Key Features
- Incredibly broad host range
- Damage between veins
- Spots have straight edges
Symptoms
In leaves with parallel veins, like hosta, nematode feeding causes 'V', or wedge-shaped, sections of dead tissue. In leaves with a net-like vein pattern, like chrysanthemum, affected areas are blocky, irregularly-shaped patches that are outlined by the veins. Foliar nematodes occasionally cause serious defoliation. Samples of infested plants can be sent to a plant disease diagnostic lab for confirmation.
Biology
Foliar nematodes are microscopic roundworms that infect plants and overwinter on infected plant debris. Adults emerge the following season and travel to leaves through standing water and films of water on plant surfaces caused by dew, fog, rain, irrigation water, or high humidity. They feed through growing season, but symptoms do not show until late in the summer. Foliar nematodes cannot infect or spread without water on leaves and stems.
Management Recommendations
Minimize leaf wetness to slow nematode movement (drip irrigation is recommended). Plant susceptible plants in locations that will receive adequate sunlight. Remove and destroy infected leaves through the season and all dried leaves and stems during fall clean up. Consider removing and destroying infected plants. Fallen, infested leaves contain thousands of nematodes that can survive on the dried plant material for a very long time. Insecticidal soap should be applied when symptoms appear. Always read and follow the product label.
Effective Pesticides
Active Ingredients include: Insecticidal soap (Potassium salt of fatty acid)
Resources
