Description
Potentially Misidentified Species - Eggs, larvae, and pupae of G. pusilla and G. calmariensis are not distinguishable, but adults differ slightly in size and more noticeably in coloration (Manguin et al. 1993). Life history and ecology of the two species appears to be very similar (Hight et al. 1995; Malecki et al. 1994; McAvoy et al. 1997), but this may reflect the difficulty of distinguishing the species in the field.
Galerucella nymphaeae feeds on a variety of aquatic plants, including Nuphar lutea, Polygonum spp., Myrica spp, and occasionally Lythrum salicaria. It is widespread in North America, including the Chesapeake Bay region. Two other Galerucella, G. quebecensis and G. stefanssoni, are known from northern parts of North America (Manquin et al. 1995).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Hexapoda | Insecta | Coleoptera | Chrysomelidae | Galerucella |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1992 | Established | Unknown | Introduced | Regular Resident | Europe | Eurasia | Biocontrol(Biocontrol) |
History of Spread
The leaf-feeding Beetle Galerucella pusilla is native to Eurasia, over much the same range as G. calmariensis (all Europe and northen Asia to Japan), but is rarer in the northern part of that range (e.g. Sweden, Finland) (Blossey 1995). Galerucella pusilla and G. calmariensis, together with the root-boring Weevil Hylobius transversovittatus were introduced into North America as part of a program for the control of Lythrum salicaria (Purple Loosestrife), an emergent Eurasian wetland plant which has become invasive in North America. This program, under the auspices of the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) and the United States Fish and Wildlife Service (USFWS), began with a study of insect herbivores which control L. salicaria in Europe (Batra et al. 1986), where this plant is common, but not dominant (Blossey et al. 1995a; Hight et al. 1995; Kok et al. 1992b; Malecki et al. 1993; Thompson et al. 1987).
The two species of Galerucella and H. vittatus were chosen as the most promising insects for biological control of L. salicaria, because of their high feeding rates and strong host-specificity (Blossey et al. 1994; Hight et al. 1995; Malecki et al. 1993). Experiments were conducted in Germany (Blossey et al. 1994) and in quarantine in the United States (Kok et al. 1992b) with North American species of Lythraceae and related plants, in order to determine whether these insects posed a threat to native plants. While some feeding on two North American species occurred in the absence of L. salicaria, the latter was strongly preferred (Blossey et al. 1994; Hight et al. 1995; Malecki et al. 1993). Subsequently, release of the three insect species was approved by USDA /ARS, and by authorities in Canada, in 1992. Thirty-five thousand Galerucella pusilla and G. calmariensis were shipped to the United States for quarantine and eventual release. In 1992-93, mixed batches of G. pusilla and G. calmariensis were released in 10 states (PA, NY, MD. VA, MN, WA, SD, OR, ID, MT) and 6 Canadian provinces (British Columbia, Alberta, Manitoba, Ontario, New Brunswick, and Prince Edward Island). Subsequent surveys in 1993-1994 indicated that both species were established at all sites were releases were started in 1992 (Hight et al. 1995). USDA-ARS terminated its involvement in the program due to funding constraints (Hight et al. 1995), but biocontrol releases have continued under USFWS and state auspices. By 1996, releases of the 3 beetle species had been made in 22 states (Skinner 1996).
In the Chesapeake Bay region, the first release, of 400 Galerucella pusilla and G. calmariensis< adults, were made in Prince Georges' County MD in August 1992. Established populations were found at the release site in 1993 and 1994 (Hight et al. 1995). In Kenilworth Aquatic Gardens DC, on the Anacostia River, where a tidal wetland had been heavily invaded by Lythrum salicaria, 4500 mixed G. pusilla and G. calmariensis were released in July 1997 (Swearingen 1997). Establishment of G. pusilla was not known, but was considered likely, based on the high success rate of other releases (Hight et al. 1995). In the summer of 1999, Galerucella spp. were abundant at some locations in Kenilworth Aquatic gardens, but were not seen in subsequent years (Fofonoff, personal observations). The Kenilworth biocontrol program was considered unsuccessful, and herbicide and cutting treatments were then undertaken (Swearingen 2001, personal communication). Since 1999, the MD Department of Agriculture has released Galerucella spp. in Howard, Prince Georges, and Caroline counties (Moser 2002).
A study of establishment of G. pusilla and G. calmariensis, in southwest VA (Coeburn, Wise County VA), outside the Chesapeake watershed, but with a similar climate, indicated slow expansion of populations, but sharp year-to-year variations in the ratio of the two species (McAvoy and Kok 1997).
