|Two of my large rose bushes (about 5' tall) suddenly started dying. Today, one of them literally fell over. All the roots were gone. What am I looking for? There is no evidence of gophers or any other animals, bugs or insects. Other rose bushes, right next to it, are doing fine. It appears something destroyed the roots.
|If you've eliminated all the obvious possibilities for the death of your rose bush, the plant may have fallen victim to a root rot. One of the most common root rots is caused by a fungus.
Phytophthora root rot greatly reduces the volume of the roots, which are needed by the plant to absorb and transport water and nutrients. The roots on diseased plants are brittle and brown to reddish-brown in color. A network of fine, discolored feeder roots may be confined to one area or include the entire root system. The causal fungi usually colonize the crown of the plants, often girdling the stem at or just above the soil line. A brown to reddish-brown discoloration of the tissues occurs just below the bark and may extend up the stem above the soil line.
Symptoms vary according to the degree of root colonization by Phytophthora root rot fungi, plant age, root-rot susceptibility, and environmental stress. It is not uncommon for some plants to remain almost symptomless until the disease takes over completely.
For a positive identification of the problem, take a sample of the plant (including foliage, canes, crown and roots) to your local Extension office, 625 Miramontes St. Suite 200, Half Moon Bay 94019. Phone (415) 726-9059.