Spraying The Caterpillars

Those of us who live on Mallorca or who visit the island in the late winter will be only too well aware of the processionary caterpillar. We look up at pine trees and see the nests, we look down and see the trails of caterpillars marching in connected formation in search of soil in which they can bury themselves, pupate and start the whole cycle of moth to caterpillar all over again. We are only too well aware of the skin irritations the caterpillars can cause or of the deaths of pets which might take too great an interest in them. We may be less aware of the harm that the larvae cause to pine trees and other conifer species. They can severely defoliate the trees, thus weakening them and leaving them prone to attack by other pests, by diseases or by environmental conditions.

There are an awful lot of pine trees on Mallorca, and so there are an awful lot of caterpillars. There are ways and means of tackling the pest, but one means - that of chemical spraying - has come in for severe criticism. The regional government's environment ministry is to undertake widespread spraying from the air during this month and during November.

The chemical that will be used is the diflubenzuron pesticide, known also by its brand name, Dimilin. This is a pesticide whose use has proved controversial and not just in the Balearics. For example, in the US state of New Jersey in 2007 environmental groups managed to overturn a decision by the state's department of agriculture to use Dimilin to tackle what was an emergency brought about by a sudden rise in the gypsy moth population. For over twenty years, New Jersey had used a biological pesticide called Bacillus thuringiensis (B.t.). The agriculture department considered this to be inadequate in tackling the emergency, despite the department itself admitting that B.t. afforded good protection for foliage and other species and for control of the gypsy moth population.

Opposition to the use of Dimilin was based on different factors. One, it was unclear whether it would in fact be any more effective than B.t. Two, it could kill other insects. Three, it could have a harmful effect on bird life. Four, it could introduce toxicity for water life. Five, one of its elements was, in all probability, a class B2 human carcinogen. Six, Dimilin was also a hormone disruptor that could harmfully affect both human and animal endocrine systems, in other words the way in which hormones are secreted into the body's circulatory system.

In New Jersey they had stopped using a different pesticide in 1985 because of its potentially harmful human effects. In Mallorca the use of Dimilin was banned by the first Antich PSOE-led government of 1999-2003. It hasn't been used in Mallorca since. Instead, the biological pesticide B.t. has been used. Now, the regional government is changing tack, and there is an outcry from environmental groups and certain political parties.

According to a spokesperson for the Més political grouping, the so-called "Company campaign" (named after the minister for both the environment and agriculture) will, through the use of Dimilin, be more expensive than alternatives and have a greater environmental impact. The cost of the spraying, some two million euros, has not been budgeted for, leading to questions over the awarding of a contract for the spraying. The environmentalist group GOB has attacked the use of Dimilin, noting a regional environmental sustainability report which says that it is not recommended for large-scale spraying on account of its indiscriminate effects; the government plans to spray more than 24,000 hectares of pine forest on Mallorca.

GOB has submitted a written report to the European Commission, drawing attention to a possible breach of a directive on the conservation of natural habitats and flora and fauna and to the regional government environment ministry going against its own sustainability report. GOB notes that the directive requires there to be an impact assessment of the use of pesticides. It further notes that there has been no such impact assessment in respect of Mallorca or indeed the other three Balearic Islands, where pine forests will also be sprayed.

The university in Palma has entered the controversy by concluding that Dimilin does not affect other insects, while it has been noted that there was limited use of Dimilin in Ibiza in 2010, permission for this having been given by the then environment minister, Gabriel Vicens, a member of the PSM Mallorcan socialists, who are part of what is now the Més grouping.

So, what do we conclude? Are Dimilin's potentially harmful effects being exaggerated? In New Jersey it seems they took them seriously enough. In Mallorca, however, they are deemed less serious. And who would bet against there being the trails of caterpillars next March, Dimilin or no Dimilin?

Photo: http://mallorcaphotoblog.com/2011/03/08/the-processionary-caterpillar/