Cause Fusarium has been reported on California poppy in CA and FL; Verticillium dahliae has been reported in CA. OSU surveys of seed fields over several years in Oregon have detected Fusarium spp. associated with wilting of plants. Both fungi survive in soil as durable resting structures; chlamydospores produced by Fusarium and microsclerotia of V. dahliae can survive years between hosts. Higher pathogen populations can be encountered in plant debris. These fungi can be spread through soil movement on equipment, tools, and footwear as well as windborne or waterborne movement of infested soil. Fusarium also produces spores that can be moved with wind or water.
Symptoms Seedlings change slightly in color initially, to a slight blue-green hue, then to a reddish-purple color on leaf tips. Growth is retarded. Wilting develops and lower leaves die; sometimes the entire plant dies. Often a color change is evident inside the tap root.
Cultural control
- Plant pathogen-free seed in pathogen-free soil or potting mix.
- Thoroughly clean and disinfect used pots or flats.
- Avoid establishment of seed fields in soils with high levels of plant residues or organic amendments.
- Remove and destroy infected plants.
- Rotating out of California poppy for 4 to 6 years will aid in reducing losses to Fusarium.
Biological control
- Bexfond at 7 to 28 fl oz/A. O
- Tenet WP at 2.5 to 5.0 lb/A at sowing will suppress certain fungal pathogens including Fusarium, Rhizoctonia, and Pythium spp. See label for specific application types and timings. 1-hr reentry. O