By land and By Air: Cotton Growers Start Defoliating Fields Across the Valley

These days, you might see spray rigs driving through green cotton fields. Or you might find airplanes buzzing over the fields around the Valley.

A tractor rig applying defoliants in a cotton field.

 

These sights, says field scout Damien Jelen, are the defoliation of the cotton fields.

While some began the process last week, Damien says more growers are ramping up this week and spraying defoliates on their cotton fields.

This flurry of activity signals that the fall harvest is around the corner.

Damien expects some harvesters to start picking cotton by the end of this month. “We can expect the harvest to go through Halloween.” 

Why do growers defoliate their cotton fields?

Some fields are defoliated by an airplane.

Defoliation is the last major field management decision that will affect the financial outcome of the crop. This process is necessary to prepare the crop for mechanical picking.

Defoliants are used to boost leaf drop and drying of the plant, which increases the timeliness and efficiency of the harvest. Growers that terminate their crop early are often trying to head off potential sticky cotton damage caused by growing white fly or aphid populations.

Here is a cotton field 12 hours after defoliants were applied..

Successful defoliation can improve cotton grades by lessening staining and trash from the leaves, make harvesting faster, speed up drying, delay boll rot and even boost boll opening.

 

Some experts consider the proper timing for defoliation more of an art than a science. Crop maturity, field conditions, and the environment are factors that go into deciding when to defoliate.

  

Here’s what UC IPM considers the best conditions for defoliation:

• Moderate to high air temperatures (daytime greater than or equal to 80 degrees, nighttime greater than 60 degrees)
• Relatively low plant and soil nitrogen levels
• Moderate soil water levels (plants not water stressed)
• Relatively uniform crop development; plants at vegetative cutout with limited or no regrowth
• Weeds, insects, and diseases under control
• Ability to get good chemical coverage and penetration of the chemicals into the plant canopy

Growers can ask their pest control advisors and UC extension specialists for recommendations about defoliant products and application rates.