Selecting plants for placement in the landscape as well as monitoring them for diseases and planning appropriate disease management strategies can be simplified if the key plants in the landscape are known and if the key diseases on those plants can be identified. Key plants, ones that frequently have diseases,should be monitored on a regular basis. Key plants should not be used in the landscape if one goal at the site is to minimize the amount of maintenance work required to assure the site looks well at all times. Key diseases (those listed in bold) are those that frequently occur on the plants. The other diseases listed sometimes occur. The following list of key plants and their key diseases was compiled from over 10 years of records from the Penn State University Plant Disease Clinic.

Ash (Fraxinus) Anthracnose	Ivy, Boston (Parthenocissus) Black rot
Azalea (Rhododendron) Botrytis blight Leaf gall Nematodes Ovulinia flower blight Powdery mildew Root rots	Ivy, English (Hedera) Colletotrichum leaf spot Bacterial leaf spot
Cherry (Prunus) Bacterial leaf spot Black knot Coccomyces leaf spot	Juniper (Juniperus) Cedar-apple, -hawthorn and cedar-quince rusts Kabatina twig blight Phomopsis twig blight Root rot
Crabapple (Malus) Cedar-apple rust Fire blight Powdery mildew Scab	Lilac (Syringa) Bacterial leaf blight Powdery mildew Witches' broom
Dogwood (Cornus) Anthracnose\Decline Septoria leaf spot	Oak (Quercus) Anthracnose Decline Leaf blister
Elm (Ulmus) Botryodiplidia canker Dutch elm disease Black leaf spot Phloem necrosis (yellows) Wetwood	Pachysandra (Pachysandra) Volutella blight
Hawthorn (Crataegus) Fire blight Leaf spot Rust	Pine (Pinus) Sphaeropsis (Diplodia) tip blight Needle blights Cyclaneusma Needlecast Lophodermium Needlecast Ploioderma (Hypoderma) Needlecast Root rots Gall and cankering rusts
Rhododendron (Rhododendron) Botryosphaeria dieback Cercospora leaf spot Ovulinia flower blight Phytophthora dieback and root rot	Spruce (Picea) Cytospora canker Rhizosphaera Needlecast
Rose (Rosa) Black spot Cankers Powdery mildew Rust	Sycamore (Platanus) Anthracnose Powdery mildew

Scouting and Controlling Woody Ornamental Diseases in Landscapes and Nurseries is a 90-page, pocket-sized guide to the key diseases of the key plants noted above. The guide contains 109 color photographs of the key diseases. It can be purchased from Publications Distribution Center, 112 Ag. Admin. Bldg., University Park, PA 16802 for $7.00 (which includes postage and handling). Make checks payable to Penn State University.