Cotton aphid

This is a cosmopolitan pest species, which has high reproductive ability. It affects more than 250 species of plants from 25 families. The cotton aphid develops on vegetable and melon crops. In glass-covered ground it causes a large damage to cucumbers. This aphid is an agent of dangerous virus plant diseases.

Biology. Life cycle

The adult aphids can be winged and wingless. The apterous (a wingless female) has a pear-shaped form. It is from 1.0 to 2.1 mm in length and from 0.9 to 1.5 mm in width. Its body is mat. The coloration of the body can vary from yellow to dark-green, almost black. The forehead is a little prominent. The antenna hillocks are absent. The proboscis (sucker) is light at the base, two its last segments are dark. The eyes are brownish-dark. The cornicules (tubules) are cylindrical, slightly widened at the base, black-colored. The spiracles (breathing openings) are oval-shaped. The caudicle (tail) colored like the body, finger-shaped. It has three pairs of lateral hairs.

The head, the thorax, the main segment, the cornicles, the ends of tibiae (shanks) and the tarsi (paws) of the alate (a winged female) are black. The eyes are brown-vinous. The tops of hind femurs are black- brown. The coxae of all the tarsi are black-brown. The caudicle is dark-brown, finger-shaped. It protrudes a little beyond the cornicles and has 3 pairs of lateral hairs. The abdomen is green and darker on a top. There are rectangular black-brown spots on each side of the abdomen.

Mode of life

The aphid produces several generations. The first generation consists of wingless individuals. The winged female-settlers arise later. The female multiplies by virgin way bearing about 50 larvae without egg stage. The development from a larva to an imago lasts from 6 to 11 days. The optimal conditions for pest development are a temperature of 23–25°C and a relative air humidity of 80–85%. This aphid is a species of not distinct-stage (incomplete metamorphosis). The adult wingless females and sometimes the larvae overwinter on the plants in greenhouses or subsidiary rooms.

Symptoms of injures

The pest injures the above-ground parts of plants causing their shrinkage, twisting and perishing. Under the considerable colonization of a leaf apparatus by the pest it is possible the formation of a whitish coating. It is formed by saprophyte fungi. The coating complicates the assimilation, the respiration and the perspiration of plants. Under the high density of pest colonies affected plants weaken and then perish.