What is in this article?:
- Peanut disease control continues to be a focus of growers
- Fungicide amount based on risk
- Other line of defense
• While improved peanut varieties have been wildly successful in controlling diseases and nematodes, they still represent the single largest input cost for growers.
IF A PEANUT producer has good rotation, resistant varieties and good management, he may be able to get by with only four or five fungicide applications.
Fungicide amount based on risk
The program, he says, is based on putting the right amount of fungicide into a field based on risk.
“If you have a high risk from short rotations and growing soybeans and less resistant varieties, you need to spray at least seven times, and in a wet year, maybe eight or nine times to maintain yields,” says Kemerait.
But if you’ve got good rotation, resistant varieties and good management, you may be able to get by with only four or five sprays, he adds. “The important thing is that the prescription program is a tangible way to benefit from using good management.”
Traditionally, and prior to 2006, most growers were spraying their peanut crop an average of seven times a season with fungicides.
Soil-borne diseases also continue to be costly for peanut producers to control, says Tim Brenneman, University of Georgia Extension plant pathologist.
“Peanuts are unique in that they flower above ground and set the crop underground, and that works very well except it exposes them to a lot of pathogens and a lot of diseases, because these pathogens reside in the soil,” says Brenneman. “We’re working with root-knot nematodes, CBR and white mold or stem rot.”
Georgia 06G, which is grown on 80 percent of Georgia’s acreage, is highly susceptible to root-knot nematode, he says. “To compound the issue, we’ve lost Temik, one of our best nematicides. Thankfully, we have the Tifguard peanut variety, which has a remarkable level of resistance to root-knot nematodes,” he says.
CBR or cylindrocladium black rot is scattered around the state, says Brenneman. “It’s not in every field, but if you have it, it’s probably your No. 1 concern because it’s so devastating. It’s a root-infecting pathogen, so if you have it, it’ll affect young secondary roots, eventually move into the taproot of the plant, and end up killing the whole plant.”
CBR is affected by cool, wet conditions, he adds. “We had unfavorable conditions this past year for CBR, especially at the beginning of the growing season. Even though Georgia 06G is very susceptible, we saw very little in growers’ fields in 2011. As the weather changes, the disease spectrum also changes,” he says.
There’s also stem rot or white mold, which is now the most damaging peanut pathogen in the state, says Brenneman. When conditions are favorable, the fungus can grow rapidly down the rows, killing stems above ground and rotting pods below ground.
Crop rotation also can reduce the disease, but when conditions are favorable, it can still cause significant losses. Hot weather favors disease development, and the hotter summers in recent years have led to severe epidemics.