Feature

Box Tree Moth – A New Threat to Boxwood

By Kripa Dhakal, TSU Post-doctoral Researcher, and Dr. Karla M. Addesso, TSU Otis L. Floyd Nursery Research Center

The box tree moth, (Cydalima perspectalis) is an invasive pest of boxwood (Buxus spp.) causing severe damage to these popular ornamental plants. The moth is native to China, Korea and Japan and was discovered in Europe in 2007 and has since spread widely across the continent (1). In 2018, box tree moth was first detected in North America in Ontario, Canada. On May 26, 2021, USDA-APHIS issued a federal order to halt the importation of host plants from Canada, including boxwood (Buxus species), its primary host, and potential secondary hosts euonymus (Euonymus species), and holly (Ilex species) (3). In addition, USDA-APHIS coordinated with states to find and destroy any imported plant material and provide box tree moth traps and lures for surveys in facilities that received potentially infected boxwood. In August 2021, the New York State Department of Agriculture confirmed the detection of box tree moth in Niagara County, near the Canadian border (3).

Box tree moths have multiple generations per year throughout the summer and early fall (4,5). The life cycle of the moth is around 30 days depending on temperature. Adult box tree moths lay eggs on the underside of the leaves (6,7). Eggs are pale yellow with average size 0.04 inches, deposited singly or in clusters of about 5-20 overlapping eggs (6,7). First generation oviposition begins in early to mid-summer. Eggs take three days to hatch, and young larvae are about ½ inch long. Newly hatched larvae are green to yellow in color with shiny black heads (Fig. 1). The larvae undergo five to seven instars depending upon the temperature and host plant (10). Young larvae feed on the lower sides of the leaves (4) (Fig. 2a). Older larvae consume entire leaves except for the midrib and hard leaf structures (4,5) (Fig. 2b). After defoliating a plant, larvae will consume the bark of the branches which can lead to girdling and dieback of branches or entire plants (6). Pupae develop inside a silk cocoon and are 0.6 to 0.8-inch long. They are initially green with black stripes on the back and turn brown as they mature (Fig. 1b). New adult moths emerge from overwintering pupae from April through July. Adult moths have a lifespan of approximately two weeks and they can travel long distance (6). During the daytime they will rest on boxwood or surrounding plants. The adult box tree moths have white wings with a brown border and a wingspan of about 1.5 in (Fig. 1c). Occasionally a dark color morph with brown wings is observed (Fig. 1d). Both color forms have small white comma-shaped spots on the forewing.

FIGURE 1 A — Cydalima perspectalis (box tree moth); larva. Copyright Ferenc Lakatos, University of Sopron, Bugwood.org

FIGURE 1 B — Cydalima perspectalis (box tree moth); pupa. Fronton, Haute-Garonne, France. April 2014. Copyright Didier Descouens-2014/Museum de Toulouse/via Wikipedia — CC BY-SA 4.0

FIGURE 1 C — Cydalima perspectalis (box-tree-moth); Adult female. Copyright 2013 by Florine Leuthardt.

FIGURE 1 D — Cydalima perspectalis (box-tree-moth) Adult. Copyright New York State Department of Agriculture

FIGURE 2 A — Cydalima perspectalis (box tree moth); early stage larval damage to Buxus sempervirens (common boxwood).

FIGURE 2 B — Cydalima perspectalis; severely defoliated Buxus sempervirens. Copyright Ferenc Lakatos / University of Sopron, Bugwood.org

Eggs, larvae and pupae of moths can be transported on infested plants, so scouting of plant material is recommended. The white webbing spun by the caterpillars and the characteristic feeding damage of leaves is an obvious sign of an infestation. It can be difficult to detect early larval stages or eggs of moths, so monitoring and surveillance of adult moths is achieved using UV-light and pheromone traps (7).

Most research on insecticide efficacy has been conducted in Europe. Some biological insecticides based on neem (active ingredient azadirachtin A) and some entomopathogenic nematode species (Steinernema carpocapsae and Heterorhabditis bacteriophora) produced significant mortality in box moth larvae (8,9). Products containing Bacillus thuringiensis (Bt) var. kurstaki were also effective controls with the caterpillars ceasing feeding within an hour of ingesting a treated leaf (9). Chemical insecticides such as carbaryl, spinosad, chlorantraniliprole, deltamethrin, and diflubenzuron are labeled for control of caterpillars in nurseries and landscapes, but efficacy data on this species remains limited. Current recommendations for growers are available online and research in this area is ongoing (10).

For more information on box tree moth or if you suspect a plant is infested with this pest, contact Tennessee Department of Agriculture Plant Certification Office (615-837-5137; plant.certification@tn.gov) and the USDA-APHIS State Plant Heath Director (615-907-3357).

REFERENCES & ADDITIONAL READING

1. Bras, A., D.N. Avtzis, M. Kenis et al. 2019. A complex invasion story underlies the fast spread of the invasive box tree moth (Cydalima perspectalis) across Europe. Journal of Pest Science. 92: 1187–1202. https://doi.org/10.1007/s10340019-01111-x

2. Maruyama, T., and N. Shinkaji. 1987. Studies on the life cycle of the box-tree pyralid, Glyphodes perspectalis (Walker) (Lepidoptera: Pyralidae). I. Seasonal adult emergence and developmental velocity. Japanese Journal of Applied Entomology and Zoology 31: 226-232

3. APHIS. 2021. Box tree moth. https://www.aphis.usda.gov/aphis/ourfocus/ planthealth/plant-pest-and-disease-programs/pests-and-diseases/ sa_insects/box-tree-moth. (Accessed 10-Sept 2021)

4. Nacambo, S., F. L. Leuthardt, H. Wan, H. Li, T. Haye, B. Baur, R. M. Weiss, and M. Kenis. 2014. Development characteristics of the box-tree moth Cydalima perspectalis and its potential distribution in Europe. Journal of Applied Entomology 138: 14-26.

5. Damman, H. 1991. Oviposition behaviour and clutch size in a groupfeeding pyralid moth, Omphalocera munroei. The Journal of Animal Ecology: 193-204.

6. Maruyama, T., and N. Shinkaji. 1991. The life-cycle of the box-tree pyralid, Glyphodes perspectalis (Walker) (Lepidoptera: Pyralidae). II. Developmental characteristics of larvae. Japanese Journal of Applied Entomology and Zoology 35: 221-230.

7. Göttig, S., and A. Herz. 2014. The box tree pyralid Cydalima perspectalis: New results of the use of biological control agents and pheromone traps in the field. Journal of Plant Diseases and Protection 121: 98-99.

8. Goettig, S., and A. Herz. 2018. Susceptibility of the box tree pyralid Cydalima perspectalis Walker (Lepidoptera: Crambidae) to potential biological control agents Neem (NeemAzal®-T/S) and entomopathogenic nematodes (Nemastar®) assessed in laboratory bioassays and field trials. Journal of Plant Diseases and Protection 125: 365-375.

9. Harry, K. K. 1991. Laboratory evaluation of entomopathogenic nematodes, Steinernema carpocapsae and Heterorhabditis bacteriophora against some forest insect pests. Korean Journal of Applied Entomology 30: 227-232.

10. Frank, S., D. Gilrein, M. Havers, and C. Palmer. 2021. Insecticide Options for Box Tree Moth Management. https://ecoipm. org/wp-content/uploads/Insecticides-to-Consider-for-Box-Tree-MothManagement.pdf.