Several in the Midsouth are dealing with cotton injured by exposure to 2,4-D.  Dr. Gaylon Morgan (Agronomist with Cotton Incorporated), Dr. Bradley Wilson (Cotton Specialist for the University of Missouri), Dr. Zachary Treadway (Cotton Specialist for the University of Arkansas), and I have walked a considerable number of acres in the Midsouth over the past week.  In this blog, we tackle many of the questions we’ve been asked concerning yield potential and management after injury.  We also provide some resources for those interested in reading more about what to expect.

Estimating the yield penalty

Estimating the yield penalty from 2,4-D injury is tricky.  The three main factors that must be considered are: 1) growth stage at the time of the exposure, 2) herbicide dosage, and 3) growing conditions and length of season following the injury.

Growth stage

The growth stage at which the exposure occurred must be determined for a quality estimate of the yield penalty to be made.  This is best determined by examining the mainstem leaves.  Keep in mind 2,4-D injury will show up on expanding, rapidly growing leaves; leaves which are almost fully expanded at the time of the exposure will often only show slight damage.  Generally, during the early vegetative stages, a node is added every three to four days.  Unless the injury was extremely severe, new nodes will continue to develop in a similar timeframe.  Identification of the first leaf injured at the base of the plant and a count of the number of nodes above this leaf can narrow down the window of time in which the herbicide exposure occurred.

One of the most recent research projects which examined the sensitivity of cotton to 2,4-D injury at different growth stages was completed at Mississippi State by John Buol out of Dr. Dan Reynolds’ and Dr. Darrin Dodds’ programs.   Buol et al. (2019) concluded cotton was most sensitive to exposure to 2,4-D in the late vegetative and early reproductive stages, with yield penalties from low doses of 2,4-D applied 5 and 6 weeks after emergence generating 18 and 21% yield reductions, respectively.   A meta analysis conducted by Egan et al. (2014) summarized 48 studies evaluating cotton 2,4-D injury.  Their results closely mirrored results of Buol et al. (2019).

Much of the Midsouth cotton which has been damaged was exposed to 2,4-D somewhere between the emergence of the third true leaf and pinhead square.  Unfortunately, based on previous research and our observations, yield penalties are often observed from exposure to moderate 2,4-D doses during this timeframe.

Herbicide dosage

Herbicide dosage is usually estimated by examining leaf distortion.  Very, very light doses are easily detected on cotton plants due to the sensitivity of the plant to 2,4-D.  Injury from light doses is best characterized by leaves with a leather-like texture, dull color, an almost alligator-skin-like rippling of the leaf tissue, a very small ruffle along leaf margins, and/or abnormal leaf shape.  New leaves will resume normal growth very quickly after injury from a light dose, often within two or three nodes.  Keep in mind this vegetative material is still photosynthetically active; slight leaf distortion should not be a major concern, especially if new growth develops normally within a week of when injury is first noted.  This level of injury, while unpleasant to see, does not typically result in a yield penalty.

Figure 1: Exposure from a low dose will generate light injury characterized by alligator-skin-like rippling of the leaf tissue, a dull color, and slight ruffling of leaf edges.  Usually, less than three nodes will be impacted from exposure to a low dose.  If only light injury is observed and normal growth resumes within a week of when the injury is first noted, no yield penalty will likely be noted.

Moderate doses of 2,4-D will result in extremely narrow leaves that appear to consist of only veins with ruffled margins.  Many appropriately characterize these as “grinch-hand-like” leaves.  Numerous nodes are typically impacted when this level of 2,4-D injury occurs.  Since these leaves are not capable of producing much photosynthate, substantial delays in maturity are associated with moderate doses, especially if no healthy leaf tissue is present on the plant.  If the plant is close to pinhead square, expect the fruiting bodies developing within the following weeks to be malformed and small.  Keep a close eye on the most recently added leaf in the mainstem terminal of the plant; after this leaf begins to expand normally, normal growth will resume.

Figure 2: Moderate injury generated from 2,4-D exposure is characterized by more severe leaf distortion, with leaves appearing almost like “grinch-hands”.  Numerous nodes will be impacted, and normal growth may not resume for several nodes.

