Weeds may develop quickly because beans are slow to establish a canopy. Use a tine-weeder or a rotary hoe if there is not too much field residue for pre-emergent mechanical weed control. Do not cultivate when the beans are starting to emerge as seedlings are very fragile and can easily snap. Cultivate 3 to 4 times when beans are 2 to 3 inches tall until canopy closure. Bean taproots are easily torn from the ground during imprecise mechanical cultivation. To minimize damage to plants, do not cultivate when leaves are wet or just after they have flowered.
NOTE: For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases, there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using.
See Stale Seedbed Technique for information on the use of these herbicides.
glyphosate (Roundup Power Max): REI 12h, Group 9. Rate based on target weed species. See label for info.
paraquat (Gramoxone SL 2.0*): restricted use. REI 12h, Group 22. Snap and lima only. Use 2–4 pts/A. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training.... The training must be completed a minimum of every three years.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons).
Preplant Incorporated/Preemergence, before weeds germinate
dimethenamid (Outlook): PHI 70d, REI 12h, Group 15. Dry beans only (including small whites, navy, black turtle soup, pink, pinto, great northern, red Mexican, red kidney, cranberry, and lentils). May be applied preplant surface, preplant incorporated, preemergence, or early postemergence (1st to 3rd trifoliate). As a single application, apply 12 to 18 oz/A on coarse-textured soil and 14 to 21 oz/A on finer textured soils. A split application may be used (10 to 14 oz/A per application, not to exceed 21 oz/A total). Allow 14 days between applications. Will not control emerged weeds. Check with seed supplier for potential varietal susceptibility to injury.
EPTC (Eptam 7E): REI 12h, Group 15. Do not use on lima beans. Apply 2.25 to 4.5 pt/A prior to planting, incorporate immediately to a depth of 2" to 4". Soil surface must be dry. For nutsedge, incorporate 4" to 6" deep. Do not exceed 3.5 pt/A on green beans grown on coarse-textured soil.
ethalfluralin (Sonalan HFP): REI 24h, Group 3. Not registered in CT or RI. Apply and incorporate before planting 1.5 to 4.5 pt/A (rate based on soil texture and target weeds, see label) prior to planting to a depth of 2" to 3".
pendimethalin (Prowl H2O): REI 24h, Group 3. Apply 2 to 3 pt/A preplant and incorporate into the soil 2" to 3". Rate based on soil texture; see label for details. Do not apply after seeding.
s-metolachlor (Dual Magnum): REI 12h, Group 15. Apply either preplant incorporated or to the soil surface just after seeding. See label for specific rates on different soil types and organic matter content (1 to 2 pt/A). May be tank mixed with either EPTC or trifluralin. Follow precautions on all labels when tank mixing. NOTE: Crop injury has been noted on both snap beans and lima beans from the use of metolachlor. Use of tank mixes, where the rate of metolachlor could be lowered, will decrease the likelihood of crop injury.
trifluralin (Treflan HFP): REI 12h, Group 3. Rate based on soil texture and crop, see label for details. Incorporate 1 to 2 pt/A before planting (1 to 1.5 pt/A for snap and lima bean). Must be incorporated into the top 2 to 3 inches of the final seedbed within 24 hours of application. Disc twice after spraying for satisfactory incorporation. See label for info on incorporation recommendations based on different equipment and single pass incorporation.
At Planting - Preemergence, before weeds germinate
clomazone (Command 3ME): PHI 45d, REI 12h, Group 13. Snap beans only. Apply 6.4 to 10.7 fl oz/A to the soil surface after seeding but before crop emergence. Use lower rate on coarse soils. Will control annual grasses and many broadleaf weeds including common lambsquarters, velvetleaf, and jimsonweed. Combining with Dual Magnum will also control yellow nutsedge and pigweed. Some temporary crop injury (partial whitening of leaf or stem tissue) may be visible after crop emergence. Complete recovery will occur from minor early injury without affecting yield or earliness. See label for replanting restrictions.
halosulfuron (Sandea): PHI 30d, REI 12h, Group 2. Rates vary based on crop and application timing (0.5 to 1 oz/A for succulent beans (snap and lima) and 0.5 to 2/3 oz/A for dry beans). Use the lower rate on lighter textured soils. Can cause temporary stunting. Heavy rains following application will increase the potential for crop injury. Use of organophosphates can increase crop injury from halosulfuron. See the label for other precautions and a list of weeds controlled.
