If your tomatoes, peppers or beans have suddenly sprouted twisted, cupped or narrow strap-like leaves this summer, the culprit probably isn't a bug or a virus. It's likely herbicide drift, according to Tarah Young, a Hubbard County University of Minnesota Extension educator in agriculture, food and natural resources.
Young writes that even a tiny amount of herbicide carried by wind or vapor can injure sensitive plants. Tomatoes, peppers, eggplants and beans are extremely sensitive, she said, while cucumbers, melons and squash are moderately so.
UMN Extension's own guide on herbicide injury identifies the same culprits: 2,4-D and dicamba tend to vaporize into the air, especially in hot, dry weather, and drift onto neighboring gardens. Glyphosate, the active ingredient in Roundup, is a different problem — it's non-selective and can injure a wide range of garden plants when sprayed too close to them on windy days.
Symptoms vary by chemical: 2,4-D and dicamba tend to produce deformed, stunted leaves with serrated margins and curling, sometimes killing the plant in severe cases, while glyphosate more often shows up as yellow or white discoloration between leaf veins along with distorted new growth.
There's no cure once the damage is done — Young said most plants recover on their own with patience, watering and reduced stress, but nothing reverses the injury itself. The better move is prevention: skip spraying on windy days and give neighbors and lawn care companies a heads-up if you're growing anything sensitive nearby. Extension's guide adds that watering lawns after a growth-regulator application can also cut down on vapor drift.