Pheromones as a means to protect beech forests

European hardwood ambrosia beetle poses a threat both for living beech populations and cut wood. To fight this pest, a new pheromone agent has been produced at the CHEMIPAN Research and Development Laboratories of the Institute of Physical Chemistry of the Polish Academy of Sciences. The substance has been developed on the order of the Austrian company Witasek Pflanzenschutz GmBH and field-tested in forests in Germany last year. „The results of the tests carried out by our German colleagues turned out to be an exceptionally pleasant surprise," says Dr Jerzy Raczko, CHEMIPAN's managing director. The new preparation proved to be efficient in attracting not only European hardwood ambrosia beetle but also other beetle species from the Trypodendron genus.

Pheromones are volatile substances secreted by living organisms to their environment for communication purposes. They play various roles: usually they indicate the presence of the female or the abundance of food, but are also used as warning signals. Attracting properties of pheromones have since long been used by foresters to fight insects. Pheromone traps allow them to monitor, reduce or fight specific pest population.

„Pheromones occur naturally at extremely low concentrations, and that's why using them is exceptionally environment-friendly and economic. For instance, each year we provide foresters in whole Poland with several dozens of thousands of pheromone traps to monitor the black arches population. All the traps contain only 12 grams pheromone in total," explains Raczko.

European hardwood ambrosia beetle (Trypodendron domesticum, Xyloterus domesticus) is a small, dark beetle, cylindrical in shape and not longer than four milimeters. It occurs mainly in beech populations, especially in the damaged ones, where it infests birches, oaks, maples, limes and other deciduous trees. Most Poland's forests are pine monocultures, where the primary threat is the striped ambrosia beetle (Trypodendron lineatum, Xyloterus lineatus) feeding on conifers. "For years we have had chemicals to effectively attract the striped ambrosia beetle. Now, we used them as a basis to develop a new pheromone, tailored to attract the European hardwood ambrosia beetle," describes Raczko.

The field tests have been carried out by researchers from the Technical University of Dresden in the tree populations near Leipzig, Dresden and Wermsdorf. The forests comprised common beeches, oaks and ashes. To the Polish researchers surprise, not only European hardwood ambrosia beetles and striped ambrosia beetles were observed in high, mutually comparable numbers in pheromone traps, but also the bark beetle (Trypodendron signatum, Xyloterus signatus). Test results indicate that the new agent is efficient against all beetles from Trypodendron genus.

The pheromone-based agent attracting the beetles will allow for better determination of dates when these pests start and culminate their swarming. Measurements with traps will contribute to a more efficient monitoring of the tree populations and allow the foresters to take preventive measures at appropriately early time, which in turn will result in reduced damages of insect infestations.