Critical Management Period

Bill Robertson, Arkansas
Bill Robertson,

By mid-June, we reached a critical time for our cotton crop in terms of preserving yield potential as a result of moisture stress. This is not the norm for Arkansas. Some fields continued to produce nodes close to what was expected. However, many fields of all ages across the state exhibited a big slowdown

in node production, indicating the need to initiate irrigation.

The rate of node production is one of our best tools to schedule irrigation in pre-flowering cotton. Management becomes even more critical to finish the year in a positive fashion with only six to seven nodes above white flower (NAWF) at first flower as the plant is often destined for premature cutout.

There is some young cotton that could possibly have only five NAWF at first flower this season. Experience has shown that there is little one can do to turn around a cotton crop in Arkansas when the plant is basically at cutout (NAWF=5) at first flower.

Ideally, 60 days after planting we will find nine to 10 NAWF at first white flower. Our goal is to maintain 80 percent retention going into first flower.

Problems that can directly affect yield and profit are associated with extremely high retention rates as well as low fruit retention rates. Going into flowering with extremely high retention rates can set you up for failure if any problems are encountered. The margin for error is small when retention is high.

Maintaining a balance between vegetative and reproductive growth will help optimize earliness and preserve yield and fiber potential. Irrigation initiation and timing plays a dominant role in this balance.

Using sensors and scheduling tools along with programs, such as Pipe Planner, helps improve irrigation water-use efficiency and profitability. An effective fruiting window of three weeks between first flower and cutout (NAWF=5) provides the yield and earliness cotton producers in Arkansas desire.

Randy Norton
Randy Norton

Proper early season cotton management is crucial to ultimately producing a profitable crop. That management includes maintaining soil moisture and plant nutrient status with adequate and timely irrigations and fertilizer applications, and achieving efficient early season insect control through scouting and effective control measures.

It is important to schedule irrigations according to crop water use and the soil’s water-holding capacity. Each week, cotton advisories that contain crop water-use data are developed for every region of the state to assist in irrigation scheduling.

Water-use estimates for the week prior to the release of the advisory are given for several representative planting dates and are a good indication of the amount of water being used by the crop.

Schedule irrigations when the amount of plant available water in the soil is depleted to 50 percent. Here is an example of how this can be done: Let’s say a crop planted on April 1 is currently in the first week of July and would have an estimated water use of about 2.4 inches per week (data from advisory) or 0.34 inches per day. Let’s say the crop is planted on a loam soil that holds about 2.5 inches of plant available water per foot of soil.

If the effective rooting depth is 3 feet, that soil will hold 7.5 inches of water. The general rule of thumb is to irrigate when 50 percent of the plant available water has been used or about 3.75 inches. At a water-use rate of 0.34 inches per day, we would have an irrigation interval of about 11 days.

This technique is effective as a guide for scheduling irrigations but is no replacement for getting out in the field and observing the crop and how it is responding to the environment.

Bob Hutmacher
Bob Hutmacher

Even with fewer cotton fields, in mid-June we still have quite a range of cotton development in the San Joaquin Valley as we head towards first bloom in some of the earlier planted fields.

In my view, about one-third of early to mid-June SJV cotton fields were a pretty good match to the “normal” stage of development. Another one-third of the fields were perhaps five to seven days behind in development, and the remaining one-third or fewer fields were closer to 10 to 14 days behind typical development for this time of year.

Since the beginning of planting, weather has been variable week to week, with cooler temperatures prevailing for some periods followed by heat and wind, and then back to cooler weather.

In Upland cotton, thrips damage has been unusually severe in some areas — severe enough to suggest control treatments to deal with heavy leaf damage and poor early growth. First irrigations were moved up in many fields by a week or more.

This was done to encourage more active growth after slow initial growth rates for weeks, and to deal with root systems that might be limited by worse-than-average early shoot growth and drying upper soil profiles.
Growth can generally be expected to improve with warmer weather and when plants outgrow early season pests.

We don’t have optimal irrigation water supplies this year. But some limits in available irrigation water have lessened, allowing for the possibility that you can reduce yield-damaging stress and try for average to above-average yields.

Particularly in fields where early growth was uneven and a bit slow, it will be important to provide good, tight management of water, nitrogen and insect pests early to mid-season to try to retain early and mid-season fruit. Then hope for some cooperation from September and October weather to allow the fruit to mature.

After difficulties in 2017 with recurring lygus and aphid problems and reduced yields, it should be obvious that scouting for developing pest problems is critical. Holding early and mid-canopy fruit will be the key to attaining higher yields in a year like this one. An extended, warm fall alone won’t make up for early losses.

Periods with very hot days and nights in late-developing fields, particularly when plants are in full bloom, can negatively affect fruit retention and increase the tendency for strong vegetative growth. Too much water stress can increase square and early fruit loss and make the situation worse. Too much water and nitrogen can do the same thing.

