OSU Extension: Why are my boxwoods looking bad?

Did you know the Ohio Department of Agriculture (ODA) has announced Box Tree Moth (BTM) (Cydalima perspectalis, family Crambidae) had been confirmed in Hamilton and Clermont counties in southwest Ohio? The location is near where the two counties meet Warren and Butler counties. It’s the first time this non-native boxwood (Buxus spp.) defoliator has been found in Ohio.

Heavy leaf and stem damage by BTM over multiple generations can kill boxwoods. Boxwoods were some of the oldest plants used in U.S. landscapes with planting records dating back to the late 1700s. They are currently some of the most common plants found in Ohio landscapes and remain a mainstay of our nursery industry. According to the ODA, the current inventory of boxwoods in Ohio nurseries is valued at over $200 million.

BTM caterpillar damage can be compared and contrasted with symptoms produced by winter injury and other boxwood problems. Boxwoods throughout Ohio were damaged by the deep-diving temperatures experienced the week of Christmas.

We have been concerned that the winter damage as well as other boxwood problems may mask BTM infestations. The leaves on winter-damaged boxwoods may range in color from slightly chlorotic to deep, reddish-brown.

However, the affected leaves are entirely intact and remain attached to boxwoods with winter injury. Thus far, leaves are not being shed in large numbers from the affected plants. So, the boxwoods are not see-through shrubs. This is the most obvious difference between symptoms produced by winter injury and damage produced by BTM caterpillars.

Although winter injury to boxwoods, and other plants, appeared early in the season, symptoms are continuing to develop. We are seeing boxwoods that had only a few stems affected earlier this season now having large areas affected, sometimes entire plants.

On the other hand, some boxwoods that suffered winter injury are showing signs of recovery as long as entire stems were not killed. Parting the damage may reveal new foliage growing beneath damaged leaves. Selective pruning to remove dead stems will help plants recover more quickly.

BTM’s lifestyle is unique among boxwood pests. There are no native pests that specifically defoliate boxwoods in Ohio and only a small number of caterpillars that may occasionally nip boxwood leaves. Defoliation by a caterpillar would point towards BTM.

The most obvious symptom of a BTM infestation is bedraggled “stick shrubs” that are totally or mostly defoliated producing see-through plants. This symptom may be seen at a distance. There are few leaves on the ground, only debris.

Early instar BTM caterpillars commonly feed on the upper or lower leaf surfaces as skeletonizers. They may also feed along the edges of leaves to produce notches. This symptom may be difficult to detect in the early stages of an infestation.

The leaf damage produced by larger, later instar caterpillars is very obvious with entire leaves being consumed. It’s the “signature” symptom of BTM. The caterpillars are also sloppy feeders with pieces of leaves left behind that remain attached to plants.

A close examination will also reveal evidence of caterpillars feeding on the tips and bark of small twigs. It’s commonly reported that the caterpillar will strip bark from larger branches if they run out of foliar food.

If You See It; Report It!! The ODA has developed an online reporting tool that includes many helpful features including an interactive map so you can pin the exact location of your observation. The reporting tool requires a picture, so make certain you take clear, in-focus pictures to upload with your report. Here is the hot link to the ODA reporting tool: https://survey123.arcgis.com/share/1b36dd2cf09e4be0a79776a6104ce1dc

For more detailed information check out Ohio State University Extension’s Weekly Buckeye Yard and Garden Line at https://bygl.osu.edu/

Cooking Matters classes to begin

Join OSU Extension Snap Education Program staff, Diane Sommers and Kacy Funk as they gear up for the Ohio SNAP-Ed Cooking Matters Cooking classes slated for Aug. 10-Sept. 21. Participants must be current or eligible SNAP recipients to participate. You will learn about recipe preparation, healthy food tips for your family, take home groceries to practice cooking for your family and receive advice on making healthy choices on a limited budget. All classes will be held at the Fairfield County Ag Center located at 831 College Avenue, Lancaster. Class size is limited, and registration is required by Aug. 1 by calling OSU Extension at 740-653-5419.

Upcoming events

Let's Preserve Series 2023: 6 to 7 p.m. July 18, Keller Market House, 134 S Columbus St.Are you planning to preserve summer produce? Join us for learning how to preserve by freezing presented by Shannon Carter, Family and Consumer Sciences Educator and Sandy Bohl, Instructor, with Ohio State University Extension Fairfield County. To register for the Keller Market House class follow this link go.osu.edu/FCFoodPreservation

Please note this program will be repeated at 6 p.m. Thursday, July 20 at the Pickerington Library-Sycamore Plaza, 7861 Refugee Road. Registration: https://pickeringtonlibrary.libnet.info/events

Bats: What You Didn't Learn Watching Batman: 6 to 9 p.m. Aug. 24, Coyote Run Nature PreserveAre bats flying rodents? Do they really get stuck in your hair? What about rabies?? Learn what’s true and what’s not about Ohio’s bats at this class.Class Fee: $15 (includes snacks and a packet of take-home information)Registration at woodlandstewards.osu.edu. Deadline: Aug. 21Contact email: brown.2766@osu.edu

Planting for Pollinators in Your Home Landscape: 6 to 7:30 p.m. Aug. 29, Fairfield County District Library, 219 N Broad St.Discover how to create a pollinator-friendly landscape! Join OSU Extension Educator, Carrie Brown, as we explore the basics behind using native flowering plants to attract local pollinators.This program is open to Adults, Teens, and their families.Register at: https://fcdlibrary.libnet.info/event/866726

This article originally appeared on Lancaster Eagle-Gazette: OSU Extension: Why are my boxwoods looking bad?