One of my friends brought some arugula leaves to the office last week, to show me the many hundreds of aphids that were on them. The arugula is growing at a community garden that she had visited, and she had permission from the gardener to pick a few leaves.
We slid the leaves under the microscope and could see that, while a whole lot of the aphids are alive and active (the green ones in the picture), some had been “parasitized” by a wasp.
That means that a little wasp had laid an egg inside the aphid, and the egg was developing into a new wasp.
The aphids that have a baby wasp inside are the puffed-up golden ones in the picture.
When each wasp-baby is mature, it will bust out of the aphid body, leaving behind an empty aphid shell.
Are images from “The Alien” movie flashing through your mind yet? Sometimes, real life is just as weird as science-fiction movies. This is part of what keeps gardening so engaging.
In organic gardening, knowing that there are predators and parasitic wasps around, waiting to take care of a pest problem, provides an odd kind of comfort. Unfortunately, though, even if a swarm of ladybugs (surprisingly effective predators on aphids) moves in to help the wasps clear up the aphid problem, this arugula is going to need a lot of washing before it is added to a salad.
My venerable copy of Rodale’s “The Organic Handbook of Natural Insect and Disease Control” (my copy is from 1996) offers some help for aphid infestations. The first suggestion is to wait for the predators to take care of the problem. Usually, in my garden, “waiting” is enough.
This is an odd year weatherwise, though, so it looks as though more active steps will be needed in some gardens. The next suggestion is to blast the little plants with strong spray from a hose to knock the aphids off. The next after that is to try an insecticidal soap spray. In a dire emergency, try a veg-garden-pest spray that contains neem.
Of course, the very first thing to have done, if anyone could have foreseen the aphid disaster looming from back in the fall, would have been to cover the little crop with a spun rowcover to keep the aphids out completely.
Hoping that other gardens are relatively aphid-free!