Turf - Volatilization and Drift of 2,4-D and Dicamba

Many broadleaf control products in turf contain dicamba and/or 2,4-D. Sometimes, late spring and summer applications of these materials are used to control broadleaf weed escapes (those not controlled by spring treatments). Unfortunately, these material may volatilize and move from the site of application in hot weather. The following is an article on the subject.

Common sense is critical for spraying dicamba and 2,4-D. Both of these products are volatile and prone to move from the treated areas as vapors. Volatility can cause dicamba or 2,4-D to move up to a few miles. Spraying these postemergence broadleaf herbicides in large turf areas may require additional considerations because of the temperature. Furthermore, many of the home gardens and landscapes have been planted with vegetables, fruits, and annual plants and they are often very sensitive to these herbicides. It is not recommended to spray dicamba or 2,4-D when the temperature is expected to be 85 degrees or hotter; or spray late in the day when temperatures drop below 85. Many turf herbicide pre-mixes have dicamba and/or 2,4-D. Use lower drift formulations of these products when available. Amines and esters are the most common formulations of 2,4-D. The esters are the most active and can be used at the lower rates and for brush control. Since vapour drift is a potential problem with the ester formulations, only the amines should be used on lawns, or near gardens. Granular products are somewhat safer but still can volatilize under certain conditions.

Information from Mark VanGessel, Extension Weed Specialist, UD and other sources.

The following is a comment from a representative of PBI Gordon, a company that produces 2,4-D products with details on safety of the newer ester formulations.

The following is an over statement "esters are the most active. Since vapour drift is a potential problem with the ester formulations, only the amines should be used on lawns, or near gardens" and very missleading. It is painted with such a broad brush and is technically inaccurate. Different products due to their potential to volatilize will carry a label statement that states that it should not be applied if the temperatures are expected to go above a set temperature like 85F. The majority of products will only state not to broadcast apply when the temperatures are above 85F. The newer longer chained esters are much lower in their potential to volatilize. We now have ester based products that volatilize no differently than amine salt formulations.What I see is more particle drift than actual volatilization. The new ride on sprayers can leave a cloud of small spray particles especially when there is minimal air movement at the time of application and then a breeze occurs and moves the cloud of small particles that were never dispersed onto off target plants.

S. Gary Custis, CPAgManager: R&D and Technical SupportPBI Gordon Corporation

Landscape - Herbicide Damage to Trees

Two common herbicides, 2,4-D and dicamba are used extensively for control of broadleaf weeds in turf and are commonly included in broadleaf herbicide formulations. Unfortunately, they can also damage nearby trees and shrubs if not used correctly. The following is information on these two herbicides and the damage they can cause.

2,4-D is one of the most common herbicides used in the home landscape and is often associated with plant injury. The most common symptoms are a twisting of the petiole which results in the leaf turning upside down. There are sucking insects whose feeding activity will also result in a leaf to curl or twist but their feeding will not cause the petiole to twist. The lowest residue that will produce symptoms in susceptible tree species is 0.02 ppm. The species that are the most sensitive to 2,4-D injury include boxelder, birch, hackberry, green ash, honeylocust, walnut, poplar, littleleaf linden and elm.

Dicamba is another frequent herbicide associated with plant injury. Dicamba will produce similar symptoms to 2,4-D at low concentrations but in addition to the leaf curling or twisting there is often a proliferation of short shoots. Oftentimes there will be a swelling of the shoot. Dicamba injury frequently occurs from root uptake as applicators ignore the precaution that this herbicide should not be applied within the dripline of trees. The dripline is considered to be the edge of the tree’s canopy, the furthest extent of the roots, but the root system can extend out a distance equal to the tree’s height. Since the concern about applications within this zone is possible uptake by the roots it is best to restrict applications to a distance further than the height of the tree. The lowest residue that will produce symptoms in susceptible tree species is 0.03 ppm. Tree species that are most sensitive to dicamba include: boxelder, birch, catalpa, honeylocust, apple (and crabapple), spruce, poplar, oaks, littleleaf linden and lilacs.

Reprinted in part from the January 2008 Pest Update from South Dakota State University