of plants, potentially causing large yield losses. It is carried by three different aphids – the grain aphid, bird cherry-oat aphid and the rose-grain aphid.
Now that the neonicotinoid seed treatment ban has taken effect, knowing the best time to apply pest control treatments is going to be key to controlling the aphids that spread barley yellow dwarf virus (BYDV), once all cultural control techniques have been exhausted. There is a calculation that can help growers to pinpoint this.
Black-grass control does not start with the pre-emergence herbicide programme. Doing everything possible to reduce the weed population before you drill the crop is key, and it means making good management decisions right from the off.