by Gaylon Morgan, Tom Isakeit, and David Kerns
The 2018 season has been a challenging one for many cotton producers in the much of South and East Texas. The multiple spring cold fronts, high winds, and lack of rain have caused multiple issues in cotton stand establishment. Many growers have had and many more are trying to make the decision on whether to replant of not. Below are some considerations for making replant decisions, and some management recommendations for thin stands.
Replant or not? The primary consideration should be based on several factors. Some are agronomic/plant pathology decision and others are risk management decisions. Each farmer will weigh these factors differently, and there are a lot of educated guessing in the process of deciding to replant or not.
Factors to consider for keeping the current crop:
- What is your plant population? In South and East Texas, where our growing season is adequately long, plant populations as low as 2 plants/ft of row will generally provide comparable yields to higher plant populations. Plant populations less than 1-1.5 plants/ft of row may have a slight reduction in yield potential, and a delay of 7-10 days in maturity should be expected. However, an established stand at this low plant population will likely have a higher yield potential than a late replanting, especially if the soil moisture situation is unfavorable and the potential for hurricane season. This is assuming the surviving plants are not diseased plants.
- How many gaps exist in the cotton stand? Cotton has a tremendous ability to compensate for lower plant populations. Skips greater than 3 feet in length are problematic, especially if adjacent rows have skips as well. When skips resulted in stand reductions of 25%, a 16% yield loss was observed from a trial in the Rio Grande Valley (1976). Considering the indeterminate growth and yield potential of our new varieties, I would expect the yield loss to be less than the 16%.
- Is adequate seed available to replant? Yield differences among current day varieties varies by as much as 25%. So, it is important to use good information and judgement in selecting varieties to replant. If a grower is going to have to settle for a sub-par performing variety, then this should also be factored into the decision to replant or not.
- Should more money be spent on inputs? This is another tough question. Unfortunately, we need to do everything possible to protect the seedling plants from any additional stress. This could be sand fighting to reduce additional sand blasting or insecticide applications to minimize thrips damage. Even later in the season, it is important to not further delay the maturity of the cotton crop, which means remaining diligent about PGR applications and protection of the fruit from fleahoppers. When plants are widely spaced, the plants will grow much larger, and PGRs will be key to keeping the plant size within reason for efficient harvesting. With this being said, do not hit the cotton too hard with PGRs early, the the multiple pass approach will be a better approach.
- Should skips be planted? Generally, it is not a good idea to replant skips in the field, because the plants will be different ages the entire year. This will severely complicate pest management, harvest-aids timing, and harvesting.
- If seedling disease or damping-off were the major reasons for stand loss, the pathogens that cause disease will not continue to affect the surviving plants as they grow, as the more mature plants will have developed defenses that can resist further disease development.
Factors to consider for replanting:
- Destroy the cotton seedlings present in the field with a burndown herbicide, such as Gramoxone, Aim, or ETX. Planting into the cotton seedlings will result in two different crops in the field which will complicate management and can potentially decrease yield due to competition among the cotton plants.
- Select a variety with proven performance and fiber quality. If possible, replanting to an early maturing varieties will likely be helpful in South and East Texas to take advantage of typical rainfall patterns and avoid hurricane season.
- Consider the herbicides that were applied to field.
- This is particularly important with the XtendFlex and Enlist Cotton varieties. For example, if 2,4-D was used at planting or following cotton emergence of Enlist Cotton, there is a 30 day + 1” rain plant back restriction to non-Enlist Cotton. Similar scenario for XtendFlex Cotton, but dicamba has a 21 day + 1” of rain plant back restriction.
- If products like Cotoran or Caparol were applied preemergence, these products can concentrate in the top of beds. So, it is recommended to knock the tops off the beds before replanting.
- If seedling disease or damping-off was the primary reason for the stand loss, there may be an increased risk of the recurrence of these diseases in replanted cotton because of the increased populations of pathogens that developed on the previous planting. These higher populations could overcome fungicide seed treatments that are normally effective, even if temperature and soil moisture is optimal for seed germination. A supplemental in-furrow fungicide application would offset this risk. A listing of fungicide options can be found at http://cotton.tamu.edu/Nematodes/Management%20of%20seedling%20diseases%20of%20cotton_2016.pdf
- If Topguard Terra was applied to the lost planting for control of cotton root rot, it may need to be re-applied to the replant cotton, unless the cotton is replanted very close (within one inch) to where the Topguard Terra was originally applied. Our research has shown that an application of Topguard Terra as a side-dress at a distance of two inches or more was not effective. The Topguard Terra does persist in soil and as long as the treated planting area is not tilled or otherwise mixed with non-treated soil, diluting it, the fungicide will still be effective later in the season.