Will The Warm Winter Produce More Disease?

Regrowth of winter host plants create a haven for disease pathogens and nematode populations.
A La Niña weather pattern is providing warmer winter temperatures for Georgia residents, sparking farmers’ concerns about potential plant diseases at the start of production season in early spring.
University of Georgia Cooperative Extension plant pathologist Bob Kemerait says that farmers rely on extreme cold and freezing temperatures during the winter for a break from one growing season to the next. Right now, that isn’t happening.

Regrowth Of Host Plants
The warmer temperatures allowed volunteer peanuts and cotton plants to regrow, increasing nematode populations and creating a haven for diseases.

Kemerait is especially concerned that unusually warm temperatures early in the peanut season will spark outbreaks of white mold. White mold threatens peanuts every year along the soil line and near the soil surface leading to the death of the limbs and crown, with pegs and pods destroyed as a result.

“When you have a winter like we just had where we had a very brief cold snap, it killed back some of the volunteer plants that might have the disease, but it’s been so short that the soil temperatures are warming back up,” Kemerait says. “Nematodes can become more active on the regrowth of peanut volunteers. This is something that farmers need to be aware of when they’re developing their disease and nematode management programs for 2017.”

Late First Frost
A warmer winter also led to a delay in the first frost experienced in south Georgia this season. It sometimes happens as early as November, but the first winter frost did not occur this season until January. According to Kemerait, this allowed more time for nematodes to build up and for pathogens to develop. If this trend continues, Kemerait worries farmers will have greater problems with diseases in the coming season.

“Now, the ideal situation for disease and nematode management on the crops would be to have a very cold February. That would send the nematodes back into a hibernation phase. The pathogens would not survive on different crops or weeds,” he says.

In cotton, Kemerait says that about 75 percent of south Georgia fields have some level of parasitic nematodes. “If these nematodes remain on plants that stay alive and remain in the ground because of warmer temperatures, that could really spell trouble for our growers once planting begins,” he says.
Watch For Late Spring Frost

UGA Agricultural Climatologist Pam Knox says that weak La Niña conditions still remain in the eastern Pacific, leaving Georgia feeling warmer and drier. Since the system has decreased in intensity, Knox believes weather conditions should return to normal within two months. She cautions farmers about the possibility of a late frost.

“One thing we do know from this kind of weather pattern is that the chance of a late frost goes up since the atmosphere often swings more wildly than usual between cold and warm episodes,” Knox says. “So don’t get too anxious to start planting if we have a warm spell because a cold wave could be just down the pike.”

Article by Clint Thompson, University of Georgia College of Agricultural and Environmental Sciences.

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