Cause The OSU Plant Clinic has found several soilborne organisms associated with skimmia root problems including Phytophthora sp., Pythium sp., and Fusarium sp. in addition to Armillaria root rot. These pathogens are typically favored by excessive soil moisture and/or poor drainage. Root rots tend to cause plants to wilt rather than become chlorotic. These plants are shade loving and may become chlorotic due to poor, dry soil, overexposure to the sun or mites.
The following have been found in nurseries and in ornamental plantings in Europe: Phytophthora cactorum, P. cryptogea, P. megasperma, P. nicotianae, and P. plurivora.
Symptoms Roots become brown and rotted. Root crowns become soft, discolored and water-soaked. Above ground, the green leaves wilt due to non-function of the root system. Stem dieback may also occur.
Cultural control
- Use new trays and pots with clean soilless media. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
- Do not overwater.
- Provide good drainage for plants in beds, fields, or containers. Place containers on gravel beds (4 inches or more deep) to allow drainage. Do not place containers on poly sheets; they can prevent containers from draining into soil and allow contaminated drainage water to spread from the base of one container to another.
Chemical control No chemicals are specially registered for this crop and none were found in the IR-4 research database.
Reference Jung, T., Orlikowski, L., Henricot, B., Abad-Campos, P., Aday, A. G., Aguín Casal, O., Bakonyi, J., Cacciola, S. O., Cech, T., Chavarriaga, D., and Corcobado, T. 2016. Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseases. Forest Pathology, 46:134-163. (See online supporting tables.)