A tomato plant brought into the Extension Office this week shows signs of stress. What can be the cause of curling, yellowing, or browning leaves? First, a diagnosis of symptoms is a must.
If you have a stressed plant, it can help to record the date and location of observed symptoms. It might further help to photograph the target plant for change through time.
Most important is to rule out separate causes of stress such as weather, soil, insects, or misapplied fertilizer. (MSUCares can help with such an examination.) After eliminating possible causes, the cause of stress to this tomato plant has been determined--herbicide damage. Leaf margins that curl and that have turned yellow-to-brown helped lead to this diagnosis.
Sometimes it is difficult to identify the source of herbicide contamination such as drift (from chemicals sprayed nearby), tank contamination (failing to sanitize gardening utensils), or manure. Research not only whether there was an application of herbicide right before the symptoms first appeared, but consider crops grown in the area for the past three seasons, for example. Further research can help identify the herbicides that caused this injury.
Although a tomato plant with herbicide damage can’t fully recover, if it lives, it may produce new growth. But, expect this tomato plant to produce fewer flowers and to yield less fruit.