Here are a few tips from UGA Weed Scientist, Dr. Eric Prostko, for late-season control of morninglory:
1) Depending upon the anticipated digging date, 2,4-DB can be used to slow down the spread/growth of annual morningglory. However, this treatment will not provide any real control or result in complete weed death. For convenience, 2,4-DB could be tank-mixed with a fungicide. The pre-harvest interval (PHI)for 2,4-DB is 45-60 days depending upon the specific product label. Only 2 applications/year of 2,4-DB are legal in peanut.
2) Aim 2EC (carfentrazone) can be used as a harvest-aid for annual morningglory in peanut (but not smallflower) . Applications of Aim will not provide complete control of large morningglories but Aim will make the stems brittle enough to improve harvest efficiency. ET (pyraflufen-ethyl) could also be used in a similar manner but I have less experience with ET than Aim. Both of these herbicides will cause minor peanut leaf burn.
3) Top-mowing can be a very effective method for removing unwanted weed-growth and improving harvest efficiency. The top few inches of the peanut plants can be mowed just prior to harvest. However, excessive top-mowing will severely effect the flow of the peanut vines over/through the digger. I prefer mowing with a flail mower (vertical blades) rather than a rotary mower (horizontal blades) since the rotary mower often leaves a bunch of debris on one side of the row which can cause problems. Top-mowing is a common practice that I use in some of my weedy research plots.