Powdery Mildew and SoCal Fall Planting

I suspect many of us in SoCal have been waging the powdery mildew (PM) war. My cucumbers on the side of the house in my non-raised bed (Back to Eden style mulching) have it bad. I knocked it back but had to take a week long trip and other than looking horrible, I suspect they're about toast too. I'm also looking at starting up some new boxes if I can get them filled.

Has anybody had luck removing plants that have had PM and replanting new? Anything to do to knock it down and out to let the new plants take off? I'd love to pull the cukes and replant some burpless starters I've seen at the nursery. I know typically, cukes in SoCal are recommended to stop planting in July but I'm more coastal so hope I can extend it a bit. If it's too late I don't mind failing that way, but don't want to plant into the PM blizzard to just have them snuffed out by PM.

Any one with experience on knocking out PM to replant?

Our September planting guide looks pretty good for a starter box. The lettuce will come in quick and provide cover and a good test of the nitrogen holding of the MM.

Best bets for the September garden planting:

Beans, Bush
Beets
Broccoli
Brussel Sprouts
Carrots
Celery
Leeks
Lettuce
Peas
Spinach
Squash, summer

boy do I hear you on the PM!! I planted some cucumbers a little while ago, and will see what happens. It's only seeds, right?? It's really hot and humid today, so that doesn't help!! When you say summer squash for planting, what type? We just planted a bunch of stuff today. My SFG just aren't doing as well as others on here for some reason? GRRRRR. We've tried the fungicide spray, and it seems to help a LITTLE, but not much. Someone on here sprayed milk on their plants, and said it worked, have you tried that? My plants in my non SFG have a little pm, but not nearly like in my SFG beds, they're pretty much toast like yours Keep us update with what you decide Good luck!

Pretty much any of the summer squashes, the crooknecks, zucchinis, pattypans, all grow well. I don't know if seeds or transplants are better. If the seeds have been soaked, the ground is so warm they should rocket out.

PM is endemic everywhere and it's bloom is totally weather driven. If you notice the weather conditions getting to be perfect for PM, my suggestion is to treat befor PM makes an appearance and try to stay ahead of it.

I had horrible issues with PM last year, but have been spraying with Neem oil every couple of weeks through most of the year and haven't had the tiniest outbreak... knock on wood!!!!

I HATE powdery mildew with a passion!

I once did a tour of a Master Garden near the coast. Her take on powdery mildew is she just accepts it as part of nature's cycle. She grows what she can until it is infested and then lets it go. LOL. An if you can't beat it, celebrate it philosophy I guess.

audrey.jeanne.roberts wrote:I had horrible issues with PM last year, but have been spraying with Neem oil every couple of weeks through most of the year and haven't had the tiniest outbreak... knock on wood!!!!

I HATE powdery mildew with a passion!

neem works on pm?? really?? hmmmmmmmmmm

Audrey, I Googled powdery mildew for photos. I have no idea if my cucumbers and cantaloupe have it or not. Found this index for PM in Fresno and Madera counties:

http://www.calagquest.com/PMI.php

I started spraying Neem today on the cukes, cantaloupe, even the beans and some tomatoes. Like I said, I can't tell from photos WHAT I have going in the garden. Removed the 3 summer squash plants that were swamped with aphids. Camp recommended Neem for the aphids and I wish I had heeded her advice and sprayed earlier.

Actually I don't recall giving that advice; I don't typically recommend neem for anything. Aphids, I usually recommend a blast of water and insecticidal soap. It is sometimes hard to remember to do, but I try to move slowly through the garden, if necessary getting down on hands and knees, peeking at undersides of leaves, at stalks, the growing medium, looking for clues to who knows what, anything that would indicate trouble is on the way. Discoloration, spots, wilt, specks.

The other day when I was looking for hornworms, I found several other things that I was not expecting, but I was LOOKING. :shock:I know that at any time the health of the garden can tank rather quickly if I am not vigilant in  doing inspections and learning about proper prevention and treatments for anything I may find that is out of the ordinary.

Sanderson, post a photo of your trouble spots, maybe it is PM.

sanderson wrote:Audrey,  I Googled powdery mildew for photos.  I have no idea if my cucumbers and cantaloupe have it or not.  Found this index for PM in Fresno and Madera counties:

http://www.calagquest.com/PMI.php

Wow, the amount of agriculture info is sometimes simply amazing.

