• Climbing hydrangea is susceptible to rust and other diseases.Hydrangea image by Stephanie Mueller from Fotolia.com
  
  Hardy to USDA zones 4 to 7, climbing hydrangeas (Hydrangea anomala petiolaris) are also clinging vines that grow to 80 feet. They begin to bloom In early to mid-summer, producing large white flowers that complement their green heart-shaped leaves. Climbing hydrangeas are susceptible to several diseases, including (but not limited to) chlorosis of the leaves, powdery mildew and rust.
  
  

Powdery Mildew

• The fungus E. polygoni causes powdery mildew, a disease that begins as a white powdery patch on the climbing hydrangea's foliage. As the infection progresses, the patch increases until spores cover the entire leaf. According to the Alabama Cooperative Extension, hydrangeas affected by powdery mildew produce fewer and less attractive flowers than healthy plants.
  
  

Chlorosis

• Chlorosis of the leaves is characterized by yellowing of leaf tissue that occurs when there's lack of chlorophyll. Several conditions cause this deficiency, including unhealthy roots, inadequate water drainage and extremely alkaline soil. In addition, plants that don't receive a sufficient supply of iron, manganese and zinc become unable to produce chlorophyll. Chlorosis is more than a loss of color. Since plants use chlorophyll to transform light into food and energy, chlorosis is a sign that the climbing hydrangea isn't able to nourish itself.
  
  

Gray Mold

• Gray mold is a blight caused by the fungus Botrytis cinerea. The fungus overwinters in dead plant tissue, leaving its dormant state in humid spring weather. As the spores multiply, the disease affects the entire plant, except for the roots. Signs of infection include brown spots and gray spores.
  
  

Leaf Spot

• The fungus Cercospora hydrangea causes leaf spot on climbing and other hydrangea species. The affected foliage develops brown and purple spots, which first appear on the lower leaves and make their way up as the disease progresses. While leaf spot doesn't usually kill the hydrangea, it makes the leaves of this deciduous shrub drop to the ground prematurely. The fungal spores on the fallen foliage transfer to healthy areas of the plants and other shrubs if the leaves stay on the ground.
  
  

Rust

• Rust is transmitted to climbing hydrangeas when spores of the fungus Pucciniastrum hydrangea blow in the wind from hemlock trees. The fungus settles on the underside of the hydrangea leaf and releases orange-yellow spores from protrusions it creates. As the growing season progresses, new and darker spores appear on the leaf's surface.