Cotton

Heat Stress (HS) results when high temperatures combine with elevated humidity to increase crop temperatures.  Upland cotton is vulnerable to heat stress during the summer monsoon season in the low desert production areas (<2,500’ elevation) of Arizona. See full post for more information about the conditions and effects of heat stress on cotton. 

Dated: Aug. 2013
Updated: June 2021

Watering up and planting to moisture are the two main methods of germinating seed at cotton planting time in Arizona. Many cotton growers in Arizona pre-irrigate their fields before planting cotton, mainly because their soil texture is too light for moisture to be consistent as needed for germination. Unlike planting to moisture, watering up can result in intense early season weed competition and can put greater reliance on selective over-the-top herbicide chemistries.

With glyphosate-resistant Palmer Amaranth, and possibly other weeds, it should be clear that a preemergence herbicide will never stop the emergence of every single weed seedling in a field. Growers and PCAs usually must still go out and spray a postemergence herbicide to control the escapes so there is an increase in the number of weed control operations. The use of dinitroaniline (DNA or “yellow”) preemergence herbicides at the beginning of the cotton season can provide a foundation for season-long weed management, along with tillage, cultivation and other postemergence herbicides at lay by. Proper utilization of preemergence herbicides can reduce weed density and make other weed control operations more manageable, especially decreasing the pressure on the available effective, selective postemergence control options.

Click Here for a short 1-page piece on the DNA herbicides that might be very useful in managing glyphosate-resistant Palmer Amaranth in Arizona cotton.

Dated: April 2014; Updated: April 2021

Assessment of the soil moisture status of your fields is essential to schedule your first “post-planting” irrigation for cotton.  In general, cotton should be irrigated at around 700-900 HUAP (Heat Units After Planting).  That’s a good rule of thumb, but should not be the only consideration. In some areas, high winds might have dried out the soil, so it is necessary to get out and do some digging around to get an estimate of soil moisture. For this first irrigation, closely examine the top 12 – 18 inches to determine soil moisture levels.  See the Timing the First Post-Plant Irrigation pamphlet for more information on determining soil moisture. Remember, these small cotton plants do not require a large amount of irrigation water. The plants are still fairly small, and the roots are not fully developed. However, they also don’t have access to all the moisture in the soil due to their limited root growth. 

Dated: April 20, 2021

With the renewed interest in Pima cotton in the area, I thought it would be a good idea to spend a little time on it. As some of you may know Pima cotton has a reputation for being more difficult and somewhat more costly to grow than Upland cotton. There is a significant amount of crop management requirements for Pima cotton that goes beyond that of Upland. On top of that, Pima yields are lower than upland. Pima can be very vigorous and, if not managed properly, will grow large plants with minimal fiber. Because of this, it is important to approach nutrient management in Pima more cautiously. Excessive N can easily lead to excessive vegetative growth. If you haven’t listened to my recommendations before on soil and tissue sampling yet, now might be the time to do so for your Pima fields. By doing analysis it will give you an idea of your N levels so you know who much you should or shouldn’t be applying in order to evade excessive growth.

Dated: May 2014

Assessment of the soil moisture status of your fields is essential to schedule your first “post-planting” irrigation in cotton. In general, we should be irrigating somewhere around 700-900 HUAP (Heat Units After Planting). That’s a good rule of thumb, but should not be the only consideration. In some areas, high winds might have dried out the soil, so you need to get out and do some digging around and get an estimate of soil moisture. The plants are still fairly small and the roots are not fully developed. For this first irrigation, you should be looking in the top 12 – 18 inches to determine soil moisture levels. Remember, these small cotton plants do not require a large amount of irrigation water. However, they also don’t have access to all the moisture in the soil due to their limited root growth.  See full article for more information on determining soil moisture.

Dated: May 2014

Back in April of last year the College of Agriculture and Life Sciences at the University of Arizona launched a new mobile web application to help growers manage their cotton more efficiently. Mobile Cotton is a free, web-based calculator that can be accessed through smartphones or tablets in the field, or any other place to track changes in cotton plant growth, water consumption, and Nitrogen fertility levels. The goal of this tool is to provide cotton growers and crop consultants with science-based baselines that define optimal levels of plant growth and fertility. With this app, users can compare the current status of their cotton and visualize the results in a user-friendly interface with plots and other graphical formats. Access to this tool is free of charge and only requires a valid e-mail address. To set up an account and start using this tool log into http://cals.arizona.edu/mobilecotton. Questions? Feel free to contact precision ag specialist Pedro Andrade (pandrade@ag.arizona.edu)

Dated: April 2014

Arizona now has a section 18 provision for Topguard in cotton for root rot. Cotton root rot occurs in all the cotton growing areas of Arizona. Several are severely affected by cotton root rot and may limit cotton production including the Safford Valley, Marana to the Santa Cruz flats areas south and east of Eloy, and areas around Florence. Topguard will be used as a soil applied fungicide at planting to control root rot of cotton caused by the fungus Phymatotrichum omnivorum.  According to the Arizona Department of Agriculture (ADA), anyone wanting to use this product must apply to ADA to get a permit. In order for you to sell to them, they must have a permit from the ADA. The applicant will get the actual Section 18 labeling from ADA as well. 

Dated: April 2014

With harvest season quickly approaching across the state, please be aware of the following presentations available on the Plant Management Network, in collaboration with Cotton Inc.  See full post for more information and links for the presentations.

Dated: Sept. 2013

In Arizona, we have many species of stink bugs; that can be encountered in cotton, alfalfa, and other crops.  Some are occasional or potential pests of cotton.  See full post for more information on identification and effects of different stink bugs.

Dated: July 2013

Stink Bugs: Last season, stink bugs were present in many cotton fields across the state. While stink bugs are not unusual guests in our fields, the prominence and widespread distribution of the Brown Stink Bug (Euschistus servus) statewide has not been seen in cotton since 1963. I found a few stink bugs in alfalfa and small grain fields I am checking, and we have received several reports of Brown Stink Bugs in cotton along the Colorado River in Parker and Blythe, where cotton planting dates were ahead of ours in central Arizona. This may be an indicator of the population and species of stink bugs we might find later in central Arizona. As a result, growers and PCAs should be especially vigilant this year looking for populations of stink bugs in cotton. Monitoring alfalfa and grain fields can give an important early indication of the stink bug populations in the region. Fields should be checked visually (don’t rely on a sweep net) for any presence of stink bugs, esp. Brown Stink Bugs.

Dated: June 2013

Long term research at the University of Arizona has found that the Upland and Pima cotton varieties grown in Arizona can be tracked over their growth cycle by the use of several simple measures.   Members of the UA Extension Ag Team have produced set of short videos demonstrates basic cotton plant structure and plant mapping procedures.  See full post for more information and video links.