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Fungicides decrease peanut rod rot risk

Fungicides decrease peanut rod rot risk
Fungicides provide insurance for peanuts. Not applying fungicides increases chances for kernel damage. Proper identification is critical.

Applying a fungicide to protect Texas peanuts against pod rot adds a bit to production costs, but may be worth the investment, says a Texas AgriLife Extension plant pathologist.

“We have not seen significantly lower returns when using fungicides,” says Jason Woodward, who works from the Texas AgriLife Research and Extension Center in Lubbock.

“But not making fungicide applications increases potential for damage to kernels. It’s risky without some protection.”

Woodward, speaking at the Oklahoma Peanut Expo at the Quartz Mountain Resort in Lone Wolf, Okla., said peanut farmers “may be better off with an insurance application than risking pod rot damage.”

Pod rot has become a “major problem for Texas peanuts,” he said. “We still work with Sclerotinia blight and Verticillium wilt, but pod rot has a major effect on Texas peanut production.”

Pod rot develops from two organisms, Pythium and Rhizoctonia. Pythium typically has a greasy look and Rhizoctonia typically has a dry appearance. “But for the last few years, it’s been hard to tell the difference in the field,” Woodward said. “Furthermore, both organisms may be present at the same time. They also may show up in the same field at different times of the season.”

Fungicides will help control pod rot, but Woodward cautions farmers they will not see activity as rapidly as with other pesticides, such as herbicides. “Growers can apply herbicides and see effects soon after; however, fungicides are applied with a boom and the material must go through the canopy and onto the soil. It may be seven to 10 days before we can see any effect.”

Woodward recommends growers properly identify the disease so that the most effective management program can be established. Initial applications of Abound fungicide are generally made 60 days to 75 days after planting with a sequential application coming approximately 30 days later. If applications are made too early a third application might be warranted. Harvest losses may occur.

“Fungicides work,” he said. But timing is critical. He says calendar approaches appear to be more effective than threshold based programs.

“We may need to refine treatment thresholds, which are less consistent than a calendar approach, which typically begins 70 days after planting.”

He said the low threshold approach results in “slightly higher yields, but we see no correlation to disease control.”

Variety selection also may play a role in pod rot management. Tamrun OL07 and Tamrun OL02 show less pod rot damage than Flavorrunner 458. Limited observations indicate that ACI 149 also may show tolerance. “One treatment on ACI 121 showed less damage than Flavor Runner 458 with two applications.”  Cultivar performance as well as fungicide timing and efficacy will remain the focus of his research program.

Woodward said tillage seems to have no effect. “We’ve seen no difference between conventional and reduced tillage systems.”

He cautioned growers not to apply fungicides too early. “We need to find that ‘sweet spot’ for best fungicide application timing.”


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