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Arboriculture & Urban Forestry Online
Volume 28, Issue 2 — March 2002

Effects of Dicamba Herbicide on Tubercularia Ulmea Canker Development    (View PDF)

Marcus B. Jackson and Robert W. Stack

Abstract: Dicamba (3,6-dichloro-o-anisic acid) herbicide was applied to the roots of potted Siberian elm (Ulmus pumila) and Russian-olive (Elaeagnus angustifolia) trees in a greenhouse. Five herbicide concentrations were used: equivalent to rates of 0 (0), 93 (1/12), 140 (1/8), 280 (1/4), and 1,121 (1) g/ha (lb/ac) active ingredient. Two weeks after herbicide application, each tree was inoculated with a single isolate of the canker-causing fungus Tubercularia ulmea. The experiment was repeated using two different T. ulmea isolates. Leaf cupping, a symptom of dicamba exposure, was evident two to three weeks after herbicide application. Symptoms occurred at rates of 140 g/ha (1/8 lb/ac) and above in the Siberian elms and the 1,121 g/ha (1 lb/ac) rate in the Russian-olives. All four T. ulmea isolates caused cankers, with canker size differences between fungal isolates and between tree species. None of the herbicide treatments increased or decreased T. ulmea canker size.

Keywords: Disease; elm; Ulmus; Russian-olive; Elaeagnus.

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