Determining the Ideal Time to Get Cracking on Defoliating Your Cotton Crop

 At the start of the month, some pest control advisors in Fresno and Merced counties predicted in the AgFax.com crop advisory newsletter that local cotton growers would start defoliating their crop around the start of this week – the first full week of fall.

A warning sign alerts people defoliation has taken place.

Well, as it turns out, some growers beat that prediction last week and got an early jump on defoliation before summer’s end – even though they may have been able to wait a little longer to allow more fruit to mature. Indeed, the early varieties of acala I’ve seen in the fields are at around six to seven nodes above cracked boll (NACB).

Remember, NACB is used as a guide to help growers determine the right time to apply defoliants. The University of California Integrated Pest Management program says the “ideal timing for defoliation is when unopened harvestable bolls are an average of four or less nodes (including missing branches) above the highest first position cracked boll.”

As a rule, plant maturity is the most important factor in making the final decision. The goal is to determine when the boll population will lead to a significant yield and the optimum time for harvesting the bolls. Here is the University of California Integrated Pest Management link that covers scheduling defoliation.

Here's a field about 12 hours after defoliants were applied.

Why defoliate a little early? There are many reasons. Some growers do it because the aphid and whitefly population are threatening the crop. My guess here is a few growers decided to sacrifice a little yield in order to get a head start on harvesting so they can in their crop sooner than later, thus avoiding potential issues such as early season rain.

But I see advantages for holding off with defoliation and allowing more fruit to mature. Right now, aphid pressure has subsided and treatments are down from earlier this month. Whitefly counts have decreased as well. Those are good signs because it reduces the threat of developing sticky cotton. We do have extra time to play with this season. By my estimates, the cotton season is about seven to 10 days ahead of normal for this time of year.

Meanwhile in almonds, our field scout Jenna Horine reports all growers are finally shaking the nuts off the trees. Nonpareils are pretty much off the ground. Other varieties remain in various stages of harvest.

Almonds are drying on the ground.

As she scouts the orchards, Jenna has been picking up a few nuts off the ground and cracking them open. From these spot checks, she is finding these random samples to be pretty clean, or free of pests. She’ll be checking all her orchard samples later to get a thorough look for any the evidence of pests in the nuts. We’re report on her findings after crack-out.

Overall, she has not found any major pest issues this season. Our hats off to growers for following good pest management practices. “It’s all about preventative measures,” Jenna says.

 

Cotton tour participants get a chance to pick some cotton.

The annual Cotton Tour is less than a month away. This popular free event is a rare opportunity to get an inside look at cotton production – from the field to the gin. Set for Friday, October 19 from 8:30 a.m. to 5 p.m., the tour begins at the Best Western Apricot Inn at Interstate 5 and West Panoche Road, about 23 miles southwest of Firebaugh. Go to the Sustainable Cotton Project website  to reserve a spot. Visit with growers and meet leading cotton experts.