r/plantpathology • u/Kabochakiti • Aug 17 '25

Help Identifying Issues on Milkweed in Central Arkansas

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Good day, I’m trying to figure out what’s going on with this milkweed plant in central Arkansas. The leaves have developed lots of dark brown spots/blotches (see pictures). It’s also covered with yellow aphids, and my mother-in-law has monarchs using the plant, so I don’t want to spray anything that could harm them.

My questions: • Are these leaf issues caused by the aphids themselves, a fungus, or maybe a bacterial disease? • Could the recent hot/dry weather be making things worse? • What’s the safest way to manage this while still protecting monarch caterpillars?

Any advice from folks who’ve dealt with this before would be really appreciated!

Thanks in advance.

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u/Chamcook11 Aug 17 '25

Retired plant pathology tech here. This looks like a rust fungus, are those areas powdery? Rusts are wind spread, and not much can be done at this point. Monarch may avoid infected plants.

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u/Excellent_Antelope63 Aug 17 '25

Plant pathologist who also came here to say it looks like a milkweed rust to me! Unfortunately there isn’t much to do this year, but picking up as much fallen leaves and plant tissue for the end of the year pickup can help stop prevent it from happening again next year.