How adjusting septoria score can protect early wheat crops

Tweaking winter wheat fungicide programmes to reflect drilling date can help mitigate yield losses from septoria, says ADAS research.

Winter wheat varieties sown on 23 September or earlier are at significantly higher disease risk from septoria than their Recommended List (RL) score suggests – most likely because these crops are exposed to septoria spores earlier in the season.

“The varietal RL ratings have been based on a drilling date of 7 October,” says Jon Helliwell of BASF. Adjusting applications of Revystar XE to reflectr the actual sowing date can prevent potential yield losses, he adds.

Bringing the drilling date forward by two weeks effectively reduces the variety's RL septoria rating by 0.6, says Mr Helliwell. Likewise, crops sown two weeks later increased the rating by 0.6.

The relationship between drilling date and actual septoria rating was proved in 25 trials over five years. The research team included scientists from ADAS, NIAB and the SRUC – Scotland's Rural College.

Mr Helliwell says: “If you drill a crop of LG Skyscraper with a resistance score of 4.9 two weeks early, this means you need to manage the septoria risk as you would a crop of KWS Barrel with its score of 4.3.

“But if you drill the same crop two weeks later than the standard date, the septoria risk is akin to a crop of Gleam.”

The principle applies to all varieties on the recommended list. And Mr Helliwell says it is an important point to consider in a season when an early harvest last year gave many growers an opportunity to get winter wheat crops established ahead of their usual drilling date.

Fungicide rates

BASF has been exploring the impact of drilling date and variety with dose rates of Revystar XE since 2021. A best-fit line shows the optimum economic dose rate is higher where cultivar resistance to septoria is reduced.

“This could come from a less resistant variety, or could come from a more resistant variety drilled earlier,” says Mr Helliwell. “Even the most resistant varieties, when drilled early, have an optimum economic dose at T2 of 1.1 l/ ha Revystar XE.”

In conclusion, dose can be used as a tool to mitigate the impact of Septoria associated with drilling early.

“By upping the rate applied to those crops sown on or before 23 September you can ‘buy back’ the yield,” says Mr Helliwell. “It more than covers the cost of the additional fungicide.”

Inherent variations within the field means growers should choose a product with protective and curative action.

“We don’t want to rely on curative activity, but it important when dealing with the natural variability found on-farm.”