Spongy Moth Concerns for Bloomfield Hills Landscapes

In Bloomfield Hills and surrounding areas, an insect of concern is the spongy moth (formerly known as the gypsy moth). While oak trees are a favorite food source for spongy moth caterpillars, they have been known to feed on many species of trees and shrubs commonly found in landscape settings. The caterpillar of this invasive species can have significant impacts on individual landscapes and on the local ecosystem.

Damage from spongy moth caterpillars include:

1. Defoliation: Spongy moth caterpillars can cause extensive damage to trees by feeding on their leaves, totally defoliating trees if left unchecked. This defoliation can stress trees, particularly if more than 40% of the foliage is consumed, forcing the trees to use energy reserves to grow new leaves
2. Tree mortality: Repeated defoliation can lead to tree death, especially in evergreens which cannot replace their leaves (needles) as easily as deciduous trees can.
3. Nutrient cycling disruption: When spongy moth caterpillars defoliate trees in spring, they change the timing and quality of organic matter input to the soil. Instead of fallen leaves in autumn, the soil receives caterpillar frass (excrement) in spring, affecting soil microbial communities and natural nutrient cycles.
4. Wildlife impact: Defoliation can destroy habitats for small mammals, birds, and native insects that depend on these trees for food and shelter. This disruption can adversely affect local food webs.
5. Water quality changes: Extensive defoliation can alter water quality in forested areas.
6. Nuisance and health concerns: Large populations of spongy moth caterpillars can pose a nuisance to residents, with their frass raining down on homeowners and potentially staining surfaces.

Controlling spongy moth caterpillars is most effective when treatments are started when the caterpillars are small. In Bloomfield Hills the spongy moth caterpillars start hatching in early to mid-May, when redbud trees start blooming. Tree spraying treatments can include biological products when the caterpillars are small or traditional insect control products for larger spongy moth caterpillars.