Some biotic and abiotic factors causal to the deterioration of roadside trees were surveyed in Fukuoka City on 23 species planted along 22 main streets. Various fruit bodies of basidiomycete, imperfect fungi and bacterial canker disease as well as insect pests were detected. Forty-six fungi strains were obtained in this survey. Aphyllophorales basidiomycete was the most abundant fungi found in surveyed raodside trees. Fruit bodies of 7 edible mushroom species were identified on the scaffold limbs, trunks and root collars of roadside trees. Population of all woodinhabiting basidiomycetes from healthy and diseased trees were significantly different. Robinia pseudoacacia declined severely with mycerial development and fruit body formation of white rot fungi, Fomitella fraxinea on root collars. It is conceivable that low soil pH might be a major factor. Fifty-one species of tree insects were identified in this survey, major pests being two species of termites (Isoptera), Reticulitermes speratus kyushuensis and Coptotermes formosanus which significantly attacked ten tree species. Cerambycid beetles, Anoplophora malasiaca and Eupromus ruber severely damaged Platanus orientalis and Machilus thunbergii, respectively. Root damage status corresponded significantly to the degree of upper tree decline. Results clearly show differences between evergreen broad-leaved trees and deciduous broad-leaved trees in tolerance to wood-inhabiting basidiomycetes and tree-parasitic insects. Overall, this preliminary survey documents some biotic and abiotic factors may contribute to roadside tree decline in Fukuoka City., 福岡市内の主要22路線に植栽されている23種の街路樹について,木材腐朽性担子菌および昆虫による衰微を調査した.全調査木1,067本のうちの約3分の1の街路樹で被率が認められた.担子菌のヒダナシタケ目サルノコシカケ科に属するものの子実体が頻繁に観察された.同定された担子菌46種のうち7種の食用担子菌の子実体が認められた.枝条部や樹幹部に子実体が認められたものは樹勢の衰えが顕著で,形成層や辺材部で二次菌糸が単離された.調査した23樹種のうちでは,特に,ニセアカシア,エンジュの衰弱が著しく,その根ざわ部分に白色腐朽菌のベッコウタケ子実体の着生がみられ,被害の激しいものは心材部まで二次菌糸の蔓延が認められた.昆虫では,寄生,共生および補食性昆虫を除き合計51種が確認された.特にシロアリ,カミキリムシ等の食材性昆虫の被害が顕著であった.そのうちシナサワグルミ,シダレヤナギおよびこセアカシアでは枯死に到る被害が見いだされた.またプラタナスではゴマダラカミキリの,タブノキではホシベニカミキリの激しい加害が認められ,幼虫のトンネルにアリ,シロアリおよび菌類の二次的侵入が認められた.また,土壌酸性度の低下が著しく,伐根調査の結果,細根部が強く侵害を受け主根部まで二次菌糸が蔓延していることが分かった.根系部の衰弱は樹木の地上部の侵害度と高い相関性を示した.今回の調査の結果,樹種や土壌要因等が街路樹の衰微に大きな影響をおよぼしているものと考えられた.