How the RAI is Calculated --The index is calculated by adding 20 points whenever the temperature in the canopy is between 70 and 85°F continuously for 6 or more hours in one day. If there are less than 6 hours in this range or if the maximum daily temperature is greater than 95°F, then 10 points are subtracted from the index. The index never goes below zero nor above 100

No wonder August in coastal SoCal is virtually impossible to stop. Our index is probably 100 for weeks on end since our temps are 70+ by 8 in the morning and 85ish for a high and rarely creeps above 95.

All I know is I'm holding a bottle of Neem Oil Extract in my hands.  It says, 3 garden products in 1, Insecticide (controls aphids, whiteflies and other insect pests listed) Fungicide (Controls Black Spot, Rust and Powdery Mildew) and Miticide (controls spider mites).

I have had good results this year when I have sprayed on a regular basis - when I have forgotten things have gotten away from me.

Oh and what an interesting index and the information you shared Sanderson! It's amazing what commercial growers need to know to be prepared.

Camp,  The subject of Neem came up recently but I can't find the topic.  If I remember correctly, Audrey was mentioning aphids on her squash???  I had just hosed with dish soap, cooking oil and baking soda and was feeling all organic about my treatment!    I thought you ditto-ed someone's recommendation of using Neem for heavy aphid infestation.  (Maybe two threads were going on one topic)  If so, my apologies.

The bean leaves feel papery and have the tiniest of black dots on them.  I used my jeweler loupe and one of the dots looked like the world's smallest iridescent black fly.

Vining Green Bean #1 (black eyed beans to the right)

Vining Green Bean #2


The cantaloupe are starting to look like some of the cucumber leaves.
Cantaloupe #1

Cantaloupe #2


Made my way to the back of the trellis and found really nasty infestation.
Zucchini #1 - Aphids

Zucchini #2


Any help is appreciated.  However, I lightly sprayed these plants with Neem right after sunrise (bee safe) before I logged on.

audrey.jeanne.roberts wrote:All I know is I'm holding a bottle of Neem Oil Extract in my hands.  It says, 3 garden products in 1, Insecticide (controls aphids, whiteflies and other insect pests listed) Fungicide (Controls Black Spot, Rust and Powdery Mildew) and Miticide (controls spider mites).

I have had good results this year when I have sprayed on a regular basis - when I have forgotten things have gotten away from me.

Oh and what an interesting index and the information you shared Sanderson!  It's amazing what commercial growers need to know to be prepared.  

If that bottle is a ready to use mix, it's anywhere from 70-99% water.  If you want slow powdery mildew or prevent, simply spraying your leaves with a coating of water is quite disruptive to the propagation.  Milk & water has been shown to work.  Baking soda and water has been shown to work.  And ironically plain water is almost as effective.  None really cure PM, but can kind of knock it out of it's lifecyle and slow it. If you get a good weather turn at the same time, it can seem like a cure.

http://organicgardening.about.com/od/diseases/p/PowderyMildew.htm

Sadly the best solution is very labor intensive, spray all leaves and snip all infected leaves.

Here are some pics from my garden. I had a bit of a problem with PM but leaf minors and aphids are much more of an issue for me. I started using 30% milk to water which was working quite well for the PM. In the mean time I had ordered Greencure Fungicide. I just started to combine the Green Cure and milk solutions into the same bottle. I'm showing you my zukes because they had the most PM problem of all plants in my garden. My squash is starting to show a bit of PM. I spray the plants with visible PM about 2-3 times a week.

I bought a zuke container at HD that had 3 plants, so i planted them separately. This one ended up being the big bro. The older leaves seem to brown on the edges and slowly turn color, but no real PM problem.




Middle Brother Zuke - He produced a few zukes. No real PM problem either. Just a bit once in  a while.


Youngest bro zuke - is the runt, never produced and he's ready to get pulled, as soon as I decide what to plant in it's place. This one has the most PM.

Growninsunshine, that does not look like PM. Are you perhaps overwatering ?

camprn wrote:Growninsunshine, that does not look like PM. Are you perhaps overwatering ?

