Before answering your question directly may I extract a promise from you that...you will send a sample of the fungus covering your yard off for testing, please! So far I see no indication that you plan to do so. The knowlege we need to help you is the identification of AND Latin name of that fungus. With the Latin name in hand I can quickly encourage or rule out cornmeal as an organic control.

Yes, cornmeal does turn interesting colors. So far in all my trials these color changes have not harmed anything. This year the cornmeal sprinkled on my container tomato soil turned jet black. Last year it was a different color.
Four years ago I was trialing cornmeal as a preventative for yellowing Gardenia leaves, a common southern problem. One morning I was shocked to find the Camellia japonicas growing around my Gardenia experiment covered in yellow 'fuzz'. Nothing to do but wait and see what would happen. The yellow fuzz disappeared, Camellias were very healthy and bloomed heavily that winter. Plus I have decided that spreading cornmeal under Gardenias after the first bloom does help to reduce leaf yellowing. Since reporting this here on GW others have indicated that it has helped their Gardenia problems.

Nandina -- Which fungus am I supposed to get tested? The one on the cornmeal, or the one (or possibly a hundred) that are in my yard and garden? From photos I've posted here and to my local master gardener association, it would seem that at the very least I have powdery mildew. But, I'm not sure about what fungi I've got on plants that are showing different symptoms.

1) Is it the cornmeal fungus or the other fungi I need to have tested?
2) How does one get it tested?

(P.S. I had not planned to get the fungi tested; I didn't know you could... I'm also worried about any time delay -- what I've been told is powdery mildew on my squash plants seems to be killing them (they're losing leaves like crazy). I've started spraying them with a diluted milk solution. How long does a fungus test take -- I'm worried that by the time results get here the plants will be toast...)

Thanks. alliemack

Powdery mildew on squash is typically a late season problem. It happens to most people who grow squash.

It's too late for a remedy so, get rid of the plants and forget the problem for this year.

I returned to your post with photos at http://forums2.gardenweb.com/forums/load/organic/msg0911360417079.html?5
But the photos don't show up.

Are the pictures available elsewhere? If so, where?

Beyond that, I doubt you have an acre full of a nasty fungus disease. More likely much is cultural, and/or environmental, and/or "normal" late season problems.

Have the white fungus on your lawn tested. I told you how to acomplish this in my first post on the subject where I indicated possible Southern Blight. Powdery mildew appears to be a secondary problem, which is weather induced. From your descriptions something else is going on in your general area worth identifying.

I have the whiteish fuzzy mold where I use cornmeal too. I have used cracked corn (for fertilizer) and it will do it too. It has not caused me any problems and I just let it go.

I agree with Jean that it is highly unlikely your entire garden is plagued with a single fungal problem. First, most fungal pathogens are rather specific to their hosts, so what infects one plant is unlikely to infect another. The exceptions are some common fungal blights that affect members of the Solanaceae (tomatoes, potatoes, peppers, etc.) and powdery mildew.

Since PM is primarily climate related, at this stage of the season, there is little you can or need to do for it, other than remove the affected plants (referring to the squash) and clean up well. PM on larger woody plants (like the maple in the photo) is primarily cosmetic, common under certain conditions and will cause no permanent damage. Again just clean up the leaves and compost thoroughly before using. Or discard.

With the exception of some extremely persistant soil-borne fungi, a great many common fungal problems can be diverted by improving cultural practices or the conditions the plants are growing in. Making sure they have adequate air circulation, sufficient sunlight, rotating susceptible crops (like the Solanaceae), mulching well to keep spores from splashing and avoiding late day or overhead watering should help a lot. And developing a good, healthy and biologically active soil will help also. But some plants are just very prone to fungal problems and there's not much one can do about weather conditions :-)

FWIW, the dogwood problems look very much like anthracnose, which is very common with Cornus florida and difficult to control. Planting resistant cultivars like kousas or many of the hybrids is the best solution.

Thanks to you all for your comments. Jean001 -- I've listed a link below for the 2nd posting I did (where the link worked for the photos)...

The white mold on the cornmeal has now turned gray. It looks awful, but so far the plants under which I placed the cornmeal don't seem adversely affected.

Nandina -- I am still waiting for a response from our local extension office (the master gardener group forwarded my info to them). I'll do the soil samples and see what they show.

Gardengal48 -- I originally thought that overcrowding in my garden was the main cause/helper with my fungus problem (I underestimated the growth of the tomato plants). However, because I had so many volunteer plants this year, and for some reason had a hard time parting with any of them, I had tomatoes planted all over the place. Even the ones that were isolated and getting more sun were affected. Must be that they're prone to the problems anyway...

So far lettuce and basil have done the best (of the things I've grown this year). Odd -- I'd have guessed that those would have been the tenderest, most disease-prone plants out of all of them...

Thanks again! alliemack

Here is a link that might be useful: Earlier Post with Pictures

Thanks for the link.

DSCF2276 sunflower
In order to diagnose rust, we need to see the underside of the leaves. Even if it is, it's too late to treat.

DSCF2893_3 Dogwood.
Looks like late season powdery mildew (the powdery stuff) added to an earlier problem of drought stress (the dry brown stuff). (Anthracnose was mentioned by someone else earlier but that is a springtime problem, with the distribution of the brown tissue different than shown in your photo.)

DSCF2883_3 Mold all over the lawn.
White mold has been suggested and may be possible as it exists in your region. Look for small black irregular firm bits, up to about a 1/4 inch on the stems, at the base of the plants, and on the ground nearby. (For the most part all the blackened bits will be within the fuzzy white stuff.) If found, it indicates white mold, a nasty soilborne fungus. Contact the Extension Service for management suggestions.

DSCF2884_3 Volunteer squash or cuke.
Late season Powdery mildew. As has been said, it's common late season, and it's time to get rid of the plants.

DSCF2890_3 Can't remember plant name; appears to be rotting.
You're probably correct. Looks like an artemisia. Such plants get by with *minimum* water after they're established. So a question: How much rainfall or supplemental irrigation has it received?

DSCF2885_3 jalapeño pepper
I'll pass on the pepper problems because I don't have that situation in my region. But I do know that humid climates enhance various leaf disease for peppers.

DSCF2280_3 zinnia.
Potential victim of both powdery mildew and root rot, the latter because they do well *minimum* irrigation after they're established. Don't know if this is the case with your zinnias, but, far too often, I see people purchase/plant straggly zinnias which should have been sent to a trash can.

DSCF2880_3 tomato in flower bed
One possibility is water/heat stress. It would have happened previously, about a week or 10 days, possibly longer because once the purpling shows up, it remains.

DSCF2894_3 Sweet gum
Sorry, this isn't anything like what I see in my region. Possibly a leaf disease. That said, have you looked at the underside of the leaves? Any critters or pock marks?

DSCF2900_3 tomato with multiples "stuck together.
A temperature induced glitch at flowering time.