Defining and Quantifying the Occurrence of ‘Crazy’ Cotton in Mid-South Cotton Production

Over the past six years, there have been intermittent and scattered reports of abnormal cotton growth in the Mid-South. This growth is often characterized by a loss of apical dominance between the cotyledonary and fourth node, a delay in resumption of normal growth by monopodial branches from released axillary buds on the mainstem, and a subsequent delay in fruiting. Many in the region have nicknamed this issue ‘crazy’ cotton. Often, only a small portion of the plants within the field have symptoms, but occasionally, over half of the plants within the field are impacted. While yield penalties are not always linked to the phenomenon, the abnormal growth and delay in maturity complicates management decisions and increases production costs.

This publication describes the disorder, contrasts it to other commonly observed losses of apical dominance, and describes what you can do to 1) mitigate the impact of the phenomenon and 2) assist the industry in determining the causal agent and preventing the development of ‘crazy’ cotton.

Introduction to apical dominance

Before diving into the characteristics of ‘crazy’ cotton, it is appropriate to first describe apical dominance within a normal cotton plant. Apical dominance is the suppression of axillary bud growth by the apical meristem, or the growing point located at the top of the plant. In a series of relatively complex hormonal activities, the apical meristem basically communicates to the axillary buds at each node, adjacent each mainstem leaf, to remain ‘dormant.’ As the plant grows and more resources (photosynthate, nutrients, sunlight, and water) become available, axillary buds are typically released in succession as monopodial branches (commonly nodes 5, 6 and/or 7) or sympodial branches (commonly nodes 6 and above). Monopodial, or vegetative, branches low on each plant grow in a similar manner to the mainstem, with axillary buds at the base of leaves on the monopodial branches frequently developing into sympodial, or reproductive, branches and subsequently producing reproductive structures.

What happens when apical dominance is ‘lost’?

If the apical meristem is severely damaged or removed, ‘dormant’ axillary positions below the apical meristem on the mainstem begin growing rapidly as monopodial branches. Typically, one, two, or three of these begin to suppress other axillary bud growth and normal growth resumes, with the larger monopodial branches effectively acting as mainstems. This loss of apical dominance often appears as a ‘split’, and will be referred to as such through this document.

It is often possible to find plants which have lost apical dominance in every field. Common causes of loss of apical dominance include equipment traffic on turnrows or tramlines, animal feeding, and/or hail damage.

Animal feeding

In recent years, deer damage to cotton has become quite common in certain growing regions. If cotton is unable to produce several nodes before deer begin feeding, deer may bite below the cotyledonary node, commonly resulting in plant death. However, if the plant has developed several leaves prior to the feeding event and the deer leaves the cotyledonary node or additional nodes present on the mainstem, axillary buds at the remaining nodes are often released after the mainstem has been ‘clipped’. This ‘clipped’ mainstem remains on the plant and is indicative of animal feeding (Figs. 1 and 2). A remnant mainstem is not typically present on ‘crazy’ cotton.

Hail damage

While damage from small hailstorms may only impact leaf tissue, large hail often damages all relatively succulent leaf tissue, including meristems, or the area in which cells divide. If hail causes a loss of apical dominance, stem scarring and leaf tattering will be evident in the field. Within a few weeks after the event, leaf injury will be very easily observed, with large portions of leaves tattered and leaf material littering the ground (Fig. 3). Later in the year, damaged leaves may shed and have decayed, but scarring on older stem tissue will be a good indication of a past hail event (Fig. 4). Tattered leaves and stem scarring or scabbing is not typically observed in ‘crazy’ cotton.

‘Crazy’ Cotton

Although there are a variety of characteristics of ‘crazy’ cotton, the one which is most consistent is a loss of apical dominance between the cotyledonary and fourth nodes with no remnant mainstem or stem scarring/scabbing (Fig. 5). Impacted plants appear to have suddenly initiated abnormal growth with no clear sign of injury.

The following characteristics are common but may not necessarily be present on every plant.

• Swollen node or nodes near the split (Fig. 6)

• Malformed leaf or leaves immediately above the split (Fig. 7)

• A more extreme release of all axillary buds often resulting in a ‘candelabra’-like growth (Figs. 5, 6, and 8)

• Termination of a branch into an abnormally long petiole and leaf at the node where the split occurs (Figs. 5 and 11)

• Malformed fruiting structures which may be characterized by a single bract, fused bracts or a cluster of bracts with no square present; occasionally fused squares are present. (Fig. 12)

• Additional ‘splitting’ occurs after the first split, occasionally after node 10.

What causes ‘crazy’ cotton?

Scientists throughout and beyond the Mid-South have been exploring potential causal agents. Currently, there is no consensus on the cause or what might be done to prevent it.

What should I do if I observe ‘crazy’ cotton?

First, please contact your local Extension agent and your State Cotton Extension Specialist. We are attempting to document the incidence and severity of the phenomenon. They will ask for information on the field that will be compiled and analyzed to help narrow down potential causal agents and better direct research.

Second, be prepared to adjust your management strategy of the impacted field. If only a small portion of plants are impacted, you may not need to change management practices. However, if a large portion of the field is impacted, changes in management practices are warranted and, at this point, the best strategy will mirror that of late-planted cotton. Insect pests should be aggressively managed to prevent additional delays in fruiting; extending the 80% retention threshold past bloom would be one effective way to help speed maturity. Reduce remaining nitrogen rates to prevent excessive vegetative growth, which can suppress reproductive growth and create an extremely dense canopy that can favor foliar diseases such as target spot. Finally, plant growth regulator use should be aggressive.

Take home

Cotton growth and development is particularly complex but generally very predictable, even when apical dominance is lost. Unfortunately, ‘crazy’ cotton grows unpredictably. Several teams are investigating this phenomenon, and additional information will be released when available. If ‘crazy’ cotton is observed, please reach out to your local Extension agriculture agent.

Acknowledgments

Authors

Tyson Raper, University of Tennessee; Sebe Brown, University of Tennessee; Travis Faske, University of Arkansas; Chase Floyd, University of Missouri; Heather Kelly, University of Tennessee; Shelly Pate Kerns, Louisiana State University; Gabriella Marotta, Texas A&M University; Tyler Sandlin, Auburn University; Zachary Treadway, University of Arkansas; and Bradley Wilson, University of Missouri.

Reviewers

Daren Mueller, Iowa State University and Kiersten Wise, University of Kentucky.

Sponsors

The authors thank Cotton Incorporated for their support on this project.