Hello Rose,

Do you have photos of the symptoms you can share, either attached to your reply, or pasted into the body of your reply? It's hard to guess what is going on without being able to see the symptoms. Based on your description, our initial guess is a heavy spider mite population, especially if it affected unrelated plants like Milkweed and Lobelia (Cardinal Flower). If you already removed the symptomatic leaves and don't have any left to photograph, feel free to send us images if that kind of damage reappears. Management tips for mites are included on the linked page; your first steps of leaf removal (for foliage heavily damaged already) was a good first step and might be all you need to do if their populations subside naturally. Established Milkweed plants tend to be vigorous enough that it's unlikely this issue will affect its long-term health, and even if it had limited regrowth this summer, we'd expect it would regrow well next spring.

Miri

Sorry,

Hi Rose, 

This is spider mite damage. What Miri described for treatment and care should help! Let us know if you have further questions. 

Emily

Thank you very much for the information, very useful. Sorry for the delay in the reply, I was out of town. I think my lobelias are recovering because they started to bloom. 

Thanks,

Rose

Thank you Emily,

You're welcome.