For those of you who are not familiar with cotton production, defoliation is a method of forcing the cotton plant to shield its foliage in order to have a timely harvestable crop. Overall, accurate defoliation is important for profitability in the over management of the cotton crop. Benefits of proper and timely defoliation include:
Eliminating the source of stained bolls or plant trash, which brings better grading.
Quicker and efficient mechanical picker functions.
Faster dry down of dew to increase the earlier harvest start times in the day.
Defoliation has the potential to open up the plants to allow more airflow and reduces the chance of boll rot and can jump start boll opening, in-turn can increase yields and profits.
Defoliation application decisions are determined by crop maturity and condition, weather and desired harvest time. It is important to defoliate in a timely manner because not making applications accurately can cause a poor lint quality and overall decrease yield.
As a general rule, it is best to defoliate when approximately 60% of bolls are open. Another method used to determine the best time to apply defoliates is the node above cracked boll (NACB). Defoliants work best in warm, humid, and sunny conditions. Applying defoliants in cool temperatures can reduce to effectiveness of the defoliate product and could cause undesirable foliage.
Defoliants are categorized in two ways. One being an herbicidal defoliate that causes injury to the cotton plants, which puts the plants in ethylene production mode. Ethylene is a hydrocarbon gas that promotes leaf drop in cotton. Some fruit such as apples and pears produce ethylene as it ripens.
The other form of defoliate is hormonal, which contains ethylene and causes the plant to produce more ethylene to promote leaf drop. In other words, it is like manually sending the plant into a fall season mode. Ultimately, cotton growers need to evaluate their fields in order to determine the best time to defoliate, so they can maximize in yield and lint quality.
Della King is an agriculture extension agent specializing in field crops with the Sampson County Cooperative Extension Center. She can be reached at 910-592-7161.