Hydrangea Leaf Scorch from Sevin: Chemical Burn, Not Disease

Sprayed three of your four new hydrangeas with Sevin (carbaryl)? The curled, browned leaves on those three—while the unsprayed one looks fine—are classic insecticide burn. High heat and humidity likely caused the chemical to linger on foliage too long, damaging tissue.

Good news: it's not a disease and won't spread. The plants will outgrow the damage. Just stop spraying, water appropriately, and wait. New growth will be clean. Avoid applying any pesticide during hot, humid conditions.

Hydrangea insecticide burn on leaves

Hydrangea insecticide burn on leaves

Hydrangea insecticide burn on leaves