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 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
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
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
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