Tag Archives: powdery mildew

Powdery Mildew Strikes Again

We have had a very cooler and wet spring and the powdery mildew is back with a vengeance.

A day before our last good rain, I sprayed all of my crops with a mixture of Garrett Juice (2 tbsp per gallon), neem oil (almost 2 tbsp per gallon), and a tablespoon per gallon of ocean minerals.  After wards, the leaves had a nice rich green shine to them and the powdery mildew could not be seen.  I suspect that it was just hidden under the glossy finish.  After a few more days of very light sprinkles, enough to wash the spray off, I can again see spots of powdery mildew all over.

I had a small pump bottle of copper fungicide, so I sprayed the most affected leaves.  Tomorrow when I go to town I will look for a concentrated bottle of copper and I plan to add that to my spray mixture of Garrett Juice, neem and ocean minerals.

Neem oil can treat fungus, mites and insects, with varying efficacy.

It starts with just a few small spots here and there.

powdery mildew on squash plants

Then it spreads.

powdery mildew on squash closeup

Another squash leaf.  Different varieties of summer squash and zucchini have differing tolerances and immunity to the powdery mildew.   Winter squash and gourds seem to have the strongest resistance, except for spagetti squash.

powdery mildew on squash plants

I cut out the leaves that are totally wiped out by the mildew.  They are light yellow, covered with the white mess and dry and stiff.  The powdery mildew if a parasite fungus that taps into the leaves and feeds off of the squash leaves.

 

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Verigated Squash Leaves vs. Powdery Mildew

I received a comment questioning whether powdery mildew might actually be the natural coloring of certain squash leaves. I am creating this post in reply.

This first picture if of a normal variegated squash leaf. Some squash plants, especially winter squash plants, have leaves with white areas. These white areas are usually at the junction of leaf vines.

verigated leaf
This next picture is of small powdery mildew spots – note the fuzzy look to the round splotches randomly located all over the leaf:

powdery mildew

This leaf has powdery mildew spots all over it’s surface.  Note that the variegation is always at the angle corners of leaf vains.
verigated squash leaf with powdery mildew

Hope this can help you differentiate between normal leaf variegation and powdery mildew.

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A Week of Rain Destroys a Squash Garden

This part of Texas is usually hot and dry during the summer.   This past week we had a very unusual event:  7 days of rain.    Every day we had some rain.   Some days we had over 2 inches and other days we had an eighth or a quarter inch of rain.  The total rain for the week was a bit over 6 inches.   You might think this is a good thing.  Not so – we had rain every day.   Along with high humidity, we had very little sunshine to dry the leaves off.   I went out to the garden a few times during the week and sprayed Neem oil on the leaves, but the rain every day just washed it off.

Before the week of rain, I had been battling powdery mildew, but the rain spread the stuff all over the garden.  I can clearly see where the white stuff dripped to leaves below, to infect them.  I can also see where it splashed around, spreading it thru rain drops.

This 8 Ball zucchini is totally infected with powdery mildew.    This is rather unusual – these hybrid zucchini plants had showed themselves to be somewhat resistant to powdery mildew.
powdery mildew zucchini

Here are some more zucchini plants that have a heavy, thick coating of powdery mildew.  See how terribly thick those white spots are.
powdery mildew after rain

This squash plant is fatally infected with powdery mildew.
powdery mildew

This yellow summer squash plant is just about dead from powdery mildew.   All of the older leaves are fatally infected.  There just isn’t enough plant left to support the growing tip – this plant will probably die before it produces another squash.    It was a full, happy plant until the week of rain spread the mildew and killed the plant.
squash almost killed by powdery mildew

Another picture of powdery mildew all over zucchini leaves.  The stuff is ALL OVER!
powdery mildew on zucchini

Look at these leaves –  the powdery mildew is on every plant in the garden.   It must have been spread by the rain that splattered all over the garden for a week.
powdery mildew closeup

These cucumber leaves seem fairly resistant to the powdery mildew blight, but the older leaves have some strange tan spots and holes in them.   I don’t know what caused those holes.
cukes with holes in leaves

The older leaves on these zucchini plants are totally destroyed and it has spread to the new growth.  I sprayed the entire garden with Neem oil today, but most plants are t00 far gone to survive much longer.   The powdery mildew is just too rampant.

