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Plantwise Technical Factsheet

gypsy moth (Lymantria dispar)

Host plants / species affected
Acacia (wattles)
Acer (maples)
Acer negundo (box elder)
Acer platanoides (Norway maple)
Acer rubrum (red maple)
Acer saccharinum (silver maple)
Acer saccharum (sugar maple)
Alnus (alders)
Alnus alnobetula (green alder)
Alnus incana (grey alder)
Alnus maritima
Alnus oblongifolia
Alnus rubra (red alder)
Alnus serrulata
Betula (birches)
Betula alleghaniensis (yellow birch)
Betula lenta (sweet birch)
Betula nigra (river birch)
Betula occidentalis (Water birch)
Betula papyrifera (paper birch)
Betula pendula (common silver birch)
Betula populifolia (gray birch)
Betula pumila (low birch)
Carpinus (hornbeams)
Carya (hickories)
Castanea (chestnuts)
Castanea sativa (chestnut)
Cedrus (cedars)
Cedrus libani (cedar of Lebanon)
Corylus
Corylus americana (American hazel)
Corylus avellana (hazel)
Corylus cornuta (beaked hazel)
Cotinus coggygria (fustet)
Cotinus obovatus
Crataegus (hawthorns)
Eucalyptus
Eucalyptus camaldulensis (red gum)
Fagus (beeches)
Fagus grandifolia (American beech)
Fagus sylvatica (common beech)
Hamamelis virginiana (Virginian witch-hazel)
Juglans (walnuts)
Larix (larches)
Larix decidua (common larch)
Larix kaempferi (Japanese larch)
Larix laricina (American larch)
Larix lyallii (subalpine larch)
Larix occidentalis (western larch)
Liquidambar styraciflua (Sweet gum)
Litchi chinensis (lichi)
Lithocarpus edulis
Malus (ornamental species apple)
Malus angustifolia
Malus coronaria (sweet crab-apple)
Malus domestica (apple)
Malus fusca
Malus ioensis (prairie crab-apple)
Ostrya virginiana (American hophornbeam)
Picea (spruces)
Picea engelmannii (Engelmann spruce)
Picea glauca (white spruce)
Picea jezoensis (Yeddo spruce)
Picea mariana (black spruce)
Picea rubens (red spruce)
Pinus (pines)
Pinus brutia (brutian pine)
Pinus contorta (lodgepole pine)
Pinus echinata (shortleaf pine)
Pinus resinosa (red pine)
Pinus rigida (pitch pine)
Pinus strobus (eastern white pine)
Pinus sylvestris (Scots pine)
Pinus taeda (loblolly pine)
Pistacia vera (pistachio)
Platanus acerifolia (London planetree)
Populus (poplars)
Populus angustifolia (narrow-leaved poplar)
Populus balsamifera (balm of Gilead)
Populus deltoides (poplar)
Populus grandidentata (Bigtooth aspen)
Populus heterophylla (Swamp cottonwood)
Populus nigra (black poplar)
Populus tremuloides (trembling aspen)
Prunus (stone fruit)
Prunus armeniaca (apricot)
Prunus domestica (plum)
Prunus salicina (Japanese plum)
Prunus serotina (black cherry)
Prunus serrulata (Japanese flowering cherry)
Pseudotsuga menziesii (Douglas-fir)
Pyrus communis (European pear)
Quercus (oaks)
Quercus alba (white oak)
Quercus austrina
Quercus bicolor (swamp white oak)
Quercus coccinea (scarlet oak)
Quercus ellipsoidalis (Northern pin oak)
Quercus garryana (Garry oak)
Quercus ilex (holm oak)
Quercus ilicifolia (bear oak)
Quercus lobata (California white oak)
Quercus montana (basket oak)
Quercus muehlenbergii (Chinquapin oak)
Quercus palustris (pin oak)
Quercus petraea (durmast oak)
Quercus robur (common oak)
Quercus rubra (northern red oak)
Quercus suber (cork oak)
Quercus velutina (black oak)
Rhus copallina (Shining sumac)
Rhus glabra (smooth sumac)
Rhus typhina (staghorn sumac)
Robinia (locust)
Robinia pseudoacacia (black locust)
Rosa (roses)
Salix (willows)
Salix alba (white willow)
Salix babylonica (weeping willow)
Salix discolor
Salix fragilis (crack willow)
Salix nigra (black willow)
Sorbus americana (American mountainash)
Sorbus aucuparia (mountain ash)
Tilia americana (basswood)
Tilia cordata (small-leaf lime)
Ulmus (elms)
Vaccinium (blueberries)
List of symptoms/signs
Inflorescence  -  external feeding
Leaves  -  external feeding
Symptoms

Hatching larvae usually start feeding on flushing buds and later on newly-expanded leaves. High populations often result in total tree defoliation, often across a large spatial area.

