To provide a protective device capable of further reducing risk of damaging a coated stem, and surely suppressing damage caused by a pest control object organism.SOLUTION: A protective device 100 comprises: a tubular body 110 whose upper and lower ends are open, and which is formed into a hollow cylindrical shape capable of surrounding a periphery of a stem T； and an entry prevention body 120 which is arranged in the tubular body 110 and comprises a plurality of protrusions 125 protruded from an inner peripheral face of the tubular body 110. In a state of inserting the stem T into the tubular body 110, the plurality of protrusions 125 are arranged to surround the periphery of the stem T at an interval capable of regulating passage of the pest control object organism, by forming an insertion part 126 for inserting the stem T by tip end edges of the plurality of protrusions 125 in a radial direction. At least some protrusions 125 out of the plurality of protrusions 125 comprise extension means 129 for changing a protrusion length of the protrusion 125 to become shorter, and at least partially radially extending the outer periphery of the insertion part 126.SELECTED DRAWING: Figure 9【課題】被覆した幹を傷付ける虞をより一層軽減しつつ、確実に防除対象生物からの被害を抑えることが可能な保護装置を提供する。【解決手段】保護装置１００は、上端及び下端で開口し、幹Ｔの外周を包囲可能な中空筒形状を有する管状体１１０と、該管状体１１０内部に配置され、管状体１１０の内周面から突出する複数の突起体１２５を有する侵入防止体１２０と、を備える。幹Ｔが管状体１１０に内挿された状態で、複数の突起体１２５が防除対象生物の通過を規制可能な間隔で幹Ｔ周囲を包囲するように、複数の突起体１２５の径方向における先端縁によって幹Ｔを内挿するための挿通部１２６が形成される。複数の突起体１２５の少なくとも一部の突起体１２５には、突起体１２５の突出長を短く変更し、挿通部１２６の外周を少なくとも部分的に径方向に拡張するための拡張手段１２９が設けられている。【選択図】図９
