Monday, December 6, 2010

Powdery mildew controls

(Every now and then a garden blogger has to narrow down his or her focus and talk to the locals, and so this posting is probably aimed at gardeners on the east coast of Australia more than anywhere else right now, but I guess it applies to anywhere when the rain doesn't stop, the humidity rises and the vegie patch takes on a grey dusting of powdery mildew disease....)

Powdery mildew. It attacks all sorts of plants. I was even reading about it attacking mighty oak trees earlier today. It's a fungal disease that's like having zillions of tiny white mushrooms infesting the leaves on your plants. It looks like the foliage has been dusted with talcum powder. (But unlike Ogden Nash's lovely little rhyme that: "A little bit of talcum is always walcum", a little bit of powdery mildew is never really walcum in the garden.)

Of all the plants it attacks, powdery mildew loves the vegie patch most: zucchinis, cucumbers, pumpkins, squash and melons are its classic victims, but it attacks many others, too. Well, I think I have found an organic product that works very well to control powdery mildew, isn't too much of a hassle to use, and is worth mentioning here. And no, this isn't a paid ad, as you (and its makers) will soon discover.

Here's my zucchini plant from last summer, its leaves dusted with powdery mildew. It's the white stuff. It doesn't actually kill your crop. You still get zucchinis coming through in droves, but upstairs the plant looks dreadful. And I like pretty plants, so this bothers me. When powdery mildew gets really bad, it can harm plants' health and shorten their season.

Sydney has had a ridiculous amount of rain recently, and this cucumber plant has no reason to look this healthy, and that is due to the product which I'll tell you about a bit later on.

No, this isn't it, but it is one organic solution that is sort-of worth a try. It's milk, diluted 1:10 with water, and used as a spray. If you do a Google search you'll find a fair bit of literature saying it works. I have tried it for two years and it just barely works. You need to re-apply it constantly, especially after every shower of rain. So it's a pain to use, as it's so much work. And if powdery mildew sets in for any reason (ie, you have a weekend away), it cannot stem the tide. As far as I am concerned, it's not all that effective, but it's not hopeless, either.

This is what's working for me this time round. The mob who makes Eco Fungicide also makes Eco Rose, Eco Oil and a range of other certified-organic 'Eco' products. To be unfair, it's a glorified bi-carb soda mixture, but I have tried the home-made bi-carb soda recipes and this one works better than them. There must be something else in it, but I'm not sure what it is (EDIT! See Alexa's comment below – it's potassium bicarbonate, not the common kitchen stuff sodium bicarbonate – thank you Alexa). It's not cheap, but one 500ml jar should last me several years, at the tiny rate at which I use it in my small garden. This 500g container cost $19.85 at Bunnings (our mega hardware chain, for overseas readers).

For each spray I use here (and there aren't many) I allocate a cheap pump sprayer, and never mix anything else in it. You can't store a mixture of Eco Fungicide for any time, so you just mix up a batch and use it all, each time. For this one-litre bottle of water, I add one level teaspoon of Eco Fungicide powder, plus 2mL of horticultural oil.

If the people who make Eco Fungicide were thinking this is a great free plug for them, they'll be horrified to see the opposition's product here! Eeeek! The Eco Fungicide people make Eco Oil, which is a vegetable based, organic horticultural oil. The opposition product, PestOil, is petroleum-based, but it's a very very mild oil that does an almost identical job to Eco Oil, and it's what I use, and what I have a 500ml bottle of already. And I only need a tiny bit, so it'll do me, as it always has done. Fab product, PestOil.

As for only needing a tiny bit, this is where my policy of "never throw out a measure of any sort" came into its own. Isn't hoarding great when it pays off? Yippeee! Anyway, this is a measure from an old packet of trace elements, and this little 1mL cup-ette is perfect for adding a tiny bit of oil to the one-litre bottle of Eco Fungicide mix. Just shake up the water, Eco Fungicide and the oil, then spray all over the foliage. So far the results have been great. The product label says to spray about once a week, which is much more user-friendly than other 'organic' sprays which have to be re-applied constantly.

I thought I would finish off with a few words in favour of powdery mildew, such as this stuff on my zucchini leaves.

The more powdery mildew you have the more ladybirds the plants attract. My zucchini foliage last year was covered in ladybirds, so every cloud has a silver lining, as they say.

Here's one more option for you to try, if a $19.85 jar of stuff sounds a bit too expensive for you. An expert gardener to whom I was speaking on Saturday night (at an excellent party hosted by Zora and Sean - well done, you two) told me that she puts the well-known seaweed product Seasol into her sprayer and uses that to control powdery mildew in her vegie garden. So if you have a bottle of that on hand already, give that a try and let me know if that works for you. You might save some other gardeners some money, some heartache and most important of all, some crops.

If you want to read a bit more about Eco Fungicide, here's a link to their website.


life in a pink fibro said...

Cool! As you know my thoughts were beginning to turn to the by-products of the rain. And here you are with products to combat them. Thanks!

prue said...

I've been waiting for the powdery mildew to hit here in Melbourne - it is in the post, guaranteed. Have always used themilk trick to good effect myself, but if that fails this year I'll take your good advice. My aunty uses season spray for everything, she insists it cures whatever ails your plants. Powdery Mildew is probably included!

lotusleaf said...

I have found that highly diluted curds (yoghurt) works better than milk.

Alexa said...

The Eco product is actually a different chemical (potassium bicarbonate) to baking soda (sodium bicarbonate), which would explain why it works better.