History References - Batra et al. 1986; Blossey et al. 1994; Blossey 1995a; Hight et al. 1995; Kok et al. 1992b; Malecki et al. 1993; McAvoy and Kok 1997; Moser 2002; Skinner 1996; Swearingen 1997; Thompson et al. 1987
Invasion Comments
Residency - Adults and larvae of Galerucella pusilla and G. calmariensis live on the emergent stems and leaves of Lythrum salicaria, but do not tolerate prolonged flooding. Although not strictly aquatic, they can be considered permanent residents of tidal wetlands.
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | ||||
| pH | ||||
| Salinity Range | fresh-oligo |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 3.5 | 3.5 |
| Typical Adult Size (mm) | 4.0 | 4.0 |
| Maximum Adult Size (mm) | 4.6 | 4.6 |
| Maximum Longevity (yrs) | 1.0 | 1.0 |
| Typical Longevity (yrs |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Releases of Galerucella pusilla, G. calmariensis, and Hylobius transversovittatus in the Chesapeake Bay region are expected to restore the diversity of wetlands which have been invaded by Lythrum salicaria (Purple Loosestrife) (Swearingen 1997). These invasions have been quite local in the Chesapeake region, and mostly confined to the vicinity of Washington DC, so effects on economically important marsh biota (fishes, waterfowl, furbearers) are expected to be small . Although the wetlands in which releases have been conducted include significant habitat for migratory birds, a major goal of L. salicaria control in this region appears to be restoration of biodiversity for aesthetic purposes in areas which serve as parkland. However, the overall costs of the release of insects, and attendant monitoring, are probably quite small compared to other possible means of L. salicaria control (Malecki et al. 1993).
Agriculture, Horticulture - Adults of G. pusilla and G. calmariensis were found to feed on an important horticultural plant, Lagerstroemia pusilla (Crape Myrtle), introduced from Asia. However, this plant did not support larval development. '...The amount of foliar damage is not likely to be a major problem that would affect the vigor of the plant. The major occurrence of L. indica is farther south than that of Purple Loosestrife. ...L. indica plants that do occur in the Purple Loosestrife region are not likely to be attacked by the Galerucella beetles because they are planted in dry, highly managed situations, such as around business and homes' (Kok et al. 1992). Risks to Crape Myrtle were considered minimal. Insignificant 'nibbling' by larvae was noted on Glycine max (Soybeans) also (Kok et al. 1992).
Refs- Kok et al. 1992; Malecki et al. 1993; Swearingen 1997
Economic Impacts Outside of Chesapeake Bay
In 1987, Thompson et al. (1987) estimated the costs of a biological program for Lythrum salicaria (Purple Loosestrife) at 0.5 million (1987) dollars, but we do not know the costs of the present program. They estimated that the economic costs of L. salicaria in North America, due to effects on wildlife habitat and food supplies to be (1987) 47.9 million. Lythrum salicaria is believed to have adversely affected waterfowl, furbearers, and nongame wildlife, resulting in declines in hunting expenditures, revenues form trapping, and from recreational wildlife observation. The basis for this estimate has been criticized by Anderson (1995), who pointed out that much of the evidence for ecological damage is anecdotal.
However, biological control of L. salicaria may be less expensive than other methods of control, including herbicides, flooding, burning, etc., which also have adverse ecological impacts. The research program leading to the release of insects for L. salicaria control included extensive studies of host specificity, reducing the probability of adverse ecological or economic consequences (Blossey et al. 1994; Kok et al. 1992; Malecki et al. 1993).
References - Anderson 1995; Blossey et al. 1994a; Kok et al. 1992; Malecki et al. 1993; Thompson et al. 1987
Ecological Impacts on Chesapeake Native Species
The deliberate introduction of Galerucella pusilla, G. calmariensis, and Hylobius transversovittatus is intended to drastically reduce the abundance of the invasive wetland plant Lythrum salicaria (Purple Loosestrife), to levels comparable to that in Europe, where L. salicaria is largely limited to being a 'pioneer species' in disturbed areas, due to feeding by insect herbivores. Careful preliminary experiments were conducted in Europe and the United States (in quarantine) to gauge the extent of grazing by these insects on native North American wetland plants (50 species tested). The host specificity of G. pusilla, G. calmariensis, and H. transversovittatus was found to be quite strong (Blossey et al. 1994; Kok et al. 1992b; Malecki et al. 1993). Because the releases began in 1992-1993, the effects of insect releases on L. salicaria populations have not been seen on any scale, and significant effects on native biota are not yet been apparent. In the Chesapeake Bay region, dense populations of L. salicaria appear to be limited to disturbed wetlands in the vicinity of Washington DC (Swarth 1996; Strong 1995 , Fofonoff 1995-1997 personal observation), so responses to the insect releases are expected to be limited to those areas.
