Many farmers are asking questions about spraying for aphids to prevent Barley Yellow Dwarf Virus at present.

The first thing to say is the research tells you in most cases not to spray insecticide on March sown crops, as the risk of BYDV is much lower. This year March was cold and the risk of BYDV was expected to be low. The higher risk areas are along the coast.

The next thing to say is the advice is to spray April sown crops as they are at higher risk of BYDV. However, this April temperatures have been cold at night and extremes in temperature from night to day have only really stopped in recent days which have been very cold. As a result, the risk of BYDV is probably low.

When you spray an insecticide, you risk killing natural predators like ladybirds and other beneficial organisms, which can help with control in the long term.

Optimal timing

The other thing is the optimal timing for spraying is probably passed on most crops. The ideal time to spray an aphicide on cereal crops is at the three to four-leaf stage. Most crops are now passed that stage, unless they were sown much later than the majority of crops.

Resistance

The target of the insecticide is the grain aphid. So, when you see aphids in a field only some of these are grain aphids. Some of these aphids are likely resistant to pyrethroid insecticides so the spray may not help to control them. However, in any given field the level of aphids with resistance to pyrethroids will vary. In some fields there could be none resistant to the spray and in other fields there could be 50% resistant.

Keep an eye on the Tillage Management notes for advice.