"My
plants are whitebut it ain't snowin'!"
"My
plants are whiteDrift injury to non-target plants from Command herbicide has been a problem both locally and statewide in 1997. It appears that many cases of the drift injury are associated with the new Command 3ME formulation. This injury could result from drifting spray particles if applied during windy conditions or from Command vapors. The typical "whitening" of foliage has occurred to both other crops, trees, and lawn/garden plants.
The Command 3ME formulation uses micro-encapsulation to limit the volatility, which was intended to make preemergence applications feasible. These usually are used in a no-till soybean situation. The 3ME formulation was introduced to the market last year.
Although there were some problems with particle and vapor drift in 1996, the number of complaints and questions has been much greater this year. According to Chris Boerboom, UW Extension Weed Specialist, several factors may be contributing to cause greater Command 3ME injury this year besides windy conditions. First, many Command 3ME applications were probably made to dry soils and may have been followed with light showers. If the Command capsules were releasing the Command with these light showers, the rainfall may have been inadequate to move the Command into the soil. This could leave the Command on the moist soil surface where it could volatilize. Under higher rainfall, the Command may have been moved into the soil and bound.
Second, the injury may seem more pronounced because several of these applications were made in mid to late May. At this time, more leaves of sensitive plants have emerged. If these leaves are injured, it results in a bigger visual impact. If earlier applications resulted in vapor drift, fewer leaves would be exposed. Since Command does not translocate to growing points well, leaves that are still emerging may show less or no injury and would help mask the injury.
A third factor that may be increasing the overall number of injury cases is simply the increase in Command 3ME use. If ten times as many acres are treated, then there is ten times increase in risk. Apparently, many farmers switched to the ME formulation from the EC formulation and many other farmers used it for the first time.
Most people are usually concerned if injured plants will die or if they can eat produce from injured garden plants. Fortunately, Command should not cause long term damage to perennial plants or trees. If leaves are yellowish or partially white, the leaves should "regreen." This is especially true if the injury was a result of Command vapors. However, if the leaves were damaged from spray drift, the survival of pure white leaves may be questionable or the edges of the leaves may die. This should not kill a tree, shrub, or perennial plant. They should resprout new green leaves.
What about injured garden plants? This is a tough issue because a tolerance has not been established for clomazone (the active ingredient in Command) in most vegetables (it is labeled for use on cabbage, peas, peppers, pumpkins and squash). The best advice is to avoid eating any early season vegetables that show injury symptoms like lettuce or radish. For mid season crops like raspberries, it could be up to the owners discretion, especially if the plant has regreened. Since Command doesn't translocate to the fruits and is metabolized in the plants (as indicated by regreening), there is probably little risk. Still, the vegetable was injured by a non-labeled herbicide. If the owner is concerned, they should avoid eating the produce this year.
How about injured forage plants? Alfalfa and oats are the most likely plants to be injured. Alfalfa generally will regreen and the stand should not be damaged in the long term. When FMC (the company marketing Command) tested alfalfa that was injured by Command vapors, they could not detect any residues, but did get one detection of residue when actual Command spray drift occurred. To be on the safe side, it might be wise to wait for alfalfa to regreen before harvesting, especially after spray drift. If dairy farmers have concerns about feeding it to milking cows, they could feed it to dry cows or heifers and can be assured that it won't affect their health. Recovery of oats from injury will vary depending on the severity of injury. Watch for evidence that the leaves are greening up. If so, residues should not be a problem. If injury is severe and the farmer is concerned about feeding the oats as forage, it might be wise to simply clip the oats and let the underseeded alfalfa grow.
How do you determine if the injury is from spray drift or vapors? First, spray drift obviously would be on the downwind side of the field and injury should appear within several days after spraying. Spray drift may also affect more plants and cause more severe damage than vapor drift. Injury from vapor drift may only appear on the most sensitive plants because the dose may be less. Some of the most sensitive plants are apple, ash, basswood, box elder, elm, poplar, walnut, willow, roses, alfalfa, oats, radish, and raspberry. Other sensitive species are listed on Command EC label (FMC does not list sensitive species on the 3ME label). Vapor drift could occur in one or more directions from the field and may not have a sharp pattern away from treated field. Vapor injury may also be delayed for many days after the application.
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