Western tent caterpillar

There are several subspecies of western tent caterpillar, Malacosoma californicum (Packard) (Lepidoptera: Lasiocampidae), M.californicum pluviale is found in the Pacific Northwest (Ciesla & Ragenovich, 2008).

The is a wide range of hosts for western tent caterpillar including red alder, crabapples, madrones, and roses.

In a central Oregon study of western tent caterpillar (Mitchell, 1990) there was one generation a year and they overwintered in the egg stage. Each female lays only one egg mass. Egg massess are found more commonly on the sunny side of trees. The eggs are laid together in a mass and covered with spumaline, a frothy substance that dries to a hard covering which protects the eggs from low temperatures and dessication. Egg hatch occured at 50 degree days. There were 5 larval stages. Dispersal of the caterpillars occurred around 300 degree days. Pupation began a week later (400 degree days). First moths occurred around 500 degree days. At 800 degree days (in July), peak moth flight was observed.

Outbreaks of tent caterpillars tend to be cyclic. Western tent caterpillars in southwestern British Columbia, Canada, were found to fluctuate in 6-11 year cycles (Myers, 2000).

Damage from western tent caterpillar is considered primarily aesthetic and not damaging the vitality of the trees. Chemical control is rarely recommended. Pruning off infested limbs can be done when they are within reach.

Biological control does occur with these caterpillars. Insect predators such as yellowjackets and parasitic wasps do attack tent caterpillars. Birds generally find the caterpillars repellent in flavor. Mortality and sublethal disease also occurs from a nuclear polyhedro virus (NPV).

Resources:

Anon. 2011. Western Tent Caterpillar. Washington, DC: U.S. Department of Agriculture, Forest Service. Rocky Mountain Region. <11 March 2016>

Bentley, W.J., Day, K.R., and R.E. Rice. Tent Caterpillars. UC IPM Pest Management Guidelines: Plum. UC ANR Publication 3462

Brunner, J. 1993. Tent Caterpillars. Orchard Pest Management Online. Washington State University.

Carmona, Alejandro Segarra, and Pedro Barbosa. 1983. “Overwintering Egg Mass Adaptations of the Eastern Tent Caterpillar, Malacosoma Americanum (fab.) (lepidoptera: Lasiocampidae)”Journal of the New York Entomological Society 91 (1). New York Entomological Society: 68–74. http://www.jstor.org/stable/25009343. <18 March 2016>

Ciesla, W.M.; Ragenovich, I.R. 2008. Western tent caterpillar. Forest Insect and Disease Leaflet 119. Washington, DC: U.S.
Department of Agriculture, Forest Service. 8 p. <11 March 2016>

Mitchell, R. 1990. Seasonal History of the Western Tent Caterpillar (Lepidoptera: Lasiocampidae) on Bitterbrush and Currant in Central Oregon

Journal of Economic Entomology Aug 1990, 83 (4) 1492-1494; DOI: 10.1093/jee/83.4.1492

Myers, J. 2000. Population fluctuations of the western tent caterpillar in southwestern British Columbia. Popul Ecol (2000) 42:231–241. <18 March 2016>

Townsend, L. 2003. Checking Eastern Tent Caterpillar Egg Masses. UK Cooperative Extension Services. Entfact 449. <18 March 2016>

 

Orginal publication 8/12/07
Lastest revision <18 March 2016>

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University/NWREC.

Western tent caterpillar larvae, molted skins, and feces. Photo: T. Murray, WSU

Western tent caterpillar larvae, molted skins, and feces.
Photo: T. Murray, WSU

Western tent caterpillar egg mass covered in spumaline

Western tent caterpillar egg mass covered in spumaline

Egg mass of western tent caterpillar

Egg mass of western tent caterpillar

Western tent caterpillar larvae in web

Western tent caterpillar larvae in web

Western tent caterpillar larvae, molted skins, and feces

Western tent caterpillar larvae, molted skins, and feces

Western tent caterpillars

Western tent caterpillars

Western tent caterpillars on web

Western tent caterpillars on web