Plastic mulch is recommended for sweet potato culture. It is important to maintain good weed control between the mulched rows before the plants run because once they do run access will be limited. Also, weedy areas between rows may harbor voles and wireworms.
Stale Seedbed
The following herbicides are nonselective and are used to control weeds which are present in a field prior to planting or before the crop emerges, which is especially useful for the Stale Seedbed Technique (see the Weed Management section for more information).
- glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
- paraquat (Gramoxone SL 2.0*): REI 48h, Group 22. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
- pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.
Preemergent Herbicides (before weeds germinate)
HRAC Group 0:
napropamide (Devrinol 2-XT): 2 to 4 qt/A. REI 24h. 1 application per year. Apply immediately after transplanting, to a weed-free soil surface.
HRAC Group 13:
clomazone (Command 3ME): 21.3 to 64 fl oz/A. PHI 95d below 53.3 fl oz/A, 125d above 53.3 fl oz/A, REI 12h. Apply broadcast after planting, before weed emergence. Temporary partial whitening of leaf or stem tissue may occur but should not affect yield.
HRAC Group 14:
flumioxazin (Valor SX): 1.5 to 3 fl oz/A. REI 12h. 1 application per year. Apply to soil before planting. Do not use if planting slips harvested more than 2 days prior to planting. Tolerance has been tested on ‘Beauregard’ only.
Pre- and Postemergent Herbicides
HRAC Group 27:
bicyclopyrone (Optogen): 2.6 to 3.5 fl oz/A. PHI 60d, REI 24h. 1 application per year. Apply before transplanting or to row middles after planting. Contact with crop will cause damage. Do not apply to greenhouse grown transplants.
Postemergent Herbicides (after weeds germinate)
HRAC Group 0:
pelargonic acid (Scythe): 3 to 10% solution. PHI 1d, REI 12h. Can use as a vegetative burndown prior to planting, directed and shielded spray during crop growth, harvest aid, or post-harvest. Contact with crop will cause damage.
HRAC Group 1:
clethodim (Select Max): 9 to 32 fl oz/A. PHI 30d, REI 24h. Do not exceed 64 fl oz/A per year. Apply to actively growing grasses.
fluazifop (Fusilade DX): 6 to 12 fl oz/A. PHI 14d, REI 12h. Do not exceed 48 fl oz/A per year. Apply to actively growing grasses.
HRAC Group 9:
glyphosate (Roundup PowerMax): 10 fl oz to 3.1 qt/A. PHI 7 d for wiper applicator, 14d for all other application methods, REI 4h. Do not exceed 5 qt/A per year. Apply during fallow intervals, prior to planting, at planting, before crop has emerged, to row middles with a hooded or shielded sprayer or wiper applicator, or over the top of the crop with a wiper applicator. Spray contact can cause plant death. Spray additive recommendations vary with formulation—see label.
HRAC Group 14:
carfentrazone (Aim EC): 0.5 to 2 fl oz/A (preplant or row middles) or 3.2 to 5.8 fl oz/A (harvest aid). PHI 7d, REI 12h. Do not exceed 6.1 fl oz/A per year. Apply as preplant burndown, or to row middles with hooded sprayers to emerged crops, including crops grown on mulch or plastic, or as a harvest aid. Contact with crop will cause damage.
HRAC Group 22:
paraquat (Gramoxone SL 3.0*): 0.7 to 1.3 pt/A. REI 48h. Do not exceed 4 pt/A per year. Apply before or during planting. May be fatal if swallowed or inhaled. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.