Cotton: The cotton crop ranges from the 5th week of bloom to defoliated. I have seen a lot of potash and other fertility issues in fields as the crop reaches its end. Growers need to pay attention to these spots and evaluate causes by looking at soil or nematode samples. According to Dr. Camp Hand, UGA Cotton Specialist, The defoliation “recipe” for this week will look very similar to last week until Friday. 3.2 oz/acre Dropp, 10 oz Folex, 32-42 oz/acre of Prep. Dropp rates should be increased in situations where there is already a significant amount of regrowth, or where regrowth potential is high. Additionally, if there is no regrowth, and low potential for regrowth, Dropp rates can be reduced or it can be pulled from the tank.
The weather this week is for dry and cooler temperatures. It will be interesting to see how this weather impacts peanut maturity. The weather forecast for the Moultrie, GA area from NOAA is below.
Below is an article written by Henry Sintin and Glen Harris titled Managing Late Season Nutrient Deficiency in Cotton.
In the August 2023 UGA Cotton Team Newsletter, we presented common visual nutrient deficiency symptoms in cotton. Deficiency symptoms become more prevalent during the reproductive and boll development stages. As the cotton plant diverts its resources towards boll formation, it becomes more susceptible to nutrient stress. It is important to diagnose and determine the cause of the deficiency so that appropriate measures can be taken. Sometimes, the appreciate measure is to do nothing in the current growing season, especially at very late stages.
Nitrogen and potassium tend to be the most affected nutrients in the late season in Coastal Plains soils typical in Georgia. As nitrogen is crucial for overall plant growth and plays a pivotal role in cotton fiber development, late-season nitrogen deficiency can result in smaller bolls, reduced fiber quality, and early cut-out. Potassium is particularly essential for boll development and fiber quality, so deficiency can lead to smaller bolls, reduced fiber strength, and increased susceptibility to diseases and pests. For instance, Cercospora, Alternaria, and Stemphylium leafspots have all been linked to potassium deficiency, and if potassium deficiency is avoided these leafspots should not be an issue. While late-season deficiencies of nitrogen and potassium are the most common, they can occur in all the other essential plant nutrient elements.
Common Causes of Late-Season Nutrient Deficiency:
Several factors contribute to late-season nutrient deficiency in cotton. Some common factors include:
1. Inadequate Nutrient Supply: Late-season nutrient deficiency is certain to occur if the recommended fertilizer rates are not applied.
2. Increased Nutrient Uptake: Cotton plants absorb nutrients at varying rates throughout the growing season, with higher demands during reproductive stages. The problem is more severe when there is a high boll load.
3. Leaching and Runoff: Heavy rainfall or excessive irrigation can lead to nutrient leaching and runoff, depleting soil nutrient levels.
4. Root Limitation: A poorly established root system will constrain the plant’s ability to access nutrients in deeper soil layers.
5. Inadequate Soil Moisture: Soil moisture is needed to solubilize nutrients and make them available for plant uptake.
How to Address Late-Season Nutrient Deficiency:
1. Diagnosis: The first step to efficiently address late-season nutrient deficiency is to properly diagnose the problem. Observation of nutrient deficiency symptoms is an initial step, and quite useful when management practices are taken into consideration. However, soil and plant tissue sampling from healthy areas and the affected areas is needed to confirm the nutrient deficiency.
2. Fertilizer Source: Once the deficient nutrient has been identified, it is important to supply that nutrient to the crop. Foliar or injection through pivot is the most convenient and efficient at this point of the season. Care must be taken when using foliar application to avoid causing significant leaf burn.
3. Timing: Apply nutrients at the right time to meet the cotton plant’s peak demand during the reproductive stage. No application should be considered when there is a significant boll opening. The effectiveness of late-season nutrient application diminishes as you pass the 5th week of bloom, and hardly will you get a yield response past the 8th week of bloom.
4. Irrigation Management: Ensure efficient irrigation practices to reduce nutrient leaching and runoff.
5. Monitoring: Regularly scout the field for early signs of nutrient deficiency symptoms before they become too severe. Periodic soil and tissue analyses are very helpful in this regard.
