The pine wood nematode (PWN) Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle (Aphelenchida, Parasitaphelenchidae), causing the pine wilt disease (PWD), is aquarantine species of Europe that was found in Portugal in 1999. High ambient temperature (above 20° C) is considered to be one of the main factors enhancing the development of PWD in pine stands. In the early 90s of the last century, Poland was considered acountry of low risk of PWN estab¬lishment. The aim of our study was to verify whether this status has changed due to the effects of climate change. We analysed changes in monthly mean ambient temperatures in June, July and August from 75 weather stations in various regions of Poland from 2005– 2010. Additional analyses of changes in monthly mean temperatures in July and August in the period 1991– 2010 were performed for the weather station where the highest temperatures were recorded.
Multi-year (2005– 2010) average of mean temperatures in June did not exceed 20° C at any of the meteorological stations. However, in July it was higher than the threshold temperature at 26meteorological stations located in the central part of Poland. The highest multi-year average temperatures were recorded at the station in Koło (52° 12′ N, 18° 38′ E). Adetailed analysis of July and August temperature changes at this station during the period 1991– 2010 revealed increasing trends that were described by polynomial functions. The most substantial increase has been ob¬served since 2001. The mean temperature in July and August over the last decade (2001– 2010) has increased by 2.4 and 1.5° C respectively when compared to the previous decade.
It is our conclusion that, although the PWN has not yet been found in Poland, the country should no longer be regarded as an area of low risk due to the effects of summer temperature increase. Other factors favourable for the pine wilt disease development and spread were discussed.
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