Abstract
Inoculation experiments were conducted to confirm results obtained by Kiyohara and Tokushige in relationship to Bursaphelenchus lignicolus capable of causing wilting, or the death of pine trees. Twenty-three healthy trees of 7-year-old Pinus thunbergii and 10 of 12-15-yearold P. densiflora were inoculated on July 5, 1971, by the insertion of a water-suspension of the nematode into hole made on the stem, or on a branch cross section. Disease symptoms appeared first as a marked reduction in the oleoresin yield within 14 days after inoculation. At 50 days after inoculation, most trees, some of which had died, showed symptoms of wilting, yellowing, and browning of foliage. Transpiration of the leaves was measured at weekly intervals, and reduction appeared 22 days after inoculation. In an infected tree, it is considered that changes of tree physiology resulting in the reduction of transpiration occurs at an early stage of disease development. Population of B. lignicolus in wood tissue increased as the disease became more advanced. A large number of nematodes was found in various parts of a tree when symptoms became noticeable.
