NC State University|Crop Science|College of Agriculture and Life Science|NC Cooperative Extension
Keith Edmisten, Cotton Extension Specialist
Department of Crop Science
North Carolina State University

Boy do we have a mixed bag to try to describe! I guess that is good because if everyone is in the same boat it might have a leak that would be disastrous for everyone. At this time we have cotton that is ready to defoliate. The dry weather in July and August really pushed an otherwise late crop into maturing early. Unfortunately drought is not the tool we would like to achieve early maturity. Last years crop was similar to that and we picked a mush better crop than I would have guessed or have seen in other similar dry years. I don't know why we did so well with so little July and August rain last year but I hope that we are pleasantly surprised this year. Last year was more surprising to me because the early season was not favorable to root development and the K deficiencies we saw were an indication of that. This year was similar in that regard too. Maybe our genetics have improved in terms of dealing with stress.

On the other hand we have some beautiful cotton (oops, I forgot it is September!). Much of this cotton is still blooming or at least has very young bolls that need to make it for this portion of the crop to reach its potential. We normally think of the last effective bloom date to be between August the 15th and 25th depending on where you are in the state and the given year. We have documented harvestable bolls set as late as September 7th at Clayton but this is certainly not true every year. A good fall and this portion of the crop could be very strong.

I have had a hard time dealing with the last effective bloom date (last date a white bloom has a reasonable chance to become a harvestable boll). Part of the problem is that cotton that is on time, that date seems to be somewhere in mid to late August. Late cotton on the other hand will fool you. You can forecast all the DD60's you want, but it seems to me there is a big difference in a late crop that has less of a boll load and it needs less DD60's to mature bolls set in late August or early September than an earlier crop.

What does that mean to you as a cotton grower? I obviously can’t guarantee you that you will harvest a bloom set on September 7th, but I can tell you that there is a decent chance if we have a warm long fall. I am not saying an exceptional fall but an average to above average fall in terms of temperature and frost date. My advice is to ride this cotton until October and then carefully follow the weather predictions and pull the defoliation trigger sometime in mid to late October.

What did Ernesto do to the cotton crop? I have seen cotton blown over and tangled up. Usually cotton will straighten up as it starts to open and this is not a really bad problem unless cloudy wet weather sits in for a good while after the storm increasing boll rot.

Storms like Ernesto injure cotton and the cotton releases ethylene as a response to the injury. The plants response to this is similar to a low rate of ethephon. Usually the activity from the ethylene will speed up boll opening and may cause defoliation of mature leaves. It is almost never enough to replace the application of defoliants and boll openers. Look at it like you got a “free” preconditioning which should help with your defoliant activity.

There are a lot of products on the market for defoliation now. It used to be that many defoliation scenarios called for fairly specific recommendations. Now there are several potentially successful ways to go about defoliating most fields.

At this point in defoliation I think that most fields will benefit from the addition of some boll opener to the defoliation mixture. The exception would be fields that will open on their own naturally prior to harvest. The old wives tale is that if your cotton will not be picked in 14 days you do not need a boll opener; your cotton will open naturally by then. This is not always true; in fact it is not true most of the time in North Carolina. It might be true if:

  1. Your cotton is 60 percent open or more. We often can defoliate prior to 60 percent open in North Carolina due to the compact nature of the crop in many cases.
  2. You will have enough heat units to open the remaining crop in 14 days. An exact number is hard to document but we are probably talking about 100+ DD60’s accumulated in the 2 weeks following defoliation. This is more likely to happen in North Carolina in September than it is in October.

The other major consideration is regrowth at this time of year. We have to assume that we will have growing conditions favorable to regrowth following defoliation in September. This is especially true unfortunately on a poor crop because there is less boll load and probably more residual nitrogen.

2006 - Carolina Cotton Notes

NCSU Cotton Team

2006 crop science©
last modified September 7, 2006 1:13 PM
page by Gary Little