Jae-hyuk Choi, Jong-woon Lee, Ho-wook Lee, Cheol Jang, Yi Seul Kim, Mwamula Abraham Okki, Nguyen Manh Ha, Jong Kyu Lee, Haerim Han, Young Woo Nam, DongWoon Lee

Korean Journal of Pesticide Science, 26(1), 43-54.

Abstract

Pine wood nematode (PWN), Bursaphelenchus xylophilus is an economically important plant-parasitic nematode that causes wilting and eventual death of pine trees. Trunk injection of nematicides is commonly preferred as the most ideal control method of PWN in live trees. For standardization of the PWN trunk injection bioassay, the rate of needle discoloration and eventual tree mortality were investigated from 3 to 9 months after inoculation with PWN in pine species, Pinus densiflora and P. thunbergii. In addition, the resin secretion rate and the density of PWNs in the tree were investigated 6 months after inoculation of PWNs. When 10,000 PWNs were inoculated, the average needle discoloration rate was over 40% for both pine species at 4 months after inoculation. In P. thunbergii, the average needle discoloration rate was over 80% after 5 months of PWN inoculation while over 70% was evident in P. densiflora at 9 months after inoculation. The density of PWNs in the tree was higher in the branches than in the trunk. Also, the density was significantly higher in P. densiflora than in P. thunbergii. The PWN detection and resin secretion rates in P. thunbergii almost synchronized with the needle discoloration rate and nematode density, and therefore, it is judged that it can be used for bioassay of tree injection agents. It is recommended to apply a needle discoloration rate of 30 to 50% as the criterion for determining the damage rate in the bioassay of tree injection agents. In addition, it is recommended to apply 50% of the minimum damage rate of no treatment.

DOI/link: https://doi.org/10.7585/kjps.2022.26.1.43