I'm trying lime sulfur as my mildew-preventer of choice this year. I bought some anyway to control rust on my pelargoniums (it's also what you use in winter to prevent fruit tree leaf curl). The only downside so far is that it stinks like sulfur!

Jamie said...

Thanks for pointing that out about the potassium bicarbonate. I was always hopeless at chemistry at school, and I still am.
And I agree with you about the smell of lime sulfur. Yuk!

Lanie at Edible Urban Garden said...

Thanks for that Jamie. I have been diligent with diluted milk with minimal success also. The Eco brand is the same one that makes the fruit fly sticky concoction that I find absolutely fantastic for my figs, citrus, persimmons and tomatoes. So I'll pop some eco fungicide on my Christmas list!

julie paterson - garden said...

thanks sooo much Jamie - that post was perfect timing for me as my pumpkin leaves have suddenly adopted powdery mildew in the last week & are now deciding to share the love with their friends....shall be trying the seaweed solution tomorrow & then on to the eco one if that doesn't work - whilst on the subject of my pumpkins, I am getting heaps of flowers but no baby pumpkins...any tips???

Jamie said...

Julie, become an honorary bee is my only suggestion with the pumpkins. Use a soft brush of some sort (got a spare soft makeup brush?) and wiggle it into a flower to pick up some pollen, then wiggle that into some other flowers to transfer the pollen.

julie paterson - garden said...

Thanks Jamie, will be a busy little bee tomorrow!!!

Anonymous said...

Hi Jamie, thank you for writing such an enjoyable, interesting and relevant (i am in Darlinghurst) gardening blog. I haven't had trouble with powdery mildew yet, but if it hits, i now have an action plan! I am struggling with baby catepillars - there will be nothing left of my balcony garden soon! Lou

Jamie said...

Thanks, Lou.

As for the catepillars, you could try "gloves on, thumb and forefinger" as the ultimate organic control, but some people find that a bit murderous.

A good general organic spray for caterpillars is Dipel, but Yates Success has the same organic active ingredient (Spinosad) and works in much the same way (ie, it doesn't harm bees, birds or people). I find it much better (ie, cheaper) to buy the concentrate and mix it up with water in a 1-litre sprayer.

Peter from Cityfood Growers said...

I use a few things which help and have quite a different focus to the ones mentioned already. I normally work with biodynamic gardening practices and one of the aspects of biodynamics which is very strong is the impact of the planets on plant growth, with the moon having a very big impact. The moon has a very strong affect on earth on reproduction and flow of fluid. You will see mould always accelerates closer to a full moon and/or when the moon is in perigee (closest to the earth in its 28 day cycle around earth). So recognising the moon cycles is important as well as observing the rain of course. This year I have used a biodynamic preparation called BD508 which is concentrated equisetum arvense. This is a herb which grows in Australia. This herb is extremely high in silica and it holds back the moon forces on the plants which in turn slows down rampant reproduction which is mould. Another biodynamic product is BD501 which is crushed quartz, also very high in silica. I also make Dandelion tea (which I make from the edible dandelions in our garden). This also has a strong silica element. These preparations have held back the mould on my cucumbers this December/Jan and I live in Brisbane where have had a radical amount of moisture.

Jamie said...

Thanks for all of that, Peter. I have only the vaguest understanding of biodynamics, but if it holds back powdery mildew in Brisbane, that's a powerful recommendation.

Anonymous said...

Hi, thanks for the mini review of this product.

I have used Seasol at various doses on a plant that had a mild case of PM. I think the strongest dose I sprayed the plant with was 1:10 ratio 50ml/500ml Seasol to water. Unfortunately the PM kept coming back after 1-3 days.

ManBearPig said...

Great blog :)

I took your advice on the eco-f and it has worked wonders in a matter of days, the powdery mildew was spreading all over the zucchini leaves but has stopped in it's tracks and all new growth is free of it. I also used it on my pumpkins, watermelons, cucumbers, and strawberries and with the exception of the strawberries (which are just as happy as the were before) they have all shown significant growth in a very short time since spraying them. They obviously really like it. I used same mix as you describe here (but used their eco-oil as i didn't have any pest oil and i figured i'd check it out). Really happy with results so far. Will check back in after another week or so and post on further results.

Thanks for the blog, and for the great tip!

ManBearPig said...

Just a question, is it wise to remove the affected leaves once theres some new healthy growth, or is it better to just leave (hehe) them? I'm inclined to think i should make room for new mildew free growth but am unsure. There is lots of new growth there. Any thoughts at all?

ManBearPig said...

Sorry, i'm talking about removing leaves from my zucchini plants, i probably should've mentioned that!

Jamie said...

Sorry Man Bear Pig for the slow reply!

I'd remove the affected zucchini leaves, as they contain fungal spores that will encourage the spread of even more fungal disease.

(But do check out the underside of the leaves, as there's usually a major ladybird party going on.)

Jimmy said...

I just got hit with this for the first time this autumn. Is it related to basil downey mildew at all? My basil plants were wiped out and I noticed it on my zucchini plants around the same time.

Jamie said...


I've never heard of basil downey mildew, but it sounds like the same thing. Basil does't survive autumn usually, it always dies off once the weather gets cool, and it dies off even faster if it's cool and wet. Same deal for zucchinis. Both are summer crops.

Pull all your plants out now, grow something else in the meantime in winter if you like, then in spring you can plant out some more baby seedlings of basil and zucchinis.