6. Consult Experts: Seek advice from extension services and agricultural experts for tailored nutrient management plans.
When are the bolls mature enough to open with a boll opener? I had a question or two about this last week. The sharp knife method is when the uppermost bolls that are expected to contribute to yield are cut with a knife or pipe cutter to evaluate their maturity. Bolls are mature enough to open with ethephon when they have developed seeds with brown seed coats and cotyledons. Below is an example of which bolls are mature enough to open. (Source: Application of Cotton Defoliation Aids in Alabama).
If you are into podcasts, then the latest edition of the Cotton Specialist Corner is below. Extension cotton specialist from multiple states discusses tips about cotton defoliation.
I had this question several times since we experienced the tropical weather a couple of weeks ago. Dr. Camp Hand, UGA Cotton Agronomist, gives us his opinion on this.
Will spraying mepiquat chloride (aka Pix) help this younger, twisted up cotton stand up?? Answer – NO!!! Mepiquat chloride has one simple function, and that is to shorten internode length in an actively growing cotton crop. I have gotten this question multiple times, I have been asked about using it in defoliation mixes to help with regrowth, and other crazy ideas as well. I’m not sure where the notion came from that Pix is a “cure-all”, but it only shortens the internode length of actively growing cotton.
Mildew!! If Dr. Bob ever decides to come back from the Philippines he will see how bad areolate mildew has gotten in cotton fields. Cotton with more than a month to go before defoliation is still a candidate for protection from areolate mildew which has been rough in some fields. Already lost 25% of your leaves? Don’t waste your time or money spraying now.
Irrigation considerations for cotton and peanuts from Wes Porter, UGA Irrigation Specialist.
- As the crop begins to mature and bolls begin to crack field moisture must be checked. This can be accomplished via hand or soil moisture sensors.
- If moisture is present shallow irrigation can be terminated, if rainfall is predicted in the near future irrigation can be terminated.
- If shallow moisture is not present and rainfall is not predicted a final irrigation event is suggested.
- Additional unnecessary irrigation events only make boll rot and hard lock worse.
- Manage your irrigation well up until you observe open bolls in the field, make a final check of soil moisture, and hopefully terminate irrigation
Peanuts: If you need peanuts checked for maturity we do offer hull scrape clinics on Tuesday, Wednesday, and Thursday from 8:30 am to 10 am at the Colquitt County Extension office.
I got morning glory in my peanuts!!!
Since we are so close to harvest, our best option would be Aim at 1-2 oz/A. Apply 7 days before digging for the late-season desiccation/defoliation of annual morningglories (Ipomoea spp.). Aim is less effective on smallflower morningglory. Use in combination with either a NIS (0.25% v/v) or COC (1% v/v). Aim may cause peanut leaf spotting or burning. Use at least 15 GPA for optimum results. Do not graze or feed peanut hay to livestock. Only 1 application per season is permitted. Rain-free period is 6–8 hours.
Spidermites!! I ran across a field or two with spidermites last week. If you have spidermite in peanuts, control options, according to the UGA Pest Management Handbook, include Portal (1 day PHI) and Comite (14 day PHI).
Below is a great article from Dr. Bob Kemerait about the current disease situation in Georgia.
Best Advice for 2023: Finish the Season Strong (Dr. Bob Kemerait):
As we enter the month of September, growers are preparing for harvest and planning to finish up their disease management programs. For a number of reasons I believe that growers should remain vigilant for protection of their crop from diseases, especially white mold and leaf spot. NOW IS NOT THE TIME TO BECOME COMPLACENT IN DISEASE MANAGEMENT! Now is the time to ensure the use of appropriate fungicides for white mold and leaf spot through the end of the season. My reasons include:
1. Reports from across Georgia indicate that leaf spot and white mold continue to develop developing aggressively in many fields. As some fields are just now 100 days after planting, it will be in the first half of October before these peanuts are dug. It is critical to protect against leaf spot, white mold. As peanut rust was recently found in Tifton, if is even more important to ensure effective fungicide programs remain in place.
2. Conditions throughout the season have provided the” fuel” for outbreaks white mold. Very warm and humid nights have stoked the white mold flame. Though current temperatures are lower, conditions are still favorable for white mold to progress if unchecked. Fungicides labeled for management to white mold to within 14 days of digging include tebuconazole and Fontelis.
