Deciding when to spray fungicides can be stressful, especially when it comes to pulse crops such as peas. How do you know you’ll get your money’s worth?
One way is to use a simple but effective score sheet developed by pulse research agronomist Ken Lopetinsky.
“I think it’s a real helpful tool — it gives you a very good benchmark of what to look for and how to assess it,” says Richard Krikke, whose Westlock, Alta., farm was one of the five test sites used to develop the scorecard.
Although quite comfortable in assessing his fields, he still uses the sheet to help make his final decision.
“The scorecard makes it easy to pick the timing,” adds Clifford Cyre, seed farmer and Alberta Pulse Growers board member.
Cyre’s farm was also one of the test sites and he also says the scorecard gives him added confidence in his spraying decisions.
The score sheet was developed after studying five field-sized plots over three years. The study looked at both the need for, and timing of, spraying the fungicide Headline (a BASF product). Over three years, a “significant” yield increase occurred at 12 out of 14 locations, the study states. There was also a significant increase in the 1,000 kernel weight, and slightly lower levels of ascochyta infections in the seed. (The full report is available at www.pulse.ab.ca, the Alberta Pulse Growers website. Go to the “For Producers” section and follow the links to Completed Research Projects to find “A disease prediction system for ascochyta in field peas” by Ken Lopetinsky.)
NOT EVERY FIELD DESERVES SPRAY
Not every pea field is worth spraying. The following criteria for selecting fields for study, “high plant populations with a minimum of 75 plants per square metre; good weed control; even crop emergence and high rhizobium nodulation.”
The study recommends scouting twice a week, starting at the end of June. Pick several spots in the field to check.
“Mark them with a flag and come back to them,” Cyre says. “You get the identification from there. You check the same spots all the time for your scorecard.”
It’s important to be non-invasive when scouting — don’t touch the plants.
“If you part the plants, you change the microclimate. The next time you come back, it’s not a true representation,” Cyre says. “We don’t go through the whole field — we follow the sprayer tracks.”
Scouting is more than just driving by the field in your pickup, says Andre Montpetit, manager of Sturgeon Valley Fertilizer Ltd. at St. Albert, Alta. He recommends “digging out plants, looking at the roots structure (and) really dissecting that plant,” when checking for disease. (Don’t use that area for your benchmark though!)
KNOW YOUR CROP
“Even if the scorecard looks simple, you really do need to be familiar with your crop,” says Tammy Jones, grower and communications director with Alberta Pulse Growers. She says farmers should know the different factors that affect disease.
The score sheet is rated on four characteristics — crop canopy, leaf wetness (humidity, dew) at noon, percentage of plants (crop) showing disease symptoms and the five-day weather forecast.
“What’s considered a dense crop?” Krikke asks. “That’s where the grey area is. It’s relative to what you’re used to.”
“It’s all about perspective for the farmer,” says Jones. “Rating your crop canopy, or rating the disease severity — it is a bit of a personal opinion and where they fall in the scale.”
Cyre notes canopy density can be seen from the edge of the field and says when checking plants for diseases, he asks himself, “Is the ascochyta coming up the stems?”
Even light hail can make an otherwise resistant crop susceptible to disease. Bruised spots on stems give disease entry points.
“The biggest problem is that last one on the scorecard. What’s the weather going to do in the next week to 10 days?” says Cyre.
Still, the score sheet gives farmers a benchmark (spraying is recommended once the “score” hits 65) and visiting the same spot twice a week helps them track the change in disease pressure.
“Once you start seeing the disease increase, then you know it’s time to go. Or if you hit 65,” says Krikke.
“As you get more familiar with the scorecard, you get more familiar with the risk factors,” adds Jones.
JOIN A CROP WALK
A good way to learn more about how to correctly size up your field is to join a crop walk in your area. Zone 3 of the Alberta Pulse Growers puts on a crop walk every year. If your area doesn’t have a crop walk yet, Alberta Pulse Growers can help to organize one.
“I wouldn’t grow any peas in this area without putting fungicide on. Even in a dry year we were still ahead,” says Cyre, adding his area (central Alberta) has the highest rate of ascochyta.
Since fungicides such as Headline only protect the crop for a two-week period, “fungicide timing is everything,” Montpetit says.
The scorecard helps “to reassure you that the $20-per-acre treatment is actually worthwhile,” he says.
Fungicide cost is why many farmers only spray once, even though two applications are recommended.
“You have to consider the price, what is your return on your investment?” Krikke says. “That’s why here (at Westlock) we usually only look at one application.” For the record, Krikke sprayed July 7 in 2010 and Cyre on July 15.
Funding for this project was provided by BASF, Alberta Pulse Growers and AAFRD
Contactherbyemailat [email protected]
Time Period Characteristic
Below is part of the ascochyta scoring sheet developed by Ken Lopetinsky. His report on the Alberta
Pulse Growers ( www.pulse.ab.ca) website has a score sheet that can be printed off. Make use of it!
Ascochyta Scoring System Field ID________________
Source: K.J. Lopetinsky1 and S. Strydhorst2 2002
1Ag Research Division, AAFRD, Barrhead 2University of Alberta, Edmonton, Alberta, Canada
1. Crop canopy
2. Leaf wetness/humidity/dew at noon
3. Per cent of plants (crop), showing symptoms
4. 5-day weather forecast Thin 0
Estimation Risk Scale
Moderate Mod/Heavy 10 15
Low Moderate 10 20
Low Moderate (<20%) (20-50%) 15 25
Unset Showers 10 15 Heavy 30
The estimated risk value is 1+2+3+4+estimated risk value. If the estimated risk value is less than 65, no fungicide application is deemed necessary, but field inspection should continue on a biweekly basis. If the estimated risk value is +65, the fungicide spray application is recommended.