Re: vining peas/ peas and mildew

On Fri 29 Jan, Edward Tucker wrote:
> Allan
> 
> I have to challenge your statement that "dryness at the roots is the main
> cause of mildew". This could be assumed as unlike most fungi, powdery
> mildew spores do not need water for germination. Some species require high
> humidity, but the moisture provided at the leaf surface when cold nights
> change to warm days or when plants are grown in crowded, low or shady
> locations without sufficient air circulation is sufficient to initiate an
> epidemic. The most favorable conditions for powdery mildew are nighttime
> temperatures of 60oF and relative humidity of 90 to 99%, with 80otemps and
> 40 to 79% relative humidity during the days -- conditions common in late
> spring and early fall. Since the spores are sensitive to extreme heat and
> direct sunlight, plants in partial shade are especially vulnerable. It
> still comes boils down to, good air circulation is probably your best line
> of defense. On Fri, 29 Jan 1999, Allan Day wrote:
> 
> Ed
> 
> >
> > Dryness at the roots is the main cause of mildew, not to be confused
> > with moulds. Mulching with compost over moist soil would help, I never
> > have enough to go round. A spray over the plants may help as well.
> > We always get it on late peas. I have just looked it up and I find a
> > recommendation of a spray of 1 level teaspoon of bicarbonate of soda to
> > 1 litre (2 pints) of water with a little wetting
> > agent.Estimated 95% effective anywhere round the garden(Source:-
> > Coventry Polytechnic/HDRA)
> > 
> > 
> > -- 
> > 
> > Allan Day  Hereford HR2 7AU allan@crwys.demon.co.uk
> > 
> 
Further to the above there is a difference between downy mildew and
powdery mildew. downy mildew favours damp conditions, powdery mildew
 dry conditions. Both are linked to poor ventilation but in the case of
 my peas they could not be better
ventilated than on a windy hillside in full sun so my opinion remains
that dryness at the roots caused the problem. In the case of the
cucumbers in the polytunnel, an automatic misting system brought it
under control. I suspect that in both cases it was powdery mildew and
the misting on the cucumbers washed it off the leaves.


-- 

Allan Day  Hereford HR2 7AU allan@crwys.demon.co.uk
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