Growers Weigh In On Tifguard

The variety’s ability to withstand nematode pressure is not
the only thing impressing growers.

By Amanda Huber

Tifguard continues to be in seed increase in 2008, but growers who conducted on-farm testing last year and an Extension agent were more than willing to share their thoughts about the variety.

Jeff Barbour, who works on the Barbour Family Farm in Brinson Ga., in Decatur County, says he only had enough seed to plant about four strips, or passes, with the six-row planter randomly in a field of Georgia Green.

“Last year, all I saw were those strips, but they out-yielded the Georgia Greens in the field,” Barbour says. “They look good growing, and I thought enough of them that I’m going to plant a whole field to them this year, about 75 acres.”

Vines Stay In Shape
Barbour says the test field had no nematicides applied, but was not necessarily a field with heavy nematode pressure. What impressed him most was how well the Tifguard peanuts held up at the end of the season.

“When the peanuts got mature and the vines started going back, the Tifguard variety stayed prettier and fresher than the Georgia Greens,” Barbour says. “We had no trouble digging, and the vines stayed in much better shape than the Georgia Greens did.”

For this season, Barbour will plant Tifguard in a field with a little more nematode pressure.

“There will be nematode pressure in several spots, but it has never been enough to justify spraying the whole field.”

If Tifguard will withstand the nematode pressure and not incur any damage, and yield good throughout the field, Barbour says that is what he is looking for.

Good Fit In Production Schemes
“My impression is good at this point,” says Joel Hudgins, Barbour’s Extension agent in Decatur County. “It has a growth habit similar to Georgia Green, which means it will be a good fit for our current production schemes.”

“It has good resistance to Tomato Spotted Wilt Virus (TSWV), and the maturity is similar to Georgia Green,” he says. “If it does prove to be as resistant to nematodes as they say, then I think we will be able to eliminate the application of Telone, and then coming back with a side-dress of Temik, which is currently standard practice in our county.”

Hudgins says the variety emerged more slowly than Georgia Green, but throughout the season, it had a dark green color right up until harvest.

“I’m optimistic about it. I think it’s going to be a good variety,” he says.

Variety Lives Up To The Billing
Georgia grower Billy Minick pulled no punches and hit the variety with heavy nematode pressure. How did Tifguard do? Minick says the variety is, in a word, “wonderful.”

“We put them on land that is terrible, with nematode counts out of this world, and these peanuts made 4,400 pounds to the acre,” says Minick, who farms with his dad, Bill, in Webster County. “At harvest, they looked like they did in July.”

Minick had enough seed to plant a 43-acre field to Tifguard, plus some test strips in another field.

Like Barbour, Minick says the variety held up well with no spotted wilt and no leaf spot damage either. “I did not spray them but six times last year. I put out chlorothanil, then put out some Provost and then Bravo at the end.”

He says they put out the regular three pounds of Temik at planting, but nothing else, and in this field it was, essentially, no prevention at all. According to Minick, nematodes were simply murder on the Georgia Greens, but the Tifguards readily sustained the barrage from the microscopic pest.

“The nematode hits were there, but there was no damage,” says Minick, who hopes to have enough seed to plant a 53-acre field this year. “If you’ve got nematodes, that’s the way to go.”

Grower Reports Are Further Evidence
The glowing reports from growers are further evidence of what Corley Holbrook, the USDA-ARS peanut breeder who developed Tifguard, has already seen in the variety.

“Our objective was to combine resistance to the peanut root-knot nematode with resistance to TSWV and high yield and grade,” Holbrook says. “We crossed C-99R with COAN, and we used greenhouse and field tests to screen the progeny for resistance to nematode and TSWV, respectively. We then selected for high yield and grade.”

COAN is a runner-type cultivar developed by Charles Simpson, Texas A&M University (TAMU) peanut breeder, and James Starr, plant pathologist at TAMU. It has a high level of resistance to root-knot nematodes. The cultivar was released by the Texas Agricultural Experiment Station in 1999. In 2002, another runner market-type peanut cultivar with a high level of resistance to root-knot nematode, NemaTAM, was released by the Texas Agricultural Experiment Station.

How Tifguard Works
Holbrook says COAN and NemaTAM are both very susceptible to TSWV, which is why these were not acceptable cultivars for the Southeast.

However, he says the level of resistance in Tifguard is very high, “near immunity,” and is similar to that observed in COAN and NemaTAM.

Holbrook explains how Tifguard works by first explaining how nematodes typically infect susceptible varieties. He also explains why they multiply so quickly.

“In susceptible genotypes, females of the root-knot nematode establish a feeding site, which causes the root galling, and they spend the rest of their life embedded at that feeding site. In approximately three weeks, each female lays up to 300 eggs in an egg mass that extrudes from the root. These eggs hatch and begin another cycle of infection. This is the reason that population levels can explode in a long-season crop like peanut.

“In Tifguard, the females cannot successfully establish a feeding site, and so they do not reproduce.”
For 2008, on-farm testing and seed increase will continue, expanding from Georgia into Florida and Alabama.


Are Nematodes Your Nemesis?

University of Georgia Plant Pathologist, Bob Kemerait, says that growers sometimes mistake nematode problems for other production problems. Therefore, a reminder of what to look for is in order.

Kemerait says the initial symptoms of damage from peanut root-knot nematodes are stunted plants that do not grow well and do not lap. However, there are other factors that can cause this.

To confirm suspicion of a nematode problem, he says growers can dig plants up and look for the “tell-tale” galling on the roots.

Kemerait says growers should be careful not to misidentify Rhizobium nodules as root-knot galls. A quick rule of thumb is that Rhizobium galls will slough off the root easily, whereas root-knot galls do not.

Next, he says growers can take soil samples and have them evaluated for the presence, or absence, of plant parasitic nematodes.

“Soil samples are a very important tool to determine how bad (or good) the nematode populations are,” Kemerait says. “It is critical to take these samples correctly to ensure accurate results.”

He says growers can submit the actual roots and pods to the lab, as well, to extract nematodes directly from the tissue to confirm the problem.

While a number of factors can cause stunting of plants in the field and Rhizobium nodules can be confused with nematode galls, putting these factors together should lead to a diagnosis of nematode problems. A soil test, or testing of the roots and pods, will give a confirmation to that diagnosis.