Updated:
Keep
The Romans discouraged and prohibited the addition of pine processionary caterpillars in the worthless concoctions that were made to break magical spells. Logical, since contact with the caterpillar is very dangerous.
At the end of winter, the pine processionary caterpillars (Thaumetopoea pityocampa) begin a characteristic pilgrimage, like a procession, from the high areas of the trees. The proximity of spring raises the environmental temperature and encourages these insects to descend, ordered and in a row, looking for a suitable site to build a gallery and pupate on the ground, in order to transform into moths.
It may seem that during this journey the caterpillars are defenseless, but this is not the case. When one of these caterpillars feels threatened, it is capable of launching large amounts of stinging hair.
The detached hairs can float in the air and cause irritation in the ears, nose and throat or trigger intense allergic reactions due to IgE-mediated hypersensitivity.
The caterpillar’s stinging hairs contain a heat labile toxin responsible for causing allergic symptoms. The toxin is known as Thaumatopin and is a protein made up of two subunits, Tha p1 and Tha p2. In extreme cases, contact with this toxin can even cause blinda o la muertewhich represents a serious threat to human and animal health.
Urticaria and dermatitis
The cyclical pilgrimage of the caterpillars from the tree canopy to the ground carries significant risks. In fact, this animal is the most frequent cause of adverse reactions to Lepidoptera in Spain, and one of the most common in Europe.
After the second molt, the caterpillar acquires its definitive appearance and reddish dorsal stinging setae appear, placed in pairs, on each segment of the body. Contact with the caterpillar induces different skin pathologies that are usually manifested, through a toxic-irritative mechanism, such as urticaria and dermatitis located in the exposed areas.
To add insult to injury, it turns out that hairs can remain harmful for up to five years. This poses a major health hazard in areas of high caterpillar proliferation and hampers silvicultural operations and forest grazing.
Pine processionary moth larvae build apparent silky nests in the canopy of conifers, especially pines and cedars, allowing the caterpillars to feed on mature needles in the winter. During the months in which the caterpillars descend from the pine trees, if we walk near the trees it is convenient to carry suitable clothing that covers any surface exposed skin. In infested pine forests it is preferable, especially on windy days, avoid walking, collecting pineapples and firewood or stirring the soil.
It is always necessary to avoid handling the nests, touching the caterpillars, stepping on them or trying to sweep them because they can project thousands of stinging hairs. Individual nests may contain many hundreds or even thousands of larvae, and a single tree can host between 10,000 and 100,000 caterpillars.
Therefore, it is advisable that citizens notify the competent authorities of the presence of processionary caterpillars in public places.
If we come into contact with the caterpillars and the symptoms begin, as far as possible we must prevent scratching. Scratching increases the symptomatology, by encouraging the caterpillar’s spicules to stick or rub more forcefully once morest the skin or mucous membranes. This measure is also valid for our pets.
forest damage
The life cycle of the caterpillar makes the insect an important defoliator in Mediterranean coniferous forests and a forest pest in the countries of the Mediterranean basin. In recent years, the pine processionary has been the second cause of destruction of Spanish pine forests, only behind forest fires. Unfortunately, global warming has favored the spread of the Lepidoptera to the north of the European continent.
The increasing abundance of processionary moths has spurred the rise of various control measures to reduce infestation levels, including chemical pesticide and biocide applications, burning of larval nests, and physical removal. However, to date, the success of these measures has been limited. Furthermore, some of them are likely to have had substantial effects on non-target or even endangered species.
For this reason, there is a marked tendency to use biological control methods that respect the environment and that are balanced in the effectiveness/effort operation. The main one is the use of pheromones to trap males adults reducing the chances of copulation and therefore population increase.
Another bet of biological control consists of using specific microorganisms that infect and kill the Lepidoptera, some of the proposed ones being the Smithiavirus pityocampae virus, the Bacillus thuringiensis bacterium or the Beauveria bassiana fungus. Parasitoid wasps can also be used, such as the species Trichogramma brassicae, which parasitize the eggs of the processionary.
In short, it is essential to analyze the population dynamics of the pine processionary caterpillar in recently invaded areas, particularly in relation to climatic factors, because it is convenient to predict the expansion and potential future pests of these insects.
Raul Rivas Gonzalez. Professor of Microbiology, University of Salamanca.
This article was originally published on
The Conversation.