Effects of Caliciopsis pinea inoculation with and without wounding on Pinus strobus

The canker pathogen, Caliciopsis pinea, and a bast scale, Matsucoccus macrocicatrices, have been found strongly associated with dieback and mortality of eastern white pine (Pinus strobus) in the Appalachian Mountains of the United States. The scale is thought to be a wounding agent that creates infection courts for fungal pathogens like C. pinea. Inoculation tests on 3-year-old containerized eastern white pine seedlings were conducted with and without wounding. Puncture wound treatments designed to mimic insect wounds were applied to stems and to branch crotches. An inoculation treatment consisting of a 0.1 ml suspension containing 30,700-32,359 C. pinea ascospores was dripped on each area with puncture wounds or a nonwounded area of stems and branch crotches in two separate tests. In another series of tests, C. pinea mycelial plugs were placed on 4 mm diameter stem wounds and on nonwounded stems. Inoculation of wounds with C. pinea resulted in expanding resinous cankers, and C. pinea was reisolated from 80% to 100% of puncture wounds on stems, 40%-75% of puncture wounds on branch crotches and 100% from the 4 mm wound with mycelial inoculum. No cankers formed in nonwounded stems and branch crotches following inoculation with both types of C. pinea inoculum. The results of this study suggest that ascospores moved by water, as occurs during rains, would be able to infect small puncture wounds on a seedling stem. The tests also found that an individual C. pinea canker was not capable of girdling a seedling within a year following inoculation, suggesting that this pathogen is not particularly lethal and likely requires multiple infection courts provided by the scale to girdle branches and sapling stems.