Staffing Up

Gray Merriam | Mar 18, 2020

A lot of folks around our Lakeland in eastern Ontario fear the worst when all the Gypsy moth eggs that we saw on the tree bark last fall hatch in the coming spring.

Many of us scraped off all the egg masses we could find and reach but many are placed high in the tree canopies, inside car wheel rims and in lumber piles. We needed help.

Like many other invaders, gypsy moths were brought in by human mistakes. In 1869, amateur naturalists in Massachusetts brought gypsy moths in to try to use them to produce silk. A container blew off a window sill and the invasion was started. Now, with our help, gypsy moths are spread widely across North America.

In the 1890's in Massachusetts, they hired many men to climb up into the tree canopies and scrape off egg masses. Times and wages have changed. And so has nature.

Over fall and winter, Red-Breasted Nuthatches, White-Breasted Nuthatches and Chickadees scour the tree canopies right out to the finest branches checking for eggs and insects to eat. They find many of the Gypsy Moth egg masses and have learned to get past all the hairy covering put on the egg masses by the female moths.

As spring warms, little Brown Creepers will join the winter birds and a little later, floods of warblers will be passing through, also looking for foods to support their long migrations. Having full forest canopies with well-developed understories of shrubs and saplings and natural forest floors should be attractive homes and stop-overs for the birds.

The current alternative technological control is a spray of Bacillus thuringiensis variety kurstaki HD-1 simply called 'Bt'. This is a bacterium that must be eaten by the Gypsy moth caterpillars so the leaves they eat must be thoroughly coated with Bt. And because it works best on young caterpillars, the leaves must be coated just when the eggs hatch. Bt is washed off by rain so the coating must be applied just when the caterpillars hatch and when there is not rain for few days. Because the tops of the trees must be coated, aerial applications are normally used and if the Bt is washed off and has to be reapplied, the costs rise. The natural workforce of birds is better. But their populations need to be safeguarded.