by Sandy Swegel
There’s yet another reason not to try to kill off aphids outside, even with “safe” organic treatments like soapy water. If you kill the aphids, the aphid-eating wasps, another of those native beneficial insects, won’t have anything to eat and they’ll leave your garden.
Aphids are eaten by so many beneficial insects that it’s rather amazing that we see any aphids at all. Yet there are so many aphids on our plants sometimes. This week I’m seeing thousands on the new growth of roses. And while my first instinct is to kill the aphids in some way, I have finally learned to just watch them. I know what I am seeing is a mini population explosion of aphids that will usually be followed in a week or so by mini-population explosions of predators that eat aphids. If we try to kill off the aphids which are the bottom of the beneficial insect food chain, then the beneficials will fly away to another garden.
I knew about many of the predators of aphids like ladybugs and lacewings, but I learned yesterday that tiny native aphid-eating wasps eat a LOT of aphids. In addition to wasps that just eat the aphids, there are the parasitic wasps that lay their eggs inside the aphids. When the eggs hatch the tiny larvae eat their way out of the aphid. A bit gory, but effective guaranteeing enough food for baby wasps.
So I challenge you to a two-week experiment. Leave the aphids be when they show up and just watch the plants for a few days. See who shows up to dine on your aphids. Some possibilities include wasps, both large and small, hoverflies, ladybugs and lacewings. It will be a fascinating discovery of how many small beings live in your garden, there to help you keep everything in balance.