How to Cure Root Rot on Orange Trees

Orange trees are a fragrant and useful addition to any garden.

Orange trees not only provide nutritious fruit, but the flowers perfume the air with their unmistakable scent. Orange trees grow well in containers as well as in the yard and make attractive patio or poolside plants. With proper care and maintenance, orange trees generally suffer few problems. Occasionally, the trees may encounter root rot from infections caused by a variety of pathogens. Phytophthora, armillaria root rot, dry root rot, citrus nematode and cotton root rot can all cause orange tree roots to rot. Get an accurate diagnosis of the infection before attempting to treat the ailing tree. Take a sample of infected tissue to a laboratory or cooperative extension service for analysis.

Things You'll Need

• Pruning shears or clippers
• Rake
• Bleach, alcohol or liquid household disinfectant
• Shovel
• Plastic trash bags or wheelbarrow

Instructions

1. Improve drainage around the tree and avoid overwatering. Orange trees like moist, well-drained soil. Poorly drained soil and overwatering keeps the tree's roots wet, a common cause of root rot even when no pathogens are present. Correcting poor drainage around an established orange tree is difficult. Try digging a channel to funnel excess water away from the orange tree, or have a professional install tile drains.

2. Prune away dead or diseased limbs, twigs and branches. Root rot interferes with the tree's ability to circulate nutrients to the canopy. Infections of the roots can cause parts of the tree canopy to turn yellow, wilt or die, and some infections spread upward from the roots to damage other parts of the tree. If the pathogen is a virus, bacteria or vascular fungus, disinfect the blades of the shears or clippers between each cut. Use a mixture of one part bleach to nine parts water, ethanol or isopropyl (rubbing) alcohol or liquid household disinfectant. Spray, soak or dip the blades in disinfectant to sterilize them and avoid spreading infection.

3. Place the trimmings in the plastic bag or wheelbarrow to keep them from exuding spores that can return to the tree.

4. Rake up any plant debris on the ground around the tree, and place it into the trash bag or wheelbarrow. Pull weeds where spores may linger and toss the weeds into the trash bag or wheelbarrow. Transport the diseased plant tissue and debris away from the tree. Burn the material, if practical.

5. Apply a commercial fungicide specifically formulated to treat or prevent the pathogen infecting the orange tree. Follow label instructions carefully for proper application amounts and timing of treatments. Fungicides are generally applied as a drench on the soil around the base of the tree. Systemic fungicides are sprayed onto the foliage and circulate throughout the tree to the roots. The type of fungicide required depends on the pathogen infecting the roots.

Tips & Warnings

• Consider replacing the orange tree if treatment is ineffective or the damage to the tree is too severe to save it. Replace the orange tree with more resistant orange varieties or rootstocks. Sour orange rootstock, for example, is resistant to phytophthora foot rot and cotton root rot, but susceptible to nematodes.

• If the orange tree is growing in a container, fungicide alone may be ineffective. Remove the tree from the pot and discard the growing medium and any mulch or decorative items. Sterilize the container and wash the tree's roots. Trim away diseased root areas and affected foliage. Dip the roots in fungicide, and replant the tree in fresh, sterile growing medium.

References

• Texas A&M University Extension; Fungal Diseases and Nematodes; Jose M. Amador
• Washington State University Puyallup; Sterilized Pruning Tools: Nuisance or Necessity?; Dr. Linda Chalker-Scott
• University of California Davis; "California Agriculture"; How Disinfectants Compare in Preventing Transmission of Fire Blight; Beth L. Teviotdale, et al.; 1991
• Colorado State University Extension; Citrus Trees: An Ideal Indoor Plant Selection; Sheri Hunter
• University of Arizona Extension; Diseases of Citrus in Arizona; Mary Olsen, et al.
• Purdue University Extension; Houseplant Problems; Paul C. Pecknold; August 1996
• Texas A&M University Extension; Identification of and Corrective Action for Poorly Drained Soils in the Landscape; Wayne K. Clatterbuck, et al.

Resources

• Iowa State University; Cleaning and Disinfecting Plant Containers; Sherry Rindels; March 1994
• Purdue University Extension; Orange; Julia F. Morton; 1987
• Ohio State University; Fungal and Fungal-Like Diseases of Plants; Sarah D. Ellis, et al.