A Successful Defoliation Strategy Brings in More Green

The green flag is out for the start of cotton plant defoliation in the Valley.

Keep out: Defoliated field.

Field scout Carlos Silva reports seeing some fields already defoliated and anticipates more growers to follow suit over the next week or two. Experts consider defoliation as the last big management effort that will impact the cotton crops financial bottom line this season.

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 burgeoning white fly or aphid populations.

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

Conditions are right to start defoliating cotton fields.

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

Pest control advisors and UC extension specialists can offer recommendations about defoliant products and application rates.

Meanwhile Dr. Pete Goodell of UC IPM says PCAs are telling him that white flies weren’t a problem this season. No one can cite a specific reason.

Carlos agrees. “Last year, we had a lot of white flies. We haven’t seen very many white flies or aphids (this year). They are pretty much under control.”

Plants are  already drying only 12 hours after defoliation.

Even so, Pete repeats his mantra that growers shouldn’t relax and continue to watch for these crop-threatening pests until the fiber is picked and headed to the gin.

To illustrate his point, he offered this anecdote to the online publication Ag/Fax this: “We still need to follow this insect all the way through. You absolutely can't walk away from that field until there's nothing left but the stalks. We've had plenty of reminders this month about the attack on September 11, 2001, and that stands out as a year when we had a lot of sticky cotton. Remember: after the attack the government grounded aerial applicators for about 2 weeks. PCAs had written recs for defoliation, but nobody could make applications. That left fields out there on their own for 14 days with very little monitoring, and white fly took advantage of the situation.”

  

Field Day Alert: Almond growers will receive valuable post harvest management tips from UCCE Merced’s David Doll and UCCE Fresno’s Gurrett Brar on Tuesday, October 7 in Los Banos. Sponsored by the San Joaquin Sustainable Farming Project, the event will be from 10 a.m. to noon at the corner of Mercy Springs Road and Cotton Gin Road. Continuing education and CCA credits will be available. For more information, contact Project Director Marcia Gibbs at (530) 370-5325 or  marcia@sustainablecotton.org

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