Are these bugs harmful?

Yes, aphids suck the sap from your plant, which drains its energy. Over time, this can lead to yellowing leaves and a stressed plant.

Will powdery mildew kill my plant?

It rarely kills a mature hydrangea, but it looks unsightly and can weaken the plant. Treating it early prevents it from spreading to all the leaves.

What are these bugs on my hydrangea? Causes and fixes

Check these first

Look under the leaves for tiny bugs.
Check for white dusty spots on leaf surfaces.
Inspect the stems for sticky residue.

Likely causes

Aphids
Most likely
How to tell: You will see tiny green or black insects clustered on new growth or the undersides of leaves. They cause leaves to curl and leave behind a sticky residue.
What to do: Spray the leaves with a strong stream of water to knock them off. If they persist, apply insecticidal soap or neem oil once a week for 3 weeks.
Powdery Mildew
Most likely
How to tell: White, dusty patches appear on the surface of the leaves. It often happens when there is poor air circulation or high humidity.
What to do: Prune away heavily infected leaves to improve airflow. Treat the remaining foliage with a mixture of 1 tablespoon of baking soda in a gallon of water.

Find out what's wrong with your bigleaf hydrangea

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

Small numbers of pests are manageable, but you should act immediately if you see leaf curling or stunted growth. Serious infestations can weaken the plant and invite disease.

Stopping it coming back

Keep the plant healthy with proper light and water, and ensure there is enough space between plants for air to move freely.

Keep your bigleaf hydrangea healthy from here

Save your plant in Pocket Botanist and you get care reminders timed for this plant, plus a care history that shows what worked. Identification and a health check are free.

Get the app · Or check it from a photo now, free

Questions people ask

Are these bugs harmful?: Yes, aphids suck the sap from your plant, which drains its energy. Over time, this can lead to yellowing leaves and a stressed plant.
Will powdery mildew kill my plant?: It rarely kills a mature hydrangea, but it looks unsightly and can weaken the plant. Treating it early prevents it from spreading to all the leaves.

What are these bugs on my hydrangea?