Anyone really selfish enough to want butterflies and baby birds without tolerating caterpillars?
Many gardeners plant fennel, milkweed, and other host plants specifically for larvae of monarchs, swallowtails, and other pollinating butterflies. But many others know the heartbreak of entire tomato plants decimated by index finger-size green hornworms and squash vines turned to mush by squash vine borers. I’ve had cabbage and broccoli laceworked by green cabbage moth caterpillars, hibiscus leaves completely skeletonized by the larvae of a tiny sawfly, azalea leaves turned gray and stippled by lacebugs, and lawns laid bare by armyworms.
Armyworms can be ignored, letting birds and spiders have all they can handle, and simply fertilize and water to help the lawn recover quickly. In the veg garden you can head off the worst of the damage with lightweight insect netting like routinely used in nearly all European and Japanese gardeners to keep butterflies and moths from laying eggs on plants in the first place.
But most folks tend to just reach for insecticides, either natural or synthetic. Trouble is, because most don’t last long, they are not effective if applied ahead of time, so have to be used as needed. Because of the short-lived effectiveness of insecticides, one application rarely works; in most cases two or three sprays are needed, every week or two, to catch both the exposed adults and any larvae that hatch from eggs after the first treatment.
By the way, though a lot of folks still cling to piling dusts on top of plants, liquid sprays on undersides of leaves nearly always work better. And no matter what insecticide you use, adding a dash of liquid dish detergent can help sprays spread out and stick onto undersides of leaves better.
There are many caterpillars that also feed, often unnoticed, on trees and shrubs, without doing a lot of overall damage and which are crucial source of protein for birds that require hundreds to feed their hungry babies. Many are cleverly camouflaged to throw off predators and some, like the bizarrely beautiful saddleback caterpillar, whose venomous spines that can inflict a painful “sting” if handled (don’t).
Bagworms, so-called for the little thumb-size sacks made of silk and bits of leaves they carry around individually, can be found on lot of different plants, but are devastating to cedar, juniper, Leyland cypress, bald cypress and other conifers which have a hard time recovering from damage.
Tent caterpillars and webworms, both of which create silken nests in trees, are more of a cosmetic issue than destructive. The difference between them is how mostly-spring tent caterpillars nest where branches and twigs join, and feed outside their tents; late summer and fall webworms weave irregular cotton candy-like masses on the leafy ends of twigs.
Most caterpillars do relatively little damage to trees which can quickly recover; the adults, larvae, and even overwintering cocoons are important sources of protein for other critters. Though very unsightly, most experts recommend ignoring them or wrap them up with sticks and toss out on the lawn for birds, spiders, and wasps to get, or spray with water to dislodge them.
Even natural insecticides like Spinosad and BT worm control work well but can kill what feeds on the dying caterpillars. And though a lot of publications say to prune out the nests, think out how this actually does far more damage to the trees than the caterpillars ever could. Ditto with setting fire to them. Sheesh.
Butterfly and moth larvae are pillars of the food chain. Do what you can to control those destroying your garden but leave some for the birds.
Felder Rushing is a Mississippi author, columnist, and host of the “Gestalt Gardener” on MPB Think Radio. Email gardening questions to rushingfelder@yahoo.com.
