See
Onion (Allium cepa) - Fusarium Basal Rot
Cause Fusarium proliferatum, a fungus. Other Fusarium species are also reported as pathogenic on garlic, including F. oxysporum f. sp. cepae and F. verticillioides. This fungus can persist in soil and plant debris. Other crop plants can be hosts to this fungus, including sweet corn. Fusarium species are good saprophytes, which enables F. proliferatum to persist more than several years in soil in spite of not producing any chlamydospores (durable survival structures). Fusarium species in general can potentially increase their population on plant debris as well as in the rhizosphere of asymptomatic plants. Infection of garlic by F. proliferatum known as dry rot has been reported in Italy, Spain, and elsewhere, where it is reported to cause large yield losses post-harvest. This disease occurs in garlic production on most continents. Researchers in Italy have developed evidence from multi-year field studies on farms that indicate that this fungus is favored by rainy weather, and have recovered F. proliferatum from basal plate portions of garlic in early stages of plant development prior to harvest. Fusarium oxysporum f. sp. cepae may co-occur with F. proliferatum on garlic. Both of these Fusarium species have been reported to occur on commercial garlic seed cloves, including from commercial seed garlic in Oregon and Washington. Severe losses can occur in garlic due to F. proliferatum. Also, this fungi can produce mycotoxins in garlic cloves, which can be harmful to humans.
Symptoms Symptoms will vary with with timing of infection and environmental conditions. This rot of garlic bulbs in storage shows symptoms similar to the neck rot. Symptoms usually start at the neck and progress down along the fleshy scales, but the basal plate may not be affected. Brown-tan spots may be observed on the basal plate area. Infected scale appears faint yellow, water-soaked, and translucent, later turning tan-brown, soften, and then dry out. Occasionally, a white to pinkish mold grows on or between rotten scales. Frequently, the rot appears to progress along a single fleshy scale in the bulb, although rotting of all the scales in a bulb also has been observed. Usually, infected bulbs do not show any pronounced external symptoms or signs of the fungus.
Cultural control At present, few control measures are recommnended because the mode of infection and conditions that favor disease development are not well understood.
- Rotate out of alliums and avoid sweet corn, wheat, potato, and sunflower for four years.
- Ensure that seed cloves are free from Fusarium species.
- Use aerial bulbils that are produced on the scapes rather than seed cloves.
- Avoid injuring bulbs during harvest and post-harvest handling.
- Clean equipment after working in infested fields; power washing to remove soil and plant debris will aid in reducing the spread on-farm.
- Examine harvested bulbs closely and cull any bulbs with evidence of disease before storage.
- Maintain ideal environmental conditions while garlic is in storage, with relative humidity maintained at 60-70% under cold conditions.
Biological control Efficacy unknown in the Pacific Northwest.
- Bexfond at 7 to 28 fl oz/A for soil applications at planting via drenches, in-furrow applications, drip irrigation, or sprays, followed by irrigation, and reapply at 4 week intervals. 4-hr reentry. O
- Prestop WG at 1.4 to 14 oz/10 gal water (0.1% to 1.0% suspension) as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Stargus at 6 to 8 fl oz per 1,000 ft row as an in-furrow treatment, or 3 to 4 quarts/A as a soil drench (drip or chemigation) on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O
References
Dugan, F.M., Hellier, B.C., and Lupien, S.L. 2007. Pathogenic fungi in garlic seed cloves from the United States and China, and efficacy of fungicides against pathogens in garlic germplasm in Washington State. Journal of Phytopathology 155: 437-45.
Gálvez, L., and Palmero, D. Fusarium dry rot of garlic bulbs caused by Fusarium proliferatum: A review. 2022. Horticulturae 8:628. https://doi.org/10.3390/horticulturae8070628.
Mondani, L., Chiusa, G., and Battilani, P. 2021. Fungi associated with garlic during the cropping season, with focus on Fusarium proliferatum and F. oxysporum. Plant Health Prog., 22, 37-46.
Schwartz, H.F., and Mohan, S.K. Compendium of Onion and Garlic Diseases and Pests; APS Press: St. Paul, MN, USA, 2008.