A worrying yellow rust presence, coupled with susceptible varieties and the appearance of manganese deficiency, mean winter wheat crops need checking regularly over coming weeks, a leading crop expert is urging.
According to Dr Tudor Dawkins, technical director for agronomy firm ProCam, yellow rust remains evident in crops, despite a number of frosts.
Manganese deficiency is now also appearing, he says, along with mildew on a number of varieties, while difficulties controlling Septoria mean this, too, must not be allowed to get out of hand.
“Around 20% of winter wheat varieties in the ground this year are at risk from yellow rust,” says Dr Dawkins, “with 30% having a significant vulnerability to Septoria, and 55% having susceptibility to eyespot.
“Check crops regularly. Disease levels and nutrient deficiencies need addressing before, not after, they become yield-limiting. As an industry, we have traditionally focused heavily on the later spray timings of T1, T2 and T3, and been more reluctant to also include earlier T0 fungicides.
“However, now that we have Septoria populations that have shifted to become more difficult to control, and new yellow rust races that are eroding confidence in variety yellow rust ratings, including early disease prevention has also become more important.”
Pointing to ProCam trials results, Dr Dawkins says consistent benefits have been seen from including a T0 application over recent years, with returns of up to 1 t/ha in higher disease pressure years.
“Even in 2016, when a lack of sunshine in June and July curtailed yield, we still saw a yield response of over 0.5 t/ha from including a T0 fungicide,” says Dr Dawkins. “At current wheat prices, that represents a return of around £50/ha net of fungicide cost.
“T0 is also a useful time to include anti-resistance fungicides against Septoria. But it’s not just the standalone benefit from controlling disease there and then that is important. Growers with a large number of hectares to protect can buy time by applying a T0, which gives a bit more flexibility with the T1 application.”
Although Dr Dawkins says not all crops will necessarily benefit from a T0, he believes that omitting one will put pressure on growers later at T1. “Growers who have planted a more resistant variety and delayed sowing into November to reduce blackgrass pressure, or sown the crop later following root crops, may be able to omit a T0. However, the timing of the T1 will need to be spot on if they do this, and T1 may need to be more robust to ensure disease doesn’t become established. We should avoid chasing disease – once established it can be more expensive to control.
“Fungicide programmes are a good investment, giving potential returns of £2 back for every £1 invested. The construction of the programme is the important element, along with spray timings. T0 should be considered an integral timing in the programme, not just an add on.” Dr Dawkins concludes.