aphid

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aphid

or

plant louse,

tiny, usually green, soft-bodied, pear-shaped insect injurious to vegetation. It is also called greenfly and blight. Aphids are mostly under 1-4 in. (6 mm) long. Some are wingless; others have two pairs of transparent or colored wings, the front pair longer than the hind pair. In typical aphids (family Aphididae), two tubes called cornicles project from the rear of the abdomen and exude protective substances. Aphids feed by inserting their beaks into stems, leaves, or roots, and sucking the plant juices. Usually they gather in large colonies.

The life cycle of aphids is complex and varies in different species. In a typical life cycle, several generations of wingless females, which reproduce asexually (see parthenogenesisparthenogenesis
[Gr.,=virgin birth], in biology, a form of reproduction in which the ovum develops into a new individual without fertilization. Natural parthenogenesis has been observed in many lower animals (it is characteristic of the rotifers), especially insects, e.g.
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) and bear live offspring, are followed by a generation of winged females, which bears a sexually reproducing, egg-laying generation of males and females. Mating usually occurs in fall, and the eggs are laid in crevices of the twigs of the host plant; the first generation of wingless females hatches in spring. Different host plants and different parts of the plant may be used at different stages of the life cycle.

Some aphids (e.g., the woolly apple aphid) secrete long strands of waxy material from wax glands, forming a conspicuous woolly coating for their colonies. Gall-making aphids live in gallsgall,
abnormal growth, or hypertrophy, of plant tissue produced by chemical or mechanical (e.g., the rubbing together of two branches) irritants or hormones. Chemical irritants are released by parasitic fungi, bacteria, nematode worms, gall insects, and mites.
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, or swellings of plant tissue, formed by the plant as a reaction to substances secreted by the insects; galls of different aphid species are easily identified (e.g., the cockscomb gall of elm leaves). One group of aphids lives only on conifers (e.g., the eastern spruce gall aphid).

Ant Cows

Many kinds of aphid secrete a sweet substance called honeydew, prized as food by ants, flies, and bees. This substance consists of partially digested, highly concentrated plant sap and other wastes, and is excreted from the anus, often in copious amounts. Certain aphid species have a symbiotic relationship with various species of ants that resembles the relationship of domestic cattle to humans; hence the name "ant cows" for aphids. The ants tend the aphids, transporting them to their food plants at the appropriate stages of the aphids' life cycle and sheltering the aphid eggs in their nests during the winter. The aphids, in turn, provide honeydew for the ants.

Damage to Plants

The damage done by aphids is due to a number of causes, including loss of sap, clogging of leaf surfaces with honeydew, and growth of molds and fungi on the honeydew. Leaf curl, a common symptom of aphid infestation, occurs when a colony attacks the underside of a leaf, causing its desiccation. The downward curl provides protection for the colony, but the leaf becomes useless to the plant. Some species also transmit viral diseases of plants. Among the aphids causing serious damage to food crops are the grain, cabbage, cornroot, apple, woolly apple, and hickory aphids and the alder and beech tree blights. The phylloxeraphylloxera
, small, sap-eating, greenish insect of the genus Phylloxera, closely related to the aphid. Phylloxeras feed on leaves and roots, and many species produce galls on deciduous trees.
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, notorious for its damage to vineyards, is closely related to the aphids.

Many larger insects that feed on aphids, such as ladybird beetles and lacewings, are used as biological controls of aphid infestations. Fungal infection and damp weather also help limit the number of aphids.

Classification

Aphids are classified in several families of the phylum ArthropodaArthropoda
[Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, spiders, scorpions, and the extinct trilobites.
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, class Insecta, order Homoptera.

aphid

[ā·fəd]
(invertebrate zoology)
The common name applied to the soft-bodied insects of the family Aphididae; they are phytophagous plant pests and vectors for plant viruses and fungal parasites.

aphid

any of the small homopterous insects of the family Aphididae, which feed by sucking the juices from plants
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The aphid mortality caused by allelopathic water extracts was presented in the form of bar graphs fitted with vertical standard error bars.
Future studies should investigate how aphids and parasitoids interact with natural and managed ecosystems at multiple spatial and temporal scales.
The larvae hatched after 7-10 days, and the total larval stage lasted 21-22 days, during which an average of 90 aphids was consumed by each larva.
Both Juniperus phoenicea and Rosmarinus officinalis resulted in mortalities to aphids that exceeded 50 % but they showed no significant differences with the other oils particularly after 48 hrs of their spray at the highest concentration.
Results revealed that members of subfamily Syrphinae were specialized predator at this stage and found to be voracious feeder on aphids.
Figure 1 shows that, out of a total of 300 individuals of the species Aphis nasturtii, the smallest length of the body established for aphids captured in West Zone of Romania was 1.
Following collection and preservation techniques described by (Martin 1983; Blackman and Eastop, 1994) aphids were collected from vegetation using a camel hair-brush, jarring the foliage on a white paper sheet and transferring the specimens into the vials containing 70% alcohol.
You can also place sacrificial plants in the garden near your precious ones to lure aphids away.
With any pest or disease problem, vigilance is very important - especially with aphids.