Prevention of pine wilt disease by soil injection with fosthiazate.

Pine wood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer 1986), has caused serious pine disease in Taiwan since 1985. Soil injection with 75% fosthiazate to control pine wilt disease was conducted at 3 locations in northern Taiwan. Twenty healthy pine trees with diameter breast height (DBH) ranging 20~40 cm were selected by oleoresin exudation for the inoculation test. Ten trees were treated with 75% fosthiazate by soil-injection application in May 2004 according to the manufacturer's protocol and a DBH table; another 10 pine trees were used as controls. One month after the soil injection, all trees at 3 locations were artificially inoculated with 30,000 pinewood nematodes (B. xylophilus). Symptoms of pine wilt disease were first observed 3 mo after inoculation; the disease progressed rapidly from September 2004. Chemical protection efficacy was evaluated 9 mo after inoculation. For chemical-treated trees, disease incidences at Zhongli, Daxi, and Zhudong were 40, 30, and 20%, and values of the disease severity index were 2, 1.1, and 1, respectively. However, for the non-treated group, disease incidences were 80, 80, and 70%, and values of the disease severity index were 4.0, 4.0, and 3.5, respectively. Our results demonstrated that fosthiazate not only decreased the incidence of pine wilt, but also retarded the disease progression.