my sweet corn seems to be dying

I have a strip of fertile ground on the south side of our house that gets full sun. It runs east-west along the side of our garage, with no trees or shrubs anywhere nearby. The area is about 25' long and sticks out from the house about 5'.
I decided to try planting corn for about the first time in perhaps 11 years as a late crop after harvesting cabbage in late June. I soaked the seeds of 3 varieties of sweet corn to give it a head start, then planted them once they started to sprout, on July 3. The plants are now roughly 8 to 8 and a half feet tall.
I fertilized the plants lightly every 4 weeks, and also mulched somewhat lightly with straw to keep the weeds down. I thinned the plants out to about 9" or 10" apart, in rows 12" or 13" apart. I figured that with the rows this short, I can just reach in to harvest the ears.
The plants did fantastic up to when they started to tassel, about 7 days ago. I noticed that lower leaves started to yellow, then brown and wither. I thought that perhaps something was eating them, and applied a bit of sevin. Then I looked at some photos online, and saw today that it might be some sort of northern leaf blight, so I applied daconil herbicide.
Today has been a windy day, and 4-6 of the plants have blown completely over. Things are not looking good! I noticed that the plants are only just now starting to put out those tiny side bracing roots that come down from about 1" above the soil surface, so they are not helping to brace the plants.
It looks like I may have to resign myself to my second sweet corn failure (2 out of 2). The first time was caused by squirrels who decided to bite the base of each plant, and eat a tiny bit, right when the ears were starting to form. Likewise, this time the ears are just starting to form, again.
Is there anything I might be able to do in order to help at least get some sort of crop? I'm wondering if I needed to thin them out quite a bit more, but everything looked great until the last 7 days.
Could part of it be due to my mulching with straw? It really kept the weeds down, and helped retain soil moisture. However, I'm wondering if it also may have retarded the root growth, and caused the corn to have a shallow root system. Then again, the corn that blew over did not come out at the roots - it bent over about 3' up.
*sigh*. I'm just not having good results with sweet corn.
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Well, my gut feeling was that each plant needed more room, so I went out there with a utility knife and cut down every other plant, and a bit more. I probably took out about 1/2 of the corn. I noticed that some still had no sign of ears at all, and I made sure to cut those off.
Some of the plants had 3" to 4" ears, so that was a bit depressing, cutting those down.
I think that with more room at least I have a chance to get some harvest, right?
The rows are still spaced the same (tight, at about 13" or 14"), but at least the plants are now 18" in the rows, instead of 9" apart. I think I could have gotten away with tight rows, or closely planted, but perhaps not both.
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I bet your night temps are too low for late season corn... here in the Catskills it's reached 75 during the day but at night it's dropped into the 40s already... leaves are already turning, gonna be a very early fall. I can tell by how the Canada geese are already grouping up that it will be an early and severe winter. I'll know for certain if my hummers leave early.
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Ohioguy said:

I think perhaps you did not fertilize enough, and I'd suggest that there may have been a particular shortage of potassium. (The scorching of the lower leaves, lack of prop roots and stalks falling over point to this.)
I plant my corn in blocks of 4 x 4 plants, 12" apart, so it isn't neccessarily the crowding that is your problem.
These blocks get a lot of compost added in the spring, plus alfalfa meal, plus potassium sulfate.
They get mulched with shredded leaves when the plants are about 8" tall and get a side-dressing of bloodmeal at that time, with another side dressing of a balanced organic fertilizer when the plants begin to tassel.
If they seem to be looking a little, hmm, "off" I will spray them with a kelp solution (Maxicrop).
My biggest problem this year is that I wasn't able to get my preferred variety of late corn, and the substitute is both much earlier than described (no fresh corn for Labor Day!) and has a bad habit of open tips, which has proven very attractive to sap beetles. Easy enough to snap off the damaged tips, though.
--
Pat in Plymouth MI

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I don't think that night temperatures are a problem - it has not gotten down below about 58 degrees here yet.
It seems like the top of the plants had optimum growing conditions, and rocketed right up. However, perhaps I was watering a bit too often, and the root systems may not be as extensive as they should be.
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