On May 7, a new campaign was launched to reduce the intensity of a plague and reduce the damage to corks and oaks

The Department of Agriculture, Livestock, Fisheries and Food applies phytosanitary treatments for the second consecutive year to minimize the damage to oak forests caused by the hairy cork caterpillar (Lymantria dispar). The treatment that was carried out last year on 2,000 hectares in 9 municipalities of Selva and Maresme was effective and today a new campaign has started on around 6,000 hectares. According to the evaluations made by the Department's technicians (in collaboration with other institutions), for this year defoliation is expected to be more important and affect more surface.

This insect is the second most important defoliator of forest masses in Catalonia after the pine processionary, and causes significant damage especially to the cork oak (want to upload) and the oak (Q. ilex), with partial or complete defoliation depending on the intensity of the pest. The protection of corks and oaks, in addition to conserving them as a Mediterranean and native species, also serves to preserve the biodiversity that develops in these habitats. Therefore, this treatment seeks to preserve Catalonia's native forests and the biodiversity they generate.


Treatments to reduce the intensity of the plague

The aim of the treatments is not to eradicate the plague but to reduce the intensity and extent of its affectation and contribute to helping the natural balance of the same, reducing the significant damage that occurs, mainly on corks and oaks. Aerial treatments are the only viable control method on a forest scale and allow improving the phytosanitary status of the trees, defending the ecological, landscape, productive and recreational values of oak groves and cork oaks.
The treatment also reduces the damage and problems that this plague causes on citizens who live in or frequent forests with high levels of affectation.

In addition, the treatments help to avoid the weakness or degradation of the masses helping them not to be more prone to subsequent imbalances produced by other insects or fungi.

Damage that prevents the use of cork

This plague causes a very important economic damage to the cork sector, which is strategic for the Catalan forestry world. Although affected corks usually resprout, defoliation prevents peeling (which takes place every 12-15 years) i they damage the entire production as they cause all the cork from the year of the attack to lose its quality.
The sector estimates in more than two million euros in damages caused by the hairy caterpillar in Catalonia in 2019 in the entire cork chain (owners, workers, industry,...) and in other forest productions (very serious effects and mortality of radiata pine plantations).

On the other hand, defoliation produces a weakening of the affected trees which together with other factors (drought, increase in waves of extreme temperatures,...) make them much more sensitive to other pests and diseases. It must be remembered that when caterpillar population levels are very high, defoliation affects almost all species and not just oaks and corks.

The major defoliations also cause a major social alarm due to the large areas of vegetation that are completely defoliated, mainly in the third and fourth year of the beginning of the episode.

Biological product and treatment areas

The phytosanitary product used is biological (Bacillus thuringiensis subsp. kurstaki), compatible with organic farming and is not classified as dangerous for the environment or aquatic organisms. 

Regarding the criteria for the selection of the areas to be treated, once the campaign is planned, the areas are prioritized taking into account different parameters such as the degree of affectation in the previous year, the reiteration of the affectations, the sensitivity of forest masses, social use, landscape impact, public demands and logistics, among others. Before applying the treatments, close information is maintained with the associations of people affected by multiple chemical sensitivity, and also with beekeepers and owners of organic livestock farms and with the management bodies of protected natural areas. The town councils are also informed before starting the applications. It is necessary to bear in mind the limitations of the regulations relating to aerial treatments that prohibit them less than 100 m from inhabited areas.

The actions are carried out in a total of 14 municipalities in La Selva (3,200 ha), Vallès Oriental (1,600 ha) and Maresme (1,200 ha) and are carried out following all the regulations in force at the time in relation to measures to prevent the spread of SARS-CoV-2 and ensuring safety measures.