Cotton ranges from just starting to bloom to hard cut-out (0 nodes above white flower). Ideally cotton will be blooming out-the-top by now; because we have reached that point when the odds of a bloom developing into a quality/yield contributing boll will drop considerably over the next several days.
In fact, the scouts and I noticed fields beginning to shed squares and some small bolls this week. We can see this a bit earlier some years.
This is a normal process of the plant making a final adjustment in what the plant can naturally hold and mature out. Be sure though that this fruit shed is natural and not being induced by Lygus or particularly cotton bollworm in the case of conventional cotton.
We are picking up bollworms activity in many fields, even very light activity in Bt cotton. We have sprayed some conventional cotton acres.
We are also finding cotton aphids. Most of these aphids are in mostly small clusters with many aphids, with good beneficial activity. Be careful to not get too aggressive with these cotton aphids, but do not hesitate if they are consistent and reach 40-70 aphids per leaf. Here is the cotton aphid guide which discusses threshold, chemical control and other considerations. Continue to scout for another 21 days or so.
By September 7th the majority of cotton acres should have well over 400 heat units accumulated since 5 nodes above white flower stage. This gauge of time tells us that a crop is safe from most insect damage.
Herbicide Resistance Info
Irrigation has been where most questions are being posed. I will admit I get fairly conservative with irrigation as we move into the last days of August, and would rather err on the side of being too dry than too wet going into September.
We have already had our chance of making quantity, now it is a matter of achieving quality through maturity. The last bolls set during this time need to be relatively stress free for 20 days (approximately September 10th). So as long as the plant recovers quickly from any wilting during a +90 degree day then those last bolls formed should mature properly.
After 40-45 days (approximately September 30th) the plant can nearly go into permanent wilt and it should not have an impact on yield or quality. So bottom line – be very careful watering over the next few weeks. Call if questions.