Amitus hesperidum
Encyclopedia
Amitus hesperidum is a tiny parasitic wasp
. It is a parasitoid
of the citrus blackfly
, Aleurocanthus woglumi, an important pest of citrus
trees. It is a native of Asia but has been introduced to many other parts of the world as a means of controlling
the citrus blackfly.
and abdomen
less than one millimetre long. The antennae have ten segments and in the female, the last three are widened making the antennae
club-shaped. The males have longer antennae of a uniform width, curved, with all segments longer than they are wide and covered with short bristly hairs. Both antennae and legs are straw coloured and the hind tarsi
have five segments. The wings are shiny and translucent.
. The egg
s are laid in any of the larva
l stages of the citrus blackfly but the first instar
is preferred. A female larval host results in the production of two or three adult wasps but parasitism of a male pupa
produces only one. Parasitism of a female pupa may result in either a male or a female adult wasp. The time taken for an egg to develop into an adult varies from 45 to 60 days under laboratory conditions at a temperature of 27°C. The wasps live for three to five days in the field during which time the female can produce up to sixty eggs. This wasp is well synchronized with its host and is capable of controlling dense populations of the pest. However it is not good at searching out scattered individuals and its numbers decrease sharply as its host population is controlled. Other hosts which are also parasitised include Aleurocanthus citriperdus and Aleurocanthus spiniferus.
is another citrus blackfly parasitoid that has been used alongside Amitus hesperidum to control the pest in both states. E. perplexa multiplies more slowly but is better at scouting for outlying blackflies and is more effective when populations of potential hosts are lower.
In Hawaii, both species were introduced in 1999 after the citrus blackfly was discovered there for the first time the previous year. They rapidly became established and were soon controlling the pest on the island of Oahu. Later releases on other islands in the group have also been an effective means of reducing infestations.
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
. It is a parasitoid
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
of the citrus blackfly
Aleurocanthus woglumi
Aleurocanthus woglumi is a species of whitefly in the family Aleyrodidae. It is a pest of citrus crops and is commonly known as the citrus blackfly because of its slate blue colour. It originated in Asia but has spread to other parts of the world...
, Aleurocanthus woglumi, an important pest of citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
trees. It is a native of Asia but has been introduced to many other parts of the world as a means of controlling
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
the citrus blackfly.
Distribution
This wasp is a native of India, Sri Lanka, Pakistan, Hong Kong, Szechuen, Java and Malaysia. It has been introduced to Guam, Venezuela, Mexico and the United States (Texas, Florida and Hawaii) for the purpose of controlling the citrus blackfly.Description
Both males and females have a shiny black thoraxThorax (insect anatomy)
The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....
and abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
less than one millimetre long. The antennae have ten segments and in the female, the last three are widened making the 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....
club-shaped. The males have longer antennae of a uniform width, curved, with all segments longer than they are wide and covered with short bristly hairs. Both antennae and legs are straw coloured and the hind tarsi
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
have five segments. The wings are shiny and translucent.
Life cycle
Several offspring may develop inside a single host but this species is not polyembryonicPolyembryony
Polyembryony is the phenomenon of two or more embryos developing from a single fertilized egg . Polyembryony occurs regularly in many plants and animals. The nine banded armadillo, for instance, usually gives birth to four identical young...
. The egg
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...
s are laid in any of 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...
l stages of the citrus blackfly but the first 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 preferred. A female larval host results in the production of two or three adult wasps but parasitism of a male pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
produces only one. Parasitism of a female pupa may result in either a male or a female adult wasp. The time taken for an egg to develop into an adult varies from 45 to 60 days under laboratory conditions at a temperature of 27°C. The wasps live for three to five days in the field during which time the female can produce up to sixty eggs. This wasp is well synchronized with its host and is capable of controlling dense populations of the pest. However it is not good at searching out scattered individuals and its numbers decrease sharply as its host population is controlled. Other hosts which are also parasitised include Aleurocanthus citriperdus and Aleurocanthus spiniferus.
Use in biological control
Amitus hesperidum was introduced into Mexico in the 1960s in an attempt to control the numbers of citrus blackfly there. Suppression of the pest was so successful that introductions were also made into Florida in 1978 and into Texas in 1983. Encarsia perplexaEncarsia perplexa
Encarsia perplexa is a tiny parasitic wasp, a parasitoid of the citrus blackfly, Aleurocanthus woglumi, which is a global pest of citrus trees. It was originally misidentified as Encarsia opulenta, but was recorded as a new species in 1998...
is another citrus blackfly parasitoid that has been used alongside Amitus hesperidum to control the pest in both states. E. perplexa multiplies more slowly but is better at scouting for outlying blackflies and is more effective when populations of potential hosts are lower.
In Hawaii, both species were introduced in 1999 after the citrus blackfly was discovered there for the first time the previous year. They rapidly became established and were soon controlling the pest on the island of Oahu. Later releases on other islands in the group have also been an effective means of reducing infestations.