Georgia is the nation’s No. 1 producer of peanuts, and visitors to the Sunbelt Ag Expo will have the opportunity this year to see many of the newest varieties being harvested in the Expo peanut plots.

Since the first Sunbelt Expo in 1978, field demonstrations of harvesting and tillage have made the annual show unique, and this year is no exception.

With rising costs for fuel and other inputs, peanut producers have enough to worry about without the added threat of tomato spotted wilt virus. University of Georgia Extension specialists and researchers are using variety trials at the Sunbelt Expo site to help determine the optimum planting date for avoiding the virus and to help growers decide which cultivars are most resistant to the disease.

“Peanut producers are well aware of the negative impact tomato spotted wilt virus has on peanut yield,” says John Beasley, University of Georgia Extension peanut specialist. “One of the most critical factors in reducing risk to the virus is planting date.”

Previous research, he says, has indicated that peanut fields planted in mid to late April have a much higher risk of tomato spotted wilt virus than fields planed in mid- to late-May.

“In this trial at the Sunbelt Expo site in 2006, we planted six runner-type peanut cultivars on April 19 and May 19. During the Sunbelt Expo Field Day this past July, visitors could observe differences in the growth habits, and in the incidence of tomato spotted wilt virus among the cultivars at each of the planting dates,” says Beasley.

The six cultivars, he says, include Georgia Green, AP-3, Georgia-03L, C-99R, Georgia-01R and Georgia-02C.

“These trials allow us look at peanuts that are about 90 days old versus some that are about 60 days old. We’re taking those varieties that have improved levels of resistance to tomato spotted wilt virus, and we’re trying to determine if we possibly can plant earlier. Many of our growers want to plant earlier. But only if we have more resistance in some of these new varieties can we plant earlier and still have as good tomato spotted wilt virus control,” says Beasely.

“We’ve seen in some of these more highly resistant varieties — in our first couple of years of looking at the late-maturing ones — that we have more virus, but it’s not nearly as severe as if it’s on Georgia Green,” he says.

The tests, says Beasley, will go into the University of Georgia database. “At Sunbelt Expo, we have mid-maturing and late-maturing varieties. We’ll look at the data and see if it needs to be included in our evaluation of the University of Georgia Peanut Disease Risk Index, or if we need to make adjustments,” he says.

All of these varieties, he adds, have different levels of resistance to early and late leafspot, white mold, limb rot and cylindrocladium black rot (CBR).

“When you look at the disease risk index, you can look at the values associated with each disease, and you can get a true picture of how the varieties might perform on your farm. For example, AP-3 has the highest level of resistance to tomato spotted wilt virus. It’s a 10-point variety on the risk index while Georgia Green is a 30. But on leafspot, Georgia Green is a 20 and AP-3 is a 25. AP-3 is more susceptible to leafspot. But Georgia Green is more susceptible to white mold while AP-3 is less susceptible. You can mix and match and make a variety selection based on your predominant disease problem. GA-01R is one of the lowest on white mold, limb rot and leafspot,” he says.

Researchers will also be looking at any possible impact varieties and planting dates have on the three-cornered alfalfa hopper, which has been a problem for some Georgia peanut producers, says Beasley. “We’ll evaluate diseases and the response to insects, particularly the three-cornered alfalfa hopper. We already have some data showing a differential response from planting different varieties. We’re using the Sunbelt Expo site to evaluate these varieties.”

The University of Georgia Peanut Team also has a demonstration at the Sunbelt Expo site showcasing all of the currently available peanut cultivars, in addition to several advanced lines that have been released this year. These peanuts are planted in both single and twin-row patterns.

“In past years, we’ve tired to have a non-replicated trial at Sunbelt — a show-and-tell of all of the different varieties we currently can plant, in addition to seed from new and upcoming varieties. For example, there will be three new releases from the University of Florida, and USDA has a line that was released this year. We’re taking a look at all of those,” says Beasley.

e-mail: phollis@farmpress.com