What's happened to my onions?

oscarato

I bought a bag of Turbo onion sets from Wilko’s in January and put them in the fridge to stop them sprouting early, then planted them out in early April. The bed had potatoes in last year and had been dug over and rotavated. It is a sheltered spot and does not get a huge amount of sun as it is next to the house and adjacent to a 6ft hedge to the south. The sets sprouted as normal (I’d had an excellent crop of Turbos last year in another bed), but then some of them started to distort and twist as shown in the photos which stunted growth and led to some rotting. I pulled up one of the sickest looking onions and examined it to find a small maggot in the rotted part (see photos) but I don’t know if this bug is the cause of the problem. Some of the onions have been less affected, particularly further up the bed. Can you tell me what’s gone wrong and suggest how I can avoid it next year please?

Obelixx

Sorry, but it sounds like you have eel worms and the only solution is to destroy the crop - do not compost it - and then grow no more members of the onion family for at least 3 years so they die out in the soil for lack of hosts.

https://www.rhs.org.uk/biodiversity/stem-and-bulb-nematode 

fidgetbones

Onion fly larvae  will feed on the roots of onions.  The remedy is same as above, dig them up, destroy, practice good crop rotation.

oscarato

Thanks guys, I’ll follow your advice

oscarato

Further update, I’ve dug up the onions and examined a dozen or so without finding any further ‘maggots’. The main two features on all of them are distorted leaves and soft/rotting outer layers. No evidence of any burrowing or eating of the bulbs. Are you still convinced that it’s an eelworm/onion fly larva problem?

Obelixx

maybe allium leaf miner then.  They can be active in spring then seem to disappear but leave the plants prone to rotting and then you can get a second wave later in summer that does more damage.

https://www.rhs.org.uk/biodiversity/allium-leaf-miner 

oscarato

Thanks Obelixx, I followed your link but I don’t think it’s allium leaf miner as there are no lines of ‘white dots’ on the leaves. It’s the distortion of the leaves that puzzles me - I wondered if it might be some sort of virus. I also googled curly onion leaves and found a forum with some blaming it on the very dry spell we had in the spring. The onion roots look perfectly healthy by the way

Obelixx

Dunno then.  I have largely given up growing edible onions here as we get too hot and dry for their teeny root systems and we get very poor results despite soil conditioning.   Oddly tho, the ornamental varieties do well as long as I plant them deep enough and some are even recommended for dry conditions.

fidgetbones

Looking at the cracks in the soil, is the soil clay and dried out?

oscarato

No I’m in south Lincs fens area the soil is lightish/sandy but does cake quite hard when dry. I’ve Ben growing onions from sets for about 10 years and not come across this problem before. Don’t usually feel the need to water the onions unless we have a long dry spell 

Dovefromabove

My brother is a big onion grower for the supermarkets … he’s had a look at your pictures and has asked for a clearer photo of the roots … he thinks it may be White Rot.