Moderation in nitrogen applications, care with irrigation timing (not too early, not too late) and plant growth regulator applications are useful tools in years that start out like this one.

A cross-section of fields was checked again this year for multiple seedling diseases plus Fusarium race 4. Where plants grew slowly due to thrips injury, Fusarium race 4 and Rhizoctonia were worse than normal in many fields.

Stand losses were moderate in most cases, even though growth was delayed. Fusarium race 4 continues to expand into more fields and is worth identifying to try to keep this disease in check.

David Wright, Florida
David Wright,

Spring flew by, and the period for any late nitrogen applications, growth regulator use and scouting for insect and other pests is upon us. Most Florida-grown cotton blooms from early July through August. This is a critical time for watering and preventing stress to get early fruit set.

Higher cotton prices have spurred many growers’ interest to do a better job of management to maximize yields. However, I would caution them not to use excess N. Rates more than 100 pounds per acre — especially rates above 150 pounds per acre — often result in lower yields than with lower rates of N as cotton will remain in a vegetative growth stage.

A long-term study where small grain cover crops are grazed through the winter shows we often produce yields of 1,500-1,800 pounds of lint per acre on 60 pounds per acre of N. This is due to recycled nutrients and a larger cotton root system than from where the cover crop is not grazed. Several growers have fenced off fields and are grazing oats and rye after having seen the benefit of this practice.

Our hope is that no big storms affect our crop from now to harvest.

Dan Fromme, Louisiana
Dan Fromme,

May and June have been abnormally dry in Louisiana, which increases the amount of supplemental irrigation used across the state. Yield increases are usually a result of precisely timing irrigations during those few weeks when soil moisture is less than optimum due to poor rainfall distribution or

soils that have low water-holding capacities.

Being short an inch of water at the wrong time can easily result in the loss of at least 60-100 pounds of lint. The objective in Louisiana is to irrigate before plant stress occurs with an amount that even with subsequent rainfall will not cause the soil to waterlog and reduce yield. This is often quite challenging to achieve.

About 50 percent of the acres in Louisiana are irrigated, and furrow irrigation is the predominant method of applying water to the crop. Ideally, about 2 inches is applied to lessen runoff and reduce plant damage if subsequent rainfall is heavy. Rates can be higher in fields with good drainage because soil saturation is less likely.

Irrigation initiation for the season varies due to soil type, weather, cultural practices and the status of the cotton plant. One method to time the first irrigation requires determining soil moisture at 6- or 12-inch intervals in and below the anticipated rooting profile. Installing soil moisture sensors in the root zone provides a good indication if irrigation is staying ahead or falling behind soil drying.

Initiate the first irrigation when 50 percent of the available moisture has been extracted from the root zone. This will insure a greater rooting depth and reduce the risk of early season soil saturation at a time when the plant is most vulnerable. If the crop blooms before irrigation is initiated, do not further delay irrigating. Under these conditions, water can be safely applied without promoting rank growth or restricting rooting.

In some years, timing the final irrigation in Louisiana can be a difficult decision. One needs to determine the last harvestable bolls (those with time to mature) without delaying harvest or increasing chances of boll rot. In general, furrow irrigation is terminated just prior to first open boll.

However, excess soil moisture from rainfall or irrigation at this time can delay maturity and make the crop more difficult to defoliate.

Calvin Meeks, Missouri
Calvin Meeks,

Rainfall has been fairly frequent and substantial across most of the Missouri Bootheel with a dry spell just in time to get fertilizer and dicamba applied before the June 10 cutoff date. As I write this, there are high temperatures predicted as well as few substantial chances for rain in the near future.

With drier weather setting in and collapsible poly tubing rolled out into the field, farmers may be tempted to irrigate squaring cotton.

Previous research has demonstrated that irrigation is rarely justified early in the growing season except in the case of severe drought stress and should be uncommon pre-flower.

missouri cottonHowever, it’s essential to start the flowering period with adequate soil moisture and make sure it remains at adequate levels to ensure proper fruit set and boll fill.

July is a critical time for setting bolls to achieve earliness in cotton. It appears that a few fields in the area may start blooming before July 4 with some blooms appearing by the end of June. Most cotton begins blooming in early July and continues through August. It is important to ensure that adequate moisture and fertilizer are available to set a good crop in the first couple of weeks of bloom.

Having an early boll set also will help reduce vegetative growth and the amount of plant growth regulator needed.

Growth regulators should be applied to maintain an appropriate ratio of vegetative and reproductive growth. Proper growth management is essential to optimize earliness while preserving yield potential and fiber quality. Past research at the Delta Center has shown that irrigated cotton will produce around 20 to 22 nodes during the season with dryland cotton producing roughly three to five fewer nodes.

Measuring the distance between the upper fourth and fifth node can help determine if a PGR application is needed.

