Here are a couple of cases of “if it seems too good to be true, it probably is.”
Does a weak citric acid solution kill powdery mildew?
No.
See Post G22-039 for background. This is based on a product offered on Amazon that said it would kill powdery mildew on plants. That product was merely a very dilute solution of citric acid in water. I was originally going to do a formal test, with a “control” patch, but the powdery mildew didn’t show up on time.
Instead, here it is firmly established on what’s left of my summer squash. Near as I can tell, a dilute citric acid solution had no impact on well-established powdery mildew. Here are two pictures, one before spraying citric acid, and one about a week after. Any apparent difference is just an artifact of the lighting, compounded by the complete loss of some of the leaves.
Do bamboo leaves make a good weed killer?
No. Or, at least, not good enough. Or maybe it’s just very slow at it. All of which is a pity, as bamboo surely kills lots of useful plants.
See Post G22-052 for background. Bamboo is one of many allelopathic plants, that is, plants that produce poisons to keep competing plants in check. I figured, why not give it a shot as weed killer.
Before:
Roughly seven weeks later, I pulled back half of the now-brown bamboo. Unfortunately, there’s still plenty of live weeds growing through the driveway, like so:
