Basal rot, a significant challenge for onion growers, is caused by the soil-borne pathogen Fusarium oxysporum f. sp. cepae. This fungus attacks the roots and basal plates of developing onion bulbs. Infection typically occurs when the pathogen penetrates the plant through wounds, insect damage, or root scars at the base of the bulbs.
Symptoms:
Basal rot is most prevalent in warm soil conditions, with temperatures exceeding 27°C. The key symptoms include:
Above-ground indicators: Progressive yellowing and dieback of leaf tips, often linked to decaying roots and basal plates.
Bulb characteristics: Small, immature bulbs. Susceptibility to soft rot caused by secondary bacterial infections.
Diagnosis: The disease can be easily confirmed by slicing an infected bulb in half and observing brown discoloration in the roots and basal plate.
Management strategies:
Since Fusarium basal rot is a soil-borne pathogen, it is challenging to eliminate once established. However, adopting the following practices can significantly reduce its impact:
1. Soil and planting practices: Grow onions in fertile, well-drained soil to promote healthy root systems. Minimise conditions that favour fungal growth by avoiding overly warm, waterlogged soil.
2. Pest management: Use preventative sprays to protect onion roots from damage caused by pests such as onion root fly maggots, which create entry points for the fungus.
3. Resistant varieties: Plant onion varieties bred for resistance to Fusarium basal rot. Sakata offers a selection of resistant onion hybrids that help mitigate the effects of the pathogen on bulb yield, quality, and storage life.
 By integrating these strategies into your growing practices, you can reduce the severity of basal rot and protect your onion crops from significant losses.
Disclaimer
This information is based on observations and sources believed to be reliable. However, crop performance depends on the interaction of genetic potential, seed characteristics, and environmental factors, including management practices. Sakata Seed Southern Africa (Pty) Ltd provides no express or implied warranty for crop performance based on this information and accepts no liability for losses resulting from its use. Please refer to Sakata Seed Southern Africa’s Conditions of Sale before ordering seed.