Common Tree Diseases in the Houston Area and How to Prevent Them
Houston's subtropical climate is great for growing trees, but it's also ideal for the fungi, bacteria, and other pathogens that attack them. Knowing what to look for can help you catch problems early and save your trees.
Oak Wilt
Affected trees: All oaks, but especially red oaks (water oaks, Shumard oaks)
Symptoms:
- Rapid browning of leaves from the edges inward (red oaks)
- Veinal necrosis with a mottled pattern (live oaks)
- Rapid defoliation
Prevention:
- Do not prune oaks from February through June
- Paint all wounds on oaks immediately, including storm damage
- Do not move firewood from infected trees
Hypoxylon Canker
Affected trees: Primarily oaks, but also pecans, elms, and other hardwoods
Symptoms:
- Bark sloughing off to reveal dark, crusty fungal mats
- Usually appears on trees already stressed by drought, construction damage, or other factors
Prevention:
- Maintain tree health through proper watering and fertilization
- Avoid root damage during construction
- There is no treatment once symptoms appear - the disease indicates the tree was already severely stressed
Bacterial Leaf Scorch
Affected trees: Oaks, elms, sycamores, and others
Symptoms:
- Brown, scorched-looking leaf margins
- Symptoms worsen each year
- Gradual canopy thinning over several years
Prevention:
- No cure exists, but maintaining tree health can slow progression
- Deep root fertilization and proper watering help
- Severely affected trees may need removal
Pine Bark Beetle
Affected trees: All pine species
Symptoms:
- Pitch tubes (small resin masses) on the bark
- Boring dust in bark crevices
- Needles turning brown from the top down
- Exit holes in the bark
Prevention:
- Maintain pine health through proper watering during drought
- Remove and dispose of infested trees promptly to prevent spread
- Avoid wounding pine trees during beetle season
Cotton Root Rot
Affected trees: Many hardwood species, especially in alkaline soils
Symptoms:
- Sudden wilting and death, often in summer heat
- Bronze or brown leaves that remain attached
- White, cotton-like fungal growth on roots
Prevention:
- Improve soil drainage
- Plant resistant species in areas with known cotton root rot
- No effective treatment once a tree is infected
Root Rot (Phytophthora)
Affected trees: Many species, especially in poorly drained areas
Symptoms:
- Yellowing leaves and canopy thinning
- Darkened, water-soaked bark at the base
- Mushrooms or other fungi at the root flare
Prevention:
- Ensure proper drainage
- Avoid overwatering
- Don't pile soil or mulch against the trunk
Best Practices for Disease Prevention
- Keep trees healthy - Well-maintained trees resist disease better
- Water properly - Deep, infrequent watering is best
- Fertilize - Deep root fertilization supports immune function
- Prune correctly - Proper cuts heal faster and resist infection
- Monitor regularly - Catch problems early when treatment is most effective
At HamodaTrees, we can diagnose tree diseases and recommend the best course of action, whether that's treatment to save the tree or removal to protect your other trees and property.
Contact us if you suspect disease in your trees.