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Clematis is subject to infection by several diseases including powdery mildew ( Erysiphe ploygoni ) , crown gall ( Agrobacterium tumefaciens ) , and various leaf spots ( Cercospora squalidula , Septoria clematidis ) . See Extension publication Culture of Garden Roses , FS-1105 , for more information on cultivation . If the pH of the soil is between 5.5 and 7.0 and the texture is sandy to sandy loam , the following method can be used . Rhizoctonia crown rot of daylilies occurs in wet years or in poorly drained soils . To manage fourlined plant bugs , spray a labeled insecticide , such as acephate ( Orthene ) , diazinon , chlorpyrifos , carbaryl ( Sevin ) or malathion as soon as you see damage in May or June . Closer planting will make training and management of the trees difficult , and the trees may shade each other so that fruit quality is harmed . However , if only part of the crown is infected , the damaged tissue can be cut out and the healthy crown section replanted in a well-drained location . Canned apples will keep without sugar , although the addition of sugar or sugar syrup results in a product with better flavor , color , and texture . Symptoms include crowns that rot from the soil surface down and dark , felt-like fungal growth on the plant crown . Surface blemishes that do not penetrate the skin , such as russetting , have very little influence on fruit quality or storage life . Some of the fruitlets will drop in mid-June , but the tree may be left with more fruit than is optimal for fruit quality development .