Chrysanthemum nematode

The Chrysanthemum nematode (Aphelenchoides ritzemabosi) is a destructive plant-parasitic nematode belonging to the family Aphelenchoididae. Unlike soil-dwelling nematodes, this species is primarily a foliar pest, invading the aerial parts of plants such as leaves, stems, and buds.

This nematode has a wide host range, including many ornamentals and some agricultural crops. It commonly infests chrysanthemums, strawberries, begonias, dahlias, and various aster-family plants. The pest can survive in plant debris, dormant bulbs, and soil, making it a persistent threat in greenhouses and nurseries.

The biology of the pest is strictly dependent on high humidity. Nematodes migrate from the soil or debris to the foliage by swimming in thin films of water (dew or rain) on the plant surface. They enter the host through stomata, where they feed on the mesophyll cells, causing significant physiological stress to the plant.

Damage is characterized by interveinal chlorosis, which progresses to dark brown or black necrotic lesions. These spots are often angular in shape, bounded by leaf veins. As the infestation advances, leaves wither and drop prematurely. In severe cases, the entire plant becomes stunted, and flower buds may fail to open or appear severely deformed.

Control strategies must be integrated. Key practices include:

• Using only certified, nematode-free propagation material.
• Sanitizing tools and equipment to prevent cross-contamination.
• Removing and destroying all infested plant parts immediately.
• Implementing hot water treatment (45-50°C) for infected cuttings.
• Practicing crop rotation and controlling weeds that act as alternative hosts.