Pseudococcus viburni
Encyclopedia
Pseudococcus viburni is a close relative of the grape mealybug (P. maritimus) and a pest of the vineyard
s of New Zealand
, the Central Coast of California
, and the tea gardens of northern Iran
. Unlike the grape mealybug, the obscure mealybug is not native to California, having most likely been introduced to the region from either Australia
or South America
in the latter part of the 19th century.
is not clear; from 1900 (when P. maritimus, the grape mealybug, was first described) to 1960, the obscure mealybug was variably misidentified as or synonomized with P. maritimus, P. longispinus, P. obscurus Essig, P. capensis Brian, P. malacearum Ferris, and P. affinis (Maskell). This taxonomic
confusion has hampered attempts to trace the exact origin of the species, but its presence in both Australia and South America strongly suggests that it is of Gondwana
n origin.
; females are flightless, larger, and longer-lived than the winged males, who cannot feed and die immediately after mating
.
and adult female obscure mealybugs are rectangular, with rounded anterior and posterior ends. Adult females range from 1-5mm in length. Like all mealybug
s, the obscure mealybug covers its body in a white, waxy secretion which accumulates in clumps along thin filaments
protruding from its exoskeleton
. This clumpy secretion lends the mealybug its characteristic mealy appearance.
and a single pair of wings. They bear a strong resemblance to common house flies, but have two white wax tail filaments.
's waxy secretion accumulates heavily on these filaments, making it appear to have several long "tails".
The obscure mealybug more closely resembles the grape mealybug than it does the vine mealybug, but the two can be distinguished by the color of the defensive fluid they secrete when disturbed; grape mealybugs secrete reddish-orange fluid, while obscure mealybugs secrete clear fluid. When crushed, the obscure mealybug's body contents (guts) are pinkish-grey.
(so-called "true bugs"), obscure mealybugs undergo incomplete metamorphosis
; nymphal young closely resemble adults in body shape, take six to nine weeks to mature, and retain the use of all six legs throughout their entire lives. Depending on temperature, obscure mealybugs may complete 2-3 generations per year; females will lay clutches of several hundred orange eggs
in cottony sacs, from which nymphs will hatch and emerge after about 5–10 days. If environmental conditions are too cold, young nymphs will remain in the sac until temperatures rise.
Obscure mealybugs lay eggs all year long, and during winter, under the bark of trees and vines (though there is no true dormancy
). These overwintering populations include individual mealybugs from all stages of development, but are dominated by eggs and first instars; overwinter mortality for young nymphs is high, but a few individuals (normally the ones quickest to hatch) will survive and feed on the first spring leaves. Mortality in non-overwintering generations is greatly decreased.
The female obscure mealybug sex pheromone has the unfortunate property of sometimes attracting parasitic wasps (such as Tetracnemoidea peregrina), and is therefore a kairomone
.
of vines and woody-stemmed plants, especially pear and apple trees and grape vines. Some individuals are vectors for infectious pathogen
s and can transmit them from plant to plant while feeding; mealybug-spread grapevine leafroll associated virus type III (GRLaV-3), in particular, has wreaked havoc among the grapes of New Zealand, reducing the crop yield of infected vineyards by up to 60%.
, a thick, sugary fluid created as a byproduct of digestion
(large colonies of mealybugs can produce enough honeydew to seep through bark and leaves, leaving shiny, sticky patches on the exterior of the plant). Some ant
s have developed a symbiotic relationship
with obscure mealybugs, tending and protecting the insects from natural enemies to increase the production of honeydew, on which the ants feed. This relationship is similar to the one that some ants have with aphid
s.
, South America, Australia, New Zealand, and Iran, especially in vineyards and fruit orchards
. The obscure mealybug has caused particularly substantial damage to vineyards in the Central Coast of California, where it is an introduced species
and has no natural predators.
Many attempts have been made to control obscure mealybug populations in commercial greenhouse
s and vineyards, using both synthetic pesticide
s and introduced mealybug parasites
. Since the obscure mealybug's waxy coating and habit of seeking sheltered feeding sites protect it from water-based pesticides, oil-based organophosphate
pesticides (among the more toxic of pesticides) are most effective in reducing population density, though such pesticides can harm plants if applied after the first budding. Even so, some New Zealand obscure mealybug populations have developed a resistance to organophosphate pesticides.
