Tuesday, August 28, 2018

Cotton Growers Still Grappling with Nasty Soil Disease

Over the years, Bob Hutmacher has visited countless cotton fields across the Valley.

He’ll field a call from a grower asking him to come check out a problem with the crop.
I feel like the grim reaper when I walk into a field and they ask if they have Race 4 fusarium wilt,” he jokes. 

This season, the University of California Cooperative extension specialist at the Westside Extension and Research Center has visited 10 cotton fields and found they have lost 5 to 15 percent of their stands due to the soil disease.

UCCE cotton expert Bob Hutmacher
“It’s going to be a continuing battle. It’s difficult to contain,” he told growers attending a recent cotton field day in Mendota. Identified in 2001 in Fresno-Kings counties area, the nasty soil disease was identified in four different locations in the San Joaquin Valley within three years. It has steadily spread northward to the upper San Joaquin Valley. 

Recently, Race 4 fusarium was discovered in West Texas cotton fields around the El Paso region. Hutmacher suspects it could be infecting fields in Arizona – although nothing has been confirmed by agriculture officials.

Race 4 is a fungus in the soil. It can infect plants and cause a vascular wilt in a number of cotton varieties. The spores can be spread through regular farming practices such as irrigation and cultivation.  It can cause damage in a variety of soil types. Over time, it can spread through an entire field and ultimately cause widespread plant losses and stunted growth, adding up to a costly loss in yield.

“It could be a couple years when you detect anything or it could be 10 years.”

Hutmacher says seed companies have developed resistant cotton seed varieties and continue to look for improvements. Researchers in California and Texas are exploring crop rotation practices that could limit the spread of the disease.

Race 4 fusarium will wipe out sections of cotton plants.
In the 10 fields Hutchmacher inspected this season, about half of them were in the second or third season in cotton. Some of the worst cases, though, were in fields planted in melons or tomatoes the previous year.

“We still don’t know of a crop rotation that knocks down its survival,” he says. However, the disease appears to be controlled the year after the field has been left fallow the previous summer. “That actually knocks down the problem.”

Hutmacher says public research institutions, government ag agencies and private ag firms need to continue working together to come up with a solution. 

Cotton plants will wilt and die from the soil disease.
“Until you get a perfect resistant variety, the solution is a really resistant cultivar along with a kind of chemical treatment that is affordable. That will reduce down the infection rate. I don’t think it will need to be perfect,” he says. 

Hutmacher urges growers to contact UC farm advisors if they see any problems in their fields.

Once growers know they have an infected field, they can take steps to slow the spread of the disease. That includes cleaning soil from equipment, limiting the movement of soil and plant debris from the infected field and planting resistant varieties.

“People have been very good about working with their PCAs, seed companies and consultants to try to get answers to know what they are dealing with,” he says.

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