Prevention and control

Cultural Control

Silvicultural manipulation has been used as a long-term management strategy to limit the ability of gypsy moth populations to increase to outbreak densities. Such strategies are based on thinning strategies. Thinning to reduce host species preferred by the gypsy moth would theoretically reduce stand susceptibility, but is not very satisfactory because the most susceptible tree species, such as oak species, are also usually considered the most valuable timber species. Gottschalk (1993) also suggested presalvage thinning to remove low-vigour trees to lower stand vulnerability. Effects of silvicultural manipulations on gypsy moth populations and tree mortality are discussed by Muzika et al. (1998) and Liebhold et al. (1998).

Biological Control

Following the introduction of gypsy moth into North America in 1869, it was the target of several early and extensive biological control programmes (Howard and Fiske, 1911; Burgess and Crossman, 1929). About 80 species of natural enemies, parasitoids, predators and pathogens were introduced from 1906 to the present but most have failed to establish, possibly due to the lack of alternate hosts (Hoy, 1976). Only 11 parasitoids, one predator and two pathogens established upon their release, some of which have become important mortality factors in North America. Of major interest is the fungal pathogen Entomophaga maimaiga, which was probably introduced accidentally from eastern Asia in the 1980s. Since then, this pathogen has become an important natural enemy of the gypsy moth (Hajek et al., 1993) and it has recently been observed to have replaced the gypsy moth nuclear polyhedrosis virus as the dominant pathogen in outbreaking populations in the USA (Hajek et al., 2015).

Classical biological control programmes have also been implemented in Morocco, where the gypsy moth lacks several of its major natural enemies. The egg parasitoid Ooencyrtus kuvanae and the nuclear polyhedrosis virus were introduced from Europe (Fraval and Villemant, 1995). Other biological control attempts against the gypsy moth include mass releases of O. kuvanae were made in Bulgaria (Chernov, 1976), which resulted in 60% higher egg parasitism. Maksimovic and Sivcev (1984) released gypsy moth eggs to sparse populations to maintain a low density of hosts and sustain parasitoids, which increased parasitism and prevented defoliation in subsequent years.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact

In the gypsy moth's native range in Eurasia, outbreaks sometimes occur, but they tend to be localized and of short duration. Severe defoliation results in reduced growth increment and crown dieback, but tree mortality is only occasionally observed. This is in contrast to North America, where major outbreaks tend to occur every 5-10 years, last 2-3 years each time, and occur over a spatially widespread area (Johnson et al., 2005, 2006; Haynes et al., 2009). Two to three years of complete defoliation often results in significant tree mortality, particularly during drought conditions or when trees are stressed by other factors, such as plant pathogens. The difference in outbreak frequency and intensity between gypsy moth in its native Eurasia and North America could be due to absence of certain natural enemies.

L. dispar is considered one of the most important non-native forest pests in the northeastern and Midwestern USA. From 1924-2013, over 37 million hectares were defoliated, including over 11 million hectares between 1980 and 1983; during this outbreak, in Pennsylvania in 1981 alone, timber loss was estimated to be more than US$ 72 million (Montgomery and Wallner, 1988). Other notable outbreaks in the USA occurred between 1989-1993 (>7.4 million hectares) and 2006-2010 (>2.3 million hectares). As the range of the gypsy moth continues to expand, these impacts are also likely to increase (Tobin et al., 2012). In addition to timber impacts, other impacts include costs and losses to the urban and suburban forest including hazard tree removal and replacement, residential impacts, and impacts to the recreational sector (Leuschner et al., 1996; Bigsby et al., 2014).

Related treatment support
 
External factsheets
USDA-NAL National Invasive Species Information Center Species Profiles, USDA-NAL National Invasive Species Information Center (NISIC), 2012, English language
University of Maine Cooperative Extension Pest Management Fact Sheets, University of Maine Cooperative Extension, 2009, English language
DPI NSW factsheets, New South Wales Government, Department of Primary Industries, Australia, 2012, English language
Plant Health Australia Factsheets, Plant Health Australia, English language
Ontario CropIPM factsheets, Ontario Ministry of Agriculture, Food and Rural Affairs, Canada, 2015, English language
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