On-Farm Nematode Trials

The nematode-resistant cultivar, TifNV High O/L, is compared to the nematicide Velum Total.

root-knot nematode foliar symptoms

 Strips of Georgia 06G exhibit chlorosis, necrosis and wilting. The rows of TifNV, a root-knot nematode resistant variety, were green and vigorous.

Root-knot nematodes are one of the most prevalent and damaging pests in peanut production in the Southeast. Crop rotation, use of resistant cultivars and nematicide applications are the primary strategies for managing root-knot nematodes.

Recently, a new root-knot nematode resistant peanut cultivar, TifNV High O/L, was released by the University of Georgia. Research trials indicate this high-oleic cultivar has greater yield potential than previous resistant cultivars such as Tifguard and Georgia 14N.

More testing is needed in commercial fields under root-knot nematode pressure in comparison to commonly used nematicides such as Velum Total.

Options Tested

In 2019, two on-farm peanut nematode trials were conducted in Florida. One trial was conducted in Jackson County on irrigated land and another was conducted in the Suwannee Valley on non-irrigated land. Treatments were as follows: 1) Georgia 06G, 2) Georgia 06G with Velum Total in-furrow at 18 ounces per acre, 3) TifNV and 4) TifNV with Velum Total. Georgia 06G is a root-knot nematode susceptible variety.

Treatments were applied in four- or six-row strips across the length of each field. Each treatment was repeated four or five times in each field.

Trial Results

pod galling resultsIn the Jackson County trial, root-knot nematode pressure was low. The amount of root-knot nematodes was not affected by cultivars or nematicide application. Peanut yield was 771 pounds per acre greater for 06G than TifNV.

Statistically, Velum Total did not increase yield, but 06G yielded 528 pounds per acre more with Velum Total than without Velum Total. Velum Total did not influence TifNV yield.

In this trial, 06G performed better than TifNV under low root-knot nematode pressure. However, this is a single trial, and caution should be shown in interpreting it.

TifNV has been more competitive with 06G in variety testing by UF peanut breeder Barry Tillman on irrigated land than is shown in this trial. Over four years of Florida peanut variety trials, TifNV averaged 350 pounds per acre less than 06G but approximately 700 pounds per acre more than Tifguard.

Under Severe Pressure

In the Suwannee Valley trial, root-knot nematode pressure was severe. There were clear above-ground visual differences between cultivars. Georgia 06G exhibited yellowing, browning and wilting with symptoms increasing in severity later in the season.

In contrast, TifNV was greener and healthier than 06G. There were no obvious visual differences between strips treated with or without Velum Total.

Galling on roots and pods at harvest was much greater for 06G than TifNV, which was nearly free of galling. Velum Total did not affect root or pod galling. TifNV yielded 750 pounds per acre more than 06G, whereas Velum Total did not improve yield. Velum Total and other nematicides have shown value in other trials, but not consistently.

Growers should not abandon use of nematicides based on these results. The results suggest that resistant cultivars are a more effective option when root-knot nematode pressure is severe.

Always soil test for root-knot nematodes. Based on the results of these trials and other research, producers with a severe root-knot nematode infestation should plant a nematode-resistant cultivar or rotate to a non-host crop.

Article by Zane Grabau, UF/IFAS crop nematologist, based on research he conducted with Ethan Carter, regional crop agent; Jay Capasso, Columbia County Extension; and Mark Mauldin, Washington County Extension.