Topic: White powder forming on cucumber leaves

[shirl]

Hello everyone

I have three cucumber plants that have been fantastic and produce far more cucumbers than we can eat, however recently I noticed that the huge leaves have started getting covered in what looks to be a white powder.  The fruits themselves dont look to be affected, but the leaves are getting worse.

I have the cucumber plants growing right next to my toms and it doesnt seem to have spread to them but im getting worried now :-/

Thank you for any advice you can give

[SpeedyMango]

I've got that on my courgette plants.

Doesn't seem to be a problem though so I wasn't worrying about it.  :)

Does anyone else know different?

[tim]

Mildew.

Bicarbonate of soda??

http://www.allotments4all.co.uk/yabbse/index.php/topic,4846.0.html

[Svea]

mildew indeed. tried with milk but so far no difference. and my suqash plants seem to be so badly hit that i am now losing fruit and the leaves are all dying off :(

bicarb, tim? must give that a go - the milk didnt work.

[Mubgrub]

Yes, I've tried the milk thing too but its still coming.  How much do you dilute the bicarb?

[shirl]

Thank you kind people  :D I shall try the bicarb this evening.

Mubgrub, Tim suggests 2tsp in a litre with a little detergent as a 'wetter'

Im relieved its nothing more serious as i'd hate to lose my cukes!

[Svea]

just checked the HDRA again and it says

Other methods: Research at HDRA has shown that sodium bicarbonate can be helpful in controlling powdery mildew. Best results were obtained using between 2g and 10g per litre of water, mixed with 10g per litre of soft soap (which acts as a wetting agent). Higher concentrations of sodium bicarbonate (up to 20g per litre) were tried, with even better results, but this caused scorching to young leaves. Urine, diluted 1:2 or 1:4, has been found effective by H.D.R.A members. This has been reported in previous issues of H.D.R.A. News (93:16-17, 102:Sup. iv).

so, no mention of milk? where does the milk treatment come from? can anyone shed light on this?
it does say that on some plants, powdery mildew develops towards the end of the season, and to do 'nothing'. however, my squashes are so badly affected that the plants seem to be dying off now :'( and it's only the beginning of august!!!

[jennym]

I get this every year and it doesn't seem to affect the crop at all, so I do nothing about it, except maybe cut off any really bad leaves. I think keeping them well watered helps.

[Icyberjunkie]

Having read this I had a look at mine this morning.  The cuc's were untouched but all the large older leaves on my courgettes are white virtually all over.  They look healthy enough though and the plant is strong and still cropping heavily so have left them alone!

Of course that might also be cos I was feeling a little lazy..... ;D

[Kepouros]

Shirl, you needn`t worry about your tomatoes.  The powdery mildews which affect the cucurbits are specific to those plants and will not affect toms (although tomatoes also have their own specific form of mildew).

However, although mildew late in the season is not a cause for alarm ( only because the plants have virtually finished producing by then) a bad attack of mildew in early August can lead to considerable damage to the plant, distorting and stunting the growing tips, attacking the buds, and sometimes causing the early death of the plant, as appears to be happening in Svea`s case.

Sodium Bicarbonate should help, but I have had the best results using urine diluted at 1 part urine to 4 parts water, although not specifically on cucurbits, which I no longer grow for digestive reasons.
I believe milk was originally also mooted by HDRA, but it has to be full fat, and I only buy semi-skimmed.

[Svea]

kepouros,

tried with the bicarb today - will see how the plants do in a couple of days. otherwise another course of full fat milk.
*sigh*

there are plenty of young shoots about the plant, but all the big leaves are dying off so not sure the plant has enough energy to produce much more. i can but hope for the best.

how often would one have to repeat treatment, anyways? does the mildew actually 'go away', or does it just get stopped and prevent further infection?

thanks

[shirl]

Many thanks again.   Well I sprayed the cucumber plants last night with Tim's suggested tonic, but I used soap instead of detergent and I really soaked the plant.

It does seem better today so I shall give it a few days and monitor it, hopefully it will keep the problem to a low level.

Otherwise I shall try the urine method, although I dont know how I shall manage the high leaves  ;) ;D

[Kepouros]

Svea, whichever option you find most effective you will still almost certainly need to repeat it several times over the season - one treatment is rarely completely effective - in addition to which the treatments mentioned can only be effective on the mildew actually present on the plants, while the fact that you have a bad attack so early in the season indicates that there is a nearby source from which further attacks will almost certainly spread. Very probably some of your neighbours also have similar attacks, and unless everybody treats their plants it will simply keep spreading back and forth. The only long term `cure` would be a systemic fungicide which, even if it were available, would not be a very good idea for food plants.  Make sure that you treat all your cucurbits - even any which do not appear to be affected.

[supernan]

Oh thanks guys. I noticed this yesterday on my courgettes/pumpkin and squash.

Am going to try bi-carb on one half and personal water on the others. Just shan't tell the neighbours who are sharing the crops.

[wardy]

I didn't think liquid gold killed mildew??   Wouldn't argue though Supernan and await your results with interest  ;D