Balance of prey and predator insects

Bob Dluzen
Special to The Detroit News

It can be argued that there are two broad approaches to gardening organically.

One way uses pesticides that are approved for organic gardening. The gardener applies them as pests arise or as a preventative measure.

Then there are organic gardeners who use no pesticides at all, not even the mild insecticide soaps or oils. Those gardeners make every attempt to build up their soil fertility mostly by adding compost and planting crops for tilling under. By doing that, soil organisms are brought into balance resulting in plants that are stronger and more able to resist pests.

The absence of applying any materials whatsoever also encourages a balance of both pest and beneficial species above ground.

This type of gardener is willing to accept some short term plant damage from insect pests while waiting for the beneficial insect population to catch up.

I visited one such garden this week and found it to have some crop damage but not enough to be concerned about. The gardener was still doing some hand picking of insects and insect eggs to help minimize any infestation.

There was plenty of evidence that her strategy was working. Very few insect pests were around and her plants were thriving. Beneficial insects had found her garden and were moving in to make it their home. I even found fourteen green lacewing egg stalks all in a row.

Lacewing females deposit their eggs on thin stalks. This keeps them out of reach from other predators such as ladybug larva or even other lacewings.

Lacewings are one beneficial insect that you will not see as often even if only organic insecticides are used in the garden.

Adult female green lacewings lay their eggs in an area where they sense there is a food source for their young. However, they will be killed no matter if an insecticide application is organic or conventional.

The growing lacewing larvae vaguely resemble a tiny alligator in shape. They are extremely voracious predators of small, soft bodied insects such as aphids which accounts for their nickname, “aphid-lion”. If it was up to me, I would have named it “aphid-gator” -- that has more of a ring to it.

Although aphid-lions are named after one of their prey species, they are actually generalized insect feeders. Any soft insect they can catch and kill with their mandibles is fair game. That includes all different kinds of insect larvae, nymphs, caterpillars and insect eggs. They will easily eat over 200 of those critters each and every day, which makes them four times more effective than the more commonly known ladybug larva.

I’m not suggesting you let your garden be devoured by pests just to encourage beneficial insects. It takes time and patience to get a garden in balance. And even then, it will still need plenty of tending.

What you can do however is to keep your organic pesticide sprays to an absolute minimum by restricting the application to only the worst infestations that can’t be kept under control by other less invasive methods and learn to recognize the difference between harmful insect species and beneficials.