What is sustainability? To University of Georgia Extension plant pathologist Bob Kemerait, it’s the capacity to endure.
“It means to be able to keep doing what we’re doing over the long term — to maintain our ability to grow crops and to feed the world,” said Kemerait at the Southern Peanut Growers Conference held recently in Panama City, Fla.
Three things are required of a sustainable system of agriculture, he says. “It must be environmentally sustainable, it has to be socially sustainable, and we have to meet the economic demands. Because none of us do what we’re doing because it’s just fun — we do it because we have to feed our families.”
Many times, says Kemerait, the term “sustainability” is mistakenly used interchangeably with “organic.”
“There’s nothing wrong with organic, but that’s not what most of us do in agriculture. Organic may be sustainable, but you don’t have to be organic to be sustainable,” he says.
Organic farming utilizes crop rotation and biological pest control but does not utilize synthetic fertilizers and pesticides.
“The kind of sustainability I’m talking about includes the use of synthetic pesticides. We may not be organic, but we can be sustainable. While there are agricultural systems that are sustainable and organic, that’s not what most of us do.”
Kemerait says that whenever he hears someone in the agricultural community say that they’re going to talk about sustainability, he tends to become defense because he doesn’t expect it’ll include conventional agriculture.
“USDA has defined sustainable agriculture as an integrated system of plant and animal production practices having a site-specific application that will over the long term satisfy human food and fiber needs,” he says. “It’s not enough just to be organic, traditional or sustainable, but you have to meet the requirement that you are able to meet the needs of the population. At the same time, we want to enhance environmental quality and make the most efficient use of non-renewable resources. Just because we don’t practice organic farming doesn’t mean we don’t want to do those things.”
If you can’t make a living for your generation and for the next generations, it’s not sustainable, says Kemerait.
Disease management critical in sustainability
For peanut producers, disease management is a critical factor in sustainability, he says.
“The best management programs may not give you absolute control. You may not clean up every leaf spot or every incidence of white mold in a field. Best management practices will integrate cultural ideas methods such as planting resistant varieties, and they also will look at the optimal use of fungicides.”
Growers cannot reduce their reliance on fungicides and nematicides if they don’t reduce their risks, says Kemerait. “We have to optimize our application strategies. If we want sustainable, and we want to continue using our inputs, then we have to do what we do better. That’ll reduce costs and risks.”
All peanut producers can do what they already do better in terms of managing diseases, says Kemerait.
“Best management practices require timeliness, calibration, attention to rates, the proper disposal of containers, and complete attention to the label. We also want to use innovative technologies and strategies. All of these things will make our peanut disease management more sustainable.”
One tool for accomplishing sustainability in peanut disease management is the Peanut Rx risk index, he says.
“Peanut Rx is a branded symbol that shows that peanut producers in the Southeast U.S. are already practicing sustainable agriculture and sustainable disease management.”
Tomato spotted wilt virus, early and late leaf spot, CBR, white mold or stem rod are the enemies of Southeastern peanut growers, says Kemerait.
“If we’re going to continue to be sustainable in producing peanuts in an economic fashion, then we have to be able to manage those, in addition to peanut root-knot nematodes. We have to be able to manage all of these pests to be sustainable.”
Requirements of sustainable peanut disease management include crop rotation, resistant varieties, tillage systems, using peanut prescriptions in risk management programs, and the careful selection of fungicides and nematicides, he says.
“This means using the ones that are most likely to give the control you need and most likely to give you the best return on your investment.”
Resistance management also is important, he adds. As azoxystrobin goes off patent, growers have to be even more diligent about resistance management, says Kemerait.
“General plant health management also is crucial in sustainability. You’ve also got to manage fertility, weed pressure and all of those other things because a healthier plant is more resistant to disease.”
Kemerait urges growers to consider those factors in Peanut Rx that’ll allow them to take the pressure off of their reliance on fungicides. “By taking the reliance off of fungicides, you give yourself a better opportunity to get improved disease management and to get better fungicide efficacy.”
Crop rotation remains the foundation of any disease control program, he says. “We’d like for you to be out of a peanut field for two years. Three years is better, and four years is even better than that. But it’s not only being out of the field with peanuts, it’s what you plant in the place of peanuts. If you have the choice of planting soybeans or corn, which one will give you better returns in your operation?
“Obviously, corn will since soybeans share some of the same nematodes and pathogens. So rotation is a cornerstone in terms of sustainable disease management.”
Great strides have been made in breeding disease resistance into new varieties, says Kemerait. “Leaf spot resistance, white mold resistance, nematode resistance – resistant varieties allow us a greater opportunity on the fungicide program we choose to use. An example is the variety Tifguard, which has resistance to the peanut root-knot nematode. So simply choosing a variety with greater resistance gives you more flexibility in all of your other production practices as well as your choice of nematicides and fungicides.”
Impressive arsenal of peanut fungicides
Peanut producers, says Kemerait, have never had a better arsenal of fungicides. “Using those effectively is a critical mission for us. We currently have four general classes of fungicides. The first one is chlorothalonil. It’s out by itself and we’re not really worried about resistance. The other three, including the triazole fungicides, strobilurin fungicides and even the SDHI fungicides all can develop resistance. These fungicides are where we want to be as far as efficacy. They’re the ones we use most often, and we need them for sustainability.”
Do growers need anything more than chlorothalonil and tebuconazole, asks Kemerait.
“It’s an inexpensive mix that gives us very good disease control in most situations. But I would argue that we have to be very concerned about that. The best tool for resistance management is to get away from inexpensive. That’s not what growers want to hear – they don’t want to overspend. But if things are too inexpensive, growers tend to put it out because it doesn’t cost much. How much tebuconazole is being used? Overuse of tebucanozole is not sustainable. It may make economic sense in the short term, but it’s not sustainable.
“We’ve got to look at cost versus efficacy versus resistance management. Azoxystrobin is going off patent soon and the wolves are probably already there. Tebuconazole is an outstanding fungicide. It’s also an inexpensive fungicide that we overuse, but we have to remember that there’s value in spending more money sometimes. Don’t start thinking you can use more of something just because it’s cheap.”
Growers who want to get the most benefit from a fungicide need to anticipate rain events, says Kemerait.
“You need to be timely and stay ahead of the disease. Research has found that night spraying improves soil-borne disease control. Work also has been done on early emergence applications. We’re talking about additional sprays but better management. Sustainable means stewardship of the environment, but it also means making more money with the limited resources we have.”
Growers no longer have Temik for nematode control, and it was a very effective nematicide when used appropriately, says Kemerait. Telone is available, but many growers won’t use it because of its cost and application requirements.
A new strategy this is now being used in cotton and soon will be used in peanuts is determining how to best predicts “response” zones in a field, he says.
“Then we can use Telone only where we need it. Nighttime applications, early applications and site-specific applications all are ways we can make peanut production more sustainable. If we can cut the rate of Telone in a field by 60 percent and maintain yields, you can’t tell me that’s not sustainable.”