3. Underground white mold has been reported in a number of fields, especially in non-irrigated fields. This variation of white mold can pass without detection by the grower until harvest. Managing underground white mold is always difficult. Our best options for improved management include a) irrigation or rainfall within 8 hours after fungicide applications and b) applying fungicides at night.
4. Cooler temperatures, if they ever occur, may delay maturity of the peanut crop, keeping the peanuts in the field longer and further exposing them to risk of disease.
5. Because of drought affecting peanut fields, especially non-irrigated fields, aflatoxin will likely be a problem in 2023. Growers are reminded to keep peanuts from non-irrigated fields and dry corners separate from harvested peanuts from irrigated fields. Best Advice for 2023: Finish the Season Strong (Dr. Bob Kemerait):
As we enter the month of September, growers are preparing for harvest and planning to finish up their disease management programs. For a number of reasons I believe that growers should remain vigilant for protection of their crop from diseases, especially white mold and leaf spot. NOW IS NOT THE TIME TO BECOME COMPLACENT IN DISEASE MANAGEMENT! Now is the time to ensure the use of appropriate fungicides for white mold and leaf spot through the end of the season. My reasons include:
1. Reports from across Georgia indicate that leaf spot and white mold continue to develop developing aggressively in many fields. As some fields are just now 100 days after planting, it will be in the first half of October before these peanuts are dug. It is critical to protect against leaf spot, white mold. As peanut rust was recently found in Tifton, if is even more important to ensure effective fungicide programs remain in place.
2. Conditions throughout the season have provided the” fuel” for outbreaks white mold. Very warm and humid nights have stoked the white mold flame. Though current temperatures are lower, conditions are still favorable for white mold to progress if unchecked. Fungicides labeled for management to white mold to within 14 days of digging include tebuconazole and Fontelis.
3. Underground white mold has been reported in a number of fields, especially in non-irrigated fields. This variation of white mold can pass without detection by the grower until harvest. Managing underground white mold is always difficult. Our best options for improved management include a) irrigation or rainfall within 8 hours after fungicide applications and b) applying fungicides at night.
4. Cooler temperatures, if they ever occur, may delay maturity of the peanut crop, keeping the peanuts in the field longer and further exposing them to risk of disease.
5. Because of drought affecting peanut fields, especially non-irrigated fields, aflatoxin will likely be a problem in 2023. Growers are reminded to keep peanuts from non-irrigated fields and dry corners separate from harvested peanuts from irrigated fields.
6. September is a key month for hurricanes and tropical storms, both of which can increase risk to disease, delay fungicide applications and delay harvest.
7. Finally, September is a key month for assessing the outcome of a grower’s disease and nematode management program. Is the grower satisfied with the control of tomato spotted wilt? Leaf spot? White mold? Nematodes? Aspergillus crown rot? Tomato spotted wilt? If the answer to any of these questions is “NO” then now is the time to decide why this happened and plan for 2024. It may require closer attention to Peanut Rx. It may require planting other varieties. It may require additional management measures at planting. It may require a revamped fungicide program.
With September comes the anticipation for harvest. However there is still plenty of season left for many peanut fields and it is too early to take one’s eyes off the threat of white mold, leaf spot, and peanut rust. 6. September is a key month for hurricanes and tropical storms, both of which can increase risk to disease, delay fungicide applications and delay harvest.
7. Finally, September is a key month for assessing the outcome of a grower’s disease and nematode management program. Is the grower satisfied with the control of tomato spotted wilt? Leaf spot? White mold? Nematodes? Aspergillus crown rot? Tomato spotted wilt? If the answer to any of these questions is “NO” then now is the time to decide why this happened and plan for 2024. It may require closer attention to Peanut Rx. It may require planting other varieties. It may require additional management measures at planting. It may require a revamped fungicide program.
With September comes the anticipation for harvest. However there is still plenty of season left for many peanut fields and it is too early to take one’s eyes off the threat of white mold, leaf spot, and peanut rust.
Have a great week and if you have questions please let me know.
Jeremy M. Kichler
Colquitt County Extension Coordinator
The University of Georgia Cooperative Extension does not endorse or guarantee the performance of any products mentioned in this update.