Gardening

Processionary

Processionary



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Processionary: Generalities




The processionary is a moth insect of the thaumatopeid family. It is a dangerous parasite especially for pines (Pinus Nigra and Pinus Silvestris) and deciduous oaks (Quercus robur and Quercus peduncolata) although it may occasionally affect the larches, cedars, hazels, chestnuts, beeches, hornbeams and birches; the insect's favorite plants are, in any case, young (2-5 years).
The adult is a butterfly with wings 3-4 cm wide, of gray color with brown streaks. The female is, in general, slightly larger than the male. Their life is very short, usually it does not last more than one / two days.
The insect, once it reaches maturity, comes out of the ground, usually during the month of July. The females are the first to climb on tall trees, where they are then fertilized by the male. At this point, the moth flies in search of the most suitable plant for laying eggs.
As for the pine processionary, the eggs are laid around a pair of needles. After an incubation of 30/40 days (towards the middle or end of August), the larvae are born. The baby girls skeletonize the needles and then move along the plant, forming, from time to time, temporary nests. In October they form a silky nest in which they will spend the whole winter. In spring they resume activity and, around the end of May, they descend towards the ground. They are buried up to a depth of 5/20 cm, where they weave a cocoon. After a more or less long period of diapause, the nymphosis takes place and the cycle begins again.
The oak processionary appears in July. Fertilization occurs almost immediately. The eggs are laid in slabs on the smooth surface of the twigs. The eggs pass the winter to then hatch when the buds open, between the end of April and the beginning of May. Once born, the larvae move on the branches and, having reached the bifurcation of the branches or throne, they form a nest. At the beginning of July, the larvae fall into the nest.
The larvae live gregariously, remaining in contact with each other with silk threads that they weave and of which they are used to mark the needles. They are active already in the first vegetative phases and it is from this moment on that they begin to devour the leaves and the needles of the plants on which they have settled. Following the attack the plant suffers a strong weakening, which leads to a delay in its development. The most obvious sign of the presence of the processionary is however the loss of needles and leaves, which in the most serious cases can result in total defoliation. Human problems can result from contact with the stinging hairs of the larvae, which can cause skin irritation, fever and redness of the eyes.
Among the most used fighting methods we find the removal and destruction by fire of the nests, as well as the use of preparations based on Bacillus thuringiensis, or of chemical products such as diflubenzuron and carbaril.
Also of note is the fact that the processionary is fought in nature by a series of predators and parasites, which live at its expense during the various evolutionary stages.