California cotton facing insidious threat

California cotton growers are facing a fungus that could not only lay waste to their livelihood, but impact other parts of the Cotton Belt, as well.

An insidious soil fungus known as Fusarium Race 4, or Race 4 for short, is threatening the ability of cotton farmers in the Golden State’s San Joaquin Valley to continue to expand, according to Western Farm Press.

“This particular race has been around awhile, but with the expanded cotton acreage this season it has been found in far more areas than ever before,” according to the publication.

Race 4 has been identified in all six San Joaquin Valley cotton-producing counties in more than 200 total locations.

“Although not as menacing elsewhere, it also poses a threat to the rest of the US Cotton Belt and could have an impact on California as a source of premium cotton planting seed for varieties to be sold throughout the US and the world,” Western Farm Press added.

Fusarium wilt is a disease caused by a soil-inhabiting fungus, according to the US Department of Agriculture. There are several strains, or races, that vary in their ability to attack cotton, and in the timing and severity of disease symptoms.

The fungus can survive for long periods in the soil, the USDA added.

Race 4 is believed to have been introduced into the valley through infected planting seed and has been found in all soil types.

California typically produces 5 to 8 percent of total US cotton plantings, but about 10 to 14 percent of total US yearly production, due to the state’s phenomenally high yields, according to Calcot, a Southwestern cotton marketing cooperative.

California is frequently the second-highest producing state in the nation, behind Texas.

While Race 4 has been a California problem, other suspected races have been found in Southern states, including Alabama and Louisiana.

“One of interesting things (University of California plant pathologist) Mike Davis has found using newer biotech approaches to more quickly identify disease is that other races in Southern states look pretty scary — a lot worse than Race 4. And they do not need nematodes to spread,” said Bob Hutmacher, a University of California Extension cotton specialist.

This heightens the need to continue screening for soil borne pathogens as well as to focus on developing disease-resistant new varieties.

Unfortunately, Western Farm Press reports, Race 4 cannot be eradicated.

“Once it is in the soil, it does not go away. A widely infected field cannot produce cotton ever again. It is spread by Race 4 contaminated soil movement, plant debris and seed. It only kills cotton, but it can live and spread in the soils where crops other than cotton are grown without affecting those other crops.”

It would appear that California cotton growers essentially ignored the Race 4 problem until recently because of declining cotton acreage.

But with spiking cotton prices over the past year, cotton acreage in the Golden State has shot up – to 450,000 from 3000,000 just three years ago – bringing the Race 4 problem to a head.

Not only is turning back Race 4 critical to lint and seed production in the valley, it could also have a devastating impact on an important element of the valley’s cotton industry – seed production, according to Western Farm Press.

Premium certified cotton planting seed is produced in the valley for varieties sold not only within the valley, but elsewhere in the US and world. California Cotton Growers Association Chairman Cannon Michael said it is critical to protect that part of the state’s cotton industry.

The first line-of-defense against the spread of Race 4 is planting resistant varieties and avoiding susceptible ones.

Phytogen 800, the most widely planted variety of Pima cotton in the San Joaquin Valley, is highly resistant to Race 4. Other varieties have varying degrees of resistance, ranging from being highly susceptible to being mildly tolerant.

California Cotton Growers Association President Earl Williams said the ultimate solution to the problem is development of more resistant Acala and Pima varieties, but that is at least five to 10 years away in a best case scenario.

In the meantime, growers must educate themselves on what to do to stem the spread of Race 4. Williams said research money will be directed at chemical and field treatments. Soil solarization is a possible option, but it is an expensive one and can likely be used on small acreage. Seed treatment and using injected steam to kill the organism are other possible ways to combat Race 4 spread.

“One of the problems with Race 4 is that it can survive nicely on a wide collection of plants and weeds without infecting those plants or weeds. The pathogen lives on root surfaces and can persist for years. It will not go away,” Hutmacher said.

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