I'm pretty sure it's not from over watering and I'm pretty sure it's PM. I water all of my plants pretty much the same, unless they are in another box and doing fine. If I don't treat it, it grows and spreads onto other leaves. I guess I've been pretty lucky so far from the stories I'm reading. Although my watermelon plants are getting torn up by LM and I think I have an aphid issue. Guess I'll try Neem and see what happens. There is always something to deal with, right?

sanderson wrote:Camp,  The subject of Neem came up recently but I can't find the topic.  If I remember correctly, Audrey was mentioning aphids on her squash???  I had just hosed with dish soap, cooking oil and baking soda and was feeling all organic about my treatment!    I thought you ditto-ed someone's recommendation of using Neem for heavy aphid infestation.  (Maybe two threads were going on one topic)  If so, my apologies.

The bean leaves feel papery and have the tiniest of black dots on them.  I used my jeweler loupe and one of the dots looked like the world's smallest iridescent black fly.

Vining Green Bean #1 (black eyed beans to the right)

Vining Green Bean #2


The cantaloupe are starting to look like some of the cucumber leaves.
Cantaloupe #1

Cantaloupe #2


Made my way to the back of the trellis and found really nasty infestation.
Zucchini #1 - Aphids

Zucchini #2


Any help is appreciated.  However, I lightly sprayed these plants with Neem right after sunrise (bee safe) before I logged on.

SO this is what my opinion is:
The dusty looking leaves with squiggly lines...... leaf miners, but not sure about the dustiness,  My pea and bean foliage often gets to looking like this when the leaves get old and are not doing a good job of photosynthesis and respiration. The leafminers are a temporary issue and generally cause no lasting harm to the plant. Remove the affected leaves, it will make it look better.

The light colored tan larger spots on the canteloup and cuke leaves looks to me like water splash  damage. Remove the affected leaves, this will make it look better. The plant will make more leaves. The light whitish spots looks like PM; remove affected leaves.

Also, the leaves are a very pale green with some variations of yellow. My gut tells me there is some nitrogen deficiency and perhaps some mineral deficiency as well. I would feed the plants in this bed, either with homemade compost tea, topdress with compost or espoma garden tone.

The colony of aphids, if they are in an area you can prune out, that is a quick way to handle them. If on a fragile terminal end, dunk them in a bucket of water to dislodge them. If you cannot dunk them spray a stream of water from the hose to dislodge as many as you can. Then with your thumb, wipe away as many as you can. Then spray with insecticidal soap. There is no reason to spray with more than one product within several days.

With pests, it really comes down to a level of tolerance. With aphids, you want to get rid of as many as you can, but be vigilant because they will be back. Read the IPM article.

I just spotted some tiny bits today.  We had company, so I couldn't go full battle immediately, LOL! but I'll be spraying first thing tomorrow.

Bump.  I suppose the nice thing about heat advisories for a week straight is it kind of slows the PM down. The bad news it also basically does in anything already struggling with PM.

NSR,  So true.  I've been spared this year, except for the cantaloupes which died early of unknown cause(s).

No_Such_Reality wrote:Bump.  I suppose the nice thing about heat advisories for a week straight is it kind of slows the PM down. The bad news it also basically does in anything already struggling with PM.

For all my complaining, PM is one I DON'T have.  This last round of heat even got rid of the aphids and spider mites.  AND tomorrow it's supposed to cool off and the wind is supposed to change direction and blow the smoke away.

I just realized my Canada Crookneck plants have a lot of powdery mildew. It's also on some of my other plants such as zucchini. I guess I saw it some time ago and just ignored it. The current hot and humid weather seems to have given the PM just the right conditions to thrive.


Now I'm wondering if I should dispose of the infected plants or put them in the compost bin. Some people say do not compost, others say the compost must get to and hold at least 140F for many days, and others seem to just go ahead and compost. I figure the PM spores are everywhere (e.g., in the MM, in the neighbor's veggie garden, in our own flower gardens, etc.). So I think I'll just take a chance and throw the infected leaves/plants into the compost bin. Maybe I'll regret that decision next year. Any thoughts?

I compost mine. I believe PM is airborne and not soil related. But you may want to check that.

CapeCoddess wrote:I compost mine.  I believe PM is airborne and not soil related.  But you may want to check that.

Thanks CC. I will do the same.

I read a few articles and it seems that they are divided between composting affected plants and discarding them.