April 14, 2016
Powdery mildew will slowly but surely suffocate a plant. Most
years it is only cucurbits (squash, cucumbers, melon…) that it affects. I have seen in more humid summers it will
also infect chilies and tomatoes.
For most of the growing year from March until November
powdery mildew is not a problem. Around the middle of August while the humidity
is 20 to 30 percent, the nights are cooling but the days are still hot, the
conditions are perfect for powdery mildew.
It peeks behind the door with a few little moldy blotches
that are on the top of the leaves. Then slowly it colonizes the whole leaf and
then the stems. I have found once it starts colonizing the leaf stems the
battle is lost.
Combating powdery mildew is more like hospice care than
really prevailing. Slowing the growth is the best you can do.
Oh but how to do this. A spray with 40 percent milk and 60
percent water has shown to be as effective sulfur sprays. One tablespoon of baking soda with ½ tsp of
liquid soap per gallon of water does control Powdery mildew. Combining the
baking soda with a 2 percent solution of clarified hydrophobic neem oil is even
more effective. I have also had
reasonable luck with a natural fungicide called Activinate.
One thing that MUST be done is to start treatment early and
continue to the end of the season or the expiration of the plant. It is even
more effective if the program is started before any mildew is seen but the
conditions are right for powdery mildews growth.
When I work my summer squash bed I will remove and collect
all infected leaves as I harvest the squash daily. It is imperative to remove these “harvested”
leaves from the garden so that the spores will not continue the infection of
your crop. I also start a bed of squash
around the first of August so that I have a younger more vigorous crop. This
also helps with the powdery mildew “thingy”.
Recently I have found a seed company (High Mowing seed) that
has propagated open pollinated yellow and zucchini squash. I intend to get some
of this seed and try it. Ah yes the makings of another future column!
Questions? I can be contacted at markdirtfarmer@gmail.com. Or more garden notes at
redwagonfarm.blogsot.com
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