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www.arborage.com ARBOR AGE OCTOBER 2014 25 of the country, but the vast majority of oaks killed by this are in forest stand or savanna settings. One tree contracts the fungus from a beetle and it quickly spreads to its neighbors. Dutch elm disease, on the other hand, is more common in urban areas and, thanks to prompt sanitation, infected elms are often removed before the fungus can grow into adjacent elm trees. Proper management of both oak wilt and Dutch elm disease often requires physically breaking the root grafts between an infected tree and a healthy tree. Like many things in arboriculture, this is often easier said than done. In the loamy soils of the Great Plains, root grafts can be severed using a vibratory plow. Trenches are usually cut four- to six-feet deep between the trees. In urban areas, this can be challenging with site factors such as buried utilities, sprinkler systems, driveways, and sidewalks. In the hard limestone soils of central Texas, the blade of a vibratory plow just won't do. Where root graft severing needs to take place, the power of a rock saw is often employed. This is a diffi cult and noisy operation but necessary to prevent the spread of the oak wilt fungus to healthy stands of trees. Studying the formation, functions, and implication of shared root systems in urban trees could open up a new understanding of how these living communities interact with each other. New sensing techniques could certainly improve how we study underground interactions, and perhaps lead to new ways to care for trees. At the very least, shared root systems serve as a reminder that there are many aspects of arboriculture we are just beginning to discover. And, who knows, it might lead to an albino tree planting craze. Brandon Gallagher Watson is creative director at Rainbow Treecare Scientifi c Advancements, and is an ISA Certifi ed Arborist (#MN-4086A). PLANT HEALTH CARE The number one choice of tree care professionals now comes in a liquid. We've combined the most widely used fertilizer in the industry with the most abundant compound on earth. The result? Three Doggett fertilizers that now come in 100% soluble liquids. Arbor 20-0-6 E A complete package with micronutrients and a 50% slow release formulation Fall Arbor 6-12-12 E Stimulates roots without pushing top growth that might not harden before a freeze Palm & Southern Ornamental 8-0-12 E A full complement of a minor element package, including manganese and magnesium With no mechanical agitation necessary, tree care professionals can feed more responsibly and easily than ever with this expanded line from Doggett. It's that simple. the doggett corporation NPK MEETS H2O 800-448-1862 | doggettcorp.com A trench line in Texas soils. In some cases, such as oak wilt, transmission through root grafts is responsible for up to 90 percent of the new infections.