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Fungicide for Plant Health?

Wednesday, December 1, 2010
filed under: Optimizing Plant Development/Yields

Using a fungicide today is not just to control a specific disease; it is also used to enhance overall plant health and, hopefully, yield as well.

There are three fungicides currently labeled for use on sunflower. Tebuconazole (Folicur® and generics) is a curative product sprayed when disease evidence is detected. Pyraclostrobin (Headline®) and azoxystrobin (Quadris®) are broadspectrum fungicides that provide curative properties recommended for the control of various plant diseases. The question remains about whether it’s more cost-effective to be proactive or reactive.

In field trials, no one fungicide stands above the rest for disease control, according to North Dakota State University plant pathologist Sam Markell. Research he has conducted in sunflower rust trials, particularly in 2008 and 2009, has not indicated a yield advantage, either. While Markell is cautious in claiming there is no evidence of an increased yield benefit from fungicide application, he simply has no data to support it.

What sets apart one of the above-listed products is that Headline is claimed to target plant health as well as disease. It’s been nearly 10 years since BASF, maker of the fungicide, hit the front lines with the product. It has been labeled on sunflower since 2007 and used for preventative control of a number of diseases, particularly rust. But other diseases are also on the label: alternaria leafspot, powdery mildew, cercospora leafspot, septoria leafspot, downy mildew. Use rate is 6 to 12 oz/ac, with a limit of two applications per season or a maximum of 24 oz/ac. There’s a minimum 21-day preharvest interval from the time of application.

According to BASF business representative Mike Odegaard, there’s a growing trend to utilize Headline tank-mixed with herbicide, followed by the fungicide tank-mixed with an insecticide at bloom for a second pass.

Disease Control & Plant Health

BASF representatives say several years of company research have resulted in data indicating Headline has a positive effect on plant health and yield in a number of crops on which the product is labeled, including sunflower. The fungicide enables plants to better withstand disease and a multitude of environmental stresses, resulting in improved crop harvestability, quality and yield.

Chris Wharam, technical service representative with BASF, works a territory that covers all of North Dakota and western Minnesota, providing technical support to the BASF sales team in the area as well as growers. He says the company considers three main components when it comes to preventing disease from interfering with optimum yield potential:

“Number one is disease control. Two is growth efficiency; and third, we look at stress tolerance.” Wharam says that when it comes to plant health for sunflower, they also focus on stalk strength. Some growers have noted less stalk breakage with Headline use when compared to test strips.

So is Headline resulting in better plant health and higher yield potential because it’s treating the stalk diseases, or is it for other reasons?

BASF reports some trials where Headline delivered significant yield bumps versus the untreated crop. It’s those yield bumps, Wharam says, that are gaining growers’ attention.

Brian Grossman, who farms with his father and uncle near Hazelton, N.D., says they go with the two applications of Headline on all their 5,000 acres of NuSun oil hybrids. They spray 6 oz. with their postemergent herbicide at the 4th leaf stage and then 6 oz. of Headline again as the bud opens.

Increased plant health is one reason the Grossmans have used the fungicide for a number of years. “The last time we had a test strip, it was a night and day difference,” Brian reports. “The plants with Headline were taller, appeared to have a bigger leaf and had a nicer green color. It was obvious.”

Grossman says yield response varies from year to year, but they consistently see an average 150 lbs./ac. increase each season. In addition to the yield gain, they’ve also noticed that Headline seems to help hold off secondary downy mildew infection. “Our BASF rep won’t claim it, but we see it. And if anyone else sees that as a problem, we’d recommend Headline,” Grossman states.

Central South Dakota grower Danny Forgey answers quickly when asked if he thought Headline was worth the input investment by saying, “Without a doubt.” That confidence comes as a result of seeing a 250- to 290-lb./ac. advantage this year when compared to the check. Thanks to 40-acre side-by-side check strips over three different quarters of land, Forgey says the results were clear.

Forgey’s Cronin Farms used Headline for the first time this season on approximately 40% of their 1,600 sunflower acres. “We’re 100% no-till, and we like to try new things,” he explains. “We also saw dry conditions to start with and what the plant might have to endure as far as stress goes. It was about plant health.”

