My real question is in the title of the post, though. I have a pansy with powdery mildew and my rosemary relapses every time it's overcast and humid, no matter how little I water it, so I started spraying them with milk spray. The neem oil hasn't helped much with the powdery mildew, but I'm still wondering if it will be an option after I introduce ladybugs.
Obviously I don't want to kill off their food supply, but right now that doesn't seem likely. There's a weird alley behind my neighbor's yard that allows us to move equipment into our backyard, because we're the middle house in a row of three. We use it so little that when I checked it recently I found it's overgrown with weeds and the weeds are all covered in aphids. Almost all of the aphids on my tomatoes and other plants have wings, but these were all wingless. Reading about aphids, this seems to make sense--they produce winged offspring when they get too crowded, and boy howdy, are they crowded back there. You can't even see the weeds' stalks. No wonder I'm overrun.
I'm thinking of releasing some ladybugs back there, too. Do you think this will help choke off their supply? I briefly considered using herbicide or getting some more gravel, but this seems more elegant.
Here's a photo of one of the barrels with the tomato (and some nasturtiums I planted with it).
The aphids themselves have proven very difficult to photograph. This may be my best attempt--it's two of them that got caught in a spider's web when they flew in. I put a leaf behind them to try and help the lens focus but... eh.
