Rob Smith had a surprise with his onions!
I’m working hard to deal with the effects of dreaded fungal disease
As the days become shorter and the temperature starts to drop, I’ve been dodging rain showers on the allotment, trying to get jobs done. One thing I’d forgotten to do was dig up some of my remaining onions I’d grown from seed – I never seemed to have a fine day to let them dry out on the top of the soil. When I did get around to digging them up, I was greeted with a nasty surprise – onion white rot ( Stromatinia cepivora). This fungal disease affects most of the edible allium family, including garlic, leeks and, of course, onions, but funnily enough elephant garlic doesn’t seem to succumb as easily to the disease.
You can tell if you have the disease as your onions will have drooping, yellowing leaves and the bulbs will feel loose in the soil if you give them a wobble. When harvesting, you’ll see a white, fluffy substance on the bottom of the bulb and you’ll get a smell of rotting onion. You’ll then have to burn the affected bulbs, and if that wasn’t bad enough the fungus can stay dormant in the soil for 10-15 years, meaning you shouldn’t grow alliums there again!
The fungus is easily spread by tools or on your footwear, so be careful you don’t spread it all over your plot. There are a few things you can do to carry on growing onions. Firstly, grow them in another bed or in a raised bed with new soil. Secondly, you can water the bed every month with garlic water (five crushed garlic in two litres of water left overnight). The fungus can only germinate once before dying, so fooling it to grow when there are no bulbs for it to affect with this dummy water solution can reduce the problem. It won’t affect other plants, so you can still grow things in the bed while treating it. You can also grow ‘Caliente’ mustard (available from Marshalls, www.marshalls-seeds.co.uk) as this green manure is a bio-fumigant, which can control disease. Make sure to chop the mustard up very small and bury it within 20 minutes to get maximum effect from the gasses given off. I use a rotavator for this. None of these methods will fully cure the problem, but I’m hoping it will reduce the effects of the fungus on my plot next year.