GROW GREEN FACT SHEETS are available to download or you can also pick hard copies from many sites around Austin that distribute Grow Green materials.
Other Common Pests and Grow Green Recommendations
The landscape problems listed below occur in Austin but we do not have the same demand for information about them as the pests that have GROW GREEN FACT SHEETS.
Bacterial Leaf Spot
Problem
Leaves yellow and may drop. Plants lose vigor and produce less chlorophyll. Bacterial Leaf Spot is caused by wet plant foliage and injury. This is commonly seen on:
Greens
Turnips
Cauliflower
Cabbage
English Ivy
Tomatoes
Fruit trees
Several ornamental shrubs and trees
Least Toxic Solutions
- Avoid wetting foliage when watering.
- Space plants to allow adequate air flow.
- Do not injure foliage. Bacteria enter plants through wounds or natural openings.
- Remove infected plant sections.
- Carefully consider use of chemical controls— they are often only marginally effective.
- If you must use a chemical control, apply a copper hydroxide product such as Kocide®.
Cotton Rot/Root Rot
Description: Fungal plant disease that attacks the roots of plants, turning them brown rather than a healthy white. Cotton root rot is common in soils with a pH over 7.2 and in areas with high summer temperatures. Problem: Plants wilt, dieback and lose vigor. Control is difficult because symptoms normally appear after damage to the stem or root is severe. Cotton Root Rot moves through the soil from plant to plant, with symptoms usually occurring in July and August.
Attacks: More than 2,000 species of plants including:
Cotton
Ornamentals
Fruit trees
Nut trees
Shade trees
Most landscape plants
Least Toxic Solutions
Cotton Root Rot
No treatment available once plant is infected. Mulch plants to keep soil cool. Add organic material to clay soils. Use resistant plants, natives and grasses. When practical, acidify soil in the root zone of the plant.
Root Rot
Ensure proper drainage and allow excessively wet soils to dry. Plant in raised beds if drainage is marginal. Avoid crowding plants in beds. Place plants at the same soil depth as they were in the container you purchased them in. Because there are several different fungi that cause root rots, have the disease diagnosed at the Texas A & M Plant Disease Lab or by Extension personnel before applying fungicide.
Fire Blight
Description: Bacterial disease that causes rapid blackening and desiccation of blooms and foliage. Affected shoots bend at the tip in a "shepherd's hook". Black, sunken twig and branch cankers develop later. Problem: Fire Blight causes twig dieback and blossom blight in up to 2-24 inches of twig length. The bacterium stays in the cankers over winter and in the spring, oozes from the cankers and is carried by wind, rain and insects to healthy foliage.
Attacks:
Pears
Apples
Pyracantha
Quince
Loquat
Indian Hawthorne
Photinia
Least Toxic Solutions
Avoid high nitrogen levels and excessive pruning. Vigorous growth is much more susceptible to fire blight. Prune four inches below visible cankers. pruning equipment between cuts with one part household bleach to nine parts of water. Clean and oil equipment after pruning. Select fire blight resistant varieties and species. Contact the Extension office at 854-9600 for a list. With the exception of Kocide® and streptomycin sulfate, chemical controls are usually ineffective.
Oak Wilt
Description
Fungus that plug water-conducting vessels, reducing flow of water up the stem of the tree. Often causes leaves to wilt and fall prematurely. Live Oaks: Tree appears weakened. One area of the tree dies at a time. Areas around leaf veins are often brightly colored.
Red Oaks: Die in a flash of fall color in early summer.
Problem
Disease spread by beetles feeding on tree wounds. Also can travel from tree to tree through interconnected roots. Oak Wilt travels 75 feet per year in all directions. Live Oaks die quickly one tree at a time.
Attacks
- Blackjack Oak
- Live Oaks
- Schumard Oak
- Spanish Oak/Texas Red Oak
Least Toxic Solutions:
- Prune oak trees only in the coldest part of winter and hottest part of summer.
- Use a pruning paint to protect cut or wounded areas immediately after pruning or wounds are discovered. Sterilize tools after pruning.
- Contact Chris Dolan, City of Austin Oak Wilt Suppression Program at 512-974-1881 for information.
- Trench 4' deep and at least 100 feet from infected and susceptible trees to sever root connections.
- Only use old, dry wood if you use oak firewood.
- Certified applicators can inject ALAMO® into tree roots. This method is best used as a preventative.
Thrips
Description
Description To the naked eye, they look like tiny threads; with a hand lens, their narrow, fringed wings are visible. When holding an infested rose bloom you can see that they are very active. They may even bite!
Infestation
Tattered flowers, deformed flowers, silvery spots or streaks on leaves - by the time damage is visible the infestation is already severe.
Attacks:
- Roses
- Daylilies
- Iris
- other flowers
Lifecycle
Adults lay hundreds of eggs in plant tissue. In Roses, the eggs hatch inside the flower bud. The resulting nymphs scrap plant tissue, then, suck the sap, damaging the flower before it opens. There are many generations per year.
Least Toxic Solutions: Thrips are notoriously very difficult to control, so early detection is important when trying to keep the populations in check.
Aim for control rather than eradication. The only way to completely get rid of thrips is to destroy the infested plants - not an option most want to consider
- Remove and dispose of infested blooms
- Clean up leaf litter
- Always read and follow pesticide labels
-
Alternate the following treatments:
- Spray with Neem oil. For best results the spray needs to come in contact with the insect, but Neem oil is also slightly systemic; meaning some of it will absorb into the plant tissue and help weaken the insect after it feeds on the plant
- Dust plants and immediate area with diatomaceous earth Use a light weight horticultural oil
Viruses
Description
Sub-microscopic infectious particles that multiply only inside living cells. Viruses enter plants through wounds and by insects that feed on plants. Symptoms vary but include abnormal color, vein patterns, shape, mottling, ring spots and mosaic patterns in leaves; Can include abnormal flower color and fruit size, shape and color.
Problem
Seldom lethal to plants, but severely affect the quantity, quality and longevity of the host plant.
Attacks
Many types of plants.
Least Toxic Solutions:
- Chemicals do not effectively control virus diseases.
- Select plant stock that is free of viruses.
- Cover susceptible annual garden plants with a row cover fabric to keep sucking insects away from healthy plants.
- Diseased plants should be removed and destroyed to prevent infection of other plants by sucking insects that move from plant to plant.