Seed maturity at harvest time is critical in dry bean production; however, due to variations within the field not all beans mature at the same time. To help reduce such variation and dry-down weeds that potentially can stain beans and interfere with harvesting operation, growers often use herbicides such as glyphosate as a harvest-aid (desiccant) to ensure adequate weed control and more uniform and rapid dry-down of beans. Desiccant chemistry and application timing is critical as it may cause crop yield losses and leave unacceptable herbicide residues in the seed.
Currently, there are few registered harvest-aid herbicides [glyphosate (Roundup), carfentrazone-ethyl (Aim), glufosinate ammonium (Ignite), and diquat (Reglone)] available to dry bean growers. Glyphosate is the most commonly used harvest-aid herbicide since it provides a uniform, gradual dry-down of the crop, it dries down existing weed foliage in the field, it provides control of emerged winter annual, biennial and perennial weeds, and it controls bean regrowth. There is little information available on the effect of desiccant chosen, desiccant tank-mixes, application timing and application rate on seed yield, seed quality and desiccant residues within the seed.