Description
Potentially Misidentified Species - All other European and American Hylobius spp. feed on the roots of conifers (Blossey 1993). Hylobius pales (Pales Weevil) is widespread in North America on cutover pine forests, H. aliradicus (Southern Pine-Root Weevil) is known in the southeast (NC-TX) (Arnett 1993; Dillon and Dillon 1960). H. pales has been collected in an MD tidal marsh (Bickley and Seek 1975).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Animalia | Hexapoda | Insecta | Coleoptera | Curculionidae | Hylobius |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1992 | Unknown | Unknown | Introduced | Regular Resident | Europe | Eurasia | Biocontrol(Biocontrol) |
History of Spread
The root-boring weevil Hylobius transversovittatus, is native to Eurasia (Sweden to Spain and eastward into Russia) (Blossey 1995; Hoffmann 1954). Hylobius transversovittatus, together with Leaf-feeding Beetles Galerucella calmariensis and G. pusilla, 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 (Hight et al. 1995; Kok et al. 1992; Malecki et al. 1993; Thompson et al. 1987). Hylobius transversovittatus and the two species of Galerucella were chosen as the most promising insects for biological control of L. salicaria, because of their high feeding rates and strong host-specificity (Blossey 1993; Hight et al. 1995; Kok et al. 1992a; Malecki et al. 1993). Experiments were conducted in Germany, and in quarantine in the United States, 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 (Kok et al. 1992a; 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. Thirteen thousand H. transversovittatus eggs were shipped to the United States for quarantine and eventual release. In 1992-93, batches of H. transversovittatus were released in 9 states (PA, NY, MD. VA, MN, WA, OR, CO, MT) and 2 Canadian provinces (Manitoba, Ontario). Subsequent surveys in 1993-1994 indicated that both species were established at most sites where 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 releases, of 3605 eggs in Prince Georges' County MD and 315 eggs in Howard County, were made in August 1992 and September 1993, respectively. Established populations were found at the release site in Howard County in 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, H. transversovittatus eggs were inserted into potted L. salicaria plants in June 1996. The eggs were kept over the winter in the Kenilworth greenhouse. Winter survival was estimated at 25-30%. Seventy weevil-innoculated pots were placed at the north (upland) margin of the marsh in May 1997. Potted plants showed no sign of leaf damage (Swearingen 1997). There were no subsequent sightings of the weevils, and the introduction is believed to have failed. It is not clear if this insect has been successfully established in the watershed (Swearingen 2002, personal communication). Releases of the weevil are continuing in wetlands along the nontidal Susquehanna River in PA (Moser 2002). Hylobius transversovittatus long life cycle and underground larval history makes the success of introductions difficult to assess in the short term (Hight et al. 1995).
History References - Batra et al. 1986; Blossey et al. 1993; Blossey et al. 1994a; Blossey 1995a; Hight et al. 1995; Hoffmann 1954; Kok et al. 1992a; Malecki et al. 1993; McAvoy and Kok 1997; Moser 2002; Skinner 1996; Swearingen 1997; Thompson et al. 1987
Invasion Comments
Residency - Larvae of Hylobius transversovittatus live in the underground roots of Lythrum salicaria plants, adults are found on the stems and leaves. Larvae tolerate submergence for periods of up to 3 weeks, but cannot survive permanent submergence. Adults lack adaptations for aquatic life (Blossey 1993; Weeden et al. 1997)
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 0.0 | ||
| Oxygen | hypoxic | |||
| pH | ||||
| Salinity Range | fresh-oligo |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | 5.0 | 5.0 |
| Typical Adult Size (mm) | 13.0 | 13.0 |
| Maximum Adult Size (mm) | 15.0 | 15.0 |
| Maximum Longevity (yrs) | 4.0 | 4.0 |
| Typical Longevity (yrs | 2.0 |
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 Hylobius transversovittatus, Galerucella calmariensis and G. pusilla, and 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).
References - 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. L. salicaria is believed to have adversely affected waterfowl, furbearers, and nongame wildlife, resulting in declines in hunting expenditures, revenues from 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 (Malecki et al. 1993).
References - Anderson 1995; Malecki et al. 1993; Thompson et al. 1987
Ecological Impacts on Chesapeake Native Species
The deliberate introduction of Hylobius transversovittatus, Galerucella calmariensis and G. pusilla 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 to gauge the extent of grazing by these insects on native North American wetland plants (50 species tested). The host specificity of H. transversovittatus, G. calmariensis, and G. pusilla was found to be quite strong (Blossey et al. 1994; Kok et al. 1994; 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 (Fofonoff 1995-1997 personal observation; Swarth 1996; Strong 1995), 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 as potential host plants for H. transversovittatus. Only L. alatum (Winged Loosestrife) and Decadon verticillatus (Swamp 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. 1992a; Malecki et al. 1993). In Kok et al's trials in the United States, only L. salicaria supported development of H. transversovittatus (Kok et al. 1992a), while in Blossey et al's (1994a), successful development to adulthood occurred in D. verticillatus and L. alatum. However, oviposition and lifespan were reduced on the native plants, and the strength of the preference for L. salicaria suggests that impacts on D. verticillatus and L. alatum will be small (Blossey et al. 1994a).