Forgey says they saw some signs of rust to warrant a fungicide treatment, but it was more about the stress tolerance that Headline boasts that sold him on the idea to use it this year. They also saw significantly less stalk breakage in the treated versus untreated acres in the test strips. They sprayed insecticide with one pass (using 6 oz. of product) when they saw 15% to 20% petal color in the field, which Forgey notes is a little later than the point at which most people apply the fungicide.

Cronin Farms has concentrated on planting dehullers for a number of years. When faced with the potential to gain a couple hundred pounds at the recent high prices, using Headline was an obvious choice, Forgey observes.

Fellow South Dakota grower Tom Young says that after three years of using Headline, it’s now part of the regular regimen for his 1,500 acres of sunflower. “I’m sold on the product. I’m not going to test anymore. It’s just going on,” he states. Young uses a one-pass program at the early bloom stage with varied rates. He’s used a limited rate on some fields at 3-4 oz. —and as much as 6-7 oz. —and combines the fungicide with an insecticide in aerial application.

Young’s decision to begin using Headline back in 2008 was motivated by the high market prices for sunflower. Anything he could do to enhance yield was going to be worthwhile. He spent the first two years testing the fungicide effectiveness by way of side-by-side trials on his oil and confection acres. On one trial, he saw a 400-lb./ac. yield increase on the treated crop. “We’ve been seeing phenomenal yields,” Young says. “We’ve taken a closer look, and it can be attributed to the fact that we’re trying to take good care of the crop.”

When focusing on growth efficiency, Wharam says there are a few factors involved. Headline increases the plant’s nitrogen utilization efficiency, leading to more-effective photosynthesis and inhibition of mitochondrial respiration. In fungi, inhibition of respiration prevents the breakdown of carbon required for production of energy to fuel fungal growth. This results in death of the fungi.

“We take a look at what’s going on a cellular level. When respiration is suppressed, that’s how fungi get the energy. Headline shuts off that power source,” Wharam explains. He adds that BASF is actively seeking solutions to common disease problems such as Phomopsis and Sclerotinia, and he’s optimistic there will be new products coming in the next few years to address them.

Emmett Lampert, representative for Syngenta, maker of Quadris, says their product is systemic, i.e., it is distributed by water moving through the plant’s root system. While good application is still important, Quadris is designed to move throughout the plant — even where the fungicide is not directly applied.

Rust was recently added to the Quadris product label for sunflower, in addition to alternaria leaf spot and downy mildew. The use rate per application is 6-7 oz./ac., with a limit of two applications per season before disease detection – once at or just before early bud stage and again approximately 45 days before harvest. There is a 30-day preharvest interval from the time of application.

The emergence of rust in the 2009 crop is what prompted central North Dakota grower Dean Ripplinger to apply Quadris on his 450 acres of confection sunflower again this year. Ripplinger, who farms near McClusky, says use of the fungicide in 2009 produced one of his best-ever sunflower crops in terms of yield, convincing him to use the same approach on this year’s crop. While Ripplinger didn’t see the same yield bump in 2010, he acknowledges that every year is different and variables can change the outcome at any time.

Ripplinger had the crop sprayed with Quadris once along with insecticide at about 15 to 20% bloom stage. He prefers treatment closer to 10% bloom, but uneven bloom in his confections this year made it more difficult to time the application.

Scott Hendrickson, who farms just south of Fargo, N.D., used Quadris on his 560 acres of conoil sunflower this year. It was applied at early bloom along with insecticide. The motivation for using the fungicide was not so much in response to disease issues, but more about plant health and the potential to gain yield. Hendrickson says the plants appeared healthier and the stalks were stronger and thicker at harvest.

Yield results were unclear this year, as a good portion of his crop fell victim to an extreme late-season wind storm just before harvest began. But despite the weather damage, Hendrickson says the plants were healthier this year; and based on conversations he’s had with other growers about yield increases they’ve experienced with Quadris, he’ll use it again next season.

“I’ve used fungicide over the years on my soybeans with good results. It might delay harvest just a bit with the greener plant, but for overall plant heath, I’ll use it again on my sunflower,” he says.

The best advice for any grower might be to evaluate the effect of Headline or Quadris in side-by-side, treated-versus-untreated comparisons, at the labeled rate and recommended timing. As with any treatment, the proof is in the plant. — Sonia Mullally
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