INDUSTRIAL APPLICABILITY According to the present invention, there are provided a tree trunk injecting agent that can effectively control pathogenic bacteria and / or pests in a tree even with a low drug amount in a short time, and a tree disease preventing method using the tree injecting agent. In one embodiment of the present invention, a sparingly disinfecting component such as thiophanate methyl is added to an aqueous solution of an insecticidal component such as acetamiprid, and the sparingly disinfecting disinfecting component is suspended in a volume-based 50% particle size of 4 μm or less, or At least one bactericidal component selected from the group consisting of triflumizole and metconazole is added to obtain a trunk injection agent.本発明により、樹木中の病原菌及び／又は害虫を、短時間の作業で低薬量でも有効に防除できる樹幹注入剤、および樹幹注入剤を用いた樹木病害防止方法が提供される。本発明のある態様では、アセタミプリドなどの殺虫成分の水溶液に、チオファネートメチルなどの難溶性殺菌成分を添加して、該難溶性殺菌成分を体積基準５０％粒径４μｍ以下の大きさで懸濁し、又はトリフルミゾールおよびメトコナゾールからなる群から選ばれる少なくとも１つの殺菌成分を添加して、樹幹注入剤を得る。
