Using fungicides under right conditions proven to increase yields
Mar. 2, 2011
Marcia McMullen, NDSU plant pathologist, said stripe rust was spotted across the state last summer in wheat fields, a crop disease seldom found in North Dakota.
According to the USDA cereal rust bulletin, wheat stripe rust and wheat leaf rust were found at low levels throughout the entire northern wheat growing area in 2010.
In addition, wheat stem rust was found in North Dakota, Minnesota, Wisconsin, Nebraska, South Dakota and Washington, and oat stem rust was found in Minnesota plots last summer.
"We haven't seen stripe rust here in a long time," McMullen said, adding stripe rust has occurred infrequently in the past, and was "never at the severe widespread levels as it was last summer. It did some damage on susceptible varieties."
The fungi that causes these diseases - leaf rust, stripe rust and stem rust on wheat and barley - are "notorious for their ability to increase rapidly and overcome the resistance of wheat and barley varieties," according to an NDSU report McMullen handed out during the session. It is only a matter of time before Ug99, a variant of a new race of stem rust, reaches the U.S., according to the report.
Some spring wheat varieties, such as Tom from the University of Minnesota, and the AgriPro wheat, varieties Kelby, Brennan and SY Soren are currently are resistant to Ug99, said David Boehm of Syngenta Cereals, but that will probably change by the time it arrives here.
According to the report, additional variants besides Ug99 have emerged in East African countries, complicating efforts to contain the problem.
Jagalene and Hawken winter wheat varieties are more susceptible to stripe rust than other varieties and both were heavily infested last summer, she added. Both had good response with fungicides last year.
NDSU field agents also spotted stripe rust in some spring wheat varieties, which was alarming to McMullen because it hasn't usually been seen in the past in spring wheat, she said.
Spring wheat varieties which had rust vulnerability included Steele-ND, Digger, Glenn, Mott, AP605CL, and Briggs.
"I don't know if stripe rust is going to be a problem in 2011, but we do have some susceptibility to that disease," she said.
According to the NDSU pest report, "by the time stripe rust spores reach our region on prevailing winds, the temperatures are high enough to be unfavorable for infection, ie. when daytime temps are above 80 degrees F, and night time temperatures around 60 degrees F." But it stayed cool enough for the infection to spread last year.
Stripe rust is distinguished from leaf rust by the color of the spores and the shape of the spore mass on the leaf surface, according to NDSU. Stripe rust consists of yellowish-orange spores found in long, linear lesions on leaf blades, while common leaf rust is more reddish-brown and found in round spore masses on leaf blades or leaf sheaths. Stem rust is orange-red in color and affects stems, leaf sheaths and leaf blades.
"We had good response with fungicides on Jagalene and Yellowstone winter wheat in particular - an average of 3 bushels per acre," McMullen said, adding that applying fungicides at flowering keeps good control across the rotations.
Ducks Unlimited has more than 16 sites of winter wheat in the state, and the organization's scientists found an average yield increase of 14 bushels per acre when using fungicides on 20 varieties, she said. The large amount of varieties tends to increase the average amount of bushels. DU applied Prosaro at 6 ounces plus NIS at flowering.
Assuming winter wheat is selling for $6 a bushel, applying Prosaro at a cost of approximately $24 an acre at flowering could bring a return of $60 an acre on a producer's investment, she said.
"You get a very good economic return on winter wheat when using fungicides," McMullen said.
From 2008 to 2010, on average, DU saw 10.7 bushels per acre more when fungicides were applied at flowering on winter wheat for an average return on investment of $40 an acre over those three years.
McMullen said another reason for using fungicides in the western regions is tan spot. That disease is common and seems to pop up in the west because there is a tendency to use more wheat on wheat and less distance in the rotation before using wheat again, she added.
NDAWN forecasts the risk of tan spot and other small grain diseases at http://www.ag.ndsu.nodak.edu/crop disease, she said. According to NDSU, when the risk for tan spot shows six days with "yes," apply a fungicide.
"It is important to use the tools at your disposal. Last spring, NDAWN said yes for tan spot at almost every location," McMullen said.
Studies done at Dickinson Research Extension Center on wheat showed the Syngenta fungicide Quilt (a combination of Quadris and Tilt) showed a return on investment of $2 to $36 an acre, depending on the site, she said.
With Bayer CropScience products, a study in Bowman with Howard using Stratego and Prosaro at flowering showed a return on investment of $20 to $35 an acre, she said.
"2010 was a good year for fungicide response," McMullen said.
In Minot trials in the summer of 2010, an often-wet area in the spring, there was a good response to fungicide use. On wheat, scientists saw a 10 plus bushel per acre yield increase, and in barley, they saw a 20 plus bushel increase.
"Applying at early flowering (four to five leaf stage) and again at flowering was found to be better than just applying at early flowering alone," McMullen said.
The barleys Lacey and Tradition had a better response to fungicide use in terms of yield increase than a barley like Celebration, she said.
To have a bushel per acre yield response, you have to break even first, McMullen said.
Assuming $7 bushel wheat in 2011, producers would only need to see a 3.4 bushel per acre yield increase to break even "on even the most expensive fungicide treatments," she said.
"Unless we have a drought this year, you should be able to achieve that."
There has been increased use of fungicides in the southwestern and south central parts of North Dakota, McMullen said. The increase is due to improved prices for commodities, wetter years, better products, cheaper generics, and more equipment.
All the early-use fungicide are effective, including the generics of the products with Prosaro and Caramba being registered in 2008.
Seed treatment products are another way to go to fight fungal diseases such as loose smut and pythium in wheat and barley fields, she said. These products can control a lot of different seed-borne diseases and "do a good job."
There is some risk of crop leaf damage with using fungicides early in combination with herbicides if it gets cold at night, she said.
McMullen encouraged producers to use disease forecasting tools to protect their yield potential.
"Be proactive, not reactive," she said.
Source: Farm & Ranch
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