[jambop]

Hi Have been growing my onions down here and they are doing really well. It has been very hot and dry for about three weeks but the weather has just broken and we have had a lot of rain over the last three or four days is this likely to cause mildew on my onions? If it is what is the best action to take it should get dryer and warmer over the coming week. The standard treatment here is Bordeaux mix.

[m1ckz]

mine are suffering from white rot...i dont think anything can stop it......it looks like a white fungus  an they just fall over when i weed them 

[sunshineband]

The trouble with spraying anything onto onions is that they have such waxy foliage it inhibits absorption, plus they constantly grow new leaves, so you would have to spray frequently.

I take the tack of trying to keep plants as healthy as possible, and this year have used Epsom salts as a soil additive, to boost magnesium, which in turn strengthens cell walls, and so disease resistance. It also add sulphur to the soil, to increase sulphur compounds in the plants themselves to boost flavour.

My Autumn onions, which for the last two years have succumbed to mildew, are terrific. Too early to tell with the Summer crop, but they are looking healthy so far. Fingers crossed 

[juvenal]

White rot on onions. No cure available. Just make sure you bin or burn them, rather than composting.

[Snoop]

Hi Jambop, are you worried about white rot or about fungal problems on the leaves. As juvenal says, there's not much you can do about white rot. But Bordeaux mixture should be just the job for fungal problems on leaves. Check the safety period mind: here they recommend three weeks. When I've used it, a single treatment was sufficient, as it's usually so dry that it remains on the leaves for quite some time.

However, you might not need it. We've had quite a rainy spell here too, and I was thinking of doing the same for my onions and tomatoes. But the forecast looks like it's going to be hot and dry for a bit, so I've decided not to bother.

I can't get Epsom salts here, but I do use a granular fertiliser that contains sulphur and magnesium. In addition to the benefits that sunshineband mentions, as I understand it, both are essential to healthy chlorophyll and to photosynthesis. So if you can add those to the soil, you'll be giving your plants a boost.

[grinling]

I know someone who used soapy water on her onions. You might need to take up early.I have managed to remove the leaves before drying and they still stored well.

[LotuSeed]

I had a similar problem with my garlic this year. If you have mulch around them moving it to let the soil dry out a bit might help. If mold starts to develop you could always pull them early. Not fun, but better a smaller crop than none at all.