Gardening principles

How moths entered America

In 1868, a professor returned to America from France clutching a package. Inside were a handful of gypsy moth caterpillars in a cage-the raw materials for the professor’s dream of breeding hybrid to make silk. Soon thereafter, wind blew open the cage, and the caterpillars escaped. 

Within a decade, they were chomping a swath through oaks, apples, birches, and other favorite hosts, infesting millions of acres. The larvae are so destructive that they can defoliate a tree in two weeks.

Numerous attempts have been made since the early 1900s to eradicate gypsy mothers with everything from DDT to beneficial insects, but they remain a serious pest.

You can often spot their brown egg clusters on tree bark or see and hear the caterpillars, which are spotted blue and red, feeding in early summer.

Adults emerge in July; males are brown and females white. You can control larvae by wrapping burlap barriers around tree trunks or by spraying Bacillius thuringiensis (Bt) every 14 days from April to June. Scrape egg masses into a pail of kerosene.

The adult moths that gather around lights on summer evenings are not gardeners’ enemies, because they seldom feed on plants. It is the moth larvae that chew on, bore into, and roll themselves up in plants whether leaves, fruits, stems, or roots. The larvae, which are called caterpillars or worms, represent the main feeding stage in a moth’s life cycle. Caterpillars eat heartily to store energy for their development in the cocoon and eventual metamorphosis into winged adults.

Not all moths are harmful. Many moth species cause little damage and should be left alone. Also keep in mind that some caterpillars turn into beautiful, harmless butterflies.

The worst pests on garden plants are gypsy moths, webworms, leaf miners, budworms, and bagworms. Watch for codling moths, cankerworms, and leaf rollers on fruit; cutworms, borers, tomato hornworms and cabbage loopers prefer vegetables. 

Eliminate codling moths by picking them off plants and squash them or drop them in a pail of soapy water.