[Mother Earth]

Hi this is my first year growing vegetables and i'm in a bit of a flap as my pride and joy in the greenhouse - cucumber plants have today started to show signs of powdery mildew on the leaves, now its only very small patches on a couple of leaves and it wasn't there yesterday but i know enough to understand that it's not good.

Have looked in a few of my books and i understand what has cause the problem, i started the plants from seed in my neighbours greenhouse as i didn't have one.... they have been growing well and just started to flower, last weekend i moved them into my own new greenhouse thinking i would be helping the plants (my neighbours greenhouse has a few windows broken that are patched up with wood...its quite old)....well that taught me didn't it my new greenhouse is that good when i have shut it all up in an evening there is very little ventilation, plus i may have been underwatering as i have been worrying about overwatering.

Is all lost or can they be saved?

I did read about Potassium bicarbonate being used, but i'm not sure where to get it from or what to do with it.

Sorry to flap and go on.

[vegikev]

yes it works i use it commercially. pot bicarb is the same as bicarb soda i think. i would try 1/4 t spoon to 2ltr that should be enough to notice a difference. this is only my opinion as i have never used it on a small scale. good luck

[camster_factor]

I've just discovered a couple of my cucumber plants are suffering from this so am reading around online.

Out of interest I came across this article on the which.co.uk Web site, and this bit caught my eye:

There is also some research
from South America, Australia and
Britain that shows that milk
solution (of 1 part milk to 9 parts
water) sprayed on some crops,
especially cucumbers, may also
help prevent mildew.

I'm planning in the first instance to remove affected leaves and see how the plants fare, though on one of them the white powdery spots have also appeared on the lower stem!

[DD.]

yes it works i use it commercially. pot bicarb is the same as bicarb soda i think. i would try 1/4 t spoon to 2ltr that should be enough to notice a difference. this is only my opinion as i have never used it on a small scale. good luck

I'm not qualified to speak about it's effects, but I can say that bicarbonate of soda is SODIUM bicarbonate, not potassium.

[Mother Earth]

Thanks all for your help and advice, i have removed the affected leaves, and sprayed the plants with the milk solution, plus improved greenhouse ventilation... hope this works.

I was unsure what cucumbers prefere full fat or skimmed milk so went with the full fat hope they approve.  

[camster_factor]

This makes sense...

I ran a quick Google search for 'milk potassium' and the first link included: An 8 oz serving of milk provides about 350-400 mg of potassium :~)

[camster_factor]

Hmmm... I'm on a reading roll now!

An article on milk as mildew killer.

In many cases, milk was both faster and more effective. After two to three weeks of spraying with milk, the area of leaves infected was in some cases only a sixth or less of the area affected on plants treated with chemical fungicide (Crop Protection, vol 18, p 489). Bettiol says several organic growers in his region have successfully controlled less severe mildew infections on courgettes and cucumber by spraying once a week with 5 per cent milk solutions.

Bettiol is not yet sure why milk works so well, but he speculates that it helps the plants in two ways. Milk is known to kill some microorganisms. It also contains potassium phosphate, which boosts the plant's immune system and so may help it inhibit the mildew's growth.

[vegikev]

I'm not qualified to speak about it's effects, but I can say that bicarbonate of soda is SODIUM bicarbonate, not potassium.

sorry yes they are different, i wasnt sure hence the statement "i think"

[DD.]

I'm not qualified to speak about it's effects, but I can say that bicarbonate of soda is SODIUM bicarbonate, not potassium.

sorry yes they are different, i wasnt sure hence the statement "i think"

Just didn't want people raiding Tesc*'s home baking aisle in the morning!

[Mother Earth]

Like i did yesterday.... :oops:  Luckly i checked the forum again before putting it on the plants and changed to the milk method.

Thanks DD., Camster and Vegikev for the help will let you know if the milk solution works.

[camster_factor]

I tried spraying a milk solution onto my affected cucumber plants this morning, leaving the infected leaves in place and concentrating on the plant that had a lot of mildew spots (splodges) on the lower stem.

I just popped out to take a look (late afternoon) and the stem appears to have cleared up completely; the spots on the leaves have distinctly subdued (I wish I'd photographed them before spraying for a before and after demonstration; if it comes back, I'll do so).

It might have additionally helped the most affected plant that, not wanting to leave the remaining solution lingering in the hand sprayer and stinking the greenhouse out, I watered that plant with the left overs.

The greenhouse does smell a little sweet in that corner and might end up suffering from the funky smell of festering milk, but it's a production environment, too hot to hang out for relaxation, so I'm willing to put up with the whiff if the technique sorts out the problems.

So it appears to be a successful method, though my pseudo-scientific side would need to see it work a number of times to be sure it's not just some other coincidental factors that sorted the issue out today (eg: it's been damp around here for a couple of days, and has turned hot and fairly dry today with heaps of fresh aid passing through the greenhouse as we catch the periphery of what must be some very strong winds further north in the UK).