Herbivory - Aproximately 50 species of native North American plants were tested in Europe, and under quarantine conditions in the United States, as potential host plants for Galerucella pusilla, and G. calmariensis. The native plants Lythrum alatum (Winged Loosestrife) and Lythum hyssopifolia (Hyssop-Leaved Loosestrife) were found to be potential food plants. However, L. salicaria was strongly preferred when the insects had a choice (Blossey et al. 1994a; Kok et al. 1992b; Malecki et al. 1993). Larval survival was very low on L. alatum, and absent on L. hyssopifolia (Blossey et al. 1994a; Kok et al. 1992b).
Food/Prey - In Europe, the two Galerucella spp. are preyed upon by spiders and parasitic wasps. In North America, experimental releases of a lab-reared native Galerucella nymphaea were made in order to identify potential predators, pathogens and parasites of Galerucella pusilla and G. calmariensis. 'No parasites or pathogens were detected, but large numbers of eggs were consumed at our field sites by ladybird beetles, Colomegilla maculata' (Malecki et al. 1993).
Habitat Change - Galerucella pusilla and G. calmariensis typically cause extensive defoliation of L. salicaria (Blossey 1995a). Among 9 Eurasian L. salicaria insect herbivores which were compared, Galerucella spp. were considered to have high potential for L. salicaria control, based on their wide habitat preferences, demographic characteristics, and high abundance in Europe (Blossey 1995a). Reductions of L. salicaria populations are expected to result in at least a partial restoration of plant diversity lost due to dominance by the exotic species (Malecki et al. 1993).
Since L. salicaria is widely considered an inferior wildlife food, control of this species is expected to result in restoration of food supplies for waterfowl. As noted above, effects of the L. salicaria biocontrol program are expected to be strongly localized in the Chesapeake Bay region, but very significant in regions to the north where L. salicaria has become a dominant in many freshwater wetlands (Thompson et al. 1987). The perceived negative impacts of L. salicaria are based largely on qualitative impressions, rather than experimental studies (Anderson 1995). Consequently, the effects of the hoped-for 90% reduction in overall biomass of L. salicaria in North America (Malecki et al. 1993) may be difficult to evaluate.
References - Anderson 1995; Blossey 1995a; Blossey et al. 1994; Fofonoff 1995-1997 pesonal obsevation; Kok et al. 1992b; Malecki et al. 1993; Swarth 1996; Strong 1995; Thompson et al. 1987
Ecological Impacts on Other Chesapeake Non-Native Species
The deliberate introduction of Galerucella pusilla, G. calmariensis, and Hylobius transversovittatus is intended to reduce the abundance of the invasive wetland plant Lythrum salicaria (Purple Loosestrife), to ~10% of its present biomass in North America, similar to that in Europe, where L. salicaria is largely limited to being a 'pioneer species' in disturbed areas, due to feeding by insect herbivores. Because the releases began in 1992-1993, the effects of insect releases on L. salicaria populations have not been seen on a large scale, and significant effects on other exotic biota are not yet apparent. In the Chesapeake Bay region, dense populations of L. salicaria appear to be limited to disturbed wetlands in the vicinity of Washington DC (Fofonoff 1995-1997 personal observation; Strong 1995; Swarth 1996), so responses to the insect releases are expected to be limited to those areas.
Herbivory - Galerucella pusilla and G. calmariensis feed on bud, leaf, and stem tissue of Lythrum salicaria. The larvae are the primary grazers, since the active feeding period of the adults is relatively short (Malecki et al. 1993; Hight et al. 1995). Addional introduced species eaten were the very similar L. virgatum (cultivated but rarely escaped) and Lagerstroemia indica (Crape Myrtle ). Feeding on L. indica was by adults only, some successful development from eggs occurred on L. virgatum (Kok et al. 1992b). In a comparison of 9 L. salicaria-specialist herbiores, Galerucella spp. appeared to have a high potential as a biocontrol species, because of their wide climatic tolerance and habitat preferences, and demographic characteristics (Blossey 1995a).
Competition - The two beetles are nearly identical in feeding sites, plant preferences, season of occurrence, etc. In spite of this, there is no evidence of competition between the two species, although resource use was extensively studied. Theoretical models suggest that spatial variation in resource availability or individual (as opposed to species) competitive ability may make coexistence of nearly identical species possible (Blossey 1995b).
Food/Prey - In Europe, the two Galerucella spp. are preyed upon by parasitic wasps. The beetles were kept in quarantine in an attempt to prevent importation of parasites and pathogens (Malecki et al. 1993).
