If you are puzzled by curling leaves on plants in your garden or landscape, you may need to do some detective work to figure out the cause. Curling leaves can be caused by many problems, including insect damage, disease, abiotic disorders, or even herbicides.
There are several insect pests that cause leaves to curl when they suck plant juices of new or young leaves that are still growing. These include aphids, thrips, and whiteflies.
Peach leaf curl
If you have peach or nectarine trees and see curled, reddish, puckered leaves, your tree likely has a disease called peach leaf curl. This plant fungus affects only peach and nectarine trees.
Leaf rolling in vegetable plants like pepper, eggplant, and tomato is very common during wet spring conditions. This isn't caused by a disease, and no action is necessary.
When spraying for weeds, herbicides (weed killers) can accidently drift onto or come in contact with desirable plants, causing damage. Herbicides containing active ingredients such as glyphosate and 2,4-D can cause leaves to curl.
Determining the Cause
For further help in finding out what is causing leaf curling on your plant, use the UC IPM plant problem diagnostic tool. This easy-to-use tool contains useful photos and will help narrow down and diagnose the problem.
Leaf curling can sometimes be a difficult problem to diagnose. If you're stumped, contact your local UC Master Gardener Program or UC Cooperative Extension Office.