![]() More information on hypovirulence Blight control #3: Chemical (See page 14 of TACF Journal Volume 7, Issue 1) There are still many unknowns when dealing with hypovirulence but there is no doubt it keeps trees alive, and has spread in several places. In time, if you keep at it, you may be able to establish many hypovirulent cankers in your planting, and it may then start to spread by itself. If you are lucky, and the two blight cankers are the same type, you may be able to convert a canker that would have killed the stem into one which will only swell up and look bad. It may help to do this in several places around the edge of the killing canker. Try cutting out a small piece of the hypovirulent canker, including as much living bark as possible, and grafting it into the canker you want to heal. The object is to transfer some of the sick fungus, still alive, to a serious canker you want to infect. If you have serious infections in your planting already, you will not have much to lose. You can try several things, all of which may work -or may lead to worse infections. Getting the weak strains of fungus transferred to your planting will not be easy. Since this is the realm of experimentation, expect a lot of failures. If you find a tree that has been surviving with a canker for several years, you may have found a case of wild hypovirulence. Look for bigger sprouts with large, swollen cankers on them. If you want to get hypovirulence established in your plantings, you might try this: Go into your local woods to someplace where you know there are many surviving chestnut sprouts. "Wild" hypovirulence, occurring naturally, is becoming easier to find. The researchers who work on this problem are seldom able to find the time to go through the long process of matching virus and fungus types to save a specific tree, but that doesn't mean you can't experiment on your own. ![]() Someday soon hypovirulence may be an easy method to use for saving chestnut trees, but right now there are no commercially available preparations of the virus and you are in the area of experimentation. What usually causes this weakening of the fungus is actually a virus, which can be spread from one fungus to another. Hypovirulence is a condition in which the blight fungus itself gets sick. Link to an article that first describes the efficacy of the soil compress method in controlling chestnut blight cankers. Obviously, this will be difficult to carry out when your tree develops cankers in the crown after it gets to be thirty or forty feet tall, but this method is a valuable management tool when appropriate. You can add water at the top once or twice if it dries out. This is usually accomplished by making a black plastic sleeve to fit around the trunk, securing it with weatherproof tape, and filling it at least 2 inches thick with moist soil. The basics of the soil compress method are simple: you must keep the blight canker, and the entire trunk all around it at least a foot above and below any signs of blight, covered with moist soil for at least a couple of months. It will not protect your tree from new infections, nor save a tree that is already girdled, but it can cure individual cankers which might otherwise kill a trunk you want to protect. This method is inconvenient to use on very large trees. Apparently there is something in soil that effectively eliminates the blight fungus and allows the tree to heal. He thought to try packing soil over trunk cankers. ![]() ![]() Wayne Weidlich, an ACF Director, noted that chestnut blight will grow on chestnut roots if they are exposed. Excerpt taken from Volume 7, Issue 1 of the Journal of the American Chestnut Foundation Blight Control #1: Soil Compress Method. ![]()
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