Why cabbage leaves roll, become colorless, and a head of cabbage not braided?
It is result of activity of a cabbage plant louse. It damages not only cabbage, but also:
· garden radish,
Eggs of a plant louse (is brilliant-black, length to 0.5mm) pass winter on biennial cruciferous weeds and stumps. In the early spring larvae leave eggs, turning to wingless females, which without fertilization gives birth larvae. Soon there are also the winged females flying on other plants. Each female is capable give birth more than 40 larvae. For a summer happens more than 15 generations of the vermin (everyone develops in 10 - 14 days). Sometimes the damaged leaves turn pink; seeds are not formed.
The sexual generation (females and males) appears in September-October. After fertilization the female postpones two-four eggs.
Reduce number of the wrecker:
· larvae of flower flies
· golden-eyed flies,
and other insects and predators. In struggle against a plant louse as precautionary action it is necessary to destroy weeds.