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15

Nov

2014

Life on Distant Hill Blog ... Grow Better Vegetables

By Leaving a Dead Log Near Your Vegetable Garden?

A female Ichneumon centrator wasp.
A female Ichneumon centrator wasp.

It is hard to believe that leaving a log or downed tree in the woods might help you grow better vegetables, but it might just be true. It turns out that there are a number of parasitic wasps of the  Superfamily Ichneumonoideathe, Braconid and Ichneumon, that are important parasites of other insects. 

This tobacco hornworm, who was feedingon the leaves of a tomato plant, is being eaten alive. It is covered with cocoons of pupating braconid wasp larva.
This tobacco hornworm, who was eating a tomato plant, is now being eaten alive by the pupating larva of a braconid wasp.

The adult female of the Ichneumon centrator wasp, shown above, hibernates for the winter under the bark of downed trees and logs on the forest floor. The females are impregnated before hibernation and will develop eggs in the spring when warmer weather returns. This subfamily of wasp, Ichneumoninae, with over 120 species native to North America, are all parasitic and lay their eggs in mature caterpillars - species of caterpillars that are often pests in the vegetable garden.

Charles Darwin was a bit repulsed by these parasitic wasps. In 1860 he wrote, "I own that I cannot see as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice."