Help, they are eating the island away!

(A nest of Processionaries)

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Greece is not really a country you enter fearing you might be stepping into a jungle full of creepy animals. You can find scorpions hidden under a stone, in spring you can meet with snakes but most of them are not poisonous. There are some spiders which like to bite but encountering them is actually an opportunity to see a very special animal because they are so rare. In the sea you might bump into a jellyfish, or out for a walk you might get stung by a wasp or a bee but generally it will mean you suffer just a few moments of pain.

There is however a small and innocent looking animal that kills and destroys, not people, but animals and small trees: the Pine Processionary (Thaumetopoea pityocampa). Maybe you have never come across a procession of caterpillars — thousands of them shuffling head to toe through the landscape, but may have seen their nests: they look like fat, white woollen candy at the end of a branch. In Holland it is mostly the Oak Processionary caterpillar which destroys the landscape. In Mediterranean countries such as Spain, France and Greece the Pine Processionary can eat whole forests away.

Their names tell you where they make their nests — either in oaks or pines (as in Lesvos). They gather at the end of a branch and spin a woolly ball. In daytime you do not see them because it is at night that they are active and go out to gnaw away at the foliage. You might notice that the branch which bears a nest will be totally bare of leaves and if it’s a young tree all its leaves or needles will be eaten. And since the leaves (or needles) function as the lungs of a tree, without them it will die.

As long as they stay in their nest the Processionaries won’t do any harm to people or animals (as long as you aren’t one for walking in the woods at night). But in spring – March and April – they leave their nests in huge processions to look for a place where they can go to ground and pupate until summer when they turn into moths. So you better not meet with them during their migration, because when they sense danger they shoot out bristles (one caterpillar can have as many as 63.000) which contain a toxin which can settle anywhere (trees, clothing, whatever) and cause allergic reactions. Dogs or cats who get it on their tongues can even die.

However the Pine Processionary are most lethal to trees. At the end of the summer the moth lay their eggs. The caterpillars hatch and wander around on their own until they gather together to build nests for winter. You can probably imagine the effect a hungry nest has on a tree especially if there are more than one.

When you travel across the heart of the island, which is covered in pine trees, you can’t avoid seeing hundreds, even thousands of nests. On the road from Kalloni to Vatera many small trees have already succumbed. And more than one big tree really looks seriously distressed. I noticed around Vatera olive and palm trees also looking miserable, but, the pines are the ones that bear the brunt of their attention. I bet when they have eaten all the pines, they’ll retrain themselves to eat the olive leaves and then you can really say goodbye to the beauty of this island.

So what can be done? In earlier times they would have sprayed them by air with chemical pesticides, but it was realised that this did killed lots more besides the caterpillars. So it’s better to use a biological spray — but that costs lots of money. I don’t think an island that doesn’t have enough money to repair its roads will be interested in buying fancy biological pesticides. Another way is to burn the nests, which is a very dangerous job because of those toxic hairs, and there are scientists who think this is not drastic enough. However, I think it might be a fine job for the army, as long as they don’t burn down the whole island.

Now the winter cold has gone from the air and temperatures are soaring upwards again lots of trees are already besieged and look very unhappy. It seems the winter just past was not quite cold enough to kill off the caterpillars (they can survive down to —16°C) and so in pretty big numbers they are eating the island away.

(with thanks to Tony Barrell)

@ Smitaki 2011