INSECT COLUMN
Potato aphid (Hemiptera: Aphididae) Potato aphid is native to North America. It has spread throughout the world to Central and South America, Europe, Asia and Africa. It is a highly polyphagous pests, feeding on over 200 species from 20 plant families. Host plants include eggplant, sweet potato, roses, lettuce, maize, sugar beet and many other cultivated plants. However, it prefers plants from Solanaceae family, especially potato and tomato.
Figure 1: Winged potato aphid. Source: https://www.cabi.org/isc/datasheet/32154#toPictures
Nozibusiso Maphumulo IPM-PROGRAMME, NORTH-WEST UNIVERSITY, POTCHEFSTROOM
Potato aphid classification: Class: Insecta (insects) Order: Hemiptera (true bugs) Family: Aphididae Genus: Macrosiphum Species: euphorbiae
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he adult potato aphid is a relatively large, slender aphid with an elongated pear-shaped body. Its body colour varies depending on the food source, it is either a shade of yellowish-green or pinkish-red. It is often shiny with distinctly reddish eyes. The aphid comprises of both winged and wingless forms. The wingless forms are 3 to 4 mm long with a dark longitudinal stripe running along the dorsal surface. In green individuals, this stripe is dark green, while in pink individuals it is dark red. This longitudinal stripe is a specific characteristic of the potato aphid and is also visible in the nymphs. Nymphs are paler than adults with a light dusting of whitish-grey wax. Aphids have a complex life cycle. The life cycle of the potato aphid is similar to that of the peach potato aphid. They reproduce both sexually and asexually. However, sexual reproduction occurs in North America where it originates. When reproduction is sexual, aphids lay eggs that overwinter. Young aphids are born as developed nymphs when reproduction is asexual. They immediately start feeding on plant sap and grow quickly. They moult four times before becoming adults (four nymphal stages). Infestations on potatoes occur from mid-June through July. Plants belonging to the rose family become alternate hosts to the potato aphid during autumn and spring. A wide variety of weeds are hosts in summer, including field crops and vegetable crops. In potatoes, potato aphid first feed on young, growing tips and spread downwards into older leaves. Both nymphs and adults cause damage by sucking sap from the foliage. Damage symptoms include leaf deformity and dieback. Potato aphid can reduce foliage when populations are high. They also spread viruses such as potato virus Y (PVY) and potato leafroll virus (PLRV) to seed and table stock
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Figure 2: The wingless stage of potato aphid on tomato. Source: https://www.cabi.org/isc/datasheet/32154#toPictures
Figure 3: Infestation on lettuce buds of different life stages of potato Source: https://www.cabi.org/isc/datasheet/32154#toPictures aphid.
potatoes which can result in the reduction of both yields and quality. Potato aphid can be managed by scouting the fields in late June. Fully grown compound leaves should be examined from top, middle and bottom of the canopy. Insecticide should be applied when there is an average of 5 aphids per leaf. The economic threshold is when 50% of the plants are infested or when one winged aphid is present in the field. Enquiries: mashimanenozi03@gmail.com
VEGETABLES & FRUIT | JANUARY • FEBRUARY 2022
