[img_inline align=”right” src=”http://padnws01.mcmaster.ca/images/gypsycaterpiller.jpg” caption=”A gypsy moth caterpillar can be identified by its red and blue spots. Photo by Marvin Gunderman. Below left, a tree that was not treated with larvicide was completely defoliated, while the tree on the right was treated and still has its leaves. Photos by Susan Bubak.”]McMaster University's decision earlier this spring to apply a larvicide to selected areas of campus to protect against the gypsy moth infestation that has affected much of Eastern Canada and the U.S. has been successful, said grounds manager Barbara Rabicki.

As a result of treatment applied to select trees around Mayfair, central campus and the south perimeter of the 10-acre field, trees are in good condition and show little to no leaf damage.

The larvicide used was Btk (Bacillus thuringiensis kurstak) — a natural disease of caterpillars, which has been used on farms since the 1980s — was applied twice at a seven to 10 day interval to selected trees. Treatment was completed by June 1.

“We selectively protected the most mature and valuable trees of prominence to the campus landscape,” said Rabicki.

Since the entire campus was not treated, gypsy moths have heavily infested trees in some areas of campus and surrounding property, particularly the RBG property adjacent to the Alpine tower and the soccer fields.

The difference in the leaf patterns of treated trees compared to those that were not treated is striking.

“Many trees are completely defoliated, particularly oaks and beeches,” said Rabicki. “The ones that we treated still have full foliage and are able to photosythesize.” Rabicki added that “trees in this area are stressed from the serious drought this season, which may further compromise the gypsy moth infested trees' ability to recover from cumulative setbacks.”

The gypsy moth caterpillars are now almost finished feeding and will form cocoons for several weeks before the adult moths emerge. There is only one generation per year. The moths will mate in the fall and lay egg cases that will overwinter, said Marvin Gunderman, curator of entomology and insect taxonomist in the Department of Biology.