Citrus Trees and Cotton Root Rot
Introduction
Citrus trees are beloved for their delicious fruits, but they can be susceptible to a variety of diseases, including cotton root rot. This devastating disease is caused by a fungus that attacks the roots of citrus trees, leading to wilting, yellowing leaves, and eventually death.
What is Cotton Root Rot?
Cotton root rot is a fungal disease that affects over 200 types of plants, including citrus trees. It is also known as Texas root rot or Ozonium root rot. The fungus that causes cotton root rot is called Phymatotrichum omnivorum.
Symptoms of Cotton Root Rot
The initial symptoms of cotton root rot can be difficult to distinguish from other plant ailments. However, there are some key signs to look for:
- Stunting and wilting
- Yellowing or bronze leaves
- Rapid progression of symptoms, with top foliage showing signs first
- Leaves dying and remaining attached by their petioles
- Cottony growth around the base of the plant
- Decayed root bark
- Plants easily pulling out of the ground
Causes of Cotton Root Rot
Cotton root rot is caused by the fungus Phymatotrichum omnivorum, which lives in the soil. The fungus is most prevalent in calcareous clay soil with a pH of 7.0 to 8.5. It can survive in the soil for several years, even in the absence of host plants.
Where Does Cotton Root Rot Occur?
Cotton root rot is most common in warm regions, such as Texas, western Arizona, southern New Mexico and Oklahoma, Baja California, and northern Mexico. It typically occurs when soil temperatures reach 82 degrees Fahrenheit (28 degrees Celsius).
Prevention and Control of Cotton Root Rot
There is no cure for cotton root rot, but there are steps that can be taken to prevent and control the disease:
- Plant Resistant Varieties: Some citrus rootstocks are more resistant to cotton root rot than others. Sour orange rootstock is one of the most resistant.
- Soil Management: Amending soil with sand and organic materials can loosen the soil and make it less conducive to cotton root rot.
- Nitrogen Fertilization: Applying nitrogen in the form of ammonia has been shown to fumigate the soil and reduce root rot.
- Pruning and Soil Barriers: Infected trees can sometimes be rejuvenated by pruning the plant back and building a soil barrier around the edge of the root zone.
Conclusion
Cotton root rot is a serious disease that can devastate citrus trees. By understanding the symptoms, causes, and prevention methods, you can help protect your citrus trees from this destructive disease.
