Pigweed control ahead of cotton, peanut, and soybean planting
It is very critical to have no pigweeds in fields at planting, but due to rain and other delays it is possible to have pigweed emerge following pre-plant herbicide burndown applications. Therefore, it would be a good idea to scout fields before planting to see if any pigweeds are coming up. If so, then spray with paraquat + crop oil or a surfactant at least 3-5 days before planting to make sure they are dead or dying at planting.
Spraying ahead of planting is recommended because spraying paraquat at planting or soon after may not provide good control due to dust/dirt on the weeds that may intercept paraquat, or from stress put on the weeds by the planting process. Spraying paraquat ahead of planting will also help avoid the problems of mixing it with several pre-emergent herbicides at planting.
The rate is 1 pint of paraquat for each inch ( up to 3 pints) of pigweed height and 1 gallon of crop oil/100 gallons of spray. Apply with 15 gallons of water per acre. This tank mix can be applied ahead of planting cotton, peanuts, and soybeans. This approach is good for pigweed that is 3 inches or less so be on the lookout to catch them when they are small.
Note: There may be a compatibly issue with tankmixes of paraquat and some of the crop oils. Therefore it would be a good idea to do a jar compatibility test before mixing them. There should be less issues mixing paraquat and a surfactant, but weed control will be slightly less effective. Check surfactant label for use rates. I have a jar test kit in the office that you are welcome to use.
For cotton only
Diuron up to 1 quart/acre can be added to the paraquat + crop oil tankmix for pigweed if you wait at least 7 days before planting cotton. Do not exceed 1 quart of diuron/acre, see label rate for your soil. There is no wait if you strip till after applying diuron. This tankmix should kill a 5 inch pigweed. If using diuron within 15 days of planting it is best to not use it as a pre-emerge treatment.
Reminder– Avoid spray drift because pine trees are extremely sensitive to paraquat.