Desiccating Edible Beans for the 2008 Season
August 21, 2008
Growing up on a farm that produced dry Beans, I can relate to the difficult decisions growers face as harvest season approaches. Harvesting edible beans in a timely fashion to insure quality can be a real challenge. Direct harvesting was not much of an option in the past due to the plant architecture. Dry bean breeders have been working for years trying to breed a bean plant that has an upright plant structure, good yield, disease tolerance/resistance, and uniform dry down along with other traits.
Unfortunately it takes many years to incorporate specific traits into a plant. The upright architecture of varieties that are now available fit a few of these characteristics but not all. With the increased availability of varieties with a more upright architecture, the direct harvested acres have increased dramatically the past few years. Trying to get the fields to dry down uniformly, along with a few weed escapes here and there can pose a few harvest problems.
Desiccating edible beans is nothing new and with direct harvest increasing in popularity, many growers are implementing an application into their yearly crop budgets. There are only a few herbicides that are labeled for desiccation and most have been used for years with varying results.
Glyphosate is labeled on edible beans for pre harvest weed control. Its good to be reminded each fall that glyphosate is NOT labeled as a crop desiccant. Dry beans are a direct food source meaning they can go from the field to the final consumer. A concern of many in the bean industry is glyphosate residue being found in the beans due to improper timing of a glyphosate application. It is important to wait until the bean pods have turned a yellowish color and have a leather texture before making an application of glyphosate. The bean should be in the hard dough stage and 30% or less seed moisture. Application before this could lead to glyphosate residue in the bean itself. It is not recommended to apply glyphosate to dry beans grown for seed because reduced germination and/or vigor may occur. There are various glyphosate trade names and formulations available. Be sure to read and follow the label directions. Glyphosate has a seven day pre harvest interval (PHI). Herbicides labeled for desiccation include paraquat (Gramoxone Inteon, and Gramoxone Max), carfentrazone (Aim), and flumioxazin (Valor). Application timing of these herbicides differs when comparing to a glyphosate application. Bush type beans should have 30% green leaves remaining while vine type beans should have 40% green leaves remaining before application with at least 80% of the pods a yellow brown color. Thorough coverage is essential with a contact herbicide to help avoid a second application. The pre harvest interval for paraquat is 7 days, Aim 3 days, and Valor 5 days.
For more information consult the 2008 North Dakota Weed Control Guide circular W-253. It is also available on the web at www.ag.ndsu.edu/weeds. Remember with all pesticides to read and follow all label directions. The label is the law.