The green peach aphid (Myzus persicae subsp. persicae) is an important insect pest in sweet pepper, tomato, cucumber and many other greenhouse crops. The aphid may originate from Asia, where its winter-hardy host plant, the peach tree, is native, however it is now a pest with a world-wide distribution. The green peach aphid (Myzus persicae subsp. persicae) is a particularly polyphagous aphid with summer host plants from more than 40 different families.
Life cycle and appearance of green peach aphid
Aphids have a complex life cycle, with both winged and wingless forms of adults and a great variety in colour. When reproduction is asexual, the young aphids are born as developed nymphs. They immediately start to feed on plant sap and grow rapidly. When reproduction is sexual, the aphids lay eggs that overwinter. In greenhouses reproduction also takes place by parthenogenesis, with unfertilized viviparous females continuing to produce new generations of females. Aphids moult four times before reaching adulthood. With each moult they shed white skin, betraying their presence in the crop.
Wingless green peach aphids (Myzus persicae subsp. persicae) may be green, white-green, light yellow-green, grey-green, pink or red in colour. They appear matt, never glossy. Winged individuals have a brown-black head and thorax and a yellow-green to green or even reddish abdomen. They have a dark brown spot on the abdomen and several transverse black bands across the body. Nymphs that develop into winged adults are often pink or red in colour.
Of all the aphids, the peach potato aphid (Myzus persicae subsp. persicae) is the most important vector of viral diseases. It can transmit at least 100 different viruses and is thus rightfully feared by many growers.
Nymphs and adults extract nutrients from the plant and disturb the balance of growth hormones. As a result, the plant’s growth is retarded giving rise to deformed leaves or, if the infestation occurs early enough in the season, the death of young plants. Retarded growth and defoliation reduce yield,
Plant sap is rich in sugars, but has a low protein content. Aphids therefore need to extract large quantities of sap to get sufficient protein. The excess sugar is secreted in the form of honeydew, making the crop and its fruit sticky. Black fungal moulds (Cladosporium spp.) grow on this honeydew, contaminating fruit and ornamental crops and rendering them unsuitable for market. At the same time, photosynthesis in the leaves is reduced, affecting production.
The aphid’s saliva can induce strong “allergic” reactions such as malformations of the growing tips.