Autumn’s Arrival Signaling Start of Cotton Defoliation in Valley

The arrival of fall on Thursday means cotton picking time is just around the corner.

Field scout Carlos Silva reports spotting the first cotton grower defoliating his cotton field. Look for defoliating to ramp up over the next couple weeks.

Carlos says caution signs warning workers and the public about the upcoming chemical applications are popping up along the borders of the fields. At the same time, a number of growers are prepping their fields by smoothing the margins around the fields to allow tractors to treat the fields by ground.  Others will use airplanes to apply defoliants.

 

Growers often will defoliant twice to ensure adequate coverage. In about a month, harvesters will invade the fields to start picking the fiber.

Why do growers defoliate their cotton fields?

Well, this is a typical cotton production management practice designed to prepare the crop for harvest and boost the quality of the fiber. 

Defoliation causes the leaves to drop and plant to start drying. This helps the harvesting machines pick the cotton cleanly off the plants and lessen the amount of leaves and debris, or trash, collected during the harvest.

The timing of defoliation is crucial. If done too early, the cotton yields could suffer because there are too many immature bolls. If done too late, growers run the risk of pest damage.

 

To determine the right time to defoliate, growers will count the nodes above cracked bolls (NACB). The number depends on the cotton variety. UC IPM offers these guidelines:

·         It’s safe to defoliate if 60 percent or more of the bolls are open.

·         For upland or acala cotton, the count is four to five NACB.

·         For pima, it’s three to four NACB.

Carlos finds most fields are about four to five nodes above cracked boll. Some are even at seven NACB.  “Defoliation is around the corner,” he says.

 

FIELD DAY ALERT: Growers are invited to hear  Merced County Deputy Agricultural Commissioner Sean Runyon talk about new pesticide regulations for crops, worker safety and protection for schools during a Thursday 

field day in Dos Palos. The free program, “Alfalfa Management: Pests, Water, Manure Use and Regulatory Update,” will be from 9:30 a.m. to 12:30 p.m. at the Scout Hut, 1910 Marguerite Street, Dos Palos.

Other speakers are:

·         UC Statewide Integrated Pest Management extension advisor Dr. Pete Goodell, who will introduce growers and PCAs to the national and UC pest management tools and discuss the importance of IPM during the past year.

·         University of California at Davis Cooperative Extension specialist Dan Putnam. He will discuss irrigation issues facing growers and trends in deficit and drip irrigation.

·         Nicholas Clark, UCCE farm advisor in agronomy and nutrient management for Kings, Tulare and Fresno counties. He will address the benefits and challenges of using manure in alfalfa and explain timing, best uses and application rates.

Continuing education credits are available. The field day is sponsored by the San Joaquin Sustainable Farm Project. For more information, contact Project Director Marcia Gibbs at (530) 370-5325.