Home > Growing tips & recipes > How to Prevent and Manage White Rot on Onions and Garlic 8 min read 21.07.2025 How to Prevent and Manage White Rot on Onions and Garlic White rot is a devastating fungal disease that affects onions and garlic, often wiping out entire crops. In this blog, we explore how to prevent and manage white rot on onions and garlic using careful crop rotation, soil hygiene, resistant planting techniques, and natural deterrents. Learn how to spot the signs early and take practical steps to keep your alliums healthy and your garden soil disease-free. There’s nothing more gutting than gently pulling up what you thought was a perfect garlic bulb, only to find it mushy, mouldy, and riddled with fluffy white fungus. White rot is a soil-borne fungal disease that targets alliums, especially onions and garlic and once it sets in, it can linger in the soil for years.But don’t panic! With a few proactive steps, you can prevent and manage white rot on onions and garlic to safeguard our future harvests.What Is White Rot?White rot is a fungal disease that specifically attacks the roots and bulbs of allium crops. It’s one of the most serious diseases for onion and garlic growers because:It lives in the soil and can survive for up to 15-20 years It spreads easily through infected sets, soil, compost, and tools Once present, there’s no chemical cure, only prevention and good garden hygieneSymptoms include:Yellowing, wilting, or stunted growth White, fluffy fungal growth around the bulb Small black dots (sclerotia) in the soil or on roots Rotting of the bulb, often before it fully maturesStart with Clean Sets and SeedWe always start with certified disease-free onion sets and garlic cloves from a trusted supplier. Avoid:Swapping sets with other gardeners unless you’re sure they’re clean Replanting cloves from a previous year’s crop if white rot was suspectedOne bad bulb can introduce thousands of spores into otherwise clean soil.Rotate Crops (Religiously!)White rot spores are highly persistent. That’s why crop rotation is absolutely essential:Try not to plant onions, garlic, leeks, or shallots in the same bed for at least 4-6 years Use a rotation plan that separates alliums from other crops like brassicas, roots, and legumesAlso avoid planting alliums where ornamental alliums (like chives) have been grown.Maintain Impeccable Soil HygieneIf there’s one place to be a garden neat freak, it’s your allium bed. You can:Clean tools and gloves thoroughly between uses Avoid walking on or moving soil from infected areas to clean beds Never compost infected material, burn or dispose of it off-siteKeeping soil clean prevents unintentional spread of spores from one bed to another.Use Natural DeterrentsAlthough there’s no cure once white rot is in the soil, you can make life harder for it:Apply sulphate of potash in the autumn before planting, it strengthens cell walls and can reduce susceptibility Mix garlic powder into the soil in late summer to trick dormant spores into germinating before planting season, when no host is present (known as “suicide germination”) Maintain well-drained soil, white rot thrives in wet, heavy conditionsRaise Your Beds and Improve DrainageWhite rot is more aggressive in wet conditions. To keep things dry underfoot, you can try:Grow onions and garlic in raised beds or well-drained rows Mix grit or sharp sand into clay soils Avoid watering too frequently once bulbs begin to swellA drier soil environment makes it harder for the fungus to thrive.Remove Affected Plants ImmediatelyIf you see signs of white rot mid-season:Pull up infected plants right away, don’t leave them to rot in place Remove a generous scoop of surrounding soil Clean tools immediately Consider quarantining that bed from alliums for future seasonsEarly action can help limit the spread within a single growing season.Grow in Containers or Clean New BedsIf your soil is infected, all’s not lost! You can still grow alliums by:Using large containers or grow bags filled with fresh, sterile compost Building new raised beds with imported topsoil and compost Trying ornamental alliums in infected soil, just don’t eat them!These methods let you enjoy growing garlic and onions without risking reinfection.White rot is one of the more frustrating garden challenges, but it’s not unbeatable. With careful planning, clean planting, and a solid rotation system, you can prevent and manage white rot on onions and garlic and still enjoy plump bulbs and fragrant harvests for years to come. Meet the author Nelly Nelly works in the She Grows Veg marketing department and is an incredible cook! She's learning how to grow veg fast in her very own container garden. Her favourites so far are the Dwarf Sunflower called 'Sunspot' and our Dwarf Pea called 'Tom Thumb'. Previous How to Prevent and Treat Rust on Leeks and Beans Next How to Prevent and Control Black Rot in Brassicas