''Brevicoryne brassicae'', commonly known as the cabbage aphid or cabbage aphis, is a destructive
aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
(plant louse) native to
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
that is now found in many other areas of the world.
[Hawaii Department of Entomology information page]
/ref> The aphids feed on many varieties of produce, including cabbage, broccoli
Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the cabbage family (family Brassicaceae, genus ''Brassica'') whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is cla ...
(especially), Brussels sprouts, cauliflower and many other members of the genus ''Brassica
''Brassica'' () is a genus of plants in the cabbage and mustard family ( Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called ''cole c ...
'',[ but do not feed on plants outside of the family ]Brassicaceae
Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leav ...
. The insects entirely avoid plants other than those of Brassicaceae; even though thousands may be eating broccoli near strawberries, the strawberries will be left untouched.[University of Minnesota extension]
Cabbage aphids, from the genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
'' Brevicoryne'' of the family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Aphididae
The Aphididae are a very large insect family in the aphid superfamily ( Aphidoidea), of the order Hemiptera. These insects suck the sap from plant leaves. Several thousand species are placed in this family, many of which are considered plant/crop ...
, are grayish-green, but a waxy covering gives them a grayish-white[ to powdery blue appearance.
]
Predator defense mechanism
Cabbage aphids produce a myrosinase
Myrosinase (, ''thioglucoside glucohydrolase'', ''sinigrinase'', and ''sinigrase'') is a family of enzymes involved in plant defense against herbivores, specifically the mustard oil bomb. The three-dimensional structure has been elucidated and is ...
(beta-thioglucoside glucohydrolase) enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
in head and thoracic muscles; the aphids also uptake glucosinolates, particularly sinigrin
Sinigrin is a glucosinolate that belongs to the family of glucosides found in some plants of the family Brassicaceae such as Brussels sprouts, broccoli, and the seeds of black mustard (''Brassica nigra''). Whenever sinigrin-containing plant tis ...
, from the plants on which they feed, storing the glucosinolates in their haemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
. (Glucosinolates are natural defenses for plants in the order Brassicales
The Brassicales (or Cruciales) are an order of flowering plants, belonging to the eurosids II group of dicotyledons under the APG II system. One character common to many members of the order is the production of glucosinolate (mustard oil) compo ...
against pests and herbivores.) The combination of the glucosinolates and the myrosinase enzyme produces a violent chemical reaction that releases the mustard oil
Mustard oil can mean either the pressed oil used for cooking, or a pungent essential oil also known as volatile oil of mustard. The essential oil results from grinding mustard seed, mixing the grounds with water, and extracting the resulting vola ...
chemical allyl isothiocyanate
Allyl isothiocyanate (AITC) is an organosulfur compound (formula CH2CHCH2NCS). This colorless oil is responsible for the pungent taste of mustard, radish, horseradish, and wasabi. This pungency and the lachrymatory effect of AITC are mediated thr ...
.[Imperial College London (2007, July 12). Aphids Make 'Chemical Weapons' To Fight Off Killer Ladybirds. ScienceDaily. Retrieved November 20, 2007, from https://www.sciencedaily.com/releases/2007/07/070711105844.htm] The defense mechanism has a dramatic negative effect on the survival of the larva
A larva (; plural larvae ) 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.
...
l ladybird predator ''Adalia bipunctata
''Adalia bipunctata'', the two-spot ladybird, two-spotted ladybug or two-spotted lady beetle, is a carnivorous beetle of the family Coccinellidae that is found throughout the holarctic region. It is very common in western and central Europe. I ...
''. The chemical defence of the aphids has been likened to a " walking mustard oil bomb".
The myrosinase from ''Brevicoryne brassicae'' appears to have evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
separately from myrosinases found in plants, possibly a case of convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. Aphid myrosinase appears to have greater similarity to animal beta-O-glucosidases than to plant myrosinases.[
]
Pest control
Different varieties of cultivar
A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...
s have varying resistance to ''Brevicoryne brassicae''.
'' Diaeretiella rapae'' is a common wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...
parasitoid of cabbage aphids.[ Other controlling insects include ladybird beetles, syrphid fly larvae, and lacewing larvae.][ Some insecticidal soaps may be effective in treating aphid infestations.][
]
References
External links
Images of cabbage aphids
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{{Taxonbar, from=Q2634837
Macrosiphini
Agricultural pest insects
Insect vectors of plant pathogens
Insects described in 1758
Hemiptera of Europe
Taxa named by Carl Linnaeus