Plant diseases

Pine longicorn (Monochamus galloprovincialis)

The Monochamus galloprovincialis is a tiny insect, specifically a beetle, which serves as a vector to carry a pine tree to another tiny worm that is able to kill hundreds of conifers and other species of trees in no time.

It is a species that comes from North America, as microscopic as it is lethal. This beetle, also called longicorn pine beetle, belongs to the family of cermbicides, whose range of action does not exceed 3 kilometers in its entire life.

Characteristics of the Monochamus galloprovincialis

During their adult stage, these insects reach the conifers loaded with the tiny worms in their antennae, which in turn come from a tree that is already infected.

Once there, the nematode or worm accesses the interior of the tree using the hyphae of the fungi, which are usually in them and also, penetrating through the wounds that these trees have, that is, any crack present in the surface of the bark it is good for entering and infecting the plant.

At the same time, this invasive process gives rise to a series of galleries in the internal part of the pine trunk, which makes it lose a good part of its attractiveness and commercial value even when it receives treatments with chemical products.

How does it affect the plant?

When the microscopic nematodes enter the pine tree, they completely invade the resin channels and there they feed on the parenchyma present in these channels, as well as on the epithelial cells. When the resin canals are affected, there is no more resin production, which prevents the perspiration of the needles.

Very soon, the pine begins to show unmistakable signs of infection, looking wilted and a yellow color in the atria. It would still be possible to observe brown to yellow needles on the branches, however, in a maximum of 3 months the tree will have died.

This small organism has a high capacity for adaptation thanks to its tremendous plasticity. To achieve a good adaptation, a temperate climate that is located above 20 degrees in the summer season is enough, being easier its distribution at altitudes lower than 1,000 meters.

For these reasons, it is currently very common to notice its presence in the southern region of Pontevedra and also in Extremadura, where the mortality of the trees between July and August when temperatures oscillate between 20 and 25 degrees, is evident.

In addition, there are other elements that favor this nematode to settle and develop rapidly in pines, these being the absence of rain, which generates stress in pines during the summer.

What to do if infection is detected in trees?

If it is detected that the pine is infected, the competent authorities in forestry must be informed immediately so that they can initiate the corresponding actions that the case warrants.

What is done in these cases is to determine the so-called zone A, which ranges from 1 to 2 kilometers within the radius where the focus was detected. There, the eradication measures that are available must be applied, among them the felling of the pines as the most radical and at the same time effective.

This felling is carried out in a radius that includes the first kilometer of the source of infection, which prevents the beetle from continuing to advance. There are even sites where logging of up to 1.5 kilometers is carried out, even when this affects high productivity hectares.

It is noteworthy that in the winter season, this nematode tends to fall into a kind of lethargy, but once the temperatures begin to be higher, when it reaches optimal conditions, it will surely expand. For this reason, felling must be done as soon as possible.

In parallel, other actions are taken that serve to eradicate the possible food sources of the Monochamus galloprovincialis vector, consisting of the elimination of dead trees or in process in a radius of 20 kilometers.

All this wood that has been felled in these 20 kilometers that are assumed to be quarantined, is limited for sale unless they receive a treatment that involves subjecting it to high temperatures inside chambers, which leads to the death of the parasite if it is still they are found within said wooden portions.

When did the spread of this plague start?

It began in 1999 in Portugal, where there are large areas of trees that were severely affected, which in fact in 2018 already covered a territory greater than half. For its part, in Spain for this same year there were 6 specific sources at a critical level located in Extremadura, Castilla y León and Galicia.

Regarding the areas with the greatest potential for the infection to spread in Spain, these are very well identified according to a propagation model that has the validation of the UPM and the Joint Research Center of the European Commission.

This model has been very useful since it allows predicting which are the areas where the pest would be most likely to enter Spain, based on the areas that are already known to be infected in neighboring Portugal and in which no measures have been taken. effective control.

Unfortunately, this scientifically known nematode, expert in generating damage to pine wood, has joined with this other species, which serves as the ideal vector to be able to go to different trees where it establishes itself with always fatal outcomes. that ends up dying in a very short time.

This vector is nothing less than a small common beetle in the fauna of Spain, which is popularly called the longicorn of the pine thanks to its long antennae. This small typical insect of the country, gets its source of food in the tender branches of the pine and from time to time in its desire for food, it carries the microscopic parasite from tree to tree.

But it is not all that it does to facilitate the spread of the nematode, since both beings have their life cycle tied to that of the other, that is, while the beetle provides new new trees to the parasite which would be impossible to reach, it rewards his work with weak specimens where he can lay, which would not be possible in a healthy one since the normal pressure of suppuration of the resin would not allow it.

The nematode, once inside the tree, unleashes a voracious appetite and reproduces at shocking speeds, which in equal measure generates irreparable damage by preventing the flow of water through the tree, ending its life very quickly.

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