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TREE & SHRUB DISEASES OF
TEXAS
Compiled by: THOMAS Isakeit, Ext. Plant Pathologist
Modified for use in Fort Bend by: Vince Mannino, CED-FBC
WOOD DECAY FUNGIMature trees affectedGradual decline over several yearsWounds and environmental stress
(e.g. drought) are pre-disposition factors
Diagnosis: presence of fruiting bodies (conks)
DIAGNOSIS OF GANODERMATHE 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
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 DIEBACKCaused by several species of fungi,
with some host specificityFungi are “weak” pathogensHost predisposed by injury and/or
environmental stressDiagnosed by the presence of the
fungus to differentiate from insectsTreatment: 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 WILTInjectors thatsupply 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 CITRUSCaused by a fungus, Phytophthora
(several species) Infection through wounds of trunk,
leading to defoliation and fruit dropSoilborne, other plants susceptible,
depending upon the fungus species involved
Treated with fungicides
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
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
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
SOIL-APPLIED HERBICIDE
Herbicide (Krovar) was applied to citrus orchard soil. Live oak roots grew into
orchard soil and picked up the herbicide.
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
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
FOLIAR DAMAGE
LEAF SPOT ON MAGNOLIA caused by algae.
SOOTY MOLD FUNGUS ON LIVE OAK. The fungus is usually
associated with insect honeydew.
FASCIATION
ON HIBISCUS ON MOUNTAIN LAURELFASCIATION is a flattening of the
stem, caused by a mutation in the plant