Sugarbush operators must learn to recognize insects that are a potential threat to sugar maple. Outbreaks rarely appear within a single year. Typically, insect populations attain damaging levels only after 2 to 3 years of favorable weather, temporary ineffectiveness of natural enemies, and abundant suitable food. Light defoliation and an unusual abundance of caterpillars, or sometimes moths, can be observed for 1 to 2 or more years before damage is significant. An awareness of these early warning signs make it possible to act rather than react. Usually, the operator has time to consult with specialists, evaluate the potential problem, compare management options, and arrange for any necessary action.

Once a threatening problem develops in an area, operators should discuss treatment options with pest management specialists and applicators. Presently, the only way to quickly reduce levels of threatening defoliator populations is to spray with synthetic organic or microbial (bacteriological) insecticides. The latter, which are available under a variety of trade names, all have the bacterium Bacillus thuringiensis (Bt) as the active ingredient. Currently, Bt costs slightly more than a chemical insecticide.

Many chemical insecticides act on contact and penetrate the skin of the insect, disrupting the nervous system and killing the pest within a few minutes or hours. To be effective, Bt must be ingested by a caterpillar. Once in the insect’s stomach, the microorganism reproduces rapidly and produces a toxic protein. This impairs the functioning and permeability of the stomach wall. This action may be rapid enough to kill the insect within a few hours. Some defoliators are more resistant to the toxin than others and die only after the bacterium has destroyed other tissues. This process may require several days, during which feeding diminishes.

If the correct formulation of a chemical insecticide is mixed properly and applied at the correct time and rate, most defoliator populations can be reduced to acceptable levels consistently and quickly. Bt is more difficult to use and its success is determined especially by weather conditions and insect vigor. However, the efficacy of Bt is continually being improved. In recent years, the effectiveness and cost of this environmentally safe insecticide have approached those of organic chemicals.

Because neither the biological nor the chemical insecticides that are currently being registered for use in sugarbushes enter the sap from treated trees, syrup produced from stands treated with these products can still be sold as pure.