Eggs: tanned yellow, covered with fuzz and found as “egg masses” in the protected areas of trees and outdoor items such as, vehicles, garbage cans, furniture and children’s toys.
Photo: Milan Zubrik, Forest Research Institute - Slovakia, Bugwood.org
Gypsy moth egg mass
Larvae: up to 6 cm in length, covered with hairs. The caterpillar is characterized by five pairs of blue dots and six pairs of red dots that run down its back.
Photo: Jon Yuschock, Bugwood.org
Gypsy moth caterpillar (larvae)
Pupal Stage: larval caterpillars transition to become winged moths. During this stage the skin of the larva hardens and metamorphosis takes place inside the dark brown shell.
Photo: Daniel Herms, The Ohio State University, Bugwood.org
Gypsy moth pupae
Adults: winged moths. Male gypsy moths are brown in colour and have feathery antennae. Females are beige in colour and cannot fly. The adult gypsy moths cannot feed due to the lack of a mouthpart, leaving them only about two weeks to mate and produce eggs before they die.
Photo: Hannes Lemme, Bavarian State Research Centre for Agriculture, Bugwood.org
Female adult gypsy moth laying eggs
The gypsy moth female lays between 500 to 1000 eggs in tree bark crevices. The eggs are covered with hairs from the female’s abdomen. The eggs hatch in spring (April), and the emerging larvae from the eggs climb up the trees to feed on leaves. The majority of the feeding occurs during the night. The larval stage lasts for approximately 40 days. At the end of this stage, the larvae seek safe shelter to pupate. In early summer (June - July), the larvae enter a transitional stage for 10 to 14 days in which the larvae transform into adult gypsy moths. Adults have less than two weeks to mate and reproduce before they die.
The gypsy moth has over 300 known host plant species, and about 150 of them are considered favoured hosts. The favourability of a forest species influences the severity and longevity of a gypsy moth infestation. As a caterpillar, gypsy moths feed primarily on hardwood trees, and may feed on softwood trees. Some favoured host tree species include:
Oak (Quercus spp.)
Maple (Acer spp.)
Alder (Alanus spp.)
Hawthorne (Crataegus spp.)
Click here for a full list of gypsy moth favoured tree hosts.
Photo: William M. Ciesla, Forest Health Management International, Bugwood.org
Infested broadleaf trees
Signs and symptoms of European gypsy moth include:
- Egg masses found on tree bark and outdoor objects.
- Leaves with holes or completely defoliated trees. Defoliation will result in the dieback of twigs and branches, and will make affected trees vulnerable to disease and other pests as they spend their energy reserves to regrow leaves in mid-summer.
Photo: Tim Tigner, Virginia Department of Forestry, Bugwood.org
The gypsy moth is native to Europe, Asia, and north Africa. European gypsy moth was introduced to North America 130 years ago, and has since been detected in states in northeastern U.S.A. and in portions of the eastern Canadian provinces of Ontario, Quebec, New Brunswick, Prince Edward Island and Nova Scotia.
The long distance spread of the gypsy moth has been largely attributed to the movement of firewood, as well as outdoor recreational and household articles; public awareness could significantly reduce and limit the spread of gypsy moth to new areas.
The map below is the EDDMapS (Early Detection & Distribution Mapping System) Ontario distribution map for the European gypsy moth as of May 2017. To see the current EDDMapS distribution map, click on the map below.
Map: EDDMapS. 2017. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed May 18, 2017.
In Canada, the gypsy moth is federally regulated by the Canadian Food Inspection Agency. The CFIA outlines the following directives pertaining to gypsy moth:
Regulated Area for Gypsy Moth in Canada
Map: Canadian Food Inspection Agency (2017)
For more information, visit the Canadian Food Inspection Agency (CFIA) website here.
Gypsy moths are most destructive in their larval stage - as caterpillars - stripping away foliage from a broad variety of trees. Repeated defoliation stresses trees and can lead to mortality, especially in urban or drought-stricken areas, and can weaken tree regeneration due to impacted seed production and root sprouting.
An estimated 595 million hectares of North America are considered climatically suitable for the establishment of gypsy moth populations (Gray, 2004). The efforts to control and manage the pathways of gypsy moths is crucial to mitigate the possible economic, ecological, and social impacts on potential areas of spread.
A gypsy moth infestation can defoliate a broad range of tree species, impacting the aesthetics of a forest. In urban areas, this can impact property values and impose costs for tree removal and replacement. In addition, tree defoliation can negatively affect tourism.
The gypsy moth was estimated to have caused the loss of roughly $120 million in residential property value per annum in the US from 1998 to 2007, and $298 million in US federal expenditure targeted at gypsy moth for the same ten-year period (Aukema, 2011). The amount for the US federal expenditure included suppression, research, and 'slow the spread' programs.
Gypsy moth invasions disrupt the ecological services provided by trees, impact wildlife habitat and reduce food production for dependent species. The dieback of twigs and branches due to defoliation causes canopy thinning, thereby weakening trees.
Gypsy moth invasions are capable of affecting forest tree composition. It is a concern that gypsy moth might affect the oak regeneration success in eastern North America, given that oak species are one of the preferred hosts by the gypsy moth.
Photo: Tim Tigner, Virginia Department of Forestry, Bugwood.org
Tree mortality caused by gypsy moth
Direct skin contact with gypsy moth caterpillar hairs could result in a rash and/or skin irritation. On a recreational level, defoliated trees and thinned canopies degrade the aesthetic value of trees.
Gypsy moth management strategies are either intended for immediate control of gypsy moth populations during outbreaks where it is established to minimize the impact, or long-term strategy methods intended to prevent the introduction and spread of gypsy moth to new areas.
In areas where gypsy moth is established, integrative pest management techniques such as burlap banding and pheromone traps are used to keep the gypsy moth population suppressed and at a manageable level. Detection traps using pheromone lures are often used as means to define the extent of gypsy moth spread over an area or where it may still exist after a treatment has taken place. Pheromone traps are also used in combination with other management methods for suppression and eradication of gypsy moth populations. In addition, education is important because the cooperation of the public can play an important role in slowing or preventing the spread of gypsy to new areas. Finally, pathway regulation and phytosanitary risk mitigation measures such as establishing quarantines can help slow the spread of gypsy moth.
Detection surveys such as pheromone-based trapping can provide information about the status of gypsy moths in Canada and the U.S. These surveys determine whether the gypsy moth is present, absent, in restricted distribution, widespread, or eradicated in a given area. This data is available on the CFIA website.
Respond & Control
Small scale gypsy moth populations can be managed mechanically through:
Both techniques are used to keep the gypsy moth population suppressed and at a manageable level.
In Canada, Btk (Bacillus thuringiensis) bacterium spray treatment has been used to control the gypsy moth where established on public trees prior to egg hatch, as it is only poisonous to the larvae.
Photo: John Ghent, John Ghent, Bugwood.org
Entomophaga maimaigi is a target species specific fungus that infects gypsy moth populations in their native range in Japan. It had been introduced in the United States and had caused mass mortality for gypsy moth populations where established. Infections are more likely to spread in a wet spring, than in any other season.
Nucleopolyhedrosis virus (NPV) is a virus that only affects gypsy moth. NPV occurs naturally but only in large gypsy moth populations. The virus severely damages the internal organs of gypsy moth caterpillars, thereby killing them. This was used in Canada to develop the biological pesticide, Dispavirus.
Photo: John Ghent, Bugwood.org
Typical position of gypsy moth larvae infected with NPV
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