West Michigan is experiencing an increase in gypsy moth population. The larvae (caterpillars) of this invasive pest feed on a variety of trees, but prefer oak trees. In areas with a high concentration of gypsy moth, entire tree canopies may be impacted, but most healthy trees recover. In recent years, the gypsy moth population has been naturally controlled by disease that attacks the caterpillars. Dry springs in 2016 and 2017, however, have likely limited the spread of disease, allowing gypsy moth population to grow. The City’s forestry experts have been monitoring the location and severity of regional gypsy moth activity.
Neighbors have reported gypsy moth around East Grand Rapids. This invasive pest feeds on a variety of trees, but prefers oak. Right now treatment options are limited because the caterpillars are almost done feeding on leaves. Most healthy deciduous trees will recover, but significant loss of needles on conifers (e.g. pines, spruces) may require the attention of an arborist. Generally, gypsy moth populations naturally decline due to disease within 1-3 years.
This has left many residents asking: “what should we do?”
By the end of June, the caterpillars are almost done feeding, so limited options are available. However, later in the summer, gypsy moth will be laying new egg masses. Residents are encouraged to scrape egg masses into buckets of soapy water to help control the population.
In the spring, residents can apply a sticky tape or band specifically designed for insect control to the base of trees. This tape limits a caterpillar’s ability to crawl up the tree. If you see dead or dying caterpillars on a tree, leave them in place. They may be infected with a virus or fungus. Leaving these caterpillars in place will help ensure the disease spreads to other caterpillars.
For more information on gypsy moth and control options, click here.
The City will hold an informational session with the City's arborist on gypsy moth during the Monday, July 16 Commission meeting, which is held in the Community Center at 6 p.m.
A: Healthy deciduous trees are likely to recover even after losing all its leaves. However, unhealthy trees may decline or die after severe impact. Significant needle loss of conifers can also be problematic, as these trees have a more difficult time recovering. You should contact a local arborist to examine any trees with which you are concerned.
A1: By the end of June, caterpillars are almost done feeding so there are limited effective controls. For trees with which you are concerned (e.g. trees in poor health, conifers), contact a local arborist for treatment options.
A2: In late summer, gypsy moth lays its eggs. These cream-colored splotches may show up in wood piles, on houses or the underside of tree branches. You can scrape these egg masses into a bucket of soapy water to help control the number of gypsy moths next year. Next spring, you can apply a sticky tape specifically designed for gypsy moth control to the base of trees to help control the movement of caterpillars. If you see dead or dying caterpillars at the base of a tree, leave them in place. They may be infected with a fungus or virus that is helping to kill gypsy moth caterpillars. Leaving them in place may help infect other caterpillars and control the population.
A: Spraying must be done in the spring, when caterpillars emerge. Inclement weather can significantly limit effectiveness. Moreover, spray treatments may not always be appropriate as the pesticides use can impact all Lepidoptera insects, which includes moths and butterflies. In many cases, gypsy moth populations naturally decline in 1-3 years due to disease. Therefore, the city is carefully monitoring gypsy moth populations and tree health impacts to ensure treatment is required before implementing a spraying program. Residents are encouraged to work with their arborist to evaluate treatment options for individual trees or groups of trees that may better control Gypsy Moth on private properties.