PURPOSE: An effective amount of morantel or its salt is brought into direct contact with the bodies of pine tree nematodes (Bursaphelencus lignicolus) to develop high nematocidal effect, thus controlling and preventing pine trees from withering.

CONSTITUTION: Morantel, chemical names: (E)-1,4,5,6-tetrahydro-1-methyl-2-[2-(3- methyl-2-thienyl)ethenyl]pyrimidine of the formula or its water-soluble acid adduct such as tartaric or citric acid adduct, which is known as a vermicide in the veterinary field, harmless to pine trees and safe to humans and animals, is used to prepare an aqueous solution containing an effective amount of the same. The effective amount is approximately 10ppm as a concentration. The above solution is injected with an ampoule into holes bored with a drill on pine tree stems at 1-meter high position, thus causing no handling problems as well as environmental pollution. the morantel is given by 2W20 grams every pine tree.