Factors affecting canker development on Populus tremuloides artificially inoculated with Hypoxylon pruinatum

A technique was devised for obtaining extensive canker development on wounded greenhouse-grown aspens (Populus tremuloides Mich.) inoculated with mycelium of Hypoxylon pruinatum (Klot.) Cke. Cankers developed rapidly only on water-stressed plants, and under such conditions often averaged 75 mm in length within 10 days. Alcohol treatment of stems before inoculation did not affect the course of canker development. Cankers developed most rapidly on plants watered every third or every fifth day, and developed least in plants watered daily. Stem wounds exposing the wood were essential for canker development. Wounds required an 8-day period before inoculation to heal sufficiently to inhibit canker development. Wound sites midway on the stem were most susceptible to canker development, while sites near the growing point were the least susceptible. Time for symptom appearance was prolonged in inoculated plants of larger diameters.