The pine processionary: damage, dangers and remedies

The pine processionary: damage, dangers and remedies

The pine processionary (Thaumetopoea pityocampa) is a particularly unwelcome harmful insect, as in addition to damaging the host plants, it can cause skin and allergic reactions to people and even pets.

This is why many will have already heard of it, although not everyone is able to recognize larvae and adults immediately. It is useful to make information on this moth for avoid unnecessary alarmism but also to learn to distinguish this species from other harmless caterpillars or butterflies, avoiding the danger of getting stung.

When the processionary moth is present on pine or other conifer plants, it becomes important to intervene in time, also to protect dogs and cats, but we can avoid doing it with conventional insecticides and instead opt for more eco-friendly measures. We will find out below how to identify the processionary and its nests is how to solve the possible presence of this insect in the garden with organic methods.

Recognize the insect

The pine processionary is an insect belonging to theorder of the Lepidoptera, that is, a butterfly. The name "processionary" is due to the behavior of the larvae, which move one in line to the other as if they were doing a procession.

The species is very adaptable to environmental conditions, so much so that we can find it both in maritime and mountain areas, and unfortunately it must also be specified that it is currently expanding its range also due to the climatic changes in progress.

Affects Conifers and in particular the black pine, the Scots pine, the maritime pine and sometimes some species of cedar. We find the larvae on these host plants from autumn to the following spring, when once mature they line up along the trunks and bury themselves, to transform into chrysalises reddish-brown in color.

The chrysalis then transforms into the adult form, the pine processionary butterfly it has gray front wings crossed by 2 or 3 darker transversal streaks and white rear wings with a black spot near the lower margin. The wingspan is 3.5-5 cm. The adult form appears in summer, after which the mating takes place following which each female lays all the eggs in a sort of sleeve built around the needles or sometimes around thin twigs.

The larvae they have gregarious behavior, live in dense colonies and move around forming typical long lines, in which each individual is in contact with what precedes him. The larvae go through 5 stages of maturation and at the end of these have a black head and a grayish body on the dorsal part, with a tuft of stinging red hairs, and the lateral hairs whitish in color.

The insect performs only one generation a year.

Nests of processionary moth

In winter it is very easy to spot the processionary on plants thanks to the presence of large whitish clusters especially in the sunniest parts of the foliage of the affected conifers. These are the nests that are used by the insect for wintering.

Damage of the processionary

The larvae of the processionary moth feed on the needles of conifers and can cause serious damage to the affected plants, even causing the loss of all the needles.

Repeated infestations over the years compromise the growth of pine or other infested conifers, and can weaken the plants, making them more susceptible to attack by other secondary parasites.

But what worries most is the direct nuisance it causes to people and animals, for example these moths pose a danger to dogs. The hairs of the processionary larvae are very stinging on the skin and can be easily carried by the wind. Also for this reason constant defense is practiced in public environments.

Prevention and precautions

Before intervening against processionary larvae or nests, it is good to be aware of the possible consequences, given the stinging power of the hairs of the larvae.

The precautions that we can take for our health and avoid being bothered by the insect consist above all of these measures:

  • Avoid standing under the plants that we recognize attacked and possibly not even get close;
  • Do not try to destroy the nests on your own with improvised means because the result could be counterproductive, namely the shedding of stinging hairs around instead of eliminating the insect;
  • Thoroughly wash the vegetables or fruit collected near the plants affected by the processionary moth;

Furthermore, although in spring we would be tempted to kill all the larvae that we notice coming down from the trunk all in a row, it is advisable to do so only if you have the adequate means and all the personal protection, and if in doubt, call an expert gardening company.

Pheromone traps

In the second half of June they can be installed sex pheromone traps to capture adult males. They must be fixed on a branch in a medium-high position and preferably on the southwest side of the canopy.

This is a great way to identify the presence of processionary and also to reduce its population. The traps hit the adult insect, but the result of the capture is to avoid a large number of future larvae.

Biological insecticides

The beginning of autumn, between mid-September and early October, it is the right moment to intervene with a treatment based on a product with a low environmental impact, for example Bacillus thuringiensis kurstaki, a selective microbiological insecticide on the larvae of harmful moths. In fact, in autumn the larvae are young and still free of stinging hairs, so there is a low personal risk. As always, treatments must be performed by first reading the instructions on the label and respecting the recommended doses and methods of use and wearing Personal Protective Equipment.

Pines are usually tall trees, therefore performing a treatment could be uncomfortable or dangerous. It is recommended to proceed in extreme safety or to have the treatment carried out by gardeners with all the necessary equipment.

Later, as the larvae grow and differentiate the hairs, they certainly become more annoying, and although the treatments with Bacillus thuringiensis are still effective, even more scrupulous attention must be paid in carrying them out.

Furthermore, in the summer, the old nests can be seen on the plants, which still have a stinging effect and therefore must be removed by expert operators.


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