Seasonal effects on Wound Susceptibility and Canker Expansion in Honeylocusts Inoculated with Thyronectria Austro-Americana
Abstract: Field-grown Gleditsiatriacanthos seedlings were inoculated each month for two years with the fungus Thyronectria austro-americana. Resulting canker sizes were recorded monthly for one year after inoculation. The season in which inoculations occurred had a significant effect on average canker size. Canker size was largest after summer and fall inoculations, and smallest after winter and spring inoculations. Canker expansion ceased 7-10 months after inoculation in the fall, winter, and summer, and 3 - 4 months after spring inoculations. Thus, cankers resulting from spring inoculations were small and only expanded for a few months before host defenses stopped expansion. Cultivars (Skyline, Imperial, Sunburst) and one seedling selection (Thornless) were inoculated at 0, 7,14, and 21 days after wounding in the spring, summer, and fall of 1986 and 1987. Wounds remained susceptible to infection between 7 and 14 days in all but one season during the experiment. In 1986, spring wounds remained susceptible for 21 days. Thus, the season of inoculation did not greatly affect the duration wounds remained susceptible.