Because of the high toxicity and strict regulation of organophosphate pesticides, some Californian vintners have imported natural parasites of the obscure mealybug from Chile
, particularly Pseudaphycus flavidulus and Leptomastix epona. Such efforts have so far produced indeterminate results; the obscure mealybug is capable of encapsulating and killing the eggs of L. epona and L. dactylopii, for example, rendering those parasites ineffective. On the other hand, significant success in reducing obscure mealybug populations has resulted from isolating them from their symbiont ants.
Vineyard
A vineyard is a plantation of grape-bearing vines, grown mainly for winemaking, but also raisins, table grapes and non-alcoholic grape juice...
s of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, the Central Coast of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, and the tea gardens of northern Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
. Unlike the grape mealybug, the obscure mealybug is not native to California, having most likely been introduced to the region from either Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
or South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
in the latter part of the 19th century.
Taxonomy
The obscure mealybug is thought to have evolved in Australia or South America. Its history in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
is not clear; from 1900 (when P. maritimus, the grape mealybug, was first described) to 1960, the obscure mealybug was variably misidentified as or synonomized with P. maritimus, P. longispinus, P. obscurus Essig, P. capensis Brian, P. malacearum Ferris, and P. affinis (Maskell). This taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
confusion has hampered attempts to trace the exact origin of the species, but its presence in both Australia and South America strongly suggests that it is of Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
n origin.
Morphology
Obscure mealybugs exhibit a high degree of sexual dimorphismSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
; females are flightless, larger, and longer-lived than the winged males, who cannot feed and die immediately after mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
.
Females
The bodies of nymphalNymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
and adult female obscure mealybugs are rectangular, with rounded anterior and posterior ends. Adult females range from 1-5mm in length. Like all mealybug
Mealybug
Mealybugs are insects in the family Pseudococcidae, unarmored scale insects found in moist, warm climates. They are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees and also acts as a vector for several plant diseases.-Distribution:Mealybugs...
s, the obscure mealybug covers its body in a white, waxy secretion which accumulates in clumps along thin filaments
Protein filament
In biology, a filament is a "long chain of proteins, such as those found in hair, muscle, or in flagella". They are often bundled together for strength and rigidity. Some cellular examples include:*Actin filaments*Microtubules*Intermediate filaments...
protruding from its exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
. This clumpy secretion lends the mealybug its characteristic mealy appearance.
Males
Male obscure mealybugs are tiny, fragile insects with long antennaeAntenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
and a single pair of wings. They bear a strong resemblance to common house flies, but have two white wax tail filaments.
Identification
It is important for vintners to distinguish between the obscure mealybug and its close relatives, the grape and vine mealybug. The obscure mealybug has longer, thinner, and more crooked filaments than does the vine mealybug, making the obscure mealybug look comparatively untidy. The most distinctive feature of the obscure mealybug is the set of two to four exceptionally long caudal filaments growing from the posterior of large nymphs and adult females. The insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
's waxy secretion accumulates heavily on these filaments, making it appear to have several long "tails".
The obscure mealybug more closely resembles the grape mealybug than it does the vine mealybug, but the two can be distinguished by the color of the defensive fluid they secrete when disturbed; grape mealybugs secrete reddish-orange fluid, while obscure mealybugs secrete clear fluid. When crushed, the obscure mealybug's body contents (guts) are pinkish-grey.
Females
Being in the order HemipteraHemiptera
Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
(so-called "true bugs"), obscure mealybugs undergo incomplete metamorphosis
Hemimetabolism
Hemimetabolism or hemimetaboly, also called incomplete metamorphosis, is a term used to describe the mode of development of certain insects that includes three distinct stages: the egg, nymph, and the adult stage, or imago. These groups go through gradual changes; there is no pupal stage...
