The canker surface may be cracked and darker than the surrounding healthy bark. Tissues below the canker face turn brown, and this discoloration often extends several inches above and below the canker margin. Unlike Seridium canker, there is little or no resin flow. Discolored bark on limb of Leyland cypress damaged by Bot canker Figure 3. Spores of the causal fungus are spread to adjacent healthy tissues by splashing water.
Free moisture is needed for spores to germinate.
Colonization of twigs and branches is largely limited to trees damaged by extreme heat or cold alone or in combination with drought stress. Control Stress-related diseases such as Bot canker can be avoided if proper establishment and maintenance practices are followed. To minimize the impact of transplant shock, new plantings of Leyland cypress should be established in the fall. Till an area three to four times the diameter of the original root ball, adjust soil fertility and pH according to the results of a soil fertility test, and amend the soil as needed with well-rotted pine bark or sawdust. Always set Leyland cypress so that the root ball sits at or just above the soil level.