Cutleaf eveningprimrose and wild radish have traditionally been troublesome weeds to manage in reduced-till fields. The most effective and economical option for controlling primrose and radish is an application of 2,4-D alone or mixed with any Roundup mixture (such as Roundup + Valor) at least 30 days before planting. For primrose, 2,4-D at 12 oz/A of a 3.8 lb/gal formulation mixed with Roundup is sufficient and would reduce the interval between application and planting non-Enlist cotton cultivars; however, rates of 1.0 to 1.5 pt/A are needed for wild radish. Dicamba will also control primrose when mixed with Roundup; dicamba is not very effective on wild radish.
For growers who do not want to put 2,4-D or dicamba in their sprayers, Liberty or a combination of Roundup plus Valor are options to provide fair (70 to 80%) control of pre-blooming primrose; full blooming primrose will be controlled about 15% better. For wild radish, regardless of growth stage, Roundup mixtures containing Harmony Extra are effective. After radish is in full bloom, Roundup + Valor will provide 75 to 90% control. Additionally, once primrose and radish are in full bloom, good to excellent control should be achieved with paraquat plus Direx.
What are my plant back restrictions when using Valor in cotton burndown?
- In strip-till cotton where the strip till rig (including ripper shank) is run after application and before planting, Valor plant-back intervals are as follows:
1) >30% ground cover = 7 days
2) 10–30% ground cover = 14 days plus 0.5″ rain/irrigation
3) <10% ground cover or tillage = 21 days plus 1″ rain/irrigation
- In no-tillage production or when the strip is implemented prior to
application. Valor plant-back interval should be 28 days. Additionally,
0.5″ (>10% ground cover) or 1″ (<10% ground cover) rainfall/irrigation is
needed. If Reflex (or generic) will be applied PRE, suggest adding an
additional 7 days to planting intervals.
- Add a nonionic surfactant or crop oil concentrate (preferred), regardless of
What rate do I need to burndown my small grain cover crop?
According to the UGA Pest Management Handbook if you are using paraquat then apply 0.63 lb ai for wheat and 0.5 lb ai for rye cover crop; cover crops must be mature (seed heads present) for adequate control.
If you are using glyphosate then consider control of cover crops:
Wheat < 12″: 0.56 lb ae
Wheat > 12″: 0.75 lb ae
Rye < 12″: 0.56 lb ae
Rye > 12″ (no seed head): 1.13 lb ae
Rye > 12″ (seed head): 0.56 lb ae
Below is data evaluating wild radish control by burndown herbicides from Dr. Stanely Cupepper, UGA Weed Scientist.