What, if anything, should I do to prevent aphids from damaging milkweed for Monarch butterflies?

Asked October 1, 2019, 2:56 PM EDT

Hello- In May, I planted 30 swamp milkweed seedlings that grew pink flowers and 1 that grew white flowers from University of Kansas’s Monarch Watch program. I live in PA, 15146. I haven’t seen any Monarch caterpillars on the 31 swamp milkweed plants since September 21st. Should I use the following Monarch Watch directions, which came with the milkweed seedlings in April, on all of the plants to remove visible aphids from the plants and also aphid eggs that might be on the plants without visible aphids, and/or cut all of the plants down to whatever height you would recommend to prevent the aphids from adversely affecting the milkweed plants? I bought a wooden bee & ladybug house, and as soon as I can find marigold plants next spring, should I plant marigolds among the milkweed plants to attract ladybugs and aphids to reduce aphids on the milkweed plants? Kind regards, Kristine “If the plants have aphids, now is a good time to spray them with the following solution to kill them, and rinse after 10-15 minutes: 1 oz Blue Dawn 1 oz Isopropyl Alcohol 1 oz white vinegar 1 gal water”

Allegheny County Pennsylvania

1 Response

Penn State Entomology recommends that you don't interfere with the milkweed aphids or any other milkweed insect because there is an established cycle of life that includes the monarch and other insects as well. Normally we don't get a front row seat for a wild plant so all we should do is watch the show.
I've had the same experience with milkweed aphids. The monarchs ignore them. I thought I could destroy the aphids, but I ended up killing some tiny caterpillars by accident. My solution in recent years has been to raise tropical milkweed (Asclepias currasavica) as an annual. I manage to save enough seeds in the fall knowing I need to germinate them in the spring each year. I transplant the milkweed to a separate 4x4 raised bed with a cheap frame that I purchased online. With the amount of wild milkweed in my area, I image the aphids are a fact of life.