Use herbicides correctly to help prevent damage
Gardeners have been bringing plant samples into my office that have severely twisted and downward cupping leaves. The most probable cause of these symptoms is drift from broadleaf herbicides.
Herbicides, when used properly, rarely cause problems on nontarget plants. However, these products can cause injury when applied inappropriately or when they are blown by the wind away from the targeted area.
Post-emergence broadleaf herbicides selectively kill actively growing broadleaf plants. This includes growth regulator herbicides that have active ingredients such as 2,4-D and dicamba. A popular dandelion herbicide has both of these ingredients. These herbicides are quite prone to drift and volatilization. Volatilization is the process of the chemical turning into a gas and dissipating. This is a reaction caused by the chemical makeup and cannot be prevented. Drift, however, can be prevented. Several factors may affect the ability of herbicides to move from the site targeted for application to a nontarget site, including formulation, application method, temperature and wind. Be sure to always follow the herbicide label carefully! The label is the law and will inform you of the important steps to prevent drift.
Depending on the level of damage, most plants can grow out of the damage caused by herbicide drift. Little research has been done on the amount of chemical that remains in the plant. It is up to your discretion to keep the plants for vegetable harvest.
(Lindsey Novak is the agriculture agent for NDSU Extension Service, Stutsman County. For more information, contact her at the Stutsman County extension office at 252-9030.)