- Preemergence: Can be applied as a preemergence after seeding and before crop emergence.
- Postemergence: Use postemergence after dry beans reach 1-3 trifoliate leaf stage or snap/lima reach 2-4 trifolate leaf stage, but before the crop flowers. Treatments applied when beans are younger increase the risk of crop injury. Application after the third trifoliate leaf increases the risk of split set. Add a nonionic surfactant at a rate of 0.25% v:v (1 qt/100 gal) spray solution. Will control yellow nutsedge and many broadleaf weeds. Will not control lambsquarters postemergence.
Postemergence to Weeds
bentazon (Basagran): PHI 30d, REI 48h, Group 6. Used postemergence on actively growing weeds. Rate varies based on weed species targeted (1 to 2 pt/A). See label for info. Apply after the first trifoliate leaf (three leaflets) has fully expanded to avoid crop damage. An effective treatment in an emergency situation to control certain broadleaf weeds and fairly effective against yellow nutsedge when 4" to 6" tall.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons). Use a 3 to 5% solution for annual weeds, a 5 to 7% solution for biennial and perennial weeds, and 7 to 10% solution for maximum burndown. Delivery rate for boom applications should be 75 to 200 gals of spray solution per acre; complete coverage of weed foliage is essential. Use a DIRECTED/ SHIELDED SPRAY; contact with crop will cause injury. For hand-held equipment, spray to completely wet all weed foliage but not to the point of runoff. Repeat applications as necessary. Tank mixes are allowed with this product. See label for complete details.
Postemergence Grass herbicides
clethodim (Select Max): PHI 30d dry beans, PHI 21d for snap beans, REI 24h, Group 1. Will control grass weeds only. Apply to actively growing grasses. See label for rate selection. For dry beans, multiple applications permitted of 9 to 32 oz/A per application, minimum 14-days between applications, not to exceed 64 oz/A per year. For snap beans, only a single application of 9 to 16 oz/A is permitted. Add 0.25% v:v nonionic surfactant (1 qt per 100 gal of spray). Can also be used as a spot-spray by mixing 1/3-2/3% (0.44 to 0.85 oz per gallon) Select Max and 0.25% v:v nonionic surfactant (0.33 oz per gallon). Spray to wet, but do not allow runoff of spray solution.
fluazifop (Fusilade DX): PHI 60d, REI 12h, Group 1. Dry beans only. For grass weed control only. Apply up to 24 oz/A. See label to select rate based on grasses targeted for control. Allow for minimum 14-days between applications, and not to exceed 48 oz/A per year. Apply to actively growing grasses (see product label for susceptible stage). Add either crop oil concentrate (0.5-1%, 0.5-1 gallon per 100 gallons of spray) or nonionic surfactant (0.25-0.5%, 1-2 qt per 100 gal of spray).
quizalofop (Assure II): PHI 30d dry beans, PHI 15d snap beans, REI 12h, Group 1. Apply to actively growing grasses. Rate based on target weed species, see label for grass growth stage and rate selection. Multiple applications permitted. Allow at least 7 days between applications. Do not exceed 24 oz/A per season for dry beans and do not exceed 14 oz/A per season for snap beans. Apply with either crop oil concentrate or non-ionic surfactant. Do not apply when crop or weeds are under drought stress.
sethoxydim (Poast): PHI 30d dry beans, PHI 15d snap beans, REI 12h, Group 1. Controls grass weeds only. Apply to actively growing grasses (see product label for susceptible stage). Maximum 2.5 pt/A per application, minimum 14-days between applications. Do not exceed 4 pt/A per year. Use with crop oil concentrate (2.0 pt/A) or methylated seed oil (1.5 pt/A). Note that crop oil can cause injury under hot and humid conditions. Can also be used as a spot-spray by mixing 1-1.5% (1.3 to 1.9 oz per gallon) Poast and 1% v:v crop oil concentrate (1.3 oz per gallon). Spray to wet, but do not allow runoff of spray solution.