Common Texas  Tree Diseases

Main Pathogens:
• Fungus – common
• Bacteria – uncommon
• Viruses – very uncommon 
Hypoxylon Canker
 Attacks weakened trees
 Common during drought
 Decays sapwood
 Crown may thin
 May see branch dieback
 Can kill rapidly
Susceptible Trees:
 Sycamore
 Pecan
 Oak
 Elms
 Many Others 
Leaf Spots
 Common during wet years
 Cosmetic damage – not a serious
 Many species are susceptible
 Rake up leaves to prevent
 Effect roots and lower trunks
 Oaks, ash, elms, many other
species effected
 Tree may show signs of: yellowing
 Wilting
 Undersized leaves
 Branch dieback
 Decline
 Death
 Look for conks
 Can take 3 -5 years for tree
death: often causes whole tree

 Foliage may thin or yellow
 May see crown dieback
 Shoot growth may be reduced
 Look for mushrooms around base
of tree
 Causes white rot – leaves wood
 Can find white fungal growth
under bark in affected areas
 Can affect many species of trees
 Prevent tree stress and keep sod
and mulch back from trunks 

Oak Wilt
Oak wilt is a fungal disease affecting oak trees caused by the fungus Ceratocystis fagacearum. Symptoms vary by tree species, but generally consist of leaf discoloration, wilt, defoliation, and death.
 Red oaks most susceptible
 Live oaks also susceptible
 White oaks are more resistant
Symptoms include:
 Browning of leaves
 Veinal chlorosis in live oaks
 Leaf drop
 Tree death
Spread By:
 Can spread by nitidulid beetles
landing on fungal mats in red
oaks, then feeding on open
wounds in another oak tree

 Can also spread from tree to tree
through root grafts
 Prune in hottest or coldest times
of the year
 Disinfect saw or pruner blades
between trees
 Paint wounds on oak trees only,
to prevent infection by beetles
 Plant resistant species of oaks –
Mexican white oak; Bur oak;
Chinquapin oak
 Treatment is possible with mixed
 Prevention is better – Fungicides
applied by an ISA Certified
Arborist can help protect trees in
oak wilt areas

 Spores dispersed by wind infect
open wounds
 Avoid wounding roots and trunks
 Remove trees with conks 
 Bacterial Leaf Scorch
(BLS) is a systemic disease caused by the bacterium Xylella fastidiosa, which invades the xylem (water and nutrient conducting tissues) of susceptible trees.

 Restricts water flow from roots to leaves
 Vectored by insects: leafhoppers
 Symptoms develop in mid to late summer
 Look for yellow band between scorched tips and green tissue of
 Can lead to early defoliation and branch dieback
 Trees are subject to secondary
infections or pests due to stress
caused by disease
 Oaks, sycamores, elms, boxelders, and several other trees are
 Good tree care practices can help suppress infection:
 Supplemental water during drought
 Mulching
 Infected trees will eventually need removed and replaced