INFLUENCE OF TEMPERATURE ON REPRODUCTION OF BURSAPHELENCHUS-XYLOPHILUS AND PINUS-SYLVESTRIS MORTALITY

In three separate experiments, one-year-old Pinus sylvestris seedlings were treated with either wound, wound + water, wound + Bursaphelenchus xylophilus culture filtrate, wound + 3,000 B. xylophilus, or unwounded controls and maintained at 15, 20 or 25-degrees-C for 340, 270 and 240 degree-days (DD-base 10-degrees-C) or 68, 27, and 16 days after inoculation, respectively. Bursaphelenchus xylophilus infected pines at all temperatures and nematode reproduction was similar and considerable at 20 and 25-degrees-C but low at 15-degrees-C. First pine death occurred at 215, 150 and 180 DD or 43, 15 and 12 days after inoculation at 15, 20 and 25-degrees-C, respectively. Visible symptoms and pine mortality at 20 and 25-degrees-C were correlated with the number of nematodes recovered from dead pines. At 15-degrees-C, nematode numbers were not correlated with visible symptoms. No control plants died in any of the experiments except that at 15-degrees-C which indicates that pine death at this temperature is not caused by nematodes alone. Furthermore, the data suggest that temperature increases B. xylophilus reproduction and possibly influences host physiology.