Phew! What a year for the gypsy moth. There are tree-covered parts of Rehoboth that have been so severely damaged that you would not even know that it is summer. And I know we are not alone. This nasty pest has been eating everything from pine trees to oaks to maples, and even my rhubarb. In theory, they seem to dislike ashes, sycamores, butternuts, black walnuts, dogwoods and balsams. However, if food competition is fierce, they will likely eat anything.
The gypsy moth was brought to the United States in 1869 with the hope that it could bolster the silk industry. Of course, things did not work out that way and the moth escaped, leaving behind it a trail of forest defoliation and frustrated gardeners.
Gypsy moth larvae appear from their eggs in early May. They go through several molting periods (getting hungrier with each molt) and typically feed at night…they are no dummies, they usually seek shade during daylight hours. Feeding continues into June and then pupation occurs. Once they emerge as adult moths, they mate. The males fly to the females, the females lay their eggs in July and September, and then both sexes die. Not exactly an exciting life.
I spoke with Kevin Brewer of Kaiser Tree Preservation to get some tips on management of this pest. Here is what he had to say:
SB: What can be done in the spring to prevent infestation once the eggs have hatched?
KB: Eggs hatch beginning as early as Mid April through Mid May and feed approximately 7 weeks. When hatched, they can be controlled. The tree can either be sprayed foliarly or injected with a systemic pesticide that will be effective within a matter of days.
SB: Can anything be done in the fall to prevent egg hatch?
KB: Nothing can be done in the fall to prevent the hatch short of physical removal of the egg sacs from the tree. In the fall, it is simply best to assess for a population of eggs and to plan ahead for a spring treatment.
SB: How can a tree be helped once it has begun to show signs of defoliation and stress?
KB: After defoliation has begun, the tree should be treated ASAP for gypsy moth and the tree should be fertilized. The fertilizer should be more natural based around sea kelp, yucca, natural sugars, and amino acids. You should not fertilize with anything high in nitrogen. This will trick the tree into forcing rapid unprotected growth. And it's worth noting that the trees can be treated with bee friendly products.