Brown Leaves on a Lemon Tree

Identification

• Lemon trees are susceptible to Phytophthora root rot caused by Phytophthora citrophthora and P. parasitica. The soil borne pathogens persist for extended periods in soil even under adverse conditions. The disease is common in trees growing in poorly drained soil.

Damage

• The fungus enters the tree through the roots. Initial symptoms include declining tree health. Foliage starts to discolor, turning light green to yellow and brown before dropping. The roots start to rot, causing the disruption of water and nutrient intake. Reserve energy levels and fruit production decline.

Management

• Keep trees in good health to avoid drought stress. Choose resistant varieties to minimize disease and plant in well-drained ground. Pre-planting soil treatments include the use of chloropicrin or metam sodium. Recommended fungicides for trees include mefenoxam and fosetyl-al.