The adage “it’s all in the timing” is never truer than when talking about peanut disease and nematode control.

And while improved varieties have been wildly successful in controlling these pests, they still represent the single largest input cost for growers.

Georgia 06G, Georgia 07W, Florida 07 and Tifguard all have a nice level of resistance to tomato spotted wilt virus and other pests, but growers still depend on fungicides for controlling leafspot management, says Albert Culbreath, University of Georgia plant pathologist.

“We don’t have varieties with a high-enough level of leafspot resistance that we can get by without spraying a crop. We’ve found a considerable level of moderate resistance in some of the lines, and we’re finding more tolerance, as well,” says Culbreath.

Early and late leafspot are very adept at knocking the leaves off the plants, he says, and yield reduction is very closely correlated with the amount of plant defoliation.

“The variety Tifguard has a low to moderate level of resistance to leafspot. Even the ones that are susceptible appear to be hanging onto their yields even in the presence of greater levels of defoliation. That tolerance could be used in programs such as the Peanut Rx program, a risk index for peanut production.

“We’re looking at what might be that critical level of defoliation with some of these new varieties. With the old variety Florunner, basically as soon as you started seeing noticeable defoliation, you knew you were losing pods. That doesn’t appear to be the case with these new varieties,” says Culbreath.

Peanut Rx — the result of a collaboration between Southeastern land grant universities and several fungicide manufacturers — continues to be evaluated and updated by researchers, says Bob Kemerait, University of Georgia Extension plant pathologist.