Gardening Essentials – Protecting Against Landscape Insect Pests

When spring finally arrived earlier this year, a sigh of relief could be heard throughout New England. We could go outside at last and enjoy the plants and trees coming back to life. Those plants and trees aren’t alone, however, in awakening from their winter slumbers. They’re joined, unfortunately, by many insect pests, including the winter moth caterpillar, which is especially destructive in our area.

Nicole Downer, of Downer Brothers Landscaping in North Andover, identifies this insect as the primary pest for homeowners in the Merrimack Valley. A native of Europe, the moth was introduced to Canada sometime in the 1930s, according to Downer. The moths have no natural predators here, so the pest traveled over the years and now can be found in Maine, Massachusetts, Rhode Island and parts of southern New Hampshire.

This insect has a healthy appetite, and it rarely meets a deciduous tree it doesn’t like. Maples, oaks, crab apples, plums and cherries are all good food as far as the winter moth caterpillar is concerned. A heavy infestation can defoliate a tree in the early spring, and the insect’s grain of sand-size droppings will coat anything below an infested tree, including decks, grills and cars.

The life cycle of the pest is similar to other lepidopterans, including all moths and butterflies. In this case, the cycle begins in late November, when the winter moths hatch. Only the male winter moth flies. The small gray female is almost wingless. Once hatched from its pupa, the female winter moth scurries up the nearest tree trunk and emits a pheromone (odor) that attracts the male moths.

After the mating ritual is complete, the female deposits egg clusters in crevices of the trunk’s bark and dies.

In the spring, just as leaf buds are beginning to grow, newly hatched winter moth larvae, not much larger than a grain of rice, crawl into the forming buds. When the leaves unfurl, the damage is evident.

This is when Downer says her company begins to receive calls from homeowners asking what they can do to combat the pest. If the tree is small (less than 10 feet tall) and the homeowner has the time and ability, the tree can be sprayed every 10 to 14 days. The UMass Extension service in Amherst recommends using Bacillus thuringiensis, a bacteria specific to caterpillars of butterflies and moths.

A more effective, longer-lasting method involves hiring a professional to inject the tree with a systemic insecticide. Downer says her company uses the “Arborjet” system, which works like a medical IV. Special equipment is used to inject the “medicine” directly into the tree’s vascular system. In addition to providing longer lasting protection for the tree (up to two years in most cases), it limits exposing the surrounding environment.

This system can be used to protect valuable trees from other insect pests common to our area, including the hemlock wooly adelgid, the magnolia scale and the emerald ash borer. This past spring, Downer Brothers was called to protect one of the oldest ash trees in North Andover from the emerald ash borer, Nicole says. The Arborjet system worked well. In fact, she says, injecting an insecticide is the only way to control emerald ash borer. There are no effective spray solutions.

In August, Downer Brothers often receive calls from homeowners complaining about a humming noise coming from their magnolia trees caused by a large number of bees. The bees congregate to feed on the honeydew (excrement) of the magnolia scale, a small insect that clings to the bark and feeds on sap.

If the infestation is acute and the homeowner is worried about bee stings, a water-soluble insecticide is injected into the tree, quickly attacking the scale. This is followed by an injection of another solution that lasts for a year to 18 months. Neither insecticide poses any harm to the bees, but both kill the scale. Once the scale is gone, the bees move on to other food sources.

Other pests often encountered in landscapes include rose slugs, leaf miners, boxwood psyllids, mugo pine sawflies, spider mites, and Japanese beetles.

While individuals can research information on the Web (the UMass Extension site is a good resource) and perhaps treat these pests themselves, a professional has insecticide products and techniques not available to the average homeowner, and the training and skill to apply them safely and limit environmental exposure. A professional can also identify cultural problems in a plant that might make it more prone to insect damage.

Downer Brothers Landscaping: North Andover, Mass.  /  (978) 975-5106  /



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