Well, sadly, it turned out to be powdery mildew. John had suggested aphids, which was a good guess on his part, since he's a regular grower of this squash. But Jill and Nancy both came back with powdery mildew, and when I inspected it again shortly before leaving for work, I could see that it had a fuzzy "fugus" look to it. Plus, I could find no aphids on the undersides of the leaves.
Nancy in particular sent me a stern warning, via email, to remove the affected leaves and treat it NOW!, as this will spread quickly and kill the plant. Indeed, by the time I got home from work the fungus had spread from just a handful of leaves to almost two-thirds of the plant. I spent about an hour after supper, braving the thick cloud of evening mosquitoes, trimming it back and throwing the waste in the dumpster (not the compost). Spraying it will have to wait until tomorrow evening--if it isn't already too late.
The saddest news of all is that in the course of trying to cut all the affected parts of the calabasas vine, I accidentally cut the vine on which the lonely butternut was growing. So it was harvested well before it was ripened. It is a fair size, however, so I'm wondering if I just stuck it in a cool place if it would continue to ripen on its own.
Here is a before and after view of the devastation of the vine. The first picture is from a couple of weeks ago:
And this one, compared to the same angle in the post below:
Nancy pointed out in her email that powdery mildew has a tendency to thrive in shady, moist environments, and trimming back all those leaves should increase air circulation and sunlight.
All of this has me thinking: what have I learned from this? Certainly, all the extra moisture last week helped things along, but this is also a shadier spot than is ideal for a vegetable garden. I thought I could probably get away with it, since our summers are usually so hot and dry, and our sunlight so strong, that plants normally requiring "full sun" seem to do all right in part shade here. However, perhaps full sun really means just that when it comes to vegetable- and fruit-bearing plants.
To get full sun in my garden means I'm going to have to trim back some very big limbs on some old pecan trees, however. I'd already taken down some scraggly Ketler junipers in this part of the yard, primarily toward the purpose of growing veggies. Apparently it wasn't enough. There is one limb in particular I am probably going to have to break down and have removed if I really want to grow produce. I've really needed to do it for a couple of years now, but I've been dragging my feet on the task, for no other reason than it provides wonderful shade for my woodshop in the summer. And there is no small premium on shade in this part of the country...
Still, it really is time for it to go.
Here is the other thing I've learned: I'm disappointed about all of this--the tomatos, the powdery mildew, accidentally cutting my pretty butternut squash--but you know, I looked on this first summer as a backyard vegetable grower as a learning year. I have the luxury of being able to make mistakes without starving my family; this year will only truly be wasted if I don't learn from it and do better next year.
Even so, what a summer it's been!