Controls for milkweed pests?
Last fall I started a large Monarch garden with lots of Asclepias incarnata and A. tuberosa. Deer have severely browsed the tuberosa, and I can care for that problem by installing some protective 2x3 wire over the plants. The A. incarnata is the bigger problem. It has been decimated by yellow aphids and milkweed tussuck (sp?) caterpillars. I've tried hosing them off and squishing them with my fingers, but they have increased throughout the summer. At this point, the A. incarnata plants are in sad shape. The aphids sucked so much sap from their stems and flowers that the plants are in sad shape. In fact, the aphids droppings under the incarnata plans is significant enough to make the hardwood mulch appear to be wet. We've seen lots of Monarchs this summer on nearby plants, but this is the first year we've not seen one Monarch caterpillar or chrysalis. Do you have suggestions about what I can do next year to control the insect pests and make the Monarch bed hospitable for Monarchs? HoCo MG.
The aphids that you are referring to are most likely oleander aphids. Next season keep an eye out for the culprits and spray with a forceful stream of water from the hose. If not effective, you can use insecticidal soap. Do not spray in hot weather as this can cause further damage to the foliage.
Milkweed tussock moth caterpillars usually feed in groups and its common food plant is milkweed. They tend to eat older foliage, sometimes which has already started to yellow. These caterpillars are also food for other predators like birds.
If doing serious damage, handpick and drop into a bucket of soapy water. mh