The cabbage caterpillar (Pieris brassicae) can devour a swede, celery, brussels sprouts, etc. in a few days, although the truth is that its favourite delicacy is cabbage (Brassica oleracea). In April, not only these caterpillars, which you can fight with biological pyrethroids, are a scourge in the garden, but also all these pests that have to be controlled.
White worms (Melolontha melolontha) are larvae of beetles. They are not too dangerous in Spain, where the most abundant species is the big-headed worm (Anoxia villosa). They have a long life span: 3 or 4 years before they become adults. The worms live in the soil and eat the roots of many horticultural species (polyphagous pest). Their fight involves keeping the soil dug and soft, and extracting any individuals that are left uncovered by hand.
Nematodes, or nematodes, are round worms (nematelmintos) that make up a multitude of genera, species and varieties. They live in the soil and are microscopic. Their presence and infestation is known from damage caused to plants, which almost always consists of root damage (deformations). It can only be controlled by meticulous cleaning of tools so as not to transmit it from one crop to another, and not to repeat cultivation in invaded plots.
Otiorhynchus sulcatus is one of the pests in effervescence in Spain. This Coleoptera from the Curculionidae family, as an adult is really harmful for a great number of ornamental plants, as well as for many horticultural plants. It feeds on both leaves and roots, and its presence is detectable by the circular and symmetrical bites on the leaf edges. Its treatment involves the manual removal of the beetles, and treatment with anti-insect products from the soil.
The white fly (Trialeurodes vaporariorum and Aleurothrixus floccosus) is a persistent pest belonging to the family Aleiródidos. It is very polyphagous, but is particularly virulent with all species of citrus grown in Spain and many ornamental species. It is similar to mealybugs in the larval stage. The treatment of choice is based on systemic insecticides, which the plant assimilates, with the active ingredient dimethoate.