Recently, I have been in several fields and have had numerous phone calls about late-season morningglory control in peanut. Here a few thoughts to consider:
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) . Please refer to page 448 of the 2013 UGA Pest Control Handbook for more info about this particular treatment. 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.