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No clear winner in FHB treatments

By Lee Hart

Field surveys across southern Alberta evaluate the level of disease on both irrigated and dryland crops and compare that with farming practices on those fields. Photos: Farming Smarter

While the differences haven’t been earth shattering, so far a three-year southern Alberta study looking at the effect of different treatments on wheat shows the combination of using a fungicide and timing of irrigation might have a slight benefit in reducing fusarium head blight (FHB).

Results of the third year of the project in 2012 still have to be tabulated, says Kristina Halma, a research assistant who coordinated the project for Farming Smarter in Lethbridge.  But, the first two years showed some benefit of the treatments, even though there were no dramatic yield or quality differences.

“We looked at two different treatments over nine farms in southern Alberta,” she says. One part of the study was to evaluate the effectiveness of fungicides in controlling FHB, and the other part was to evaluate timing of irrigation water application, and the effect that might have on disease development. Aside from the treatment component, a third aspect of the study involves a random survey of fields.

 “Depending on the year and the farm, there was some response, but nothing consistent or significant,” says Halma. “In some cases, we did see where the combination of using a fungicide, as well as limiting the amount of water applied to the crop just as it was flowering, did have some benefit in reducing the disease. Once the data is processed from this year’s growing season, we’ll be able to write the final report.”

Valid questions

The study looked at two good questions. Do three of the more common fungicides marketed to protect wheat crops against FHB work? And, can the risk or degree of FHB developing in the crop be reduced by eliminating irrigation during the critical two- or three-week flowering period?

Farmer’s participating in the study were asked to use any of three common fungicides—Caramba from BASF and Folicur and Prosaro from Bayer Crop Science—to see if a product, applied at the recommended 75 per cent heading to 50 per cent flowering stage, had an affect on development of FHB. Halma says it wasn’t a trial comparing the effectiveness of the individual products. The study compared the effectiveness of treated versus untreated crop on a field scale basis.

The nine participating producers are spread across a large area of southern Alberta from Bow Island in the east, west to the Carmangay area and north to Duchess.

“There is a lot of variability in that area,” says Halma. “Growing conditions vary and the level of FHB varies as well. Overall, I would say there was some benefit to using a fungicide. In one case in 2010 there was a 4.1 per cent reduction in the amount of kernels affected by fusarium.”

On untreated crop, the level of infection was 6.4 per cent, and on treated crop, it was reduced to 2.3 per cent. Halma says looking at the fusarium tolerance levels for various grades in amber durum, the fungicide treatment would have made the difference of the crop grading a #3 to #4 or coming in a grade lower, a #5. 

In the 2011 study year, the most notable improvement between treated versus untreated was a 2.4 per cent reduction of fusarium in spring wheat.

Irrigation timing

On the other side of the study, looking at the affect of irrigation timing, the objective was to adjust the timing of the water application to avoid the peak flowering period, which is when the crop is most susceptible to disease infection.

“We didn’t want to reduce the amount of water the crop received, but rather just adjust the timing to avoid that critical two- or three-week period, which is likely in late June and early July,” says Halma. “So producers were asked to pick a portion of a field, and perhaps top up irrigation just before flowering, avoid watering during flowering, and then resume after flowering.”

Again, the first two years of the study showed no significant difference on most farms between full water and limited watering sites. However, in one case there was a 3.9 per cent reduction in disease on a field where irrigation was stopped during the flowering period.

“We also had a producer who saw a slight benefit from both treatments,” says Halma. The farmer reported a 1.3 to 1.8 per cent reduction of fusarium in crops that received the adjusted water application, as well as a 0.5 per cent reduction in disease on wheat treated with fungicide versus no fungicide.”

“So far we are not seeing any significant benefit of the treatments, so a lot may depend on the degree of disease pressure on a particular farm,” she says. “The benefits aren’t significant but there may be a slight yield advantage and perhaps also opportunity to increase the quality of the crop by a grade or two.”

Good to know

Bow Island-area producer Will Van Roessel, who has participated in the study for the past three years, says he really hasn’t seen any advantage of either treatment in his crops.

“In one sense, the results have been a bit disappointing, but on the other hand at least you know whether something makes a difference or not,” says Van Roessel.

“Farmers in southern Alberta are realizing that fusarium head blight is becoming more of a problem and we need to look at whatever tools are available. These treatments haven’t made a difference on my farm, but they may work for someone else depending on where they farm and their specific conditions.” 

Van Roessel says there was “minimal” yield or quality difference in crop he treated with fungicide versus untreated. “And we also did some comparisons of fungicide on our own, outside of this particular study,” he says. “The benefits were pretty marginal, and not enough to pay for the cost of the fungicide. To me, if I’m using a crop protection product, I need to see a 2:1 payback.”  He estimates the cost of the fungicide application at about $20 per acre.

He also saw no great difference in disease levels or quality improvement in a field of durum wheat where the timing of water was adjusted during crop flowering. “Not irrigating during flowering is probably a good practice, but I didn’t see a great difference,” says Van Roessel.

He also says it is a bit more difficult to measure differences too because water is being adjusted on a quarter of a circle, so when combining he has to know where that pie-shaped area is in the field. And even though the pivot starts and stops spraying over that quarter circle, it isn’t necessarily an exact line in the crop either “so it may not be a perfect trial”, he says.

Field surveys too

A third component of the Farming Smarter fusarium project involves a random survey of fields across southern Alberta, evaluating the level of disease on both irrigated and dryland crops and comparing that with farming practices on those fields.

In this part of the project, Halma selected 25 fields in an area that includes Lethbridge, Forty-Mile, and Newell counties and the Municipal District of Taber.

In each of the three years of the survey, she selected 25 fields at random, collecting 300 wheat head samples from each field. She did a visual inspection and also sent a sample away for testing. And along with that, she interviewed the producer to get background on cropping history, variety used, fungicides used, and other production practices.

 “We hope from this part of the project we may see some trends or common farming practices that may affect the level of the disease in cereal crops,” says Halma.