Galerucella calmariensis
Encyclopedia
Galerucella calmariensis is a species
of leaf beetle
in the family Chrysomelidae. It is commonly known as the black-margined loosestrife beetle and is native to Europe and Asia where both adults and larvae feed on purple loosestrife (Lythrum salicaria). It has been introduced in North America as a biological control agent for purple loosestrife.
are spherical, white and usually topped with frass
. The larva
e are yellow speckled with black and resemble small caterpillars.
larvae feed on growing shoot tips and may kill them. Later instars feed on stems and leaves leaving the upper cuticle
of the leaf intact. When the density of the larvae is high enough, the plant can be completely defoliated. After feeding for about three weeks and undergoing further moults, the larvae move down the plant to pupate in the soil or leaf litter. If the water level is high, larvae sometimes pupate in the hollow aerenchyma
tissue in the plant stems. Both adults and larvae can float and may be wafted by water currents or wind to new host plants.
capability and means there is less starch
stored in the roots which may cause plant death in adverse winter conditions. It also results in less vigorous plants which do not compete so strongly with native plant species such as cattails
, grass
es and sedges
.
and the leaf beetles G. calmariensis and G. pusilla. When purple loosestrife was introduced into North America no insects were available to keep it under control and it became rampant. It is now found in large stands throughout the northeastern United States, southeastern Canada and the American Midwest where it crowds out other species and is a threat to biodiversity
.
The black-margined loosestrife beetle and the closely related golden loosestrife beetle (Galerucella pusilla) have been released in over 27 states in the United States and 6 Canadian provinces. The adults of both species have become well established and proved very effective. They show great ability to find new stands of the host plant and can locate patches of purple loosestrife a kilometre away within a few days of emergence.
Before these beetles were introduced to North America, the susceptibility of approximately 50 native plants of North America to the beetles was tested in Europe. Among the plants were several close relatives of purple loosestrife. Only winged loosestrife (Lythrum alatum
) proved to be susceptible, and was not used by the beetles as a host when purple loosestrife was available.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of leaf beetle
Leaf beetle
Beetles in the family Chrysomelidae are commonly known as leaf beetles. This is a family of over 35,000 species in more than 2,500 genera, one of the largest and most commonly encountered of all beetle families....
in the family Chrysomelidae. It is commonly known as the black-margined loosestrife beetle and is native to Europe and Asia where both adults and larvae feed on purple loosestrife (Lythrum salicaria). It has been introduced in North America as a biological control agent for purple loosestrife.
Description
The black-margined loosestrife beetle is cylindrical in shape, mid brown, three to six millimetres long and half that width. When seen from above it often has two blackish lateral lines down either side. The eggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are spherical, white and usually topped with frass
Frass
Frass is the fine powdery material phytophagous insects pass as waste after digesting plant parts. It causes plants to excrete chitinase due to high chitin levels, it is a natural bloom stimulant, and has high nutrient levels. Frass is known to have abundant amoeba, beneficial bacteria, and fungi...
. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are yellow speckled with black and resemble small caterpillars.
Biology
Adults overwinter in leaf litter near purple loosestrife plants. They emerge in the spring and start to feed on the young growth. They cause damage to the leaves characterised by neat rounded shot holes between the veins. The females lay up to 500 eggs from May to July in small batches on leaves and stems. On hatching, the first instarInstar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
larvae feed on growing shoot tips and may kill them. Later instars feed on stems and leaves leaving the upper cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
of the leaf intact. When the density of the larvae is high enough, the plant can be completely defoliated. After feeding for about three weeks and undergoing further moults, the larvae move down the plant to pupate in the soil or leaf litter. If the water level is high, larvae sometimes pupate in the hollow aerenchyma
Aerenchyma
Aerenchyma is an air channel in the roots of some plants, which allows exchange of gases between the shoot and the root. The channel of large air-filled cavities provides a low-resistance internal pathway for the exchange of gases such as oxygen and ethylene between the plant above the water and...
tissue in the plant stems. Both adults and larvae can float and may be wafted by water currents or wind to new host plants.
Damage
Larval damage to buds and shoots reduces the growth of the purple loosestrife plant and its ability to flower and produce seed. Damage to the leaves reduces their photosyntheticPhotosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
capability and means there is less starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
stored in the roots which may cause plant death in adverse winter conditions. It also results in less vigorous plants which do not compete so strongly with native plant species such as cattails
Typha
Typha is a genus of about eleven species of monocotyledonous flowering plants in the family Typhaceae. The genus has a largely Northern Hemisphere distribution, but is essentially cosmopolitan, being found in a variety of wetland habitats...
, grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es and sedges
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
.
Use in biological control
Purple loosestrife is a native of Europe, Asia, northwest Africa and parts of Australia. In these countries a number of insects are associated with it. These include the weevil Hylobius transversovittatusHylobius transversovittatus
Hylobius transversovittatus is a species of weevil in the family Curculionidae. It is native to the Old World where both adults and larvae feed on purple loosestrife...
and the leaf beetles G. calmariensis and G. pusilla. When purple loosestrife was introduced into North America no insects were available to keep it under control and it became rampant. It is now found in large stands throughout the northeastern United States, southeastern Canada and the American Midwest where it crowds out other species and is a threat to biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
.
The black-margined loosestrife beetle and the closely related golden loosestrife beetle (Galerucella pusilla) have been released in over 27 states in the United States and 6 Canadian provinces. The adults of both species have become well established and proved very effective. They show great ability to find new stands of the host plant and can locate patches of purple loosestrife a kilometre away within a few days of emergence.
Before these beetles were introduced to North America, the susceptibility of approximately 50 native plants of North America to the beetles was tested in Europe. Among the plants were several close relatives of purple loosestrife. Only winged loosestrife (Lythrum alatum
Lythrum alatum
Lythrum alatum, commonly known as winged loosestrife or winged lythrum, is a species of flowering plant belonging to the family Lythraceae. It is endemic to wetland areas in central and eastern United States and Ontario.-Description:...
) proved to be susceptible, and was not used by the beetles as a host when purple loosestrife was available.