PGR Best Practices for Your Cotton

Managing cotton vegetative growth in season is an effective way to ensure improved insecticide and fungicide efficacy, canopy airflow, dry down, and defoliation throughout and at the end of the season by which improving harvest efficiency. Cotton vegetative growth is best managed with plant growth regulators (PGRs).

Is cotton a perennial or an annual crop?

Cotton is a plant with an indeterminant growth pattern, managed as an annual, which makes it unique among row crops grown in the US. Because it is a perennial managed like an annual, differences with respect to maturity, growth, and development can occur across varieties classified in the same maturity group.

PGRs for Cotton Production

The most common PGRs for cotton production are mepiquat chloride (Veto™) or mepiquat pentaborate. Applying PGRs properly can have complex based on cotton variety and growth habit.

Using PGRs to manage vegetative growth in cotton will improve your overall crop health and pest management. Fine tuning PGR use includes timing of application, application best practices, and understanding weather conditions before, during, and after PGR application can greatly improve its effectiveness.

When to use PGRs while Growing Cotton

Plant growth regulator use in cotton generally begins at matchhead square, when the plant has approximately 8-10 nodes. Applications of plant growth regulator can be made at weekly or biweekly intervals from that point forward in the season. However, PGR applications are dependent upon cotton growth and development as well as changes in rainfall, temperatures, or other abiotic and biotic factors.

PGR Selection and Application Rate

Research has shown little difference in brand or salt type of mepiquat (chloride or pentaborate). A PGR from our INNVICTIS® product line, VETO™, is labeled for use from 2 to 16 fl oz/A. The optimal rate is dependent on several factors to include length of plant internode space, what the weather forecast in the next 7-14 days, as well as how much additional vegetative growth you anticipate this season.

Figure 1. Cotton plant with leaves removed to highlight internodes on the main stem to better determine timing and rates for PGR application. Courtesy of UGA Extension.

How well does this variety respond to PGR Applications?

When cotton plants are stripped to just the main stem branches, plant growth and development is easier to assess (figure 1). By looking at the length between Node 4 and Node 5 PGR rate can be determined.

Why length between nodes is important

PGR application should be considered if the length between nodes 2, 3, or 4 is greater than 2 inches. As most of us fail to carry a tape measure with us into the field, consider using your smart phone or knuckles as your guide. The width of the smallest smart phones on the market is 2” and as a generalization one knuckle is approximately 1” – which is the key determining length between nodes PGR applications. 

Figure 2: Determining whether or not to spray PGRs based on length between nodes in cotton.

Determining need for PGR application 

Additionally, in Figure 2 the cotton pictured on the far left has nodes which are ≤ 2” long; therefore, PGR application would not be needed. The middle photo shows the node distance as 3”; therefore, a PGR application would be warranted, but not too aggressive. The right photo shows cotton node length of nearly 5”; therefore, an aggressive PGR application rate would be recommended.

How weather impacts PGR Rate

Another consideration is to assess the weather forecasted over the next 7-14 days which is critical to determine PGR rate. If PGR rates are too great during hot and dry weather, cotton growth and development can be severely limited.

However, if weather is forecasted to be hot with rainfall, then consider a higher application rate. It’s always better to spoon-feed the rate and error on the lower side than risk being too aggressive. This could cause cotton shutting down and potentially impacting yield potential.

Cotton varietal response to PGR Use

The last consideration is cotton varietal response to PGR use. This information can be found in any seed company’s guide for cotton varieties they sell. For example, a known aggressively vegetative cotton variety that routinely needs some type of PGR application – even in West Texas, is DP 1646 B2XF.

Figure 3: Response of Deltapine® brand cotton varieties to growth management with mepiquat plant growth regulator. Fg 3 adapted from credit resource found at: https://www.cropscience.bayer.us/articles/dad/cotton-growth-management.

The Takeaway

This season consider how effective your PGR management program can be to improve and protect your yield. Please consult any of your local Agronomic Sales Enablement Team or your local Simplot Grower Solutions Crop Advisor to answer your application questions.

Authors

Connor Ferguson, Texoma
Ben Lawrence, Bayou
Jeffrey Mansour, Midsouth
Justin McCoy, Southwest

Click to read more about the authors