Weed control and dry pea response to preemergence application of metribuzin and sulfentrazone

A trial was conducted at Hettinger, ND, to evaluate weed control and dry pea response to preemergence applications of metribuzin and sulfentrazone applied alone and in combination (Table 1).  Field pea “Pizzaz” was planted on May 1, 2024 at a depth of 2 inches using a John Deere no-till drill. Herbicide treatments were applied after planting on May 2 (Table 2).  Peas emerged on May 14.  Herbicide treatments included metribuzin (Tricor 75DF) at 4, 5.3, and 8 oz/A (product rate) and sulfentrazone (Spartan 4F) at 3.75, 5.25, and 6.75 oz/A (product). Dry pea were evaluated at 21 and 43 days after treatment (DAT); no visible injury was observed at either evaluation.  Kochia, common lambsquarters, and green foxtail were evaluated for control at 43 DAT.  Control of all three increased when metribuzin rate increased from 4 to 8 oz/A. Increasing the rate of sulfentrazone from 3.75 to 6.75 oz/A did not result in increased weed control for these three weeds.  Combinations of metribuzin and sulfentrazone in most cases increased control of all three weeds compared with when these herbicides were applied alone. Dry pea stand was not affected by any of the herbicide treatments and was similar to the untreated control. There were slight differences in pea height when measured 8 WAT, but all treatments resulted in heights similar to the untreated control.  Dry pea yield was greater in nearly all combination treatments compared with the untreated control. From this trial, it appears that under these growing conditions and soil, both metribuzin and sulfentrazone were not injurious to the pea variety tested in this trial. Some pea varieties are known to be sensitive to either metribuzin and/or sulfentrazone. If using these herbicides, check with seed supplier to verify that the pea variety you are planting have a known tolerance to these herbicides. The soil type in this trial is a loam with 37% sand, 39% silt, and 24% clay, with a pH of 5.9 and organic matter of 3.0%. Metribuzin should not be used for weed control in peas grown in coarse soils (sand, sandy loam, or loamy sand) with organic matter of 2% or less. Lower rates of metribuzin are recommended for all soils with organic matter of 2% or less. Similarly, the rate of sulfentrazone labelled for use in dry peas is dependent both on soil texture and organic matter. It is important to know these soil parameters in fields where these herbicides will be used for weed control in dry peas in order to apply the correct labelled rate and to minimize risk of injury to the dry pea crop.