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Catalpa

Why are caterpillars eating my Southern catalpa leaves?

Seeing your tree suddenly lose its leaves is alarming, but the Catalpa sphinx moth is a common visitor. These caterpillars love the foliage, but they rarely kill a healthy, established tree. Check the undersides of the leaves for small clusters of eggs or active larvae.

Check these first

  1. Inspect the undersides of leaves for eggs or larvae.
  2. Look for droppings on the ground under the canopy.
  3. Check for sticky residue on the leaves.

Likely causes

  1. Catalpa sphinx moth caterpillars

    Most likely

    How to tell: You will see large, striped caterpillars eating the leaves and potentially stripping branches bare. Look for small black droppings on the ground beneath the tree.

    What to do: If the infestation is small, pick them off by hand and drop them into soapy water. For larger outbreaks, apply a spray containing Bacillus thuringiensis, or Bt, which targets caterpillars specifically. Repeat the application every 7 to 10 days if you see new activity.

  2. General aphid infestation

    Possible

    How to tell: Leaves may look sticky or shiny due to honeydew, and you might see ants crawling on the branches. The leaves often curl or look slightly stunted.

    What to do: Spray the foliage with a strong stream of water from your garden hose to knock them off. If they persist, use an insecticidal soap spray once a week until the population drops.

When to worry

Do not worry unless the tree is very young or already stressed by drought. Most mature trees will grow a fresh set of leaves later in the season.

Stopping it coming back

Keep your tree healthy with consistent deep watering during dry spells to help it recover from leaf loss quickly.

Not sure which one it is? Photograph your catalpa.

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

Will the caterpillars kill my tree?
Usually, no. While they can defoliate a tree, it is rarely fatal to a mature Southern catalpa.
Should I use heavy pesticides?
Avoid broad spectrum insecticides, as they kill beneficial insects that actually help control the moth population.

More problems with Catalpa

Back to the Catalpa guide

This article was generated with AI from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.