The Ohio Department of Agriculture (ODA) has announced that the Box Tree Moth (BTM) (Cydalima perspectalis (family Crambidae) has been confirmed in southwest Ohio near the borders of Hamilton and Clermont Counties. This is the first time this non-native pest of boxwoods (Buxus spp.) has been confirmed in Ohio.
Boxwoods are some of the most common plants in Ohio landscapes and remain a mainstay of our nursery industry. BTM caterpillars defoliate boxwoods and will strip bark once they run out of leaves to eat.
The literature notes that the moth has anywhere from 1 – 5 generations per year, depending on geographical location. It is suspected that we could have around 3 generations per year in Ohio. Of course, the damage increases with each successive generation, and sustained high populations can kill boxwoods.
Boxwoods are the primary host of BTM. However, the literature notes that in its Asian native range, caterpillars have been observed feeding on the leaves of burning bush euonymus (Euonymus alatus), Japanese euonymus (E. japonicus), purple holly (Ilex purpurea), and orange jasmine (Murraya paniculate). These secondary hosts may only be exploited if the caterpillars run out of food by completely defoliating boxwoods.
Background Information and the Ohio Discovery
BTM is native to East Asia. It was discovered in southern Germany and the Netherlands in 2007 and is now found in 30 European countries. Its rapid spread in Europe was fueled by the wide distribution of two species of native boxwoods that served as natural bridges for the moths to spread between urban areas. Also, DNA analysis has shown that the moths were introduced multiple times from Asia into Europe.
The moth was found in Canada in 2018 infesting boxwoods in a home landscape in an urban neighborhood in Toronto, Ontario. In 2021, the moth was confirmed in St. Catharines, Ontario, as well as in Niagara County, New York. In 2022, the presence of BTM was confirmed in Lenawee County, Michigan.
The BTM confirmation in Ohio was based on two moths collected from different locations using pheromone traps baited with the Cydalima perspectalis lure. The ODA was alerted to the possible occurrence of the moth by a homeowner who sent a picture of a moth found in their home landscape.
Investigations have been initiated to learn the range and extent of the Ohio BTM infestation. This includes the deployment of pheromone traps and visual inspections of boxwood plantings in the area.
A Diagnostic Dilemma
Unfortunately, boxwoods are looking particularly bad this year throughout Ohio. Boxwood leafminer (Monarthropalpus flavus, family Cecidomyiidae) damage coupled with severe winter injury has produced symptoms that may mimic or mask BTM damage. It’s common to see boxwoods that are almost entirely brown or have sections that are brown. A close examination may be required to detect BTM.
You can see more pictures of some of the look-a-like symptoms on boxwoods in this BYGL Alert posted earlier this season titled, “Bad Looking Boxwoods”: https://bygl.osu.edu/node/2102
Fortunately, BTM’s lifestyle is unique among boxwood pests. There are no native leaf-consuming defoliators specific to boxwoods in Ohio and only a small number of caterpillars that may occasionally nip a few leaves. Heavy defoliation by a caterpillar would point towards BTM.
Tips for Identifying BTM
- MOTHS: Look closely at moths flying to your porch lights at night. It’s important to note that the moths have two different color forms as shown in the pictures below. Moths with light-colored wings are more common than those with dark-colored wings. However, both have two distinctive white dots as noted below.
- CATERPILLARS: Distinctive green to greenish-yellow caterpillars with black stripes and black dots on boxwoods. There are no native caterpillars that defoliate boxwoods. Small, disorganized collections of silk may be found within the defoliation.
- DAMAGE: The caterpillars produce two types of damage. As shown in the led image for this Alert, BTM caterpillars may completely devour the leaves. As shown below, the caterpillar may also feed on the upper leaf surface producing leaf skeletonizing damage. Look closely at browned boxwoods to make certain the damage is from winter injury and not BTM!
REPORT BTM: We Need Your Help
The ODA has developed an online reporting tool with many helpful features, including an interactive map to pin the exact location of your observation. The reporting tool requires a picture, so make sure you take clear pictures that are in focus to upload with your report.
Here is the hot like to the ODA reporting tool: