In the last few weeks, we’ve heard reports from many Midwestern soybean growers who have noticed tightly whorled leaves on the top of their crops. Some have also noticed stippling or blistering and even some minor burn on the edge or tip of soybean leaves. Growers may also notice that the tops of the soybean plants have wildly roping branches.
Growers, don’t panic. These symptoms are likely indicative of rapid growth syndrome (RGS), an environmental response to quickly changing growing conditions.
Growers in the Midwest may see this condition if wet weather persisted after planting, if areas had hot and dry conditions before the first application of herbicides or if significant rain fell after the first application of post-applied herbicides. Favorable growing conditions after these events cause crops to grow so quickly that branches and leaves do not unfurl as they typically would.
Causes of RGS
Like all plants, soybeans are regulated by hormones, which can become unbalanced when the plant encounters stressors. This is what causes abnormalities to the soybean leaves. Hormones tend to accumulate in certain parts of plants during stress periods when growth is not occurring. When good growing conditions follow poor growing conditions, the hormones will be translocated to the rapidly growing sections of the plants, often the leaf tips. The hormones can’t be metabolized fast enough, sometimes causing leaf blistering or stippling, minor cupping and edge burn.
Applying herbicide to plants during unfavorable growing conditions can add additional stress. The plant has to metabolize the herbicide, making the recovery phase much more drastic than normal. Though herbicides can impact RGS, they do not necessarily cause the issue.
In many cases, growers assume soybean plants are suffering from dicamba drift, which causes extreme leaf cupping and some blistering. However, RGS is the likely culprit if you spot leaf blistering without cupping or with only minor cupping and blistering on some leaves.
To determine if your fields are experiencing RGS:
- Review the weather patterns for the past four weeks.
- Make multiple field visits to see if the problem is improving or worsening.
- See if the newest leaves are the only effected part of the plant.
- Determine if flowering is occurring at all nodes, indicating that visible damage is only cosmetic.
If you do identify RGS in fields, don’t worry. Impact to your overall yield will be minimal.
Contact your local Stine representative with questions or assistance in diagnosing RGS.