Virginia Cotton: Do ‘Cutout’ and ‘Insect Safe’ Mean the Same Thing?

Cotton field at cutout. Photo: University of Tennessee

I believe the most important distinction we need to make for cotton currently is in determining when the crop has cut out.

  • Sometimes we talk about cutout being after cotton stops blooming and changes color, but that is actually way past true cutout.
  • The old definition of cutout is the point where 95% of the harvestable crop has established itself as a boll. There is a fair consensus that this occurs when cotton has reached 5 nodes above white bloom (NAWB).
  • However, our modern cotton production uses higher nitrogen rates and with variable pix strategies, a good rain pattern and more indeterminant cotton varieties, we might have a different dynamic than we did 25 years ago.
  • There was a good bit of cotton that reached 5 NAWB by the third week of bloom this year around the third week of July; however, farmers backed off a little bit on Pix and let it go a little bit. Two weeks later, it was still 5 NAWB so it can maintain this stage for a while.
  • Perhaps a better way to measure the most important fruit is from the bottom up.
  • Dr. Frame has some recent research indicating when cotton puts bolls on the first 10 fruiting branches, then the bolls that establish themselves higher than this only contribute 1% to 5% of the total yield.
  • This gives us at least a target on how to evaluate our crop this year. It typically takes 5 full weeks of bloom to set bolls on 10 fruiting branches.
  • In a way, if you marked the day your cotton started blooming, then you could almost calculate the cutout date. For example, cotton planted May 4th started blooming around July 4th and should have cut out on August 8th.
  •  By now, much of our cotton has cutout, and in a week or so, all but the double cropped cotton will reach this stage.

How does ‘Cutout’ relate to ‘Insect Safe’

Since we are defining cutout as the point where 95% of our harvestable bolls have bloomed, then another way to phrase this question is ‘what percent of the yield is still susceptible to insect damage?”

  • I’ll start by saying, I think some more research could be done to streamline the answer here, but speaking as an Agronomist, I think the answer comes from potential yield.
  • For a 1000-pound crop, we only expect 50 pounds to be able to come from future blooms after cutout (approx. 5 weeks of bloom).
  • However, small bolls that have bloomed for the last 10 days are still vulnerable to bugs. This could be a hundred pounds to a couple hundred pounds of yield to protect.
  • It looks like to be insect completely safe, you have to get about a week or 10 days past cutout for 95% of the bolls to be past susceptibility. That should be during or after the 6th week of bloom.
  • From a practical standpoint if you are insect free at cutout, it would be unlikely that a new population of insects could build up a damaging population.
  • That means even if you have a few insects 10 days after cutout, then you can go get the picker ready.
  • For me, when I am in a field that has only a few squares left to bloom and several of the bloom tags are coming off in my hands when I am trying to check them for damage, then I am ready to go to another field.
  • One thing is for sure, that 3rd week of bloom spray is worth a lot, and by the 6th week of bloom, we are never talking about more than 10 to at most 75 pounds at risk. That high number would be in a 3 bale field.

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