Severe doses will display many of the same characteristics as moderate doses, but the leaf damage will be more pronounced, and even more new nodes will be impacted.  It is very common for plants with this level of 2,4-D injury to abort the terminal and begin growing vegetative branches from axillary buds at nodes lower on the plant.  The release of these axillary buds results in a candelabra-like growth and is extremely important in the recovery of the plant, as these branches will be the primary source of fruiting structures after the loss of apical dominance.  Keep in mind that recovery will require photosynthetically active structures to provide sugars to developing tissues.  Since these plants have very little photosynthetically active tissue, axillary bud growth will be slow and the recovery will take a considerable amount of time.  This delay in resumption of normal growth coupled with a period of deformed and small fruiting structures most often results in severe yield penalties.

Figure 3: The most severe injury from greater exposures to 2,4-D is characterized by in a prolonged period of abnormal leaf growth and a very substantial delay in the release of axillary bud growth.  While the plant pictured here will likely not die, the yield potential of this plant has been greatly reduced.

Figure 4: If injury is severe, apical dominance will be lost and vegetative branches will begin to grow from axillary buds at nodes low on the plant.  These vegetative nodes often begin to function in a similar manner to the mainstem, resulting in candelabra-likee plant growth.

It is very common to see substantial differences in crop response to 2,4-D exposure within a given row.  This is easy to understand if you again consider how sensitive cotton is to 2,4-D; while a plant which is growing only slightly more aggressively may receive a few more molecules of 2,4-D than its neighbor, the differences in leaf distortion will often be striking.  Again, recall that we only need one plant per row foot in most scenarios to reach 75+% of our yield potential.  If healthy plants are relatively evenly spaced, it is likely you may not observe a severe yield penalty or delay in maturity.

Figure 5: It is common to observe plants expressing symptoms from a moderate to severe dose immediately adjacent plants with only slight injury.  Difference in response is likely due to the very high level of sensitivity of cotton to 2,4-D and the variable nature of herbicide movement across a given field.

Growing conditions and length of season following the injury

The compensatory growth characteristics of cotton often results in an overestimation of the yield penalty associated with 2,4-D injury.  For the plant to compensate for injury, however, the plant must be given the resources and length of season to make up for the delayed development of harvestable bolls.  Although there are sources for long-term weather forecasts, the level of confidence associated with these forecasts is quite low.  Subsequently, the length of season following injury is often where a large amount of variability is introduced into the estimation of yield after injury.

What is the yield penalty?

Dr. Savana Denton, Senior Agronomist with the National Cotton Council, recently published her graduate work evaluating a range of 2,4-D and dicamba injury in Tennessee.   The graph presenting the relationship between lint yield and 2,4-D rate is included below (Denton et al. 2025).

Figure 6: Relationship between application rate of 2,4-D and cotton lint yields observed at Grand Junction, TN during 2019, 2020 and 2021 by Dr. Savana Denton (Denton et al., 2025).  Applications were made at either matchhead square or two weeks after first bloom.

As you can see in the above figure, the injury from 2.4-D was generated from a variety of rates at either the matchhead square (black bars) or two weeks after first bloom (grey bars).  Although much the injury in the Midsouth occurred earlier in the season than matchhead square, expect the yield penalty from exposure to be similar to those observed by Dr. Denton.

In the herbicide dosage section of this document, we discussed light, moderate, and severe doses.  We have not measured a definitive level of active ingredient associated with the images above, but based on our experience, light injury would likely be generated from 0.4 g ai/ac; moderate injury would be generated by 1.6 g ai/ac; and severe injury would be generated with less than 6.9 g ai/ac.  In Dr. Denton’s research, 6.9 g ai/ac generated considerable epinasty of both petioles and mainstems.  Even in the most severe off-target movement scenarios (either volatilization or drift of the spray particle), that level of epinasty is not typically observed.

The yield penalties from 2,4-D exposure reported by Denton et al. (2025) closely mirror those reported by Egan et al. (2014), who found 19% yield reductions from vapor drift, 32% yield loss from particle drift, and 49% yield loss from misapplication exposures that occurred during the vegetative stages.   Manuchehri et al. (2019) also observed very similar yield reductions from 2,4-D exposure, with 0.74, 7.4, and 74 g ai/ac generating 3-20%, 45-58%, and 80-96% yield reductions, respectively.