Habitat Change - Hylobius transversovittatus attacks L. salicaria at the roots, resulting in reduced shoot and bud growth, and reduced seed output. In a comparison of 9 Eurasia L. salicaria herbivores, H. transversovittatus was considered the most effective biocontrol species, in part because its feeding activity (by larvae) occurs year-round (Blossey 1995). 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. 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, these effects 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). However, experimental studies of L. salicaria's impacts as a competitor, or as an influence on wetland foodwebs, are very limited (Anderson 1995), so 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.
One native plant, Decadon verticillatus (Swamp Loosestrife), which is eaten at low rates by Hylobius transversovittatus, is a host for an endangered moth (Paraipema sulphurata) (Blossey et al. 1994a).
References - Anderson 1995; Blossey 1995a; Blossey et al. 1994a; Fofonoff 1995-1997 personal observation; Kok et al. 1994; Malecki et al. 1993; Swarth 1996; Strong 1995; Thompson et al. 1987
Ecological Impacts on Other Chesapeake Non-Native Species
The deliberate introduction of Hylobius transversovittatus, Galerucella calmariensis, and G. pusilla 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 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 (Swarth 1996; Strong 1995, Fofonoff 1995-1997 personal observation), so responses to the insect releases are expected to be limited to those areas.
Herbivory - Larvae of Hylobius transversovittatus feed on the stem and root tissue of Lythrum salicaria, 'devastating large parts of these storage tissue' (Blossey 1993). Adults feed on newly formed leaves (Malecki et al. 1993). Herbivory by H. transversovittatus results in reduced root and shoot growth and reduced seed output (Blossey 1995a). This species was considered to have the highest biocontrol potential of 9 species studied, in part because herbivory by the larvae occurs year-round, and because root damage has profound effects on the whole plant. However, its protracted life-cycle was seen as increasing the difficulty of establishment in North America (Blossey 1995a). Feeding and development also occurred on the closely related, possibly conspecific, Lythrum virgatum (European Wand Loosestrife), but an important horticultural plant, Lagerstroemia indica (Crape Myrtle; Lythraceae) was not eaten by any life stage (Kok et al. 1992a). A number of introduced and crop plants [Rumex crispus (Curly dock); Triticum aestivum (Summer Wheat); Beta vulgaris (Beet)] were tested but not eaten (Blossey et al. 1994a).
Food/Prey - In Europe, Hylobius transversovittatus 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 'vacuum' 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 et al. 1994a; Blossey 1995a; Fofonoff 1995-1997 personal observation; Kok et al. 1992a; Malecki et al. 1993; Swarth 1996; Strong 1995; Thompson et al. 1987
References
Anderson, Mark G. (1995) Interactions between Lythrum salicaria and native organisms: A critical review, Environmental Management 19: 225-231Arnett, Ross H., Jr. (1993) American Insects: A Handbook of the Insects of America North of Mexico., In: (Eds.) . , Gainesville, FL. Pp.
Batra, 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
Bickley, William E.; Seek, Timothy R. (1975) Insects in four Maryland marshes., Agricultural Experiment Station University of Maryland, College Park, Maryland: Miscellaneous Publications 870: 1-27
Blossey, Bernd (1993) Herbivory below ground and biological weed control: life history of a root-boring weevil on purple loosestrife, Oecologia 94: 380-387
Blossey, Bernd (1995) A comparison of various approaches for evaluating potential biological control agents using insects on Lythrum salicaria, Biological Control 5: 113-122
1998 Purple Loosestrife Project Page. http://www.dnr.cornell.edu/bcontrol/purple.htm
Blossey, Bernd; Schroeder, Dieter; Hight, Stephen D.; Malecki, Richard A. (1994) Host specificity and environmental impact of the weevil Hylobius transversovittatus, a biological control agent of purple loosestrife (Lythrum salicaria), Weed Science 42: 128-133
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
Dillon, Elizabeth S.; Dillon, Lawrence S. (1960) A manual of common beetles of eastern North America, , Evanston, IL. Pp.
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
Hoffmann, Adolphe (1954) Coleopteres Curculionides (Deuxieme Partie), In: (Eds.) Coleopteres Curculionides (deuxieme partie). , Paris. Pp. p 269-278
Kok, L. T.; McAvoy, T. J.; Malecki, R. A.; Hight, S. D.; Drea, J. J.; Coulson, J. R. (1992) Host specificity tests of Hylobius transversovittatus Goeze (Coleoptera: Curculionidae), a potential biological control agent of Purple Loosestrife, I L. (Lythraceae)., Biological Control 2: 1-8
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
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
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 ---missing info----. Conversation
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