Can I use a fungicide on my purple loosestrife?

Yes, a copper based fungicide can help manage fungal spots if applied early. Follow the label instructions carefully for the best results.

Will these spots kill my plant?

Usually, leaf spot is just cosmetic and won't kill the plant. Crown gall, however, is much more serious and often fatal.

Why are there spots on my purple loosestrife leaves?

Check these first

Inspect the undersides of the leaves for fungal growth.
Check the base of the stems for any unusual bumps or tumors.
Ensure the plant is in a spot with good air movement.

Likely causes

Fungal leaf spot
Most likely
How to tell: You will see small brown or black spots, often with a yellow halo, scattered across the leaves.
What to do: Remove and destroy any infected leaves immediately to stop the spread. Improve airflow around the plant by thinning out crowded stems and avoid overhead watering.
Bacterial crown gall
Possible
How to tell: Look for rough, tumor like growths on the lower stems or near the soil line.
What to do: Unfortunately, there is no cure for crown gall. Remove and dispose of the entire plant to prevent the bacteria from spreading to your soil.

When to worry

Worry if the spots are spreading rapidly across the entire plant or if you see large galls on the stems. A few minor spots are common in very humid summers.

Stopping it coming back

Space your plants properly to allow for good airflow and keep the foliage dry by watering at the base.

Not sure which one it is? Photograph your purple loosestrife.

This page lists the usual causes. Pocket Botanist looks at your actual leaf and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Can I use a fungicide on my purple loosestrife?: Yes, a copper based fungicide can help manage fungal spots if applied early. Follow the label instructions carefully for the best results.
Will these spots kill my plant?: Usually, leaf spot is just cosmetic and won't kill the plant. Crown gall, however, is much more serious and often fatal.