During the spring and early summer one of the most common plant problems often inquired about is that of herbicide injury. The spring and early summer is a popular time to spray weeds in the lawn and landscape, but unfortunately many herbicides can be very damaging to desirable landscape plants as well.
All herbicides are capable of drifting and broadleaf weed herbicides are especially prone to moving with the breeze. This herbicide drift is what often causes damage to numerous other plants in the landscape. Damage will be found on trees, shrubs, vegetables, and other landscape plants when herbicides are incorrectly applied. Some herbicides are more volatile, meaning that the warmer the temperature is, the more likely the spray is to drift as an invisible vapor in the air.
Many forms of 2,4-D can volatilize at or above temperatures in the mid-80s and this means that spraying without caution on a warm and windy spring or summer day can create clouds of vapor that can potentially harm non-target plants. It is also important to keep in mind that drift can occur from many blocks and even miles away if the wind is blowing, so pinpointing the source can be difficult.
Symptoms of herbicide injury can vary, but usually include new leaves and shoots being shrunken, curled, puckered, bent, twisted, or distorted. Tomatoes are very sensitive to herbicide injury and are often one of the first plants to show damage. Redbuds and grapes are also very sensitive. All plants can be susceptible depending on the amount of herbicide in the air and their stage of growth.
What to do
After herbicide injury has occurred all you can do is wait. Many woody plants will simply grow out of it later on. If the drift was light there will likely be no long term effects. Plants may look bad for several weeks or even longer. Plants with injury should be kept from incurring more stress as much as possible and may need supplemental water during times of heat, wind, and drought.
If herbicide drift occurs in a vegetable garden the yields can be greatly reduced and sensitive plants like tomatoes or green beans can be easily stunted or killed. If herbicide drift occurs early in the growing season it is usually best to replant any vegetables that were significantly affected.
The best way to prevent herbicide drift is to avoid spring and early summer applications of herbicides as much as possible. Plants are easily damaged in spring and early summer because they are actively growing and have young growth that isn’t hardened off. If herbicides will be applied plan to apply very carefully on a calm day when the temperature isn’t too hot.
Fall applications of broadleaf herbicides to control common lawn weeds such as dandelions, henbit, chickweed, and bindweed are preferred and safer. Apply fall applications in October through early December depending on the weather. This is the ideal time for broadleaf weed control because many landscape plants are going dormant and weeds are much more likely to translocate the herbicide to the plant roots for a better kill.
Remember to be very careful when applying any herbicide early in the growing season as it is easy to unintentionally damage other plants in the landscape. Spring herbicide injury can lead to an entire season of unsightly growth or even long term damage on other landscape and vegetable plants. Before applying any herbicide, always read and follow label directions very carefully.