Cotton Defoliation

— Written By Curtis Fountain and last updated by
To:  Duplin Co. Cotton Interests 

From:  Curtis D. Fountain

            Agricultural Extension Agent – Field Crops

National Weather Service Kenansville 7-day forecast notes low-mid 80s for daytime temperatures and high 50s-low 60s for nighttime temperatures. Bright, sunny days are also predicted.

Hopefully you have some cotton ready for defoliation. Please take advantage of this opportunity. Hopefully the above conditions (if soil moisture/nutrients are present) will advance development for later maturing fields as well.

Field Readiness

Two techniques are suggested to determine defoliation field readiness. Fields with 2-3 plants per row foot can be safely defoliated when the topmost 1st position harvestable boll is 4 nodes or less above the 1st position cracked boll. A cracked boll is defined as a boll with some visible lint but not enough for spindle grab. This nodes above cracked boll (NACB) technique considers the unopen portion of the crop and is based on the fact that a high percentage (85% or more) of late season bolls are set at the 1st position. For fields with a significant percentage of harvestable late bolls (bolls present on vegetative branches or outer positions of fruiting branches), a NACB of 3 may be more appropriate.

Harvestable bolls that are not open can be cut to determine maturity. Mature bolls are not damaged due to defoliation. Mature bolls are defined as 1) hard bolls that are difficult to cut in cross section with a sharp knife, 2) bolls that string fiber when cut, and 3) when observing a boll cross section, the seed cavity is completely filled (there is no gel within the seed cavity).

Weather & Spray Coverage Important

Preferred defoliation weather conditions are sunny, warm, high humidity days. If possible, apply defoliants when the expected average temperature will exceed 65 degrees F for at least 3 days following treatment. Ideally, defoliants should be applied 10-14 days prior to anticipated harvest for optimum lint weight and quality.

Since defoliants are not translocated, good spray coverage is essential. For ground applications, 15-20 gallons/acre of spray solution should be applied at 40 psi (or higher) using flat fan nozzles.

Product(s) Selection

There are many boll opener/defoliation/regrowth prevention brand products available. In most cases, there is more than 1 product or combination of products that will achieve satisfactory results. Focus on weather forecast, plant condition, harvest timing, and product(s) costs when selecting product(s).

Regrowth Prevention?

First defoliated cotton that will be picked 10-14 days after treatment should not require regrowth prevention. First defoliated cotton will likely require a boll opener to hasten unopen boll opening and defoliation.

Second defoliated cotton may require regrowth prevention. Warm temperatures, good soil moisture, and remaining soil plant available nutrients will promote regrowth of cotton. Remember cotton is a perennial plant. Since harvest timing is less certain, regrowth prevention is more important.

Final defoliated cotton (defoliated mid-October or later) should not require regrowth prevention. Cotton defoliated in mid-October should be ready to harvest at the end of October. Typically the end of October brings cooler temperatures and frost, unfavorable conditions for regrowth.

Please refer to 2013 Cotton Information page 159 for product information. Please call if you have questions.


Disclaimer:  The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina State University nor discrimination against similar products or services not mentioned