Needlecast Diseases of Evergreens: Identification and Fungicide Timing

Overview Needlecast diseases of evergreens are caused by several fungi. Much remains to be learned about infection timing, latency period, optimal fungicide timing, and best chemicals. However, progress is being made

Nectria Canker: Opportunistic Fungal Pathogen on Hardwoods

Nectria fruiting on a twig Pathogen and Hosts The fungus Nectria invades wood damaged by freezing, hail, animals, and insects. Most hardwoods with such injuries are susceptible. Slightly sunken cankers develop around

Mountain Laurel Leaf Spot: Cercospora Identification and Control

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Leaf Spot Large tan to brown spots on leaves with dark line on perimeter and purple halo. Dark-brown pimple-like fruiting structures scattered within s

Mountain Ash Diseases: Cankers, Fire Blight, and Leaf Spot

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Cytospora Canker Trunks/larger branches: brown sunken cankers, circular/irregular, enlarge and girdle wood. Black pimple-like fruiting structures on in

Maple Diseases: Anthracnose, Root Rots, and Verticillium Wilt

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Anthracnose Norway maple: narrow purple/brown streaks along leaf veins. Sugar maple: large irregular brown/red-brown areas along/between veins (like dr

Lilac Diseases: Blights, Mildew, and Witches' Broom

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Ascochyta Blight Spring: current years shoots and flower stalks girdled, wilted, brown. Base of dead area tan/gray, shriveled. Wet weather: dark gray p

Leucothoe Diseases: Cylindrocladium Leaf Spot and Root Rot

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Cylindrocladium Leaf Spot Dark spots on leaves. Lesions on stems can girdle and kill them. Cylindrocladium Avoid overhead irrigation. Apply fungicide a

Juniper Twig Blight: Phomopsis vs. Kabatina Identification and Control

Overview Junipers (Juniperus spp., red cedars) are susceptible to twig tip death. Most severe in nursery stock/seedlings grown closely; established plants also attacked. Two fungi cause this: Phomopsis juniperovora a

Juniper Diseases: Rusts, Blights, and Management Strategies

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Cedar-Apple Rust Smooth, round galls on twigs up to golf ball size; surface dimpled like golf ball. Gymnosporangium juniperi-virginianae Prune and dest

Tree Hazard Inspection: Identifying Structural Defects and Disease Risks

Defining a Hazard A tree presents a hazard if a defective part poses a high risk of structural failure causing personal injury or property damage. Also a hazard if it obstructs routine activities (blocking vision, raisin

Insect-Vectored Pathogens in Woody Ornamentals: Oak Wilt, Dutch Elm Disease, and More

Key Vectored Pathogens Devastating pathogens in woody ornamentals are moved by insects (vectored): fungi Ceratocystis fagacearum (oak wilt) and Ophiostoma ulmi (Dutch elm disease); bacteria Xylella fastidiosa (bacterial

Horsechestnut Leaf Blotch: Symptoms and Management

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Leaf Blotch Small irregular reddish-brown spots and large blotches with yellow halos in late June/early July. Most infected leaves brown and fall prema

Powdery Mildew on Honeysuckle: Identification and Control

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Powdery Mildew White fungal growth on upper surface of lower leaves. Microsphaera If frequently severe, apply fungicide as soon as any mildew is observ

Holly Diseases: Root Rots, Leaf Spots, and Nematode Problems

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Leaf Scorch Circular to irregular tan spots in early spring/summer. Tiny black fungal fruiting structures pepper spot surface (secondary fungus). Young

Hickory Leaf Spots: Symptoms and Management

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Leaf Spot Irregular reddish-brown spots on upper leaf surface; brown spots on lower surface. Severe cases: premature leaf fall. Gnomonia caryae No cont

Hemlock Diseases: Cankers, Needle Blights, and Rusts

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Cytospora Canker Slightly sunken cankers girdle and kill branches. Valsa (Cytospora) Prune infected branches. Fabrella Needle Blight Needles in lower

Common Hawthorn Diseases: Fire Blight, Rusts, and Leaf Spot

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Fire Blight Flower clusters killed, turn dark brown/black. Dead leaves/aborted flower parts remain. Long, slightly sunken cankers at dead/live wood jun

Hackberry Witches' Broom: Causes and Management

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Witches Broom Many short twigs develop close together from a swelling on a branch. Tree may be covered with witches brooms. Sphaerotheca phytophila (po

Forsythia Diseases: Gall and Twig Blight Identification and Control

Disease Reference Table DiseaseSymptomsPathogen/CauseManagement Galls Knobby galls along branches. Uncertain causes. Crown gall, Phomopsis fungus, and genetic abnormality blamed but none conclusively proven. Possibl

Fire Blight: Symptoms, Disease Cycle, and Management for Rosaceous Plants

Pathogen and Hosts Fire blight is caused by the bacterium Erwinia amylovora75 species of trees and shrubs including apple, pear, quince, mountain ash, crabapple, hawthorn, cotoneaster, serviceberry, and pyracantha. T