Frequently roots will appear healthy in the upper 2 to 4 inches of soil where soil drainage is not a problem, while the deeper roots are rotted because of poor drainage in the lower soil profile. Root injury caused by root rot fungi will frequently show the same symptoms as described above. However, a key symptom to look for if root rot fungi are the primary problem is a dark discoloration of the tissues under the bark, close to the ground level. If dieback symptoms are accompanied by many rounded notches eaten out of leaf margins this could indicate the presence of the black vine weevil. Inspect further for small white-bodied larvae in soil at the base of the plant.
Management Always consider drainage and soil type before planting.
Future problems are best avoided before, not after planting. Improving drainage is the primary aim for controlling dieback, whether it is caused by excess soil moisture or root rot fungi. Surface drainage refers to the removal of free water from the soil surface to an adequate outlet. Outlets might include a street curb, natural drainage channel, or an underground drain. Soil surfaces should always slope away from buildings .