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) even if it can, occasionally, also affect larches, cedars, hazelnuts, chestnuts, beeches, hornbeam and birch trees; the insect's favorite plants are, in any case, young (2-5 years).
The adult is a butterfly with 3-4 cm wide wings, gray in color with brown streaks. The female is usually slightly larger than the male. Their life is very short, usually lasting no more than one / two days.
Once the insect has reached the stage of maturity, it comes out of the ground, usually during the month of July. Females are the first to climb tall trees, where they are then fertilized by the male. At this point, the moth flies in search of the most suitable plant for spawning.
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 the end of August), the larvae are born. The newborns skeletonize the needles and then move along the plant, forming, from time to time, temporary nests. In October they form a silky nest where they will spend the whole winter. In the spring they resume their 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 moth makes its appearance in July. Fertilization occurs almost immediately. The eggs are laid in pad-shaped plates on the smooth surface of the twigs. The eggs survive the winter and 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, coming near the bifurcation of the branches or the throne, form a nest. In early July, the larvae crystallize inside the nest.
The larvae live gregariously, remaining in contact with each other with silky threads that they weave and which they use to mark the needles. They are active already in the early vegetative stages and it is from this moment on that they begin to devour the leaves and needles of the plants on which they have settled. Following the attack, the plant undergoes a strong weakening, which entails a delay in its development. The most evident 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. Problems for humans can arise from contact with the stinging hairs of the larvae, which can cause skin irritation, fever and redness of the eyes.
Among the most used methods of fighting we find the removal and destruction of nests with fire, as well as the use of preparations based on Bacillus thuringiensis, or chemicals such as diflubenzuron and carbaril.
It should also be noted that the processionary moth is fought in nature by a series of predators and parasites, which live at its expense during the different evolutionary stages.