Cabbage butterfly
The cabbage butterfly is a wide spread pest of vegetable crops (particularly the family Сruciferae). It also populates some species of wild plants. The insect is spread on the territory of former Soviet Union everywhere. This species is distinguished with the high activity of life reactions.
Biology. Life cycle
The fore-wings are mealy-white with a dark dusting at the base. The wing-spread of the butterfly is 55–60 mm. The female is bigger than the male. The top of wings has a deep-black sickle-shaped border, which reaches the middle of an external edge. Besides, there are two spherical spots on each wing. The males have 2 spots only on the underside of the fore-wings. The hind-wings have a black smear on a frontal edge. From below they are grey-yellow with a thick black dusting. An average fertility is 150 eggs. The maximum is 300. The eggs are lemon-yellow. They are laid in clumps on the underside of a leaf. Their development span is 4–16 days. Having just been born the caterpillar is ochreous. The adult caterpillar is yellowish-green with yellow strips at the sides of its body and a light strip along a back. The adult caterpillars develop during 13–38 days dependently on temperature reaching 50–60 mm in length in the last 5th age. The pupa is green-yellow with black spots on the back and at the sides. Pupa stage takes 8–30 days. The pupa overwinters in diapause near the places of the growing of food plants on the trunks and the branches of trees, fences and in various lees.
Mode of life
The insect reproduces 2–5 generations dependently on areal. The flight of butterflies proceeds from May to August or from the end of March till the middle of October. Before the laying of the eggs the butterfly needs in additional nutrition with flower nectar. The caterpillars are able to migrate for food search colonizing the neighbouring plants. If the summer is cold and rainy the caterpillars of summer generations are able to enter diapause till the next spring. Unfavorable for development of the cabbage butterfly is the combination of high temperature (higher 26°C), low air humidity (to 60%) and also low temperatures in winter (lower -20°C of frost). All these conditions limit spreading of the pest.
Symptoms of injuries
The caterpillars of young ages keep together scrapping the flesh off a leaf underside. From the 3rd age the caterpillars live separately. They eat away holes in the leaves of cabbage heads, contaminating them with excrements. The caterpillars of elder ages roughly eat leaves round leaving the thick veins only.
