He says leaving those plants for their limited yield potential is not worth the risk of spreading millions of Fusarium Race 4 spores across a field from infected plants.

“It is probably not necessary to take the plants completely out of the field as you would with dodder, but make sure the plants are dead after you pull them out of the ground,” he said.

“I would hate to see someone pile a bunch of infected plants in the back of a pickup and then dump them somewhere else on the farm where Race 4 might be spread,” he said.

Getting fields off to a good start is another way to reduce Race 4 spread. Later planted cotton seems to fare better than cotton planted early under less than ideal conditions, he said.

“The fewer challenges a plant has to grow off quickly, the better chance it has to stave off Fusarium Race 4,” Hutmacher says.

Hutmacher said disease-preventing seed treatment is also a good investment against Race 4. The UC cotton research team will be looking at seed treatments specifically for Fusarium Race 4 control, as well.

Soil solarization/tarping fields in the summer to heat up the soil to reduce the inoculum is a proven method of reducing Race 4 inoculum. However, it is not always practical in the San Joaquin Valley where summer fallow is not economically acceptable in high value, irrigated agriculture.

However, summer fallow without tarps could be an option in a drought year like 2010 when irrigation water supplies were limited.

“A grower on the West Side planted two different fields to the same cotton variety at the same time in fields where Fusarium Race 4 has been identified. The only difference was that one field had been summer fallowed the year before because of limited water supplies and the other had not,” he said. “The difference between the two fields was obvious.”

The Race 4 threat is so serious many growers are trying to control it without much research to back their efforts. This has included roguing small, infected areas, injecting soil fumigant and then tarping. Another grower injected Vapam through sprinklers to a limited, infected area with good results.

In Australia, where Race 4 was identified earlier than in California, growers leave defoliated, harvested cotton stalks standing for 30 days before shredding and disking to reduce inoculum in the soil. This may not be practical in the San Joaquin Valley, due to plowdown regulations to control overwintering pink bollworm.

“A lot of what we are seeing growers do now here in California is anecdotal, but in many cases it seems to be working. We are looking forward to researching more thoroughly what growers are doing on their own,” he said.

“Regardless, we are seeing a lot of cooperation and support from growers as we tackle this problem” said Hutmacher.

The UC cotton website has a wide range of information about recognition and containment of Fusarium. Go to http://cottoninfo.ucdavis.edu/.