At the expense of showing my own Maple I want to show you what I mean by one form of Phytophthora and Verticillium. Please bear in mind that many of our plant related books do not identify specific strains or species of many of the plant pathogens that cause diseases. I am guilty of doing the same thing as I have not assayed the fungus or grown the bacterium in culture in order to identify a specific invader of Maples. I have, however, taken the necessary steps to identify organisms in other plants when I was an extension researcher for four years in Plant Diseases of Fruit & Nut trees as well as Field Crops in a former life. The jury is still out as to whether a specific Phytophthora is at work on Maples. I happen to believe that one form of Phytophthora does indeed hit Maples. Most of us know of Phytophthora as being a root rot causal agent but other forms of the same organism also can be a blast or a blight causal agent as well. Most of the research done on Phytophthora has been specific to a certain plant and thus Phytophthora fragaria is named after a fungal disease on certain Berries (Raspberry, Blackberry, Strawberry, Blueberry). This Maple was superb looking two years ago with little or no die back. Even after last years trimming and some removal of dead wood during the winter you can still see the die back on the twigs. Notice the color of the twigs as that to me is the give away that Phytophthora was the primary invader. What you see at work now is the result of Verticillium, the lethal form. What has happened is that the plant two years ago was hit by Phytophthora which weakened this plant and now the Verticillium that has been in the plant all along will kill this plant. Notice the drooping of the leaves as one week ago the leaves were turgid and erect, now they are limp and listless. This stage is the initial hint that Verticillium is in fact plugging up the vascular system right now and in about a week the leaves will turn brown, shrivel up and there will not be any new vegetative buds to appear to serve as re-growth. This plant is a goner pure and simple. What I found two days ago on the internet is that what we were told was a form of Phytophthora by a Plant Pathologist back in the 80's may indeed be another form of Verticillium, the second form I mentioned in a previous post. After seeing how the bark turns a grayish black in color with brownish red splotches of color just underneath the outer bark that the one article I read may be correct in that it is a non-lethal but destructive form of Verticillium. Most of us still equate Verticillium in Cotton as being the most destructive disease for us on seedling Cotton. I have always felt it was the Plant Pathologists that should be determining which forms of Phytophthora and which forms of Verticillium are the primary attackers of Maples. Someday we will know the straight and skinny on which species are indeed our primary killers of our Maples and what we can do to ward off and prevent such organisms from hurting us again. Jim
