St. Louis has been blessed over the last few weeks with lots of Monarchs flying around our gardens. There are plenty of eggs and caterpillars to keep the next generation going and with milkweed also comes aphids.
If you look at the recent picture, you will see not only a beautiful Monarch butterfly, but also lots of aphids. This happens every year, but this year the aphid population has waited to explode. Normally, they come out in June and are gone by July. This year they waited until July and August.
The normal response of most gardeners is to rush to their local big box store and get the most deadly pesticide they can find. They then spray their milkweed over and over until every aphid is dead.
If you love butterflies, this is exactly the WRONG thing to do. Any pesticide that will kill aphids will also kill Monarchs in the egg and caterpillar stage. I’ve recently heard of people spraying their milkweed with Insecticidal Soap. While this will certainly kill the aphids, it will also kill any Monarch caterpillars who are trying to make it into the butterfly stage.
You could try and use a high power water hose to wash them off, but that is only a very short term answer and they will quickly find their way back to your plants.
The response I have is to do nothing at all. Aphids, while not aesthetically pleasing are not hurting the plants or the caterpillars. Aphids are also food for goldfinch and hummingbirds.
When you do find yourself getting upset over aphids in the garden, take a deep breath and try to relax – this is all part of Mother Nature’s plan.