; nymphal young closely resemble adults in body shape, take six to nine weeks to mature, and retain the use of all six legs throughout their entire lives. Depending on temperature, obscure mealybugs may complete 2-3 generations per year; females will lay clutches of several hundred orange eggs
Egg (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...
in cottony sacs, from which nymphs will hatch and emerge after about 5–10 days. If environmental conditions are too cold, young nymphs will remain in the sac until temperatures rise.
Obscure mealybugs lay eggs all year long, and during winter, under the bark of trees and vines (though there is no true dormancy
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...
). These overwintering populations include individual mealybugs from all stages of development, but are dominated by eggs and first instars; overwinter mortality for young nymphs is high, but a few individuals (normally the ones quickest to hatch) will survive and feed on the first spring leaves. Mortality in non-overwintering generations is greatly decreased.
Males and mating
Male obscure mealybugs do not feed, and have very short lifespans (2–3 days); males will spin cocoons shortly after hatching, where they develop wings. Upon emerging from their cocoons, male obscure mealybugs will fly toward the scent of the female's sex pheromone, mate as many times as possible, then die. Given the male's short lifespan, the timing of the female's emission of sex pheromone is crucial; females will emit the pheromone day and night around the time of male emergence (especially in the spring), then cease immediately after fertilization. Obscure mealybugs generally mate at dusk and at dawn.The female obscure mealybug sex pheromone has the unfortunate property of sometimes attracting parasitic wasps (such as Tetracnemoidea peregrina), and is therefore a kairomone
Kairomone
A kairomone is a semiochemical, emitted by an organism, which mediates interspecific interactions in a way that benefits an individual of another species which receives it, without benefiting the emitter. This "eavesdropping" is often disadvantageous to the producer...
.
Diet
Obscure mealybugs feed on the phloemPhloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word "bark"...
of vines and woody-stemmed plants, especially pear and apple trees and grape vines. Some individuals are vectors for infectious pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s and can transmit them from plant to plant while feeding; mealybug-spread grapevine leafroll associated virus type III (GRLaV-3), in particular, has wreaked havoc among the grapes of New Zealand, reducing the crop yield of infected vineyards by up to 60%.
Symbiosis
Female mealybugs excrete honeydewHoneydew (secretion)
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...
, a thick, sugary fluid created as a byproduct of digestion
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
(large colonies of mealybugs can produce enough honeydew to seep through bark and leaves, leaving shiny, sticky patches on the exterior of the plant). Some ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s have developed a symbiotic relationship
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with obscure mealybugs, tending and protecting the insects from natural enemies to increase the production of honeydew, on which the ants feed. This relationship is similar to the one that some ants have with aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s.
Pestilence
This species is a pest in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, South America, Australia, New Zealand, and Iran, especially in vineyards and fruit orchards
Orchard
An orchard is an intentional planting of trees or shrubs that is maintained for food production. Orchards comprise fruit or nut-producing trees which are grown for commercial production. Orchards are also sometimes a feature of large gardens, where they serve an aesthetic as well as a productive...
. The obscure mealybug has caused particularly substantial damage to vineyards in the Central Coast of California, where it is an introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
and has no natural predators.
Many attempts have been made to control obscure mealybug populations in commercial greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...
s and vineyards, using both synthetic pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s and introduced mealybug parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
. Since the obscure mealybug's waxy coating and habit of seeking sheltered feeding sites protect it from water-based pesticides, oil-based organophosphate
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
pesticides (among the more toxic of pesticides) are most effective in reducing population density, though such pesticides can harm plants if applied after the first budding. Even so, some New Zealand obscure mealybug populations have developed a resistance to organophosphate pesticides.
Because of the high toxicity and strict regulation of organophosphate pesticides, some Californian vintners have imported natural parasites of the obscure mealybug from Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, particularly Pseudaphycus flavidulus and Leptomastix epona. Such efforts have so far produced indeterminate results; the obscure mealybug is capable of encapsulating and killing the eggs of L. epona and L. dactylopii, for example, rendering those parasites ineffective. On the other hand, significant success in reducing obscure mealybug populations has resulted from isolating them from their symbiont ants.