Monday, August 22, 2016

Wilting Cotton Plants: Race 4 Fusarium Expands to the North

 It’s a nasty ailment that has traveled northward to cotton fields in the Northern San Joaquin Valley over the past five years.

 It can spread easily by foot, water and farm equipment, leaving swaths of bare spots in fields.

Bare spots will show up in Race 4 fusarium infected fields.
“Race 4 fusarium wilt continues to be a problem for many growers in the Valley. Unfortunately this area has been a hot spot to identify newly recognized fields with race 4 fusarium wilt,” says Bob Hutmacher a University of California Cooperative Extension specialist at the Westside Research and Extension Center.

Over the years, we’ve talked about Race 4 and how it has been heading our way from the south end of the valley in Kern County.  Today, Bob says growers around here are starting to recognize this issue – a big plus – and huddling with their pest control advisers, farm consultants and UC experts to explore ways to address the issue.

“After quite a few years of continuing cotton production in this area we are seeing more damage in the upland and acala fields,”Hutmacher told us recently. “It takes a long period for the inoculum levels to build to where you see those type of problems in the upland fields.”

A young cotton plant suffering from fusarium wilt.
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.

Hutmacher points out that farmers will reseed a field that had been out of cotton for a few years. Then suddenly, the disease crops up – the first clue comes early in the growing season as  seedlings wither and die.

In the past, growers generally ignored the issue. Now, more are being proactive and want to know if their fields are infected. “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.”

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.

“They (growers) seem fairly receptive that they need to grow resistant varieties,”Hutmachersays. One concern that he hears from growers: While seed companies have come up with good choices for resistant pima varieties, the firms have been slow to put resistant upland varieties on the market.

The first cotton boll opening up was reported in Dos Palos.
Meanwhile in the fields, field scout Carlos Silva reports the first sighting of cotton bolls cracking open in a Dos Palos field. That’s exciting news and a sign of things to come.

Carlos is finding more aphids and whitefly showing up. That’s something to keep an eye out for as more bolls start to open. Sticky cotton is always a concern. We willcover that topic down the road.

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