I have planted milkweed in my garden for over 15 years with great success. One day I counted over 30 Monarch caterpillars feeding on them.
However, over the last three years the plants became decimated by a black and red flying insect. They are prolific breeders and even though I hand pick them off the plants, it is a losing battle. I feel fortunate if I can find two or three caterpillars in a day.
Unfortunately, pesticides cannot be used, and I feel these bugs are a contributing factor to the loss of the Monarch's habitat.