I maintain a garden which has a number of Acers in it. There are 12 A.griseum and there were 8 A.japonicas, but 3 have succumbed to Verticilleum Wilt this past year. Am I going to lose them all? Also, any suggestions for replacements? My client wants the red foliage, if possible. I am very careful about hygiene, sterilizing tools, etc.
It is difficult to know what your particular situation is like. In my experience, verticillium is a fairly opportunistic organism, attacking plants that are already weakened by some kind of root stress--in this area, typically drought in summer and/or flooding in winter. Once verticillium becomes established, however, it then becomes more virulent, and will infect more plants, more often and more severely. This is probably due to an increase in the amount of spores present in the area. Because the resting spores of the verticillium pathogen are extremely resistant and long-lived (up to 4 years in the soil without a host), planting susceptible stock is a recipe for disaster. Even maintaining adjacent susceptible plants may be impossible when the inoculum load becomes high. For most maples, adequate drainage is paramount to their survival. Summer irrigation is also important, particularly on thin soils or in overheated surroundings. Most maples, given optimal conditions, will tolerate a low level of verticillium, but heavily infected plants need to be removed quickly, as the dead and dying tissues (including the roots) are themselves sources of disease. The following link to Virginia Cooperative Extension gives a brief overview of the disease and lists both susceptible and resistant species.
