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Long Beach, CA

Yesterday I noticed the first signs of powdery mildew on a few leaves, and sprayed with Daconil. Instead of getting better, it seems that the disease has spread since yesterday. What am I doing wrong? I used the recommended concentration of one tablespoon per gallon of water, and when I sprayed I covered the whole surface of the leaves with fungicide (I didn't spray on the undersides, though). Any help would be greatly appreciated.

Thanks,
Oliver

5/26/2005 7:07:14 PM

C N Y

you need to spray the undersides of the leaves as well.
that junk is just LOOKING for a place to hide and grow,
and what better place than where none of us really want to
have to look or spray! i do not know why it looks as though it is spreading, but someone will answer you soon....eric

5/26/2005 7:53:31 PM

Hilpoltstein, Bavaria, Germany

use a good systemic fungicide, saves lots of time as you don't have to spray the underside of the leaves...

5/27/2005 2:51:33 AM

[email protected]

PM starts on the undersides of the leaves. If you don't spray the undersides it wont work at all. Systemics penetrate but don't really translocate, so even they should hit both sides.

5/27/2005 4:53:47 AM

Sioux Falls, SD [email protected]

My Daconil wasn't working. . .
Then saw post by Tremor
Stuff's no good after winter in garage!
Got new Daconil
Worked better. . .

5/27/2005 10:49:16 AM

Long Beach, CA

Don Langevin in How to Grow World Class Giant Pumpkins III writes that Quadris is especially effective in controlling PM. Maybe I should try it instead of Daconil? In any case, thanks for the tips about spraying under the leaves, I went back and did that.

Oliver

5/27/2005 6:17:38 PM

Long Beach, CA

Also I forgot to mention that my Daconil must be many years old as I can no longer remember when I got it; maybe I will buy a new bottle as Dakota Gary suggested.

Oliver

5/27/2005 6:24:35 PM

Oz

Try large fans and some black lights(uv).
If you can change temp,humidity,or ph it does not live.
I have used copper solution,,
My HP SODIUM light burns up fungus.

5/27/2005 8:14:24 PM

[email protected]

Daconil stores fairly well between 40-80*F. But don't ever let it freeze. All garden chemicals & fertilizers should be protected from extreme temperatures.

Heritage/Quadris is a good example of a (somewhat) translocating systemic fungicide. Indeed it is so good that some farmers refused to rotate it with other fungicides even after fair warning. We have them to thank for the new Azoxystrobin resistant strains of Powdery Mildew that were identified in upstate New York last summer. This doesn't mean we shouldn't use it. But it does emphasize the importance of responsible fungicide rotation.

The new organo-silicone surfactants (Hawkeye & Silwet 77 are the only two I can recall) can also help make fungicides work much better. These don't just reduce the spray particle angle & surface tension. They also keep the fungicide application wetter longer to help maximize leaf cuticle penetration. Indeed even a sloppy application might perform adequately if the right spreader is employed. Don't confuse these with conventional non-ionic Spreader Stickers. They are engineered to both reduce surface tension (not as well) but also make the treatmet dry quickly & resist rainfall. That's all good & well in the face of a pending rain event, but not so great when the forecast is for clearer skies.

Al Eaton said it well when he recommended using three fungicide products from different families in rotation.

Here are the high points of the various fungicide families & what they can do for us.

1.) Daconil (chlorothalonil) or Dithane/Mancozeb (or both) for the required "contact" element. These are broad spectrum & long lasting "protectant" fungicides. Mancozeb controls Downey Mildew but not Powdery Mildew. Daconil does Powdery but not Downey Mildew.

continued

5/27/2005 9:03:06 PM

[email protected]

2.) A DMI acropetal penetrant like Eagle/Nova, Bayleton, Banner, Rubigan, etc for a systemic family. Eagle (myclobutanil) is especially strong against Powdery Mildew.

3.) The Benzomidazol family is now represented only by Thiophanate-methyl marketed as Cleary's 3336, Topsin, T-Storm, etc. Especially good on Fusarium & Rhizoctonia - consider drenches. Good PM fungicide too.

4.) The strobilurin family includes Heritage/Quadris (azoxystrobin), Compass/Flint (trifloxystrobin), Insignia/Cabrio (pyraclostrobin), & Emerald/Endura (boscalid) but Boscalid isn't of much use to us alone. Pristine combines boscalid & pyraclostrobin for an outstanding (but expensive) Downey Mildew, Powdery Mildew & Gummy Stem Blight controling monster mix. Never apply 2 consecutive strobilurin fungicides. Instead alternate another mode of action between strobis.

5.) Copper hydroxide based fungicides like Phyton-27, Kocide, Nu-Cop, etc are HOT & best suited for cool season use against Angular Leaf Spot. Two half rate sprays a day apart are less risky for young plants since this treatment protocol is best started as the young vine runs at the 5-8 leaf stage.

continued

5/27/2005 9:03:35 PM

[email protected]

6.) Pythium & Phytophthora root rots are only controlled by very specific fungicides. Banol, Subdue Maxx, Prodigy/Aliette, Banrot/Truban are examples. The phosphonate fungicide Aliette (aluminum-tris) is the only TRUE SYSTEMIC fungicide. It can be foliar or root drench applied & will find all plant parts. Now that the patent is expired there are plenty of lower priced versions available.

Worth noting is that Aliette (aluminum-tris) is converted to potassium phosphite then phosphorus acid in the plants during which process it is fungistatic to certain vascular diseases. Potasium phosphite is now being legally sold as a fertilizer at MUCH LOWER COST than any registered Phytophthora or Pythium fungicde could be since the manufacturer/formulator/distributor incurs no pesticide registration expenses.

So here we have it; accurate disease identication, appropriate fungicide selection, proper timing, application technique, & the use of carefully selected adjuvants or surfactants absolutely *WILL* determine the outcome of a fungicide program.

Always read & follow all labels.

5/27/2005 9:03:45 PM

Long Beach, CA

Thanks for the info on various fungicides, Tremor. If I start now with an appropriate fungicide program though, will it do any good in at least preventing the spread of the disease? I've heard people say that it is already too late when one sees the first signs of PM, and that spraying is only effective in prevention.

Oliver

5/28/2005 12:00:35 AM

[email protected]

Oliver,

No problem. It was that time of year again.

Once PM starts it is hard to stop. But if you don't try the season will likely end. Get some systemic Myclobutanil (Eagle or Nova are the pro versions) or Propiconizole (Banner Maxx or Spectator) ASAP. These 2 offer the best curative properties if you use them diligently. There is a consumer version of Myclobutanil you can buy at garden centers or you might find it online somewhere. www.pumpkinsupply.com or Rosemania has Banner. A contact fungicide like Daconil should still be in the mix, but stress the systemics until you get a handle on the PM.

5/28/2005 5:41:00 AM

Oz

TREMOR,does the PM spread in the surrounding soil along with the plant?

5/28/2005 6:08:25 AM

Long Beach, CA

Thanks again for the advice, I ordered Eagle today from pumpkinsupply.com.

Oliver

5/28/2005 3:31:35 PM

[email protected]

PM spores are airborne. The results of national monitoring by the USDA are listed in another post. PM is always in bloom somewhere in the world. The PM we deal with in the Northeast is carried here from South America then Florida.

5/28/2005 4:46:55 PM