TREE & SHRUB DISEASES OF TEXAS Compiled by: T HOMAS Isakeit, Ext. Plant Pathologist Modified for use in Fort Bend by: Vince Mannino, CED-FBC

FUNGAL DISEASES AFFECT A WIDE HOST RANGE AND CAUSE DEATH

WOOD DECAY FUNGI Mature trees affected Gradual decline over several years Wounds and environmental stress (e.g. drought) are pre-disposition factors Diagnosis: presence of fruiting bodies (conks)

WOOD DECAY FUNGI

LIVE OAK IN A NATIVE STAND AVOCADO IN AN ESTABLISHED ORCHARD

DIAGNOSIS OF GANODERMA THE PRESENCE OF FRUITING BODIES (CONKS) OF GANODERMA LUCIDUM ON TREES THAT ARE STILL ALIVE IS DIAGNOSTIC FOR THIS SPECIES OF WOOD DECAY FUNGUS. IT CAN ALSO OCCUR ON DEAD TREES AS A SAPROPHYTE.

OTHER WOOD ROT FUNGI A CONK ON A LIVING TREE IS EVIDENCE OF INFECTION ! GANODERMA LUCIDUM seems to be the most prevalent species in south and central texas, but other species of wood decay fungi have been identified (INONOTUS RICKII shown here).

WOOD ROT FUNGUS - DIAGNOSIS sometimes conks may not be produced on infected trees until they are dead. the presence of rhizomorphs (white or brown fungus strands on the root surface) on a tree that is gradually dying may support a tentative diagnosis of fungal infection

WOOD DECAY FUNGI There is no treatment once trees are infected. Prevention: keep trees watered, try to minimize other stress. Prevention: proper pruning technique to promote rapid wound healing. there is no benefit to pruning paint. Wood decay fungi may be transmitted by wood-boring beetles A living, infected tree may be in danger of falling!

COTTON ROOT ROT Rapid death (weeks or within season) of trees and shrubs of any age Symptom onset during summer months Diagnosis: microscopic examination of fungal strands on roots, presence of spore mats on soil surface (not always produced) If cotton can grow in the vicinity, then so can cotton root rot!

COTTON ROOT ROT

ASH TREE & CAPE HONEYSUCKLE

COTTON ROOT ROT Progression of cotton root rot on Pittosporum

COTTON ROOT ROT Spore mats of the fungus are sometimes produced on the soil surface near the dying plant, in moist, shaded areas

COTTON ROOT ROT No treatment for infected plants Fungus survives indefinitely in soil & doesn’t move; infection occurs when plant roots grow to it Monocot plants (e.g. agave, banana, palms) are immune Dicot plants vary in resistance: see tx plant diseases handbook (b-1140) or tx ag. expt. station bulletin 527

DISEASES CAUSED BY FUNGI AND OTHER ORGANISMS THAT CAUSE DEATH AND HAVE A MORE LIMITED HOST RANGE IN TEXAS

FUNGAL CANKER AND DIEBACK Caused by several species of fungi, with some host specificity Fungi are “weak” pathogens Host predisposed by injury and/or environmental stress Diagnosed by the presence of the fungus to differentiate from insects Treatment: corrective pruning

FUNGAL CANKER AND DIEBACK Canker on Oleander stem, caused by Botryospaeria obtusa spores are produced in black, pimple-like structures in the bark.

OAK WILT Caused by a fungus Affects: live oak, shumard oak, spanish oak, and blackjack oak Spread by sap-feeding beetles, root grafts Prevention: prune during periods of low insect activity, removal of infected trees and soil trenching to prevent root grafts

OAK WILT Some trees will not die, but are stunted forever.

OAK WILT CHARACTERISTIC LEAF SYMPTOM ON LIVE OAK

OAK WILT Injectors that supply fungicides will do little, but cost a lot. NOTE: This tree’s infection was caused by stress from too much soil added…Where are the root flares?

SLIME FLUX (WETWOOD) This is a water soaking of heartwood affecting many tree species & is associated with various bacterial species. Liquid will drain from openings of trunks, often staining the outside. it is associated with branch dieback, but its role in tree mortality is not certain. there is no treatment or prevention for this condition.

FIRE BLIGHT Caused by a bacterium Affects plants in the rose family: in Texas, particularly apple, pear & photinia Bacterium can be spread by pollinating insects at bloom time Confirm diagnosis since may mimic herbicide damage Prune affected branches at least 8” below symptoms

FIREBLIGHT left: branch dieback right: quick death of leaves, often associated with flowers (source of infection)

FOOT ROT OF CITRUS Caused by a fungus, Phytophthora (several species) Infection through wounds of trunk, leading to defoliation and fruit drop Soilborne, other plants susceptible, depending upon the fungus species involved Treated with fungicides

FOOT ROT OF CITRUS

DETAIL OF SYMPTOMS ON LOWER TRUNK

PHYTOPHTHORA ROOT ROT AND LEAF BLIGHT OF HIBISCUS Too much soil moisture and/or poor drainage

PHYTOPHTHORA ROOT ROT AND LEAF BLIGHT OF HIBISCUS

PYTHIUM ROOT ROT OF HIBISCUS EXTENSIVE ROOT ROT LEADS TO WILTING AND DEATH. CONTROL WITH SANITATION, GOOD DRAINAGE AND FUNGICIDES.

