Cause The OSU Plant Clinic has diagnosed root rot on rockrose a few times by the oomycetes Pythium or Phytophthora. The primary cause is overwatering. These plants are well adapted to growing in hot, dry situations, and in relatively poor soils.
Symptoms Leaf chlorosis, defoliation, and wilt associated with root and collar rot. Note: they may drop leaves during prolonged periods of drought.
Cultural control
- Use ground sources for irrigation and avoid surface water sources for propagation of the crop.
- Good drainage and water management are essential components of a management plan. Ensure growing media and holding areas are well drained.
- Use new pots, trays, or treat any reused items with a disinfectant, use steam, or solarization techniques (such as with anti-condensation film) to clean them.
- Plant in full sun and well drained areas in the landscape. Easily grown without summer irrigation.
Reference Cacciola, S. O., Scibetta, S., Pane, A., Faedda, R. and Rizza, C. 2009. Callistemon citrinus and Cistus salvifolius, two new hosts of Phytophthora taxon niederhauserii in Italy. Plant Disease, 93:1075-1075.