Again, yield penalties caused by moderate 2,4-D injury are often associated with a delay in vegetative development, a decrease in the number and size of first position fruit from nodes 8-12, and an increase in more distal fruiting positions.  The penalty from injury is often masked by compensatory growth if growing conditions following the injury are good (adequate water, sunshine, fertility) and August, September, October (and maybe early November) provide adequate heat units to mature late developing secondary and tertiary bolls near the top of the plant.  Unfortunately, our challenging spring has delayed maturity already; injured plants were already behind, and now they are even further delayed.

How should I manage 2,4-D injured cotton?

If the level of injury is light, no change in management is likely warranted.  However, if the injury is moderate or severe, the best approach is to manage the injured crop like late-planted cotton.

Insect thresholds

After normal growth resumes, insects should be managed more aggressively.  Insects will also need to be managed for considerably longer, since fruiting positions that develop later will be needed to compensate for those that weren’t produced earlier in the year.

Plant Growth Regulator (PGR) use

Injured cotton often generates excessive vegetative growth after normal growth resumes, since the first fruiting bodies that help naturally regulate vegetative growth will likely not be present or will require far less photosynthate.  Aggressive PGR applications may be necessary later in the season, but these aggressive applications should not be applied until the plant has begun to recover and grow normally; aggressive applications prior to resumption of normal growth may limit compensatory boll production.

Nitrogen (N) Use

If Nitrogen (N) has not been applied, it would be best to reduce the amount of N applied by approximately 25%.  Given injured plants are already prone to excessive growth and delayed maturity, the overapplication of N will exacerbate these issues.  Furthermore, since yield potential has been impacted, less N will be needed by the plant.

Snake Oils

Unfortunately, several growers with acres damaged by 2,4-D have already been approached with some special frou-frou juice capable of bringing injured cotton back to life.

In one word, no.

During his graduate work at Texas A&M University, Dr. James Griffin evaluated a wide range of treatments to help injured cotton plants recover from auxin herbicide injury.  Treatments included foliar fertilizers, a variety of plant hormones, and several PGRs (Griffin, 2019).  No treatment increased yields compared to an untreated control, which consisted of a modest soil fertility program.  You can watch Dr. Griffin explain this research on a Plant Health Exchange presentation.

Take Home

Cotton which does not contain the Enlist (Corteva Agriscience, Indianapolis, IN) trait is particularly sensitive to 2,4-D injury.  The yield penalty associated with 2,4-D injury to cotton depends on the timing of the injury, the herbicide dosage, and the season following exposure.  It is common to overestimate the yield penalty associated with 2,4-D injury because cotton often compensates.  However, 2,4-D can generate a tremendous yield penalty.  If moderate or severe injury is noted, cotton should be managed like late-planted cotton.

References

Buol, J.T., D.B. Reynolds, D.M. Dodds, J.A. Mills, R.L. Nichols, J.A. Bond, J.N. Jenkins, and J.L. DuBien. 2019. The effect of cotton growth stage on response to a sublethal concentration of 2,4-D. Weed Technol 33: 321–328. https://doi.org/10.1017/wet.2019.9

Denton, S., T.B. Raper, D.M. Dodds, C. Main, and T. Mueller. 2025. Auxin injury on cotton, II: Effects on yield components.  Agron J. 117:e70014. https://doi.org/10.1002/agj2.70014

Egan, J.F., K.M. Barlow, and D.A. Mortensen. 2014. A meta-analysis on the effects of 2,4-D and dicamba drift on soybean and cotton. Weed Sci. 62: 193-206. https://doi.org/10.1614/WS-D-13-00025.1

Griffin, J.A. 2019. Efficacy of recovery sprays to auxin injury on cotton [Webinar]. Grow Plant Health Exchange. https://doi.org/10.1094/GROW-COT-12-19-211

Manuchehri, M.R., P.A. Dotray, J.W. Keeling, G.D. Morgan, S.A. Byrd. 2020. Non–2,4-D–resistant cotton response to glyphosate plus 2,4-D choline tank contamination. Weed Technol. 34: 82–88. https://doi.org/10.1017/wet.2019.85