Coccus viridis
Encyclopedia
Coccus viridis is a soft scale insect
in the family Coccidae
with a wide host range. It is commonly known as green scale or sometimes coffee green scale because it is a major pest of coffee
crops throughout the world.
ous body wall. It has a flattish elongated oval dome shape and is about three millimetres in width. The front end is rounded while the rear end has a distinctive groove. Adults retain their legs and antennae
but mostly remain sedentary. The nymphs
are a flattish oval shape, yellowish green, with six short legs. The nymphs shed their skin three times and each instar
is larger and more convex than the previous one.
and keeps them underneath her body to protect them. She usually chooses the underside of a leaf and adult scales may often be seen in a line on both sides of the midrib and beside the lateral veins. Eggs hatch in anything between a few minutes and a few hours. The newly hatched crawlers wander off to find somewhere suitable to settle on a leaf or near the tip of a green shoot. Both nymphs and adults suck sap from the phloem
of the host plant. When a large number of scale insects are present, their collective feeding causes a yellowing of the leaves which may later fall, a loss of plant vigour and a reduction in crop yield. The scale insects excrete honeydew
on which bees, wasps, ants and other insects feed. Sooty mould fungus often grows on the honeydew and this decreases the area of leaf available for photosynthesis
, spoils the appearance of the plant and reduces the marketability of fruit. It is especially damaging to young trees after transplanting.
. The host range includes vegetable, fruit and ornamental crops as well as many native plants. Economically important crops include Anthurium
, atemoya
, avocado
, cacao, celery
, cherimoya
, coffee
, custard apple
, flowering ginger
, guava
, lime
, Macadamia
, orange
, orchid, Plumeria
and sugar apple
. It is a serious pest of coffee in many countries causing so much damage that in some areas, coffee production ceased.
have been shown to affect green scale but attempts to infect healthy insects with these fungi have been unsuccessful. Controlling ant colonies will assist in reducing levels of attack by green scale (see below).
This scale is susceptible to a number of pesticides including carbaryl
, malathion
, methomyl
and volck oil. Consideration should be given to the harmful effects of these chemicals on beneficial insects.
such as lady beetles
. Research showed that the relationship between the ants and scales is mutualistic. The trials involved adding lady beetle larvae and lepidoptera
n larvae to plants infested with green scale with or without ants being present. It was found that the ants actively removed both kinds of larvae, usually within an hour of introduction. The direct effect of this was an increase in scale reproductive success and the indirect effect was a decrease in scale mortality resulting from the removal of predators and a decrease in parasitism rates.
Another research study conducted in the field found a positive correlation between the presence of ants on host plants and the success of green scale insects. On coffee trees from which ants had been excluded the number of scale insects had declined after fifty days and after seventy days, none remained, whereas scales had thrived on ant-infested trees.
A study found that the entomopathogenic fungus, Cephalosporium lecanii, was highly effective in controlling coffee green scale. A study examined the effect of the fungus on coffee green scale in combination with lower than normal applications of either of two insecticides, fenthion
and phosphamidon
. The use of fenthion resulted in the highest percentage mortality of the scales at the lowest dosages of insecticide. The results from the use of phosamidon were inconclusive, with the results differing in the laboratory and the field.
Scale insect
The scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
in the family Coccidae
Coccidae
The Coccidae are a family of scale insects belonging to the superfamily Coccoidea. They are commonly known as soft scales, wax scales or tortoise scales. The females are flat with elongated oval bodies and a smooth integument which may be covered with wax. In some genera they possess legs but in...
with a wide host range. It is commonly known as green scale or sometimes coffee green scale because it is a major pest of coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...
crops throughout the world.
Description
The adult scale insect is a glossy pale green colour with black internal markings that are visible through the chitinChitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
ous body wall. It has a flattish elongated oval dome shape and is about three millimetres in width. The front end is rounded while the rear end has a distinctive groove. Adults retain their legs and antennae
Antenna (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....
but mostly remain sedentary. The nymphs
Nymph (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...
are a flattish oval shape, yellowish green, with six short legs. The nymphs shed their skin three times and each instar
Instar
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...
is larger and more convex than the previous one.
Biology
Males have not been recorded for this species so the populations are composed entirely of females. A mature female lays whitish oval 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...
and keeps them underneath her body to protect them. She usually chooses the underside of a leaf and adult scales may often be seen in a line on both sides of the midrib and beside the lateral veins. Eggs hatch in anything between a few minutes and a few hours. The newly hatched crawlers wander off to find somewhere suitable to settle on a leaf or near the tip of a green shoot. Both nymphs and adults suck sap from the phloem
Phloem
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 the host plant. When a large number of scale insects are present, their collective feeding causes a yellowing of the leaves which may later fall, a loss of plant vigour and a reduction in crop yield. The scale insects excrete honeydew
Honeydew (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...
on which bees, wasps, ants and other insects feed. Sooty mould fungus often grows on the honeydew and this decreases the area of leaf available for photosynthesis
Photosynthesis
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...
, spoils the appearance of the plant and reduces the marketability of fruit. It is especially damaging to young trees after transplanting.
Hosts
This scale is believed to be of Brazilian origin but is now widely distributed throughout the tropicsTropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
. The host range includes vegetable, fruit and ornamental crops as well as many native plants. Economically important crops include Anthurium
Anthurium
Anthurium , is a large genus of about 600–800 species, belonging to the arum family . Anthurium can also be called "Flamingo Flower" or "Boy Flower", both referring to the structure of the spathe and spadix....
