The Forest Tent Caterpillar is the most widespread forest defoliator in North America and is a natural pest, not an introduced pest like the LDD Moth (Gypsy Moth).
Contrary to their name, the Forest Tent Caterpillar does not make a tent and can be identified by the blue stripes and cream-colored keyhole pattern on its back. Do not confuse the Eastern Tent Caterpillar with the Forest Tent Caterpillar. The Eastern Tent Caterpillar can be identified by the tents they produce in the trees but are not a significant problem for tree health and defoliation.
During an infestation, the FTC can cause widespread damage and leave trees weakened and susceptible to other insects and disease. A single defoliation event will not have a severe detrimental effect on the trees however a typical infestation may last 3 to 6 years.
Tree Host Preference
The caterpillar can be found feeding on Trembling Aspen, White Birch, Poplar, Sugar Maple, and Oak.
Although weather related, the Forest Tent Caterpillar will typically hatch out at bud break and begin to feed in mid-May. Feeding will continue until June, and the caterpillar will grow in length to up to 50MM.
The caterpillar will then pupate and emerge as a tan colored moth. The adult moths will mate; the female lays its eggs in July and early August when the process will repeat.
The eggs are laid in a band around a branch in the canopy of a host tree. The Forest Tent Caterpillar will overwinter in the egg stage and are difficult to see by the human eye. Typically branches are cut in the canopy in late fall or winter to determine the level of infestation expected for the following year.
Application Control Programs
An aerial application program can be designed to meet your specific goals providing sufficient time is provided. Putting an effective inclusive program together is quite time consuming, and securing the btk control product which is manufactured through the fermenting process into the control product is done in the USA and requires substantial lead time to obtain. As the btk has a shelf life, you cannot simply go to the supplier and have them fill an order from the warehouse. The product is produced based on customer pre-orders. As the Forest Tent Caterpillar is much more susceptible to the btk product that we use, a single application at a lower dose can achieve significant larvae reduction. A single application on a Maple Bush engaged in the production of Maple Syrup has realized significant yield gains by limiting defoliation damage.
Programs designed for residential/cottage properties may have different goals in that they want higher levels of caterpillar control, not just for tree health, but also for quality of life issues. Many homeowners do not want to see caterpillars crawling around the picnic table, or sides of the cottage during an infestation. In this scenario, a two-application program would be more appropriate.
The btk product we use, Foray 48B which is a biological insecticide certified for organic use and will maintain the organic designation of your Maple Syrup production. These products can potentially have some control measure on other types of Lepidopteran caterpillars but will have no effect on other insects, aquatic life, birds, bees, or mammals.
Due to the safety of btk, you can apply it right up to the water’s edge without the requirement of buffers that makes it quite beneficial for reducing caterpillar populations on cottage properties. These applications could not be carried out using chemical based pesticides.
Forest Tent Caterpillars tend to hatch earlier than the LDD Moth (gypsy moth) so if you have both caterpillars which is unlikely, you can expect the Forest tent Caterpillar will be controlled by applications for the LDD Moth. Controlling any LDD Moth will not be achieved during a Forest Tent Caterpillar program as the LDD Moth hatches later than the FTC and the rates used to control the FTC are much lower than the rates required to control LDD larvae.