Thoughts on Defoliation With Regard to the Impending Hurricane (Collins & Edmisten)
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Now that the weather forecasters seem more certain that Hurricane Matthew will make landfall in NC, we’ve received a ton of phone calls today concerning whether or not growers should defoliate some cotton before the storm while weather is relatively nice, or should growers wait until the storm passes before resuming defoliation. The forecast on Monday was relatively uncertain with regard to if this storm would even make landfall, therefore this issue was debatable at the time. The situation has changed now that meteorologists seem more certain that we will be impacted by the storm. Below are a few thoughts on this issue, however there is no way to know the best approach with any certainty, until we know the full impact of the storm.
Cotton that still has a number of unopened bolls: In fields where there are still several upper bolls that have not yet cracked, it is generally wise to wait until the storm passes before defoliating. When bolls are not yet opened, they are relatively protected from the elements. There are several fields where the top crop represents a significant proportion of the total crop, therefore it is important to protect these bolls. There is not much we can do about the bolls that have already opened.
When a boll first cracks open, ideally the weather would be dry so that the burs (carpal walls) can dry out. As the burs dry, they retract, which exposes the lint appropriately so that it can be grabbed by spindles. If conditions are damp, wet, cloudy, etc. during the first few days following boll cracking, the burs will not dry appropriately, therefore resulting in hard lock and or boll rot. If this occurs, it is unlikely that affected bolls will be harvestable. Therefore, if we initiate defoliation slightly before the storm hits, we could crack a few bolls right in the middle of high-moisture conditions which would not be good.
Additionally, cotton will likely lodge and tangle in periods of high winds. This has been observed in many fields already, and is generally more common when a number of closed bolls in the upper part of the plant make the plant top heavy. Generally speaking, defoliation after the storm passes can sometimes be more effective in “standing the cotton back up”.
Lastly, regrowth is always a concern when tropical events result in significant rainfall. This has been a big issue already with the heavy rains a couple of weeks ago. If significant rains result from this impending storm, we can expect to see even more regrowth. Additionally, heavy rains will delay our ability to re-enter fields and resume defoliating, therefore regrowth will increase the more we are delayed. Defoliating now may not adequately prevent additional regrowth, depending on how much time elapses before sprayers can re-enter fields, and some fields will likely need a second “clean-up” application. Waiting until after the storm passes will likely help us address regrowth issues a little more effectively once we can get back into fields.
Cotton with all bolls opened: We are not likely to have much impact (good or bad) with regard to defoliation timing in fields where all bolls are already opened. Theoretically, the presence of leaves could somewhat shield against heavy rains, but may also not allow for rapid drying of lint after the storm passes. The protection of lint from leaves may be miniscule if we experience very heavy rain and wind. However, defoliating in the next day or two could promote some ethylene activity in the plant, and perhaps the formation of an abscission layer, in which the winds from the storm could somewhat accelerate defoliation more rapidly than normal, but this is very difficult to predict. For these fields, we still advise defoliating in sunny conditions (cloudy weather may result in suboptimal defoliation. On the other hand, as mentioned above, we might be better suited to address regrowth issues by waiting to defoliate after the storm passes.
Pros versus Cons: Depending on the situation and severity of this storm, there is little incentive to defoliating now or the remainder of this week, other than potentially being able to start or resume harvest a little earlier after the storm passes. There may or may not be much advantage in waiting to defoliate depending on your particular situation, but we recommend thorough evaluation on a field by field basis with consideration to the situations described above to decide which approach may be best.
Cotton defoliated at the end of last week or over this past weekend: For fields defoliated last week or over last weekend, there may be a few fields that could be harvested before the storm hits. This may be the best use of our time at this point for the remainder of this week while weather may still be suitable, however this is a very short time for harvest aids to work effectively. The ability to harvest now largely depends on how effective your defoliation strategy was during this recent time frame, as well as when it was defoliated. Regardless, we won’t likely be able to harvest very much before the storm hits, but any little bit helps.
As mentioned earlier, the forecasted path of this storm noticeably changed today (Tuesday) from the forecasted path on Monday. At this point, we sincerely hope that the weather man changes his mind again.