Habitat Change - Reductions of Lythrum salicaria populations are expected to result in at least a partial restoration of plant diversity lost due to dominance by that exotic species. A potential concern is that other invasive species could fill the 'vaccum' left by L. salicaria (Anderson 1995).
Introduction of exotic species for biological control has well-known risks, which have largely been addressed in the research program leading up to the selection and release of beetles for the control of Lythrum salicaria. These risks have to be considered in relation to the damage caused by L. salicaria's invasion, and also to ecological damage caused by other control methods, such as herbicide, flooding, mechanical cutting, etc. (Malecki et al. 1993).
References - Anderson 1995; Blossey 1995b; Fofonoff 1995-1997 personal observation; Kok et al. 1992b; Malecki et al. 1993; Strong 1995; Swarth 1996; Thompson et al. 1987
References
Anderson, Mark G. (1995) Interactions between Lythrum salicaria and native organisms: A critical review, Environmental Management 19: 225-231Batra, S. W. T.; Schroeder, D.; Boldt, P. E.; Mendl, W. (1986) Insects associated with purple loosestrife (Lythrum salicaria L.) in Europe, Proceedings of the Entomological Society of Washington 88: 748-759
Blossey, Bernd (1995) Coexistence of two leaf-beetles in the same fundamental niche. Distribution, adult phenology, and oviposition, Oikos 74: 225-234
Blossey, Bernd (1995) A comparison of various approaches for evaluating potential biological control agents using insects on Lythrum salicaria, Biological Control 5: 113-122
Blossey, Bernd; Schroeder, Dieter; Hight, Stephen D.; Malecki, Richard A. (1994) Host specificity and environmental impact of two leaf beetles (Galerucella calmariensis and G. pusilla) for biological control of purple loosestrife (Lythrum salicaria), Weed Science 42: 134-140
Hight, Stephen D.; Blossey, Bernd; Laing, John; DeClerck-Floate, Rosemarie (1995) Establishment of insect biocontrol agents from Europe against Lythrum salicaria in North America, Environmental Entomology 24: 967-977
Kok, L. T.; McAvoy, T. J.; Malecki, R. A.; Hight, S. D.; Drea, J. J.; Coulson, J. R. (1992) Host specificity tests of Galerucella calmariensis (L.) and G. pusilla (Duft.) (Coleoptera: Chrysomelidae), potential biological control agents of Purple Loosestrife, Lythrum salicaria L. (Lythraceae), Biological Control 2: 282-290
Mal, Tarun K.; Lovett-Doust, Jon; Lovett-Doust, Lesley; Mulligan, G. A. (1992) The biology of Canadian weeds. 100. Lythrum salicaria, Canadian Journal of Plant Science 72: 1305-1330
Malecki, Richard A.; Blossey, Bernd; Hight, Stephen D.; Schroeder, Dieter; Kok, Loke T.; Coulson, Jack R. (1993) Biological control of purple loosestrife, BioScience 43: 680-686
Manguin, Sylvie; White, Richard; Blossey, Bernd; Hight, Stephen D. (1993) Genetics, taxonomy, and ecology of certain species of Galerucella (Coleoptera: Chrysomelidae)., Annals of the Entomological Society of America 86: 397-410
McAvoy, T. J.; Kok, L. T. (1997) Establishment and phenology of Galerucella calmariensis (L.) and G. pusilla (Duft.), Coleoptera, Chrysomelidae, biological control agents of pruple loosestrife, Lythrum salicaria L. (Lythraceae) in southwest Virginia, Virginia Journal of Science 48: 152
Mills, Edward L.; Leach, Joseph H.; Carlton, James T.; Secor, Carol L. (1993) Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions., Journal of Great Lakes Research 19: 1-54
Mills, Edward L.; Scheuerell, Mark D.; Carlton, James T.; Strayer, David (1997) Biological invasions in the Hudson River: an inventory and historical analysis., New York State Museum Circular 57: 1-51
Skinner, Luke (1996) Biological control of purple loosestrife- a new control method for a tough wetland invader, Aquatic Nuisance Species Digest 1: 43-45
1995 Introduced plants in the Chesapeake Bay region, conversation with Paul Fofonoff.
Swarth, Chris (1996) Marsh notes: Newsletter of Jug Bay Wetlands Sanctuary, , . Pp. 1, 5-6
September 24 1997 email, Loosestrife biocontrol beetles. jil_swearingen@nps.gov National Park Service, Washington DC
Thompson, Daniel Q.; Stuckey, Ronald L.; Thompson, Edith B. (1987) Spread, impact, and control of Purple Loosestrife (Lythrum salicaria) in North American wetlands, Fish and Wildlife Research 2: 1-55
1997 Biological control: a guide to natural enemies in North America.. http:/www.nysaes.cornell.edu/ent