Management of Vegetable Diseases

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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
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FUNGAL DISEASES AFFECT A WIDE HOST RANGE AND
CAUSE DEATH

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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)

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WOOD DECAY FUNGI
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WOOD DECAY FUNGI
LIVE OAK IN A NATIVE STAND
AVOCADO IN AN ESTABLISHED ORCHARD
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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.
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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).
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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
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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!

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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!

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COTTON ROOT ROT
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COTTON ROOT ROT
ASH TREE CAPE HONEYSUCKLE
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COTTON ROOT ROT
Progression of cotton root rot on Pittosporum
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COTTON ROOT ROT
Spore mats of the fungus are sometimes produced
on the soil surface near the dying plant, in
moist, shaded areas
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COTTON ROOT ROT

• No treatment for infected plants
• Fungus survives indefinitely in soil doesnt
  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

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

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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

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

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OAK WILT
Some trees will not die, but are stunted forever.
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OAK WILT
CHARACTERISTIC LEAF SYMPTOM ON LIVE OAK
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OAK WILT
Injectors that supply fungicides will do little,
but cost a lot.
NOTE This trees infection was caused by stress
from too much soil addedWhere are the root
flares?
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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.
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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

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FIREBLIGHT

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

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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

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FOOT ROT OF CITRUS
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FOOT ROT OF CITRUS
DETAIL OF SYMPTOMS ON LOWER TRUNK
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PHYTOPHTHORA ROOT ROT AND LEAF BLIGHT OF HIBISCUS
Too much soil moisture and/or poor drainage
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PHYTOPHTHORA ROOT ROT AND LEAF BLIGHT OF HIBISCUS
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PYTHIUM ROOT ROT OF HIBISCUS
EXTENSIVE ROOT ROT LEADS TO WILTING AND DEATH.
CONTROL WITH SANITATION, GOOD DRAINAGE AND
FUNGICIDES.
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OLEANDER LEAF SCORCH

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

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OLEANDER LEAF SCORCH
Landscapers nightmare!
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OLEANDER LEAF SCORCH
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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

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PHOENIX LETHAL DECLINE
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PHOENIX LETHAL DECLINE
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RACHIS BLIGHT OF PALMS
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NON-INFECTIOUS (NON-LIVING) CAUSES OF TREE AND
SHRUB DEATH

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FREEZE DAMAGE
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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

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DROUGHT SALT STRESS
Right typical symptoms. Left salt residue on
soil surface
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SOIL-APPLIED HERBICIDE
Herbicide (Krovar) was applied to citrus orchard
soil. Live oak roots grew into orchard soil and
picked up the herbicide.
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SOIL-APPLIED HERBICIDE
variations in foliar damage from krovar
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SOIL STERILANT
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INFECTIOUS DISEASES (FUNGI AND OTHER ORGANISMS)
THAT DISFIGURE OR BLEMISH SHOOTS AND LEAVES, BUT
DO NO CAUSE DIEBACK

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CROWN GALL

• Cause bacterium
• wide host range
• spread by pruning tools and splashing water
• galls formed at base of shoot

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OLEANDER OLIVE KNOT
Caused by a bacterium with a narrow host range.
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GALL RUST FUNGI
Gall Rust on Acacia
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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.
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FUNGI INFECTING FOLIAGE
TOP LEFT Entomosporium on photinia. TOP RIGHT
Rust on live oak BOTTOM LEFT Lembosina quercina
on live oak
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CERCOSPORA LEAF BLIGHT OF PITTOSPORUM
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ANTHRACNOSE FUNGI
Shows up mostly in summer. Treat at budbreak.
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DOWNY MILDEW OF ROSE
Cool weather fungus
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POWDERY MILDEW FUNGI
TOP on wild olive RIGHT on live oak
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VIRUS DISEASES
Ring Spot Virus on rose.
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NON-INFECTIOUS (NON-LIVING) CAUSES OF TREE AND
SHRUB DISFIGUREMENT OR BLEMISHES, BUT NOT DEATH

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HERBICIDE DRIFT
HERBICIDES (E.G. 2,4-D) -can drift onto foliage,
causing growth deformations
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NUTRIENT DEFICIENCIES
IRON DEFICIENCY IN TEXAS IS USUALLY RELATED TO
HIGH PH SOILS
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NUTRIENT DEFICIENCIES
Zinc Deficiency less pronounced than iron def.
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INSECTS AND PLANTS THAT DISFIGURE OR BLEMISH
SHOOTS AND LEAVES, BUT DO NO CAUSE DIEBACK

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INSECT GALLS
GALL MITE on live oak leaf. INSECT GALL on bark
of Texas ebony.
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INSECT DAMAGE (FOLIAGE)
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TRUE MISTLETOE
Parasite popular during Christmas, better than
Love Potion 9.
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DODDER
Parasite like mistletoe.
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OTHER, LIVING CAUSES OF TREE AND SHRUB
DISFIGUREMENT OR BLEMISHES, BUT NOT DEATH

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FOLIAR DAMAGE
SOOTY MOLD FUNGUS ON LIVE OAK. The fungus is
usually associated with insect honeydew.
LEAF SPOT ON MAGNOLIA caused by algae.
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LICHENS
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BALL MOSS
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FASCIATION
ON HIBISCUS
ON MOUNTAIN LAUREL
FASCIATION is a flattening of the stem, caused by
a mutation in the plant
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Questions??