Re: White powder on pumkpkin leaves



Powdery Mildew. I use baking soda, but coppersulphate based fungicides work fine, Some folks used powdered milk with good results. It is an acid loving fungus so any thing which is basic will work to some degree.
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snipped-for-privacy@aol.com (FarmerDill) wrote:

I have white spots developing on most of the pumpkin leaves. Suspecting it might be the same powdery mildew I tried baking soda on them. The next morning (after another night of rain) I came out and all the leaves I put baking soda on were brown where the baking soda was. Although the white spots are gone...the leaves look like they are near dead.
Is this what happens with a baking soda remedy??
DiGiTAL ViNYL (no email) Zone 6b/7, Westchester Co, NY, 1 mile off L.I.Sound 1st Year Gardener
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Usually; The baking soda is mixed one small box with 10 quarts of water and sprayed or sprinkled on the plants. Never had any problems although yhe commercial equivalent uses potassium bicarbonate instead of sodium.
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DigitalVinyl wrote:

DV, It sounds like you applied the baking soda as a powder. Baking soda is in fact a pretty strong chemical.
The baking soda needs to be applied as a weak water dilution. It acts by changing the surface pH of the leaves. Only a very tiny change is needed. Try a tablespoon in a two gallon sprayer and apply just to the point of wetting the leaves. Since the goal is not to modify the soil pH, avoid runoff.
You could also add a 'spreader/sticker' such as a tablespoon of Palmolive green dishwashing liquid or a similar quantity of molasses to the spray solution.
Most anti-mildew preparations work best as preventatives that serve as a barrier to penetration by the fungi. Once the leaf is penetrated, the fungi have a toehold and it is hard to dislodge them since they are also plants and anything powerful enough to kill the fungi is also powerful enough to harm your desireable plants.
AFAIK, Lime, powdered milk, copper sulfate compounds, lime/copper mixes, baking soda and compost teas all work on the concept of presenting a barrier that will prevent colonization on the leaf by fungi. The chemicals work by presenting a poisonous environment (to the fungi ... not necessarily to humans) and the compost tea by pre-infecting the leaves with beneficial bacteria that can defend the leaf from invaders. This year I am trying compost tea because I want to avoid applying any harsh chemicals wherever possible to do so. I got whopped by powdery mildew last year (see the archives for this group on google.com) so this year I am taking a pro-active stance and spraying defensively. The problem with this is that I have too small of a garden to allow for a test plot to know if powdery mildew would have been a factor or not so it's difficult to access the benefit of one treatment regimen or another.
Hope this helps. I think your problem with the baking soda is simply that you applied it at too intense of a concentration. Back off to a very dilute concentration and you should be fine.
Bill
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Zone 5b (Detroit, MI)
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len brauer wrote:

Well, it has spread to my zuccs, which have powder on the leaves and white spots on the fruit. Fruit still edible?
Andrew
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