Investigation of Pinewood Nematodes in Pinus tabuliformis Carr. under Low-Temperature Conditions in Fushun, China

Abstract

In recent years, the pinewood nematode has continuously adapted to low-temperature environments and expanded from the South to the North of China. In December 2018, a large area of pinewood nematode was suspected to be harmful to Pinus tabuliformis under natural conditions in Fushun City, Liaoning Province. In order to clarify the low-temperature environment and population characteristics of pinewood nematodes in this new epidemic area, we analyzed the difference in temperature between the inside and outside of P. tabuliformis in low-temperature environments, conducted the morphological and molecular identification of pinewood nematodes in P. tabuliformis, summarized the distribution characteristics of the wintering of pinewood nematodes and explored the population structure of pinewood nematodes under different low-temperature conditions. The results indicated that the diurnal variation of temperature in dead P. tabuliformis was significantly less than the environment temperature. The lowest temperature in P. tabuliformis was 3.2 °C higher than the lowest temperature in the environment in one day; the pathogen of a large area of dead P. tabuliformis in Fushun was pinewood nematode (Bursaphelenchus xylophilus); 84.9% of the average populations of pinewood nematodes were third-stage dispersal juveniles, which mainly gathered in 5 cm within the pupal chamber of Monochamus saltuarius Gebler. At −40 ℃, most of the third-stage dispersal juveniles of pinewood nematode in dead pine can still survive. Our study laid a foundation for the understanding of the low-temperature adaptation mechanism of pinewood nematode and contributed to the monitoring of pine wilt disease in the mid-temperate zone.