Merida is ‘vaccinating’ its pines

The trees are susceptible to being attacked by the processionary caterpillars

Authorities in the Extremaduran city if Merida announced that annual preventative treatments on some of the pine trees in the city against infestation by the larvae of the pine processionary moth have begun earlier this week. Although recent years have shown an increase in this type of parasitic infestation, control has been considered satisfactory. However, if left untreated the trees can become completely defoliated by the larvae of that insect.

Pine processionaries are called that way because the caterpillars form long snake-like chains when they move

Now is the right season to do the prophylactic treatment on the southern pines that are the common targets for the processionaries. Namely, these are the Aleppo pine (Pinus halepensis) and the stone pine (Pinus pinea), both of which are only found mostly in Spain and along the Mediterranean coasts of other countries.

The municipal services in Merida have chosen two methods to fight infestation, both of which are based on practice and technical expertise.

The first of these is the spraying of the tree trunks by going with a tractor equipped with a tank. The products used are pesticides authorized by the Ministry of Agriculture.

Some trees, however, are resistant to that method, so there is a second procedure that had been devised as an alternative. This one is called endotherapy and it involves municipal personnel manually injecting the trees with a special small pump, which has been loaded with 1.8% abamectin solution.

The technician makes a small hole in the trunk and introduces the substance. The internal pressure of the tree takes care of the rest as it provides rapid absorption throughout its system. Depending on the size of the tree, it may require two or three doses of that “vaccine”.