Monitor Maturity, Defoliate Timely and Wisely (Collins & Edmisten)
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In our previous article, released 3 weeks ago, we discussed what COULD happen to this crop depending on the weather. Alot of those questions have been answered by this point in time. A few parts of the state recieved somewhat timely rains during the month of August, and there’s a decent chance of having an acceptable top crop in those areas. In other areas that were impacted by severe heat and drought during August (which is the majority of our acreage), a few recent rains have helped fill out a few bolls, but very few late August / early September blooms were retained, eliminating chances of making an acceptable top crop. The exceptions, in these drought stricken areas, are irrigated acres. As normal, the crop is variable from field to field, and even within fields, therefore, careful examination of the crop on a field by field basis is necessary in order to make adequate and timely decisions moving forward.
For irrigated fields, or areas of the state that recieved timely rains during August, it will be important to monitor the status and development of any top crop. Try to determine how many younger bolls are retained at this point in time, and guage their maturity. In most cases, those bolls are still developing and are a few weeks away from maturity sufficient for defoliation.
For most of the NC acreage, where drought was experienced, there isnt much (if any) top crop and maturity of the uppermost harvestable bolls has been reached or will be reached very soon. Defoliation of a few of the earliest maturing acres has already begun within the last week to 10 days, and on a limited acreage. We expect to see more widespread defoliation in the coming week(s). Only close monitoring on a field by field basis, and slicing the uppermost harvestable bolls, can determine if maturity is reached. Bolls that are mature enough to initiate defoliation will be difficult to slice, low in moisture, have well developed seed with a darker colored seed coat, and lint will string out when sliced. Immature bolls that are higher in moisture should be easier to slice, have poorly developed seed and a lighter colored seed coat, etc., and therefore need more time. Any futher development will be slightly slower now that somewhat cooler temperatures have set in, although there are plenty of heat units expected in the forecast to continue maturation.
Most of this drought stricken acreage experienced a “hard cutout” and ceased blooming altogether, albeit some fields did this later than others. A “ride by” observation of these fields might suggest normal plant height with darker colored foliage (maroon to reddish brown) as was expected in situations like this. However, closer examination of these fields is likely to reveal very few harvestable bolls in the top 6-8 inches or more of the plant. This is because the plant aborted most (if not all) later blooms during late August or early September in an effort to continue developing some of the less mature lower bolls. So, at this point in time, what we have is a bottom crop. The size of this bottom crop varies quite a bit, but all of it is a bottom crop that is rapidly approaching maturity. As an expected product of recent rains, it appears that the plant has met the demands of the boll load, and is now regrowing. This is mostly been observed in the terminal, however basal regrowth is to be expected, especially once the crop is defoliated.
So what do we need to do for this crop now?
First, be timely with defoliation and pay close attention to weather forecasts. If the crop is mature enough and ready for defoliation, AND harvest can be conducted within 2 weeks of defoliation, there is no need to delay defoliation. Go ahead and defoliate fields that are ready, and harvest them in a timely manner. If the crop can not be harvested for a while, there’s no need to force it open and expose it to the elements longer than necessary. Pay attention to weather forecasts when defoliating. Since all we have in these areas is a bottom crop, we dont need to lose any of it to tropical winds/rain nor can we afford to lose any of it to hardlock, assuming we can prevent either. Once bolls pop open, all that needs to occur is the burs (carpal walls of the boll) to dry out….As they dry out, they retract and expose (fluff out) lint for harvest. Hardlocked cotton occurs when wet conditions prevail (longer than a day or two) once bolls start to open, by preventing the drying of the burs, and these bolls are often shattered or otherwise missed by the picker. Try to determine the proportion unopened bolls you have (percentage of total bolls that are open, and also count the number of nodes between the highest opened boll and the highest unopened harvestable boll). Given the current temperatures and status of boll maturity, try to determine how long it might take to open them. For example, the current weather forecast for this week suggests that most of this week will bring sunny days with highs in the low 80’s. If you have very mature bolls (as determined by slicing them open), and less than 4 nodes above cracked boll, with the right tank mix, you can probably open most of them by Friday. If you have more than 4 nodes above cracked bolls (to the highest harvestable boll), or less mature bolls, the chances of opening them this week are lower. As of right now, rains are expected this weekend and into next week, therefore you don’t want bolls to be opening during that time, so you might want to wait until wet weather passes or at least wait to see if the forecast for next week might change for the better before deciding to defoliate. Using products like Finish or Terminate can accelerate boll opening and buy you a few extra days compared to ethephon alone. However, it is important to harvest in a timely manner in order to capitalize on that added value. If you’re not in a hurry to open this crop, ethephon alone may still be suitable in these temperatures, but you still may not want bolls to open in wetter weather.
Secondly, regrowth is here and will only get worse with recent rains. As long as we have warm weather and halfway decent moisture, regrowth is to be expected, especially when the crop went into a hard cutout, met its boll demands, and cycled back around to renew vegetative growth. Removing older leaves through defoliation only accelerates regrowth by allowing direct light contact in the lower parts of the plant. The current forecasts suggests daily highs in the high 70’s to low 80’s with lows in the high 50’s to low 60’s. There is some variation in forecasts within the state, so its important to monitor your local forecasts. Thidiazuron (TDZ) products such as FreeFall and several other generics (the old tradename “Dropp) should still be effective for a while, although a little bit slower than when temperatures are higher (highs in upper 80’s, lows in mid to high 60’s). In the current forecasts, we are kind of right on the line to where TDZ activity will be diminished if it gets much cooler, but it is also cool enough to safely and effectively use TDZ+diuron products, such as GinStar, Adios, CutOut, and several others. Whichever one you decide to use will influence what other products can be used in that tankmixture, along with rates of each, so be sure to seek advise on appropriate rates and tankmixtures if you are not comfortable with those decisions.
Also, pay close attention to the weather on the day of defoliation and the day following. Defoliating when you have a warm/sunny day, followed by another day of the same, is ideal. Defoliating when overcast/cloudy conditions occur, or when rain is expected within 24 hours, does not allow for effective overall defoliation or boll opening. Use appropriate application volumes (no less than 15 GPA, 20 GPA is preferred if using a ground rig) and appropriate nozzles. Short cotton with a fairly open canopy can be defoliated with TTI or AI tips (larger droplet, low drift nozzles) but you need to apply at 20 GPA. Larger cotton with slightly thicker foliage needs a flat-fan or twin-fan with a mixture of droplet sizes to be effective. Even so, 20 GPA is still preferred but 15 GPA is often acceptable.