If an internode length of 2 inches is found, growth is inadequate and PGR use is not warranted. An internode of 2 to 3 inches would be adequate, and internode lengths greater than 3 inches would be excessive, requiring PGR applications for earliness and to limit rank growth.

Past research has established that growers in the Missouri Bootheel should have a final plant height goal 2 inches greater than the row spacing, with 38-inch rows typically in the range of 40 to 45 inches.

Darrin Dodds, Mississippi
Darrin Dodds,

Blooms, bugs and banged-up cotton — what a year 2018 has been so far! Planting season was relatively smooth unless you were in northeast Mississippi where numerous areas received as much rainfall in six months as we typically get in a year. Needless to say, establishing cotton in that region has been a challenge.

In general, thrips were light this year and leading into bloom, spider mites have been more problematic than plant bugs. However, tarnished plants bugs will almost certainly make an appearance during July.

It is not uncommon for folks to apply non-selective herbicides (i.e. glyphosate, glufosinate, etc.) in a separate application from residual herbicides due to potential crop injury. However, where they were tankmixed in 2018, injury was very noticeable.

In addition, cotton injury from off-target movement of dicamba and 2,4-D has not been uncommon. Regardless of the injury source, little can be done to alleviate injury other than time and good growing conditions.

For the most part, cotton in Mississippi is off to a good start and looking good. Timely irrigation and proper insect management during the next six weeks will set the stage heading into fall.

Keith Edmisten
Keith Edmisten
North Carolina

Heavy May rains left many growers with two different cotton crops — an early one and a late one. Successful completion of a late crop can require more precise management than an early crop.

Weed control should be well underway by the time you read this. But plant growth regulators and insect control could be critical, especially for later-planted cotton. Late-planted cotton has a shorter window to set the boll load. Therefore, a lapse in bollworm, plant bug or stink bug control can be devastating.

Late-planted cotton is also likely to be more attractive to insects. Good scouting and rapid response to triggered thresholds will help improve the chance of having a good late-planted crop.

Mepiquat applications can decrease the time it takes to mature a crop by as much as one week. This decrease in maturity can be beneficial on late-planted cotton.

It can also be helpful on the portion of the early crop that you anticipate harvesting first. Mepiquat applications, when warranted, can get those pickers in the field earlier and possibly reduce the potential for weathering losses.

Mepiquat applications should be based on plant growth and moisture and will not affect crop maturity under drought stress.

Tyson Raper, Tennessee
Tyson Raper,

Plant growth regulator use has shifted in recent years. The large reduction in price per ounce of our mepiquat products and issues with weed resistance have allowed/pushed the first application later in the year. As these applications creep past the first week of flower, we start to see a substantial increase in the amount of product required to keep growth in check.

We should be watching a large number of our fields move into the first week of flower as you read this during the first week in July. If you have not applied a plant growth regulator to your crop by this point in the season, it is likely that an application is warranted on many of your fields.

Monitor internode length, consider variety and watch the weather forecast when determining rate. Keep in mind the maximum rate per acre per season of a standard 4.2 percent mepiquat chloride product is 48 ounces. Keep an eye on for variety response ratings and details on fine-tuning rates.

Galon Morgan, Texas
Galon Morgan,

The drought situation had worsened in the Lower Rio Grande Valley and Coastal Bends of Texas, until June 19-20. Then these regions received anywhere from 2 to 10-plus inches of rain. Unfortunately, it was too much too late for the dryland production in these regions and will likely only have a minimum positive affect on cotton lint yield and quality. Most of the dryland cotton in the Lower Rio Grande Valley had already been disastered-out, and cotton in the Coastal Bend is well past cut-out.

These late rains will cause some additional management challenges with excessive regrowth and the plants wanting to start over. The Upper Gulf Coast has also received some good rain and it was early enough to help the cotton lint yields and quality. But it will also present some management challenges and probably fruiting gaps on the cotton plants and excessive vegetative growth.

Parts of the Southern Blacklands continue to look decent after catching some early scattered showers and some more June 19-20. Unfortunately, the Central Blacklands is in desperate need of rainfall, and it looks like they will receive only scattered showers.

The Northern Blacklands is starting to bloom, and the cotton looks decent considering the challenging start to the season. Most of the Rolling Plains has caught some precipitation during May and June, and most people were able to obtain adequate stands. However, a substantial amount had to be replanted due to windstorms, hail and extreme heat in May and June.

With the recent rains, growers will likely see some significant fruit shed. If this is the case, plant growth regulator applications will be needed to keep growth in check for the taller varieties. Additionally, these rains will lead to new weed flushes. With mid- to late-season herbicide applications in South and East Texas, applicators need to be conscientious when applying XtendiMax, Engenia, Enlist Duo or Enlist One and follow the label exactly.

We have observed some off-target movement of auxin herbicides. In the cases I have heard or observed, the off-target movement appears to be the result of physical drift and the result of not following one or more of the label requirements for applications with a susceptible crop downwind.

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