Early Season Defoliation Strategies for 2022 (Collins & Edmisten)
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We’ve recently concluded our defoliation meetings across the state. Below are a few highlights of those meetings and subsequent discussions pertaining to strategies for this year. All indicators at this point in time suggest that we will have an earlier crop than normal. The last two weeks of August were warm and dry for most areas of the state. As a result, the earlier planted crop went into a hard cutout and in many cases, ceased blooming altogether. We are now beyond our average last effective bloom dates in NC, so it’ll become less likely that any new blooms will have any reasonable chance at being harvestable. Regardless of that fact, most of our earlier planted crop is fairly mature from top to bottom, therefore new blooms would either abort anyway, or at the very least, require significant time before they reach maturity, which would risk our largely mature bottom crop. There are a few instances of late planted cotton that is still actively blooming, and other cases where the bottom crop is lost to plant bugs or was poor in general. Both scenarios might be tempting for growers to chase the top crop, therefore flagging a few upper nodes now might help later in deciding which bolls might have a reasonable chance of being harvested. These cases are few and far between this year, as the majority of our crop is mature or very near it. Therefore, we expect to see more cotton defoliated in September / warmer weather this year than normal.
Juvenile growth removal / regrowth prevention:
Juvenile growth / regrowth is young vegetative growth that occurs normally once the plant meets its boll demands and when warm temperatures prevail, especially when there is residual nitrogen to fuel it. Since it is small plant tissue, there isn’t a great demand for water, therefore even a little soil moisture can promote this new growth. Regrowth is expected during the first half of our defoliation season in nearly every, but given the earliness of most 2022 cotton, we expect to encounter more of it this year, if temperatures remain warm and we have any soil moisture at all. To properly address regrowth when weather is and will continue to be warm, TDZ (4 lbs a.i. per gallon of thidiazuron) products such as FreeFall (or other tradenames with the same concentration of TDZ) should be used at no less than 3.2 oz/A in a tankmixture with other defoliants and/or boll openers. If daily highs fall below 80 degrees, and nighttime lows fall substantially below 60 degrees on a consistent basis, switching to TDZ+diuron (Ginstar,Adios, CutOut, etc) may be appropriate. This switch will influence rates of other tankmix partners or could change the tankmixture completely.
As it pertains to ground sprayers (not airplances), defoliants should be applied at no less than 15, but preferably 20 GPA to ensure adequate coverage using a flat fan or twin fan nozzle equipped to handle 20 GPA. Water is the cheapest ingredient in the tank. There’s no need to cut corners. The argument for lower application volume pertains to efficiency. That argument falls apart if you have to spray twice.
Take advantage of Time Gains:
During the warmer, early season, if you use Finish or Terminate in your tankmixture, take advantage of any time gained from it. In other words, if these products allow you to harvest 3 days earlier, then go ahead and harvest. During warmer weather, these products often accelerate boll opening and defoliation compared to other tankmixtures containing equivalent rates of ethephon (Prep, SuperBoll, others). For example, depending on other factors, in warmer conditions, Finish/Terminate can allow for harvest in maybe 10 days versus 14. If so, harvest as soon as the crop is ready. Yield contribution and quality of any boll is the best itll be on the day the boll opens. Beyond that, yield contribution and quality can remain the same or degrade. If you use one of these tankmixtures during warmer weather, but you don’t intend to harvest within 2 weeks time, then you gained nothing and could’ve used a cheaper tankmixtures. Once we are in cooler weather, you may have to use these products to open bolls properly, but that isn’t usually the case during the early part of our defoliation window.
Along these lines, timeliness can mean the difference between high yields and low yields. This is very clear in cases of hurricanes, but it doesn’t have to be a hurricane to encounter problems. Our first frost typically occurs around the end of October. Cotton begins weighing lighter after a freeze. Our effective harvest hours per day (time after dew dries and before dew falls) decreases over time, but it becomes very noticeable in early November. Rains and dew take longer to dry during time, the dew falls earlier in the evening, and boll opening or defoliation require more time in November. We can accomplish a lot more in October than we can in November, when progress slows down. Therefore, be prepared for defoliation and timely harvest, and try to do as much as you can in October.
Watch the Weather:
The first thing growers think of is tropical weather, and rightfully so. While we’re on the subject, we must remind you…..DO NOT defoliate prior to a hurricane, UNLESS you can harvest it. If you cant harvest it before a storm, DON’T DEFOLIATE until a storm passes. Closed bolls are protected bolls. Opened bolls will fall out or will hardlock.
In other context, watch the weather for defoliation. Defoliating when the weather is warm and sunny, followed by another day of the same, tends to be noticeably better than defoliating in cloudy weather or when rain occurs within 24 hours.