Knowledgebase

Neem #942224

Asked August 12, 2026, 10:06 AM EDT

Can I use Neem on my asclepias? Will it harm monarchs? Thank you

Dakota County Minnesota

Expert Response

Thank you for writing. 
It does affect monarch caterpillars. 
https://hort.extension.wisc.edu/articles/common-milkweed-insects/
Without seeing the severity of the problem on your plants or the insects involved, I can not comment further. 
Most cases of minor damage should be left alone. Aphids for example can live in your milkweed, eat some of it and in turn become food to sustain beneficial predators like ladybugs and lacewings,
Please send photos. 
I
Steve Miles, Master Gardener, Hennepin County, (I am a volunteer human being: not a bot, not AI). I'm an avid gardener but not a degreed or certified horticulturist or arborist. I will do much better if you also send a photograph. I like follow-up questions.  The University' garden soil tests are excellent.  https://soiltest.cfans.umn.edu/testing-services/lawn-garden This is how to find a tree expert.  https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional  A Directory of ISA certified arborists is at https://certificates.directory.isa-arbor.com/  The Minnesota Landscape Arboretum is a wonderful place to see and learn about plants that grow in Minnesota. https://mngardens.horticulture.umn.edu/minnesota-landscape-arboretum  Ask a Master Gardener is a public service of the University of MInnesota's Extension Division.  Please donate if we make you happy.  https://give.umn.edu/gardener Replied August 12, 2026, 10:15 AM EDT

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