Symptom/Description |
Common Host |
Cause |
Algal Leaf Spot: ("Green Scurf"): RAISED greenish-brown to rusty spots |
Magnolias Magnolia spp
Live oak Quercus virginiana
Avocado Persea americana
Other "leathery" leafed trees |
Algal leaf spots, or green scurf, caused by Cephaleuros virescens on the leaves of magnolia (green-orange patches). Grayish-white and darker "crusts" are lichens of the genus Strigula resulting from fungal colonization of the alga. |
 Comments: Cephaleuros sometimes times forms lichens with certain fungi. These lichens ( Strigula spp.) appear as green to white crusts with black spots on leaves.
Photo: An alga Cephaleuros virescens |
Anthracnose:
Large, irregular BLOTCHES of necrotic (dead) tissue, often along or delimited by veins in leaf tissue |
White oak Quercus alba
Other oaks Quercus spp.
Sycamore Platanus occidentalis
Elms Ulmus spp |
Fungus Gnomonia quercina (Asexual stage: Gloeosporium quercinum)
Fungus Gnomonia platani (Asexual stage: Discula platani)
Fungus Gnomonia ulmea (Asexual stage: Gloeosporium ulmeum) |
 Comments: Severe infections often progress into twig infections resulting in branch dieback.
Photo: Anthracnose symptoms on leaves and twig of sycamore |
Blight: RAPID DISCOLORATION AND DEATH OF FOLIAGE, often most serious on younger foliage at branch tips |
Pears Pyrus spp.
Loquat Eriobotrya japonica
Other hardwoods
Various hardwoods |
Bacterium Erwinia amylovora
Unseasonal frost or freeze, chemical damage, certain fungi. |
 Comments: Fire blight. Infections typically progress into twig and branches
Photo:
Branches and foliage of pear blighted by the fire blight bacterium Erwinia amylovor. |
Blister:
Irregular, raised or wrinkled BLISTERS on otherwise green foliage |
Oaks Quercus spp.
Peach Prunus persica |
Fungus Taphrina caerulescens
Fungus Taphrina deformans |
 Comments: Oak leaf blister
Peach leaf curl
PHOTO: Oak leaf blister caused by the fungus Taphrina caerulescens. |
Chlorosis:
General or interveinal YELLOWING of foliage tissue |
Oaks Quercus spp.
Various hardwoods |
Nutritional imbalance or deficiency often related to soil conditions (esp. high soil pH), root disease (including nematode infections), certain types of herbicide damage, vascular dysfunction, etc. |
PHOTO: Severe interveinal chlorosis on leaves of grape, sumac, and cherry resulting from acute herbicide toxicity. (Note: some herbicides cause entirely different symptoms.)
|
Leaf Spots:
Discrete circular to irregular, variably colored SPOTS on otherwise green leaves |
Various hardwoods |
Miscellaneous fungi. Some bacteria. |
PHOTO: Leaf spots on leaves of black cherry caused by a fungus (Phyllosticta sp.) |
Marginal Scorch or Necrosis: Narrow to wide BANDS or patches of dry (papery), brown, dead leaf tissue at tips or margins of leaves |
Various hardwoods |
Drought, root disease, vascular dysfunction, salt water intrusion, excessive fertilizer, etc. |
 Comments: Basically indicative of lack of water to the leaves.
PHOTO1: Marginal leaf necrosis on oak leaves indicative of water deficiency. MORE
PHOTO 2: Severe leaf scorch on leaves of eucalyptus due to excessive fertilization. |
Mottling, flecking variegation or Ring Spots:
Discrete PATTERNS of tissue yellowing in otherwise green leaves |
Various hardwoods |
Certain types of air pollution, chemical injuries, viruses. |
PHOTO: Ring spots and chlorotic mottling typical of virus infections. |
Powdery Mildrew: WHITE, POWDERY TO CHALKY OR MEALY FUNGUS GROWTH on the surface of green and sometimes slightly shriveled, distorted or malformed leaves. |
Elms Ulmus spp.
Crape myrtle Lagerstroemia speciosa
Various hardwoods |
Powdery mildrew fungi including Uncinula macrospora (elm) and Erysiphe lagerstroemiae (crape myrtle). |
PHOTO: Chalky white fungus growth on leaves of winged elm; a typical powdery mildew (Uncinula sp.) |
Sooty Mold: DARK MEALY OR SPONGY TO SOMEWHAT CRUSTY FUNGUS GROWTH on leaves (and sometimes stems. |
Various hardwoods |
Various dark pigmented fungi. |
 Comment: Sooty mold fungi are not parasitic. They feed on and are generally associated with natural or insect (aphids, scales, etc.) created exudates. When abundant, may reduce photosynthetic activity of leaves.
PHOTO: Dark-pigmented sooty mold fungus on the leaf surfaces of a Ficus sp.. |
Tar Spots: HARD, BLACK, RAISED TAR-LIKE OR CRUSTY FUNGUS GROWTHS on the upper surface of infected leaves. |
Yellow poplar Liriodendron tulipifera
Elms Ulmus spp.
Maples Acer spp
Various hardwoods |
Fungi Rhytisma spp. including R. acerinum (maples). |
PHOTO: Tar spots caused by Rhytisma acerinum on leaves of red maple. |
Wilt: a DROOPING AND FLACCID (LIMP) APPEARANCE OF LEAVES, may be accompanied by degrees of chlorosis and marginal scorch or necrosis (above). |
Various hardwoods |
Drought, root disease
Vascular dysfunction, etc.
Comments: Indicative of a lack of water to the foliage. |
