Rearing Monarchs on milkweed - Knowledgebase Question

Anita, Io
Question by jackieathear
May 2, 2010
The past two years my milkweed have turned black sooty like. Will this hurt the monarchs? How can it be stopped? What causes it. The monarchs had a rough winter in Mexico and the trees are dying because of some bug there. The monarchs need all the help they can get. Thanks!

Answer from NGA
May 2, 2010


What you describe sounds like sooty mold. It's the result of insects such as aphids feeding on the leaves. When they feed they exude a sticky substance called honeydew which turns into a black film. The sooty mold won't hurt your tree or the monarchs but it doesn't look very nice. Since your have monarchs feeding, I wouldn't spray to get rid of the aphids at this time. Wait until the monarchs leave and then use insecticidal soap to get rid of the aphids. Good luck with your projects.

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