Fusarium Wilt Problematic on Chrysanthemum in 2020
The number of chrysanthemum samples diagnosed with Fusarium wilt this year is well above average, according to NC State University Plant Disease and Insect Clinic records. The cause of this increase is unknown, but it highlights the importance of frequent scouting and sanitation for growers.
Fusarium wilt of chrysanthemum is caused by the soil-borne fungi Fusarium oxysporum f. sp. chrysanthemi and F. oxysporum f. sp. tracheiphilum. The fungi produce microscopic structures that can survive for years in soil or crop debris. The fungi enter their host plant through the roots and colonize the vascular tissue up into the stem.
Symptoms typical of Fusarium wilt on chrysanthemum often include uneven wilting, where one shoot or one part of the plant wilts while the remainder of the plant appears healthy. Wilting of entire plants can also occur.
Fusarium oxysporum can be introduced into greenhouses and nurseries via infected propagative material. The material can appear to be healthy at the time of planting, and weeks or even months may pass before symptoms develop. Rouging unhealthy propagation material is the first step in avoiding this disease, but is a challenge because of this latency.
Sanitation practices such as using clean pots and potting media, disposing of infested crop material, potting media, and pots, and sanitizing the planting area between crops also help to minimize the impact of this disease.
For more information on this disease, Ann Chase has an article in Greenhouse Magazine. For fungicide recommendations to manage this disease, see the NC Agricultural Chemicals Manual (starting on page 505). Products such as Heritage (azoxystrobin), Compass (trifloxystrobin), Hurricane (fludioxonil+mefenoxam), Insignia (pyraclostrobin), Tourney (metconazole) and Trinity (triticonazole) have shown some efficacy, although results can be inconsistent.
If you suspect Fusarium wilt of chrysanthemum, contact your local Cooperative Extension agent or submit directly to the NC State University Plant Disease and Insect Clinic.