Relatively low disease pressure throughout much of the 2017 season prompted some growers to make savings on fungicide inputs. Crop Focus looks back to see if decisions were justified and what we can learn for the months ahead.
Yellow rust and mildew were first to show, Septoria maintained a low level season-long presence where there was enough moisture, while both brown rust and Fusarium came into crops later, recalls ADAS principal research scientist, Jonathan Blake.
Additionally, the early warm and dry spell meant many crops’ growth stages were more variable than normal, making spray timings more difficult and giving growers lots of nuances to deal with.
“Each spray timing had a different challenge,” says Dr Blake. “We also saw regional variations depending on the amount of rainfall. In the east, disease pressure was much lower than in the west.”
Fortunately, early yellow rust infections were dried-up by hot conditions in early June, he says, with temperatures of 22-23°C preventing further disease development.
“Yellow rust always had potential to cause problems in 2017, as there were new races out there and we didn’t know how they were going to behave in the field,” he notes.
“Despite the diversity in the pathogen population, we have the chemistry to deal with it.”
The heat may have stopped yellow rust in 2017, but the situation remains very fluid, and growers cannot be complacent, he warns.
Unusually, Septoria was not at the forefront of spraying plans last year, he says. “There was some disease around at T0 and T1, but it didn’t cause huge concern and was mainly confined to lower leaves.”
The first two sprays took care of any infection, with dry, sunny conditions throughout April allowing some savings.
“At the time of making the decision to cut back, it is very difficult to know whether it is the right thing to do. One lesson from the 2017 season is to aim your fungicide programme at the situation you are facing, not what you are expecting to see.”
Variety-specific fungicide programmes also made their mark, reports Dr Blake. “There was quite a bit of tailoring done according to variety and drilling date, which is also where some were able to reduce their spend.”
However, rain just before T2 sprays were applied prompted a change of tack, with growers easily persuaded to include some eradicant action and use robust rates.
“There were two new SDHI products launched for T2 last year, including Ascra, and they performed as expected. We didn’t see Septoria progress beyond T2 in the way we have before, as it turned dry again.”
Although disease was not visible when the T1 application was made, including Aviator at this timing had a lasting effect on crop performance, with highest yields coming from the SDHI/triazole mix, he reports.
“It demonstrated clearly that earlier spray timings are aimed at tomorrow, rather than today. While you might not necessarily see Septoria at this stage, that could be due to the pathogen’s latent period.”
The same effect was seen from using Ascra at T2, he says. “Again, the differences didn’t show up until July, when it became possible to pick out the treatments by their effect on keeping the crop greener.”
Drag or swipe the slider left/right on each image to compare the untreated and treated crop from April through to July
If you have any questions, please contact your local CTM or Tweet @Bayer4CropsUK.
Receive regular in-season Bayer Wheat Crop Focus emails to stay up-to-date on wheat agronomy advice
Although disease was not visible when the T1 application was made, including Aviator at this timing had a lasting effect on crop performance, with highest yields coming from the SDHI/triazole mix, he reports.
“It demonstrated clearly that earlier spray timings are aimed at tomorrow, rather than today. While you might not necessarily see Septoria at this stage, that could be due to the pathogen’s latent period.”
The same effect was seen from using Ascra at T2, he says. “Again, the differences didn’t show up until July, when it became possible to pick out the treatments by their effect on keeping the crop greener.”
