The recent rainfall throughout the county has many fields too wet for ground equipment applying fertilizer and spraying for weeds, insects, and diseases. So, how much has it rained? We have had from 6-10+ inches of rain over the last two weeks in Worth County.
Following are a few things to think about regarding “Wet Weather Concerns” and weed control from Dr. Eric Prostko, UGA Weed Scientist:
- Keep an eye on rain-free periods for post-emergence (POST) herbicides. For my crops, these are listed in the UGA Pest Control Handbook (Remarks and Precautions).
- Cool, cloudy, wet weather has a significant influence on the cuticles of plant leaves (i.e. makes them thinner). Thus, pesticides applied during this type of weather can cause more crop injury symptoms.
- Residual weed control will likely be compromised (shorter than normal). Applications of additional residual herbicides should be strongly considered (Anthem Flex, Dual Magnum, Outlook, Warrant, Zidua).
- It is also very likely that some growers will not be able to get back into their fields on a timely basis to make POST herbicide applications. There are no POST herbicides, in any of my crops, that can consistently control a pigweed that is bigger than about 3-4″ tall. Thus, applying herbicides to very large weeds (revenge spraying) is a waste of time and money! Hand-weeding, mechanical cultivation, non-selective applicators, and mowing are the only effective options for large weeds.
- Since applications of POST herbicides will be delayed, experience tells me that many growers will want to apply broadleaf and grass herbicides together. Tank-mixing grass herbicides with broadleaf herbicides (Cadre + Select or 2,4-DB + Select), is labeled/legal but will often result in reduced grass control (~10-20%). Growers can increase the rate of the grass herbicide (within label) but I prefer a split application (grass herbicide first then broadleaf herbicide ~3-5 days later).
Questions growers may be asking:
1) What’s my best peanut weed control recipe for a disaster field?
a) Apply Select 2EC (clethodim) @ 8-16 oz/A + COC @ 1% v/v then
b) 3 days after the Select application, apply the following combination: Cadre @ 4 oz/A + Cobra @ 12.5 oz/A + 2,4-DB @ 16 oz/A + any Group 15 herbicide (either Anthem Flex @ 3 oz/A or Dual Magnum @ 16 oz/A or Outlook @ 12.8 oz/A or Warrant @ 48 oz/A or Zidua SC @ 2.5 oz/A). Include NIS @ 0.25% v/v when using Anthem Flex, Warrant, or Zidua.
c) Costly for sure but desperate times require desperate measures!
2) Can I also add Strongarm to that mix?
Yes, I did that in 2022 to clean up a peanut field and observed no major problems. Check out the following pics:
3) Can peanut herbicides be applied aerially by plane or drone?
The short answers is yes (but not Cadre. It does not have an aerial application label) but I have some concerns. I have been conducting weed control research since 1987. During this 36 year time frame, I have never applied herbicides in water volumes less than 10 GPA. Coverage, crop injury, and efficacy are my concerns. There is a ton of work being conducted with drones but I have not seen a sufficient amount of replicated university data to confirm true weed control efficacy. But in this current rainy situation, perhaps something is better than nothing??????
4) What are the minimum labeled GPA requirements for aerial applications of peanut herbicides?
Butyrac 200 (2,4-DB) = 5 GPA; Classic = 3 GPA; Cobra = 7 GPA; Gramoxone = 5 GPA; Select = 3 GPA; Storm = 5 GPA; Ultra Blazer = 5 GPA
5) Is Gramoxone (paraquat) still labeled for use in peanuts in a non-selective applicator such as a rope-wick or weed wiper?
Yes! Gramoxone applied in this fashion is very effective on Palmer amaranth, Florida beggarweed, and sicklepod.
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