OLEANDER LEAF SCORCH Caused by a bacterium, Xylella fastidiosa: a pathovar (strain) specific to oleander Started showing up in late 1990’s Bacterium can be spread by some leafhoppers & sharpshooters Confirm diagnosis at p.d. clinic No treatment, but some cultivars may have resistance

OLEANDER LEAF SCORCH Landscapers’ nightmare!

OLEANDER LEAF SCORCH

PHOENIX LETHAL DECLINE Cause: a phytoplasma (ultra-small, wall-less type of bacterium) Some strains spread by leafhoppers & planthoppers Confirm diagnosis at p.d. clinic Phoenix spp. susceptible, Sabal and Washingtonia palms resistant recent outbreak (2001) in Corpus Christi

PHOENIX LETHAL DECLINE

RACHIS BLIGHT OF PALMS

NON-INFECTIOUS (NON- LIVING) CAUSES OF TREE AND SHRUB DEATH

FREEZE DAMAGE

LIGHTNING DAMAGE If lightening makes a spiral the trees is DEAD. If the strike is mostly straight up and down, then there is a chance

DROUGHT & SALT STRESS Right: typical symptoms. Left: salt residue on soil surface

SOIL-APPLIED HERBICIDE Herbicide (Krovar) was applied to citrus orchard soil. Live oak roots grew into orchard soil and picked up the herbicide.

SOIL-APPLIED HERBICIDE variations in foliar damage from krovar

SOIL STERILANT

INFECTIOUS DISEASES (FUNGI AND OTHER ORGANISMS) THAT DISFIGURE OR BLEMISH SHOOTS AND LEAVES, BUT DO NO CAUSE DIEBACK

CROWN GALL  Cause: bacterium  wide host range  spread by pruning tools and splashing water  galls formed at base of shoot

OLEANDER OLIVE KNOT Caused by a bacterium with a narrow host range.

GALL RUST FUNGI Gall Rust on Acacia

GALL RUST FUNGI GYMNOSPORANGIUM SPECIES - infect members of the cypress and rose families. infection of both types of plants are required to complete the life cycle of the fungus and different spores infect each type.

FUNGI INFECTING FOLIAGE TOP LEFT: Entomosporium on photinia. TOP RIGHT: Rust on live oak BOTTOM LEFT: Lembosina quercina on live oak

CERCOSPORA LEAF BLIGHT OF PITTOSPORUM

ANTHRACNOSE FUNGI Shows up mostly in summer. Treat at budbreak.

DOWNY MILDEW OF ROSE Cool weather fungus

POWDERY MILDEW FUNGI TOP: on wild olive RIGHT: on live oak

VIRUS DISEASES Ring Spot Virus on rose.

NON-INFECTIOUS (NON- LIVING) CAUSES OF TREE AND SHRUB DISFIGUREMENT OR BLEMISHES, BUT NOT DEATH

HERBICIDE DRIFT HERBICIDES (E.G. 2,4-D) - can drift onto foliage, causing growth deformations

NUTRIENT DEFICIENCIES IRON DEFICIENCY IN TEXAS IS USUALLY RELATED TO HIGH PH SOILS

NUTRIENT DEFICIENCIES Zinc Deficiency – less pronounced than iron def.

INSECTS AND PLANTS THAT DISFIGURE OR BLEMISH SHOOTS AND LEAVES, BUT DO NO CAUSE DIEBACK

INSECT GALLS GALL MITE on live oak leaf. INSECT GALL on bark of Texas ebony.

INSECT DAMAGE (FOLIAGE)

TRUE MISTLETOE Parasite – popular during Christmas, better than Love Potion #9.

DODDER Parasite like mistletoe.

OTHER, LIVING CAUSES OF TREE AND SHRUB DISFIGUREMENT OR BLEMISHES, BUT NOT DEATH

FOLIAR DAMAGE LEAF SPOT ON MAGNOLIA caused by algae. SOOTY MOLD FUNGUS ON LIVE OAK. The fungus is usually associated with insect honeydew.

LICHENS

BALL MOSS

FASCIATION ON HIBISCUSON MOUNTAIN LAUREL FASCIATION is a flattening of the stem, caused by a mutation in the plant