Wednesday, July 11, 2012

Aphid Mummies

With the popularity of biological control rising, I thought I would talk a little about a common pest and how you know a specific beneficial insect is helping you deal with it.

I'm talking about aphids and parasitic wasps.

Aphids on my kale
There are about as many different kinds of aphids as there are plants (a slight exaggeration). Even though most of us recognize an aphid when we see it, we aren't always looking at the same kind of aphid. It is of little concern however, because whether you have an aphid on your kale or on your roses, there are several insect predators and parasites that will be happy to dine on them. My favorite is the parasitic wasp.

These wasps are often difficult to see unless you know what to look for because they are much smaller than what people typically think of when they imagine a wasp. Here is a picture from UC Irvine School of Biological Sciences:

Parasitic wasp getting ready to lay eggs inside aphids
As you can see, the wasp is the size of the aphid. To the naked eye you might think this is a small fly or gnat. However she will lay eggs in the aphids, and her babies will leave behind a tale-tell sign that they have been working for you- aphid mummies.

aphid mummies on kale

An aphid mummy is what is left of the aphid after the larvae hatches from the egg. The larvae consume the aphid from the inside. Then the little darling eats it's way out, and all that is left is the shell we see, which is the small brownish thing on the kale pictured above with a little hole bored in the back.

What is nice about these guys is there is physical evidence efforts in biological control are working. Some other great insects like lady beetles (ladybugs) and their larvae, lacewing larvae and hoverfly larvae consume aphids, but I only know it if I see them in action. I guess I just like to have proof, even though I have faith my system works.

Sure, I have aphids on a few of my plants but it never turns into an epidemic. This is the key to allowing the garden to work as a system. I understand there must be some food for my beneficial insects to dine on. Otherwise, they won't make my garden their home- eating, reproducing, and overwintering. I don't use any sprays at all- not even "organic" ones. This is because I want to preserve the beautiful balance in my garden of pest, predator and/or parasite, and I don't end up spending any money on bottles of potions at the garden center.

No comments:

Post a Comment