A minimum amount of rainfall translated into a minimum amount of disease pressure for Alabama peanut producers this past year, says Austin Hagan, Auburn University Extension plant pathologist.
“We didn't have much tomato spotted wilt virus around here, which is good, and we didn't have any leafspot diseases anywhere in the state because we didn't receive enough rain. Even under irrigation, we just didn't see much,” says Hagan.
The only peanut disease that did show an increase in severity — where there was moisture — was white mold, he says. “If you have a history of growing soybeans or you were growing watermelons or vegetables, then white mold might enter into the mix,” he says.
There are several peanut fungicide updates for 2008, says Hagan, included a reduced rate for Abound.
“They've changed the leafspot rate from 12 fluid ounces down to 6. It's an option for some growers, especially those who are new to peanut production and don't have a history of disease. More than likely, you'll have less leafspot pressure. If you're in this situation, you probably won't have to worry about white mold. You can reduce the rate and that would be fine during the course of the season,” he says.
But when you want to start picking up the soil-borne diseases, you'll have to start spending money, he adds. “For white mold, you need at least 18 fluid ounces. We haven't worked that much with the higher rates, but 18 ounces usually works fine,” says Hagan.
Another product — more of a white mold material — is Artisan, he says. “It's priced like a generic product, so it's a good option if you already have or if you are concerned about soil-borne peanut diseases like white mold or limb rot. The same goes for Echo and Muscle. These are both generic products, and they will be in twin containers, so when you put one in the tank, you'll be putting in both of them,” he says.
Echo is a chlorothalanil fungicide and Muscle contains the same active ingredient as Folicur, he says.
“If you go down into the traditional peanut production areas of Alabama, Folicur doesn't give the same level of leafspot control that it did 10 years ago. We're running into some resistance or tolerance in the disease fungi. That's why Echo is in there — to take care of leafspot,” says Hagan.
Provost fungicide, he says, is a replacement for Folicur that has been available since last year. It's more of a fit in those areas that have a history of white mold, he notes.
“If you're just looking at leafspot, it certainly will control that disease. But you probably don't need this material in your mix unless you're trying to pick up soil-borne diseases,” he says.
Another new fungicide is Convoy, which is also for controlling white mold, says Hagan. “It used to be called Moncut, but it will be priced much less than that material,” he says.
Many leafspot products are available to growers, he says, and they are generic and priced less than some of the name brands.
“We've done some research, particularly with the chlorothalanil fungicides, on peanuts. In Fairhope, Ala., we haven't seen any difference in performance among these different formulations. So you can make a decision on which way you want to go with these products. They all work pretty well. If you're just getting into peanut production, you're not going to have a lot of disease problems in the first year or two. You can get by with a reduced or lower rate of the chlorothalanil fungicides. They're relatively inexpensive when you compare them with the cost of some of the other materials,” says Hagan.
The first application of these products should be made about 30 to 40 days after planting, with subsequent applications every two weeks up until about two to three weeks prior to harvest. “In east-central Alabama, we're talking about approximately six applications over the course of a season. That's a pretty intense program for new peanuts, but it should eliminate any risk whatsoever that you'll have a leafspot problem on your peanuts.”
Another tool for combating peanut diseases is the Peanut Rx program — developed by researchers and specialists in Alabama, Florida and Georgia, says Hagan. “This program based on risk assessments, allowing you to go out and look at each of your fields using the information generated from field trials and put into a point system. You can get an idea of whether or not your field falls into one of several risk categories. Based on that category, you can make adjustments in the management of diseases.”
With tomato spotted wilt virus, a grower may want to think about changing varieties to lessen his risk to the disease, he says. “If you're talking about leafspot or white mold, and you get into a low-risk category, you can look at using fewer fungicides.”
For someone who is new to growing peanuts, it may take awhile for disease pressure to become a problem, and for some of the Peanut Rx components to become relevant, says Hagan.
“In Fairhope, we have a rotation where we had to plant peanuts for four consecutive years before we got into severe white mold problems. By the second year, we had severe leafspot pressure. It takes a while to get into a situation where these diseases become worse.”
But growers can use the information in Peanut Rx to make decisions on variety selection even if they don't use the entire risk assessment program, says Hagan. “If you're going to plant peanuts before May 5, you had better plant a variety that's resistant to tomato spotted wilt virus. If you plant Georgia Green, plant it after May 15 to be on the safe side. The later peanuts are planted, the less virus you'll have.”