All squash plants are affected, even the once resistant hybrid zucchini and Waltham butternuts.  I have found out that Crenshaw squash are super- sensitive to powdery mildew.
grey zucchini with powdery mildew

This pic was taken before the rain week.  It shows what powdery mildew does to leaves.  A mild case of powdery mildew causes the leaves to become dry and stiff.   They then dry out, develop holes and then die.  This is the result of a mild case of mildew – after the week of rain I have a massive infection of powdery mildew.  I can see it killing entire groups of leaves at a time.
old leaves killed by powdery mildew

I usually burn my old squash plants at seasons end – I do not put them in the compost if they show any sign of disease of bug infection.  I’m not sure if powdery mildew will preclude my composting these plants.  I really do need green plants in the compost, but I don’t want to risk feeding the compost pile an organism that may survive composting and spread next season.  I’ll have to do some research on this matter.

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Overview – From July 10

This is the middle walkway between the 2 long rows of raised beds.  The beds are 5 feet wide and 16 feet long – to accommodate the 16′ cattle panels.  I planned to plant climbing plants – mostly beans, squash and cucumbers – under the cattle panels on both sides of the bed and plant other things along the outer 2 feet of each long side.  I planted these squash so that they could grow down into the 4′ aisle between the beds.  In the very front, left you can see a long vine growing along the outside of the raised bed.  This is one of 4 Crenshaw winter squash that I grew.  These seem overly sensitive to powdery mildew and I don’t believe they will live long enough to produce a single fruit.   The winter squash growing on the cattle panel on the front left are several varieties including Seminole pumpkin.  These did very well last year.  On the bottom right side is the cattle panel where my cucumbers are growing.

At the top middle left of the pic is the raised cattle panel on which my Long Red Chinese Beans are growing.  They have really taken off  but have yet to start producing the 12″ red ‘green’ beans.  At the old place, I grew them up twine in a narrow bed in front of the carport.  That gave them at least 10′ – which still wasn’t enough room.  These cattle panels are no where high enough for the beans.  They are growing wildly, but when I try to tuck the growing ends in and out of the cattle panels, they easily snap.  Next year I will have to find some place better for them to grow.
overview july 10

I need to get the garden in on time next spring.

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Another Look At Powdery Mildew

This summer yellow squash leaf has spots of powdery mildew on it.  This is just the beginning . . . If I do nothing, it will quickly spread.  To try to hold the spread of the mildew, I am spraying it with Neem Oil almost every day.  This seems to be slowing the spreading down.  It does not eradicate the stuff, but it seems to be hold the spread.  Once powdery mildew takes off, it will quickly spread and kill the squash plant.
powdery mildew

This summer yellow squash plant has many sploches of powdery mildew on the leaves.  It is slowly spreading, but hasn’t wiped any squash plants out yet – thanks to neem oil.   The mildew will spread with water splashes – it gets spread around.  I can see where leaves above have spread it to leaves below.
powdery mildew a continuing problem

This is one of the 3 Crenshaw winter squash plants that I planted – I had the seeds and just wanted to see what these long vines (they will grow maybe 20+ feet, the longest is now about 10 feet and still has only male blooms.  The female blooms grow on the second half of the vine) will do – since they were planted a month late, I really don’t expect any mature fruit from them.  The mildew seems to be thicker on the Crenshaw squash.
july 10 powdery mildew

Once powdery mildew arrives,  I have never been able to completely eradicate it.  I just have to try to keep it under control – keep it from spreading too rapidly.

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Powdery Mildew Makes An Appearance

Powdery mildew has shown up.  I have been using Neem oil to treat it.  Seems to keep it from spreading.  A few years ago I tried to go organic and used a potion made with baking soda – yes, it stopped the powdery mildew, but it also killed all of the leaves it was sprayed on.
powdery mildew

This pic was taken a couple of days ago.  I treated with neem oil spray on the day the pic was taken.  As of today, I nave not noticed any spreading of the mildew.

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A Volunteer Squash At The Old Compost Pile

Originally published Summer of 2011

Lots of things pop up at the edges of the compost piles.  This squash plant has managed to survive and has buds on it.  I sprayed it a few times with neem oil to get rid of it’s powdery mildew.  (Last year I used a homemade formula of baking soda and dish soap to kill the powdery mildew – and it did stop the mildew.  The problem was that it was too harsh on the leaves and hardened them and they died.)  Neem oil is my pesticide and fungicide and all around pest killer of choice this year, and I am very pleased with it so far.

Volunteer squash at the old compost pile

Squash plants seem to be the most susceptible to powdery mildew, and because this plant is at the edge of the woods in the shade and beside a creek area, it has been afflicted several times.

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