Caterpillars in the Garden

“We have an enormous number of caterpillars in our yard this spring. Why is this and how do we control them?” -Brenda

Caterpillars are actually immature moths and butterflies, which go through several stages of development (egg, larva/caterpillar, and pupa) before the winged adults emerge. The larva/caterpillar stage of development isn’t called the “feeding stage” for nothing – these critters are constantly munching on leaves and plants, growing very rapidly before entering the cocoon or pupa stage and transforming into their adult selves.

Not all caterpillars are the same, and not all are considered pests. For instance, one gardener may be battling to save the vegetable garden from the destructive cabbage looper, while another gardener may be planting host plants specifically to attract the larva of monarch butterflies.

Before you do anything about your caterpillars, you should answer a couple of questions:

What kind of caterpillars do you have?

• Helpful caterpillar identification guides are available from University of Missouri and Virginia Cooperative Extension.

Are they doing any serious damage to your garden?

• If not, I would suggest that you let them be. The caterpillars will soon spin their cocoons and settle in for a long metamorphosis, and the temporary invasion is simply part of the natural ecology.
• If they are damaging your harvest or seriously injuring ornamental plants, there are a couple of natural options available. You can buy a product called Bacillus thuringiensis (also called BT or sold as Dipel, Thuricide, or Safer Brand Caterpillar Killer). It’s a natural bacteria with a protein that is toxic to caterpillars but does not affect any other insects, animals, or humans. Or, as a biological control, you can release trichogramma wasps, a natural predator that eats over 200 species of caterpillars! They can be ordered from Orcon.