Beschreibung:
<jats:p>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.</jats:p>