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North Carolina Cotton: Not Too Early to Prepare for Defoliation, Harvest

Ernst Undesser
By Keith Edmisten and Guy Collins, North Carolina State University Extension Cotton Specialists September 6, 2017

North Carolina Cotton: Not Too Early to Prepare for Defoliation, Harvest

It’s still early in the game, but its not too early to be thinking and planning defoliation and harvest strategies for this fall. The 2017 crop appears to be more variable than this time last year, however we still have higher than normal yield potential across the state compared to most years, at this point in time.

Naturally, we are all nervous as we have seen how fall weather can negatively impact high yield potential at the very end of the season, for two years in a row now. Every year is different, but we can apply what we’ve learned to hopefully be better prepared for the harvest season.

Once again, our crop is later than normal. This is not necessarily a bad thing, however it makes it difficult to strategize defoliation with any certainty at this point in time. Given that we had some later planted cotton in 2016, it wouldn’t hurt to revisit our thoughts on defoliation suggestions from previous articles here.

With that said, I sincerely hope and pray that we can somehow avoid any tropical storms, hurricanes, or prolonged wet and cloudy periods this fall. Our growers badly need a clear and open harvest season. We can not control the weather, nor predict it beyond a few days at best, however there are some things that we can do in a few situations to perhaps minimize the impact of weather. Below are a few scenarios worth discussing.

Storms that may occur in the next couple of weeks:

There’s not much we can do in this scenario, and the outcome will depend on severity of a potential storm and the weather following. We don’t know IF we will experience a storm in the next couple of weeks. We don’t know how strong winds will be nor how much rain it will bring, IF we get one.

There is no good time to have a storm, but early is usually less damaging than later, when more cotton is open. This is especially the case when ideal conditions occur following a storm.

Most, if not all of the cotton crop is made at this point but it is still too early to begin defoliating most fields. There may be a few smaller bolls towards the top of the plant that may benefit from a little more rain, but these bolls do not require much rain and will need sunny weather too.

Another component in determining risk or potential impact from near-future storms is planting date and maturity of each field. Earlier planted cotton, or otherwise earlier maturing cotton, already has several more bolls opened at this point in time, compared to later planted or later maturing cotton. Earlier maturing cotton is more vulnerable to a storm because of its opened bolls, or bolls that will be cracking during the next couple of weeks.

Naturally, high winds and significant rainfall will have a greater impact on opened or cracking bolls, which obviously can lead to weathering losses, boll rot and hardlock. However, as we observed in 2016, the weather following a storm is also important. In 2015, prolonged rainy weather caused widespread seed sprouting and severe quality losses.

In 2016, Hermine brought significant rains followed by prolonged cloudy and wet conditions, leading to severe boll rot and hardlock of the bottom crop of later maturing cotton and the entire crop of earlier maturing cotton.

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However, if a storm moves through quickly, and sunny and dry weather quickly replace it, the impact of the storm could be less, especially on later maturing cotton. Ideally, IF we HAVE to have storm, it will bring minimal rains and wind, followed quickly by sunny and dry weather. In the worst case scenario, high winds and heavy rains can cause plants to topple over and tangle, and will be followed by prolonged damp or wet conditions.

Bolls approaching maturity and those that are touching the ground or entangled by leaves are more prone to hardlock or rot, especially if they do not dry out quickly following the storm. Earlier maturing cotton will be most susceptible to these effects.

Storms that occur in late September or early October:

Hindsight is always 20/20. During the week prior to hurricane Matthew that hit on October 8 of 2016, many growers were frantically defoliating their crop to avoid additional delays in defoliation and harvest.

This is understandable, but it can be costly, depending on the situation. Again, there was a lot of uncertainty over the likely path that Matthew would take, and some forecasters thought that it would move off of our coast, even on the day that it hit. The weather following Matthew was ideal, but we did not know that at the time.

IF a similar situation occurs again, there are a few recommendations to consider for a few likely scenarios.

1. 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 in terms of both yield and quality. 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 storm hits. 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 a 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 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. If significant rains result from a potential storm, we can expect to see more regrowth than normal. Additionally, heavy rains will delay our ability to re-enter fields and resume defoliating, therefore regrowth will increase the more we are delayed.

Defoliating just prior to a storm may not adequately prevent additional regrowth, depending on how much time elapses before harvesters can re-enter fields, and some fields will likely need a second “clean-up” application.

Delaying defoliation until after a storm passes will likely help us address regrowth issues a little more effectively once we can get back into fields.

2. 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 mild 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.

A storm can occasionally thrash leaves around, producing ethylene, which may allow for self-defoliation to some degree. This could theoretically improve defoliation efficacy later by ridding of some leaves prior to our harvest aid application. Regardless, we still advise defoliating in sunny conditions (cloudy weather may result in suboptimal defoliation).

As mentioned above, we might also 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 any potential storm, there is little incentive to prior to a storm, 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. Regardless, it is always wise to only defoliate the fields that you are fairly certain can be harvested within 10 days to two weeks after defoliation.

Defoliating too much at one time may result in the inability to harvest in a timely manner, prolonging cotton’s exposure to weathering and likely resulting in regrowth. Within your power, harvest cotton as timely as you can following defoliation.


Source: : https://cotton.ces.ncsu.edu/2017/09/as-we-prepare-for-defoliation-and-harvest-in-2017-collins-edmisten/

Ernst Undesser
By Keith Edmisten and Guy Collins, North Carolina State University Extension Cotton Specialists September 6, 2017