Spray or not to spray: that is the question

Alberta Agriculture

New research trials revisit how early fungicide applications can affect the spread of disease and a grain farmer’s bottom line.

Alberta Agriculture

When is a good time to spray to manage leaf disease on cereal crops? Some producers include fungicide application at herbicide timing – the 3 to 5 leaf stage – believing it will reduce leaf spot disease levels later in the growing season.

“This practice is not supported by previous research trials,” explains Sheri Strydhorst, agronomy research scientist with Alberta Agriculture and Forestry. “By revisiting this research, we wanted to make sure that farmers are making the best use of their input dollars while still protecting their crop.”

Strydhorst and her research team wanted to see if the same lack of yield response trends were still occurring with early fungicide applications as in trials from thee arly 1990s, and they wanted to prevent the development of fungicide resistance.

“All Alberta farmers are aware of herbicide resistance, but sadly, fungicide resistance needs to be put on their radar as well.”

The team conducted research trials in 2018 and 2019 at 4 locations in the province – Bon Accord, Barr head, Red Deer and Le th bridge under irrigated conditions. They applied fungicide treatments to

2 CWRS wheat cultivars.

Trials we reseeded into can ola stubble-fields that had a history of short wheat rotations – wheat-canola-wheat-canola. This increased chances of cereal leaf disease and mimicked the typical rotations used by many farmers in Alberta.

Strydhorst found that fungicide applications resulted in significant differences in leaf disease levels at all site years. The lowest levels of leaf disease were achieved with a fungicide application at flag leaf timing. The highest yields were achieved with either a flag leaf or head timing fungicide application.

“By the end of the growing season, fungicide applications at herbicide timing had similar disease levels as the untreated control. This suggests that there is no value in early season fungicide applications.”

She also found that the results were very weather driven. Under dry conditions and low fol ia rd is ease levels, the team did not see any benefit from any of the fungicide treatments.

“This data so nicely shows that to get fungicide response, you need the environmental conditions conducive to disease development,” she adds. “They say that rain makes good grain, but rain also makes disease.”

S tr yd horst will present the findings of the study and offer her recommendations at Wheat Stock, taking place August 6 and 7.