Every gardener knows the sinking feeling of dread after stepping out to find some new, hungry bug with its teeth sunk deep into the leaves of a healthy plant.
A big hornworm, it seems, can strip a tomato branch bare in an afternoon. Left unchecked, caterpillars and beetles together can quickly turn any backyard Eden into an apocalyptic scene of death and decay. But not every bug signals the end a fresh vegetable bounty, nor does one little insect nibbling on the edge of an eggplant leaf mean it’s time for napalm.
In fact, successful management of garden pests, without constant reliance on chemicals, is a matter of vigilance and understanding — and sometimes a little elbow grease.
“In a small garden, any bug at low densities might be controlled with physical means,” said Stormy Sparks, Extension Vegetable Entomologist with the Georgia Cooperative Extension Service.
For example, Sparks recalls one event involving a strange caterpillar brought into the lab. A home gardener wanted advice about insecticide treatment, but none of the scientists could identify the caterpillar.
“Finally,” Sparks said, “about the fifth or sixth scientist asked how many were present. The gardener indicated that after searching all the plants, only the one caterpillar had been found. The scientist dropped the caterpillar on the floor and stepped on it — problem solved.”
Likewise, flea beetles, in low enough numbers, can usually be hand-picked and crushed between one’s fingertips. And tomato hornworms, while insatiable, are normally not plentiful and are easy to eradicate.
But according to Fern Marshall Bradley, author of Rodale’s Vegetable Garden Problem Solver, not every hornworm should be picked and killed at once, in particular those with “ricelike projections sticking out of their backs.” These caterpillars have been attacked by parasitic wasps. They won’t live long, as the wasp larvae has been feeding inside the caterpillar’s body. The “ricelike projections” are pupae, waiting to hatch and attack the next hornworm in the garden.
“Producers should be aware of all stages of good and bad bugs,” said Sparks.
He related the story of visiting a grower suffering from aphid problems. While the farmer recognized lady beetles had arrived and were eating the aphids, he was preparing to treat his field for another kind of bug, one which he didn’t recognize and which surely was up to no good.
“The unknown ‘pest’ was the lady beetle pupae,” said Sparks. “He knew what larvae and adults looked alike, but did not know the pupal stage.”
While biological controls are almost always effective and some occasions demand chemical solutions, at the same time it’s important to be knowledgeable of and comfortable with the damage from certain kinds of pests.
Eliminating earworms in sweet corn requires “heavy pesticide use in commercial production,” said Sparks. But, earworms are cannibals. There’s usually only per ear, and that only damaging the tip.
“You can simply cut the tip off and use no pesticide,” he said.
According to Bradley, other ways to avoid costly pesticides include rotating crops, working with local Extension Service personnel to time planting before or after the presence of major pests and regular cultivation. When all else fails, sucking up bugs with a portable vacuum cleaner is a valid option.
At the end of the day, tolerance of garden pests is relative. As Sparks suggests, some folks are fine eating what the bugs leave behind. By that same token, caterpillars on pepper plants is hardly as much cause for alarm as caterpillars on collards.
It’s a case-by-case basis, and there is no teacher like experience.