by Leslie Cox; Wednesday, October 15, 2014

While picking the Spartan apples off our tree the other day, John spotted some forest tent caterpillar egg masses on a few branch tips.

Autumn is a really good time to check all of your trees and shrubs for this pest, Malacosoma disstria. When the leaves have dropped. Much easier to spot the blobs of eggs. Pruning them out now will decrease the size of an infestation next spring.

Back in August, the female moths were busy laying their eggs. They lay upwards of 350 in a circular mass, about one inch long (2.5 cm), around the tip of a branch…typically in the upper reaches of the host tree or shrub they have selected.

Three weeks later…the larvae hatched but went dormant shortly afterwards, still within the eggs. They will diapause in this state until the temperatures warm up in spring.

So now, with the leaves dropping off the trees, is a really good time to go searching for the egg masses. For every one you snip out and put in the garbage means there will be about 350 fewer little furry caterpillars emerging in spring…hungry to defoliate your trees and shrubs.

Concentrate on your fruit trees and roses but also check out any Sambucus spp. (elderberry species). Last spring, we had a lot of caterpillars descending out of our Sambucus nigra ‘Marginata’. Sambucus nigra Black Lace™ had a few caterpillars too. At about 25 feet (7.5 m) high, the ‘Marginata’ is too tall to do a thorough search for egg masses. Can only reach the lower ones. Thankfully, Black Lace™ is shorter. Have removed all the egg blobs on the three specimens in our garden.

Two years ago, there were hundreds of caterpillars dropping out of one of our birch trees…another of this pest’s host plant species. They also like maples, oaks, aspen and other related species. This year we had oodles of forest tent caterpillars in our vine maple (Acer circinatum).

To date, we have had two back-to-back bad years with this pest in our garden. Hoping next spring will be substantially lighter in numbers. Especially since we are paying due diligence in removing the egg masses to help cut down on the numbers.

For more information about this pest, click here.