Two yellow crookneck questions

First, my plant isn't looking so good. Old foliage is yellowing, then turning brown and dying, while new foliage is coming in nice and green. I've been checking carefully, and I see no signs of bugs on the leaves--not even the ubiquitous spider mites that are all over everything else right now. Is this heat stress, or something that I can fix, or should I just be yanking the plant and starting something else in that spot once it cools down a tad?

(Sorry the picture isn't the greatest--had to get outside early before it got too hot. It was also slightly wilty at the time; it was getting its morning drink from the soaker hose as I took the pic.)

Second question, what's causing this? I've had several "good" squash (and they were very tasty indeed!), but then several that turned bright canary yellow and hard. Some turned when they were small, some actually grew to a respectable size (say, 4-5") before this happened. Is this a pollination problem, or something else?

Thanks for the help!

The good news: It is not a pollination problem. The bad news: That plant is showing real signs of stress. It may be the heat , but could be a disease or even an insect problem. Squash bugs rarely kill a plant but can puts ome real stress on them. You know about the Squash vine borer I presume. Those things destroy the vine just above ground level, you rarely see them, but the frass is evident. At any rate, those look like the OP Summer Crookneck. Pick them within 3-4 days of blossom close rather than waiting for them to size up, will give you small but edible squash. Even some of my hybrids are maturing small as we get into triple digit temps.

Looks like I need to do some more research, then, and see if I can find any bug signs I missed. I'll definitely start snagging them earlier--I bet they'd be great sauteed!

As always, thanks for your help, Farmerdill!

Okay, after checking my plant over thoroughly, I see no signs of bugs at all. It seems like if there were enough squash bugs to do this kind of damage, I'd see the adults, eggs, etc.--but nothing. A few aphids, maybe, but that's it. No sign of any squash vine borers, either--no frass, the stem looks undamaged, etc. It's putting on lots of new growth that looks great, so I guess I'll just watch it and see what happens.

Most of my veggies mature small and quick during the heat of the summer. Spaghetti squash that were 11 inches long now mature at 6 inches. They are still good, just won't put on the size. Peppers turn red on me without putting on any appreciable size as well. Just part of the Arizona summer me thinks.

I have a similar type of squash and it looks pretty good to me. But the first squash that developed, shown on the bottom in the picture, shriveled up and died a few days later. So what I'm getting from this thread is to pick the tiny ones off a few days after the blossom dies, don't sweat it, and maybe they'll get bigger later in the season? Good to know, thanks.

Ooops. Here's the pic, if it makes a difference.