Scientists are testing what could prove the definitive way to save pine trees from a slow and certain death
Researchers from Athens University and the National Institute for Agricultural Research have developed a program to try out an environmentally friendly solution to a scourge that is causing the slow death of pine trees – the insect Marchalina hellenica. The insect drains trees of their sap, causing them to wither and die. In the process, it secretes a distinctive white fluff, which is a major source of food for bees. The Hellenic Society for the Protection of Nature is to take part in the program, which will focus on the pine trees on the Athens University campus and Mt Hymettus and in the Diomedes Botanical Garden in Haidari, Attica. The researchers expect to provide a functional and ecologically sound way to deal with the problem. The Marchalina hellenica insect, contrary to its name, is not native to Greece but was brought here, probably during the Roman or Byzantine period. Evidence for this appears in archaeological findings and biological data – there is no reference to the insect’s honey-producing properties in inscriptions at Knossos or Pylos, in the writings of Theophrastus or Pliny or in texts from the Classical period. Over the past decade, funding from the European Union’s 2nd Community Support Framework was used to encourage the spread of the insect in Greece and to introduce it to areas where it was unknown, despite the introduction of laws in neighboring countries such as Italy that called for eradication programs after the insect was found to be draining the pine trees of their sap. But Greek honey producers persuaded the authorities that there was a supposed mutual dependence between the host – the pine tree – and the insect. The insect population was deliberately spread in violation of all the principles of entomology and biological science. The decision to fund the spread of Marchalina hellenica appears to have been influenced by the large number of honey producers and the value of honey exports, against the loss of biomass, tree coverage and the sight of dead pine trees in many parts of southern Greece. Greece’s stance has been more similar to Turkey’s than Italy’s, but even in Turkey, research groups have recently been studying the insect’s impact on pine trees. There, as in Greece, no organization has funded any research of this kind, therefore the problem has burgeoned and honey producer associations are claiming that there is no research to back up the theory that the insect harms the trees. This is despite the evidence that pine trees are dying because there is not enough water pressure within the tree to allow the water to reach the foliage. Moreover, secondary infestations by Coleoptera beetles in the Scolytaidae family are made easier when the tree has been undermined by Marchalina hellenica. The trees’s foliage is gradually thinned out as a result, eventually killing the tree. Sooner or later, all affected trees will die, the question of when depends on the general environment. Controlling the insect with the help of pesticides, apart from the practical difficulties involved, involves the use of synthetic chemicals. Even the most advanced preparations have been accused of chronic toxicity linked to carcinogenesis and other problems, apart from the fact that they cause serious mutations in invertebrate fauna (although the manufacturers have tried to reduce the acute toxicity). All insecticides, meanwhile, can upset the balance between Marchalina hellenica and its natural predators. Apart from the difficulties and the arguments regarding the mortality rate of the insect’s natural enemies from the use of pesticides, this is not a successful way to control the population of Marchalina hellenica. In fact, there is a greater risk of a population explosion as the insect can undergo many kinds of mutations that make it invulnerable to pesticides. As a result, it has not been controlled even on farms. Therefore laboratories around the world, including our own, have undertaken research into methods that are ecologically compatible and environmentally friendly. This has been achieved after many years of research into all the species of pine trees growing in Greece and into behavioral ecology. Now it is possible to manage pine trees growing on private property, in urban areas and in easily accessible forest ecosystems. A preparation has been patented and we have given it free of charge to a private chemical firm that will put it on the market. Our ongoing research has also shown that this preparation reduces the number of eggs in the insects’ ovaries. One of the most effective ways to control parasites is to increase the number of their natural predators (arthropods and birds), even in urban settings. In recent years we at Athens University and the National Institute for Agricultural Research have developed a research program for this purpose. The Hellenic Society for the Protection of Nature is to take part in the work. The focus area will be the Athens University Campus, Mt Hymettus and the Diomedes Botanical Garden in Haidari, Attica. The program is expected to provide a functional and ecologically sound solution to a problem that originated in the greed and stupidity of a few people. Various methods such as high-pressure washing of the tree trunks, applying a glue to the trunks and the use of synthetic insecticides on the lower part of the tree trunk will not be tested since their ineffectiveness has been shown in existing theories. (1) Panos Petrakis is an entomologist at the Institute of Mediterranean Forest Ecosystems at the National Foundation for Agricultural Research. Vassileios Roussis and Constantinos Vayias are associate professors at Athens University’s Pharmacy Department.
