PHYTOPHERA – Root rot
Also known as collar rot or crown rot is a common and dreaded disease of fruit trees. It is caused by the fungus pathogen Phytophera spp. Symptoms depend on the extent of the infection to roots and crown tissue. In general, warm weather from Spring to Summer will increase the rate of rot, and will rapidly collapse and kill trees. Leaves wilt and dry, but remain on the tree. This is a sign of a disease troubling the trees over time, rather than a sudden cause that will typical cause trees to shed their leaves.
Growth reduction and senescence is a sign of chronic infections. These trees can years to succumb to this disease. Typically, phytophthora is fatal to younger trees, since their root systems are not well developed to sustain infection.
Solutions and Management
Irrigate properly to prevent and control root and crown rot. Pythopher thrives in wet areas. Especially when moist for a longer than full day. By not allowing water to collect and remain around the crown of trees, we prevent a favorable habitat for Phytophthora. Well draining soil is a key to prevent water from rotting roots. Do not plant in low spots that flood frequently and water can stand. Plant your trees higher than ground level or on berms, improving draining.
When Phytophthora is present, it is not yet possible to eradicate. Therefore, it’s important to not introduce infected plants, soil, water, and materials. Applications of fungicides reduce tree loss. Frequent but short irrigations, known as pulse irrigation can also reduce the risk of rot and plant loss. Choose rootstocks less susceptible, but none are resistance to all species of Phytophthora. Therefore, knowing the species of fungus present will help to choose appropriate rootstocks. M9 and M 26 are less susceptible to Phytophthora.