Peanut Rx — an index that allows producers to get the most benefit from their crop management options — assigns a point total to each variety based on its resistance to certain diseases.

But what’s the true value of a variety’s resistance, from the viewpoint of growers?

“How do we integrate these varieties into a peanut disease management program?” asks Bob Kemerait, University of Georgia Extension plant pathologist. “We’ve got a number of different varieties out there now, but my question is, does disease resistance really matter?”

Tomato spotted wilt virus (TSWV) resistance certainly matters, and breeders have spent considerable time breeding resistance to other diseases, he says.

According to Peanut Rx, Georgia Green has 30 points for TSWV and AP-3 has 10, which means that AP-3 has three times as much resistance to TSWV than Georgia Green. And York is five times more resistant to white mold than Georgia Green.

Peanut Rx was developed by researchers at the University of Georgia, Auburn University and the University of Florida and has been endorsed by Syngenta, Nichino, BASF, Bayer CropScience, and Arysta LifeScience.

“A lot of effort went into breeding those varieties, but for whatever reason, the grower community, the sheller community, or the buyers have decided that despite the resistance, the variety was not adopted widely by growers. So growers must be selecting varieties based on something more than just resistance,” says Kemerait.

In the past five years, many disease-resistant varieties have been phased out because they were not widely adopted. “Resistant varieties are being made available to growers, but we don’t keep them,” he says.

Judging from the varieties currently being grown, producers obviously are demanding resistance to TSWV. We have five varieties that are now being grown, and they have different levels of resistance.

In a survey conducted in Miller County, Ga., peanut growers said that white mold, CBR and peanut root-knot nematodes are all severe problems, says Kemerait. Ninety-five percent of the acreage in Miller County this year is expected to be planted in the GA-06G variety.

“This is despite the fact we have Tifguard, which has near immunity to the peanut root-knot nematode. They’ll go with GA-06G and put nematicides underneath them. What’s so special about GA-06G? It has less disease resistance of any of the other varieties that’ll be planted this year. But it’s all about yield potential, which translates into money. Yield potential drives what you’ll plant,” he says.

Growers will adopt varieties that are more resistant to TSWV and CBR, says Kemerait. “You must have resistance to TSWV, and if you have CBR in your fields, you’ll probably choose Georgia Greener or GA-02C over GA-06G.