Myzus Persicae

''Myzus persicae'', known as the green peach aphid, greenfly, or the peach-potato aphid, is a small green aphid belonging to the order Hemiptera. It is the most significant aphid pest of peach trees, causing decreased growth, shrivelling of the leaves and the death of various tissues. It also acts as a vector for the transport of plant viruses such as cucumber mosaic virus (CMV), potato virus Y (PVY) and tobacco etch virus (TEV). Potato virus Y and potato leafroll virus can be passed to members of the nightshade/potato family (Solanaceae), and various mosaic viruses to many other food crops.

Originally described by Swiss entomologist Johann Heinrich Sulzer in 1776, its specific name is derived from the Latin genitive ''persicae,'' "of the peach". The syntype specimen of this species is located in the Illinois Natural History Survey Insect Collection.

Life cycle

Life cycle of the green peach aphid varies depending on temperature. A fully completed generation takes approximately 10 to 12 days with over 20 annual generations reported in mild climates. Aphids overwinter on ''Prunus'' plants and once plants break their dormancy, the eggs hatch and nymphs feed on the flowers, young foliage and stems of the plant. After several generations, winged individuals deposit nymphs on summer hosts. In cold climates, adults will return to ''Prunus'' plants in the autumn, where mating occurs and eggs are then deposited. All generations except the autumn generation culminating in egg production are parthenogenetic (non-sexual). Females give birth to offspring 6–17 days after birth, with an average age of 10.8 days at first birth. Length of reproduction varies but averages 14.8 days. Average length of life is approximately 23 days, without the presence of predators. The worst damage on plants is in the early summertime for the aphid breeding peak, because winged dispersants from ''Prunus'' spp. where the egg of overwintering aphid stage deposit nymphs on summer hosts migrating to tobacco, potatoes and cruciferous vegetables to be harmful continuously after a few generations.

Distribution

The green peach aphid is found worldwide but is likely of Asian origin, much like its primary host plant, '' Prunus persica''. This species does not prefer areas of extreme temperature or humidity. These particular aphids can be transported great distances by wind and storms. However, previous studies suggest that long-distance migration is uncommon in ''M. persicae'', thus the spread of diverse genotypes over distance geographic regions is likely a result of anthropogenic influence.

These insects are not only a pest towards field crops, but tend to invade greenhouses as well. Thus, when young plants are infested by these aphids in greenhouses and are then transported to other locations, they are widely distributed. This explains their great distribution lengths, as well as their ability of high survival in areas with inclement weather and their ability to be readily transported on plant material.

This species has been introduced into 16 countries or islands (see global distribution figure). It is found in terrestrial habitats, and as mentioned previously, its native range is likely of Asia-Temperate origin. Its European Nature Information System (EUNIS) habitat is classified as lines of trees, small anthropogenic woodlands, recently felled woodland, early-stage woodland and coppice.

Description

Morphology

Eggs of this species measure about long and wide, and are elliptical in shape. The eggs are initially yellow or green but turn black. The nymphs are initially green, but soon turn yellowish and resemble the viviparous adults. Nymphs that give rise to winged females may be pinkish.

Adult winged aphids have a black head and thorax, and a yellowish green abdomen with a large dark dorsal patch. They measure approximately in length. The wingless adult aphids are yellowish or greenish in colour, with the possibility of medial and lateral green strips being present. Their cornicles match their body colour, are moderately long and unevenly swollen along their length. The appendages are pale. The adult green peach aphid can be yellowish-green, red, or brown in colour because of morphological differences influenced primarily by the host plants, nutrition, and temperature.

Distinguishing morphological traits from this group include their convergent inner faces of the antennal tubercles in dorsal view, and the slightly clavate siphunculi which are dark-tipped and approximately as long as the terminal process of the antenna.

Reproduction

The green peach aphid normally reproduces through cyclical parthenogenesis, where there are several generations of apomictic parthenogenesis followed by a single sexual generation. Mating takes palace on the primary host, where eggs are laid and undergo diapause over winter, and when spring comes, the parthenogenetic females hatch in spring and their descendants disperse to secondary host plants where they produce numerous parthenogenetic (asexual) generations. This species accepts secondary host plants across 40 different families, many of which are important crops economically. Due to decreasing day lengths and temperature in autumn, sexual morphs of this species are formed. Some genotypes have lost the ability to sexually reproduce and thus reproduce through parthenogenesis on secondary hosts throughout the year. These types are known as obligate parthenogens.

Habitat

Host plants of this species during overwintering include tree hosts from the genus ''Prunus'', particularly peach, peach hybrids and apricot and plum trees. During the summer, aphids abandon woody tree hosts for herbaceous hosts which include vegetable crops in the following families: Solanaceae, Chenopodiaceae, Compositae, Brassicaceae, and Cucurbitaceae. Crops differ in their susceptibility to green peach aphid, but it is actively growing plants, or the youngest plant tissue, that most often harbors large aphid populations. Once the aphids have established colonies, some redistribution may occur throughout the progress of the infestation, and before overcrowding obscures preferences.

Predation

Natural enemies of the green peach aphid include lady beetles, soldier beetles, hoverflies, acalyptrate flies, gall midges, flower bugs, leaf bugs, damsel bugs, stink bugs, lacewings, parasitic wasps, mites, fungal pathogens as well as other aphids. Many of the natural enemies of the green peach aphid are limited to them due to their certain chosen habitat or by unsuitability of other aphid species as food. Most enemies of the peach green aphid are general predators that move freely in nearby habitats. Many of their enemies are influenced by the host plant, crop cultural practices and environmental conditions.

Food habits

Some groups of aphids feed predominantly in the parenchymal tissue of plants while most aphid species feed on the phloem sap. The green peach aphid ingests sugary fluids via a membrane. While feeding on a plant long term, ''Myzus persicae'' can uptake chloroplast DNA, even though the chloroplasts themselves are uninjured. Process of exudation from ''M. persicae'' stylets is exhibited to ingest phloem sap on plants with assisted pressure within the plants. On artificial diets, this species is also able to ingest food from a source with negligible pressure and can even produce honeydew on certain artificial diets.

Genetics

The green peach aphid has 2n=12 chromosomes normally, but there is a form of a chromosomal translation seen worldwide that is relatively common. ''M. persicae'' is a highly variable species; strains, races and biotype