, atemoya
Atemoya
The atemoya, Annona × atemoya, is a hybrid of two fruits – the sugar apple and the cherimoya – which are both native to the American tropics. This fruit is popular in Taiwan, where it is known as the "pineapple sugar apple" , and is sometimes mistaken for a cross between the sugar...
, avocado
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...
, cacao, celery
Celery
Apium graveolens is a plant species in the family Apiaceae commonly known as celery or celeriac , depending on whether the petioles or roots are eaten: celery refers to the former and celeriac to the latter. Apium graveolens grows to 1 m tall...
, cherimoya
Annona cherimola
Annona cherimola , and originally called Chirimuya by the Inca people who lived where it was growing in the Andes of South America, is an edible fruit bearing species of the genus Annona from the family Annonaceae is now widely cultivated mostly for its sweet fruits that share the name...
, coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...
, custard apple
Annona reticulata
Annona reticulata is a small deciduous or semi-evergreen tree in the plant family Annonaceae.It is best known for its fruit, called custard-apple, a name it shares with fruits of other species from the same genus: A. cherimola and A. squamosa or sometimes it is called wild-sweetsop,...
, flowering ginger
Ginger
Ginger is the rhizome of the plant Zingiber officinale, consumed as a delicacy, medicine, or spice. It lends its name to its genus and family . Other notable members of this plant family are turmeric, cardamom, and galangal....
, guava
Guava
Guavas are plants in the myrtle family genus Psidium , which contains about 100 species of tropical shrubs and small trees. They are native to Mexico, Central America, and northern South America...
, lime
Lime (fruit)
Lime is a term referring to a number of different citrus fruits, both species and hybrids, which are typically round, green to yellow in color, 3–6 cm in diameter, and containing sour and acidic pulp. Limes are a good source of vitamin C. Limes are often used to accent the flavors of foods and...
, Macadamia
Macadamia
Macadamia is a genus of nine species of flowering plants in the family Proteaceae, with a disjunct distribution native to eastern Australia , New Caledonia and Sulawesi in Indonesia ....
, orange
Orange (fruit)
An orange—specifically, the sweet orange—is the citrus Citrus × sinensis and its fruit. It is the most commonly grown tree fruit in the world....
, orchid, Plumeria
Plumeria
Plumeria is a genus of flowering plants of the family that includes Dogbane: the Apocynaceae. It contains 7-8 species of mainly deciduous shrubs and small trees...
and sugar apple
Annona squamosa
Annona squamosa a small well-branched tree or shrub that bears edible fruits called sugar-apple, species of the genus Annona and member of the family Annonaceae more willing to grow at lower altitudes than its relatives Annona reticulata and Annona cherimola making it the most widely cultivated of...
. It is a serious pest of coffee in many countries causing so much damage that in some areas, coffee production ceased.
Management
Green scale is transported to new areas on infected plants. There should be a thorough inspection of planting material for scale and other insects before it is introduced into a greenhouse. Certain entomopathogenic fungiEntomopathogenic fungus
An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them.-Typical life cycle:These fungi usually attach to the external body surface of insects in the form of microscopic spores...
have been shown to affect green scale but attempts to infect healthy insects with these fungi have been unsuccessful. Controlling ant colonies will assist in reducing levels of attack by green scale (see below).
This scale is susceptible to a number of pesticides including carbaryl
Carbaryl
Carbaryl is a chemical in the carbamate family used chiefly as an insecticide. It is a white crystalline solid commonly sold under the brand name Sevin, a trademark of the Bayer Company. Union Carbide discovered carbaryl and introduced it commercially in 1958...
, malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...
, methomyl
Methomyl
Methomyl is a carbamate insecticide. It was introduced in 1966, but its use is restricted because of its high toxicity to humans. Its current primary use is on alfalfa for forage....
and volck oil. Consideration should be given to the harmful effects of these chemicals on beneficial insects.
Research
This scale is often associated with ants which feed on the honeydew excreted and defend the insects from attack by predatorsPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
such as lady beetles
Coccinellidae
Coccinellidae is a family of beetles, known variously as ladybirds , or ladybugs . Scientists increasingly prefer the names ladybird beetles or lady beetles as these insects are not true bugs...
. Research showed that the relationship between the ants and scales is mutualistic. The trials involved adding lady beetle larvae and lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
n larvae to plants infested with green scale with or without ants being present. It was found that the ants actively removed both kinds of larvae, usually within an hour of introduction. The direct effect of this was an increase in scale reproductive success and the indirect effect was a decrease in scale mortality resulting from the removal of predators and a decrease in parasitism rates.
Another research study conducted in the field found a positive correlation between the presence of ants on host plants and the success of green scale insects. On coffee trees from which ants had been excluded the number of scale insects had declined after fifty days and after seventy days, none remained, whereas scales had thrived on ant-infested trees.
A study found that the entomopathogenic fungus, Cephalosporium lecanii, was highly effective in controlling coffee green scale. A study examined the effect of the fungus on coffee green scale in combination with lower than normal applications of either of two insecticides, fenthion
Fenthion
Fenthion is an organothiophosphate insecticide, avicide, and acaricide. Like most other organophosphates, its mode of action is via cholinesterase inhibition. Due to its relatively low toxicity towards humans and mammals, fenthion is listed as moderately toxic compound in U.S. Environmental...
and phosphamidon
Phosphamidon
Phosphamidon is an organophosphate insecticide first reported in 1960. It acts as a cholinesterase inhibitor.The commercial product typically exists as a mixture of 70% -isomer and 30% -isomer.- Toxicity and regulation:...
. The use of fenthion resulted in the highest percentage mortality of the scales at the lowest dosages of insecticide. The results from the use of phosamidon were inconclusive, with the results differing in the laboratory and the field.