South Georgia Crop News

Crop News Covering Crisp, Turner, Worth, and Wilcox Counties

Cotton Defoliation

The following information is provided by Turner County Extension Agent Josh Gravitt.


As we get into the month of September it is time for some growers to make decisions on cotton defoliation.  Some of our fields that were planted in April are opening up the stalk rather rapidly with temperatures we have seen in recent days.  A cotton plant will open 3-5% of its bolls per day depending upon environmental conditions once it opens its first boll.  The hotter and sunnier the day the more towards the 5% range it will be.  When making defoliation decisions there are several factors that should be taken into consideration.  There are several methods that can be used when making a defoliation decision.

One method is the percent open boll method.  Generally if 60% of the bolls on the plant are open then the plant is mature enough for defoliation.  If the plant has less than 60% open bolls then it is usually too early for defoliation.  This formula is best used when the cotton matures normally and doesn’t exhibit a split crop.

The nodes above cracked boll method can also be an effective way of determining defoliation timing.  This is when you count the nodes above the highest cracked boll that has a harvestable boll on it.  This generally means that the unopened bolls are mature enough that defoliation can occur.  Generally at NACB=4 it is safe to apply a harvest aid.  If stand counts are lower NACB=3 may be more appropriate.

Another indicator is slicing bolls with a knife.  If you slice a boll and it is firm enough to where the lint strings it is mature enough for a harvest aid.   Bolls are mature enough when the seed embryo only contains tiny folded leaves and no “jelly” inside them. Also the seed coat should have turned a yellow-tan color.

It is important to remember that every field has the potential to be different when it comes to defoliation. Many factors are considered when making harvest aid decisions. Soil Type, Variety, Environmental conditions, etc. All can make a big impact on timing of defoliation. There is not a one solution fits all in most cases. Taking these methods and using them in combination with one another can be an effective approach to a successful defoliation program.