White dusty mould on brassica seed leaves?

[kathyd]

My brassica seedlings had been looking quite healthy until I noticed today that some of them have got a dusting of white powdery stuff on their seed leaves. I've removed the seed leaves where affected, but the mould dust had fallen onto the soil in some cases too. Again, I scraped off and removed this, and everything looks fine again, apart from one seedling where it had spread to the stem just above the soil.

I've not experienced this before - is it common? What could be causing it? They've been potted into individual pots, and spend daytime outside and nightime in the polytunnel. The compost is quite wet today after heavy rain yesterday - could the warmth in the tunnel overnight be causing problems? If so, do you have any suggestions please? I wouldn't have thought they're big enough to leave outside permanently just yet, or to plant out...

Help! I'd really hate to lose the lot after they've come so (relatively) far unscathed! Thx.

[RedThorn]

you got some pic's? possibly damping off disease?

[Scarlet]

Downy mildew maybe? A few pics might help...

[Samurailord]

Sounds like mildew, but without pics is hard to confirm

Andy

[veggiechicken]

Could be damping off as RT says Damping off / Royal Horticultural Society

[kathyd]

Oh dear, I tore the leaves off and stuck them in the slug bucket... I'll go see if I can find anything left to photograph!!

[kathyd]

OK, found a couple more with the white stuff under the leaves, so I missed them this morning - the earlier ones showed it on top of the leaves. The compost got a real drenching in yesterday's rain as you can see, so you're probably right ... I hope they'll recover, or is it always fatal...?

[Potstubsdustbins]

Downy mildew is usually accompanied by a yellowing of the upper surface as well as the fungus below.

Is there a chance they have been frosted as this can cause whiting of the leaves plus it aids fungi and bacteria attack.

Potty

[rustylady]

Your pots look too big for the seedlings, and the compost has obviously been very wet for quite some time - hence the green algae on the top of it.

[kathyd]

The pots are only about 2-3" square, I don't have anything smaller, and the roots reached the bottom of the pots at the time ... I sowed 4 seeds in this size pot, then separated them out into a single pot each. I do use compost that's been kept indoors though, so it's not too cold. I agree about the green algae though, most of the pots aren't like that, I'm not sure why these are. Presumably they've gotten soaked on a previous occasion and I've not realised how wet they were or something. I guess I've been putting them outside too soon . The problem is that the tunnel has been swinging from the high 20's on a sunny day even if it's been cold outside, to -1 deg at night, so I've been putting the brassicas outside during the day because I thought they prefered it cooler, and to minimise the changes in temp. But that's meant they've been subject to lots of heavy showers and some quite cold winds at times. I really don't know what to do for the best with them at the moment.

[rustylady]

Where are you intending to grow them to maturity Kathy? In the polytunnel or outside?

[kathyd]

I was going to wait a while until the weather settled down a bit, and then put them outside. I've got 2 beds currently sitting waiting for them...

I had a few in the tunnel last year, mainly over the winter, and they did quite well, but I have a horrible feeling the cauliflowers which are still in there have picked up a different kind of virus or whatever, (maybe a different thread later??), and I'm wondering if I should avoid it completely this year?

[rustylady]

I think if I were you I'd plant them out, maybe cover with cloches or fleece. At least if they are in the ground the surplus water will drain away better than if they are in pots.

[kathyd]

OK thanks, maybe I'll try that then . I'd intended to repot them today by removing as much of the cold wet compost as possible, and replacing with something a bit drier, then keeping them indoors for a while, but maybe outside would be a better option, at least for the slightly larger ones. The reserved beds were covered with cardboard, but the chickens have scratched it all up over the past week or two - would you suggest I warm the soil with polythene first? Or do you think it'll be OK as it is? Night time temperatures are currently forecast to be about 6 deg min, usually slightly higher. Luckily I bought loads more hoops yesterday, and have the remains of a roll of fleece left to play with too . And there's always those faithful plastic bottle cloches of course, if I get desperate .