And you need magnesium sulfate why....?

Since an imbalance of Magnesium could hinder a plants ability to uptake Calcium why do you need to add Magnesium Sulfate? A plant needs a balanced level of Magnesium and Calcium to properly utilize either one. Did a good, reliable soil test indicate the need to add Magnesium to your soil?
However, the amount of MgSO4 in those Epsom Salts more than likely is not enough to make any difference on way or the other and mostly using that as a soil amendment or a foliar spray is unlikely to do much more then cause you to spend money unnecessarily.

I know. I didn't want to do it, but I read a magnesium sulfate foliar spray would help keep ants and aphids and other leaf pests off my plants. Since my neighbor is willing to share (he keeps a big bag of the stuff for his soil, which is poor in magnesium), I thought I could at least give it a try, but I'd feel terrible if it made the other animals sick. I feel like I've tried just about everything else I can afford (plants are getting too big and leafy for manual pest control).

Aphids are usually on plants because of nutrient imbalances, most often when the plant is exposed to too much Nitrogen in the soil. Look closely at your soil and correct any nutrient imbalances, or soil pH problems.

I've never heard of using magnesium sulfate as an insect spray, but if Linda Chalker-Scott is against it, then I must be for it. ;-)

Aphids are soft-bodied, so anything that would coat them will kill them. Flour works well (dust the aphids with the flour), as does a hard blast of water, squishing with fingers, ladybugs, or insecticidal soap. Or, just leaving them be, they gotta eat too...

Aphids are soft-bodied, so anything that would coat them will kill them.

Not exactly -- it has to stick to them long enough to smother their ability to transpire. If that was the case, even rain or irrigation water would kill them. The hard blasts or sprays of water from a hose dislodges them and can even squash them, but just getting wet isn't gonna do it. And since the MgSO4 has nothing included to make it adhere or stick, it will not smother aphids or any other soft bodied insects.

GG, thank you. I will amend my discussion on this topic in the future.

Thanks for the advice. I'm still new at this, so maybe I'm worrying about all the wrong things, but...wouldn't dusting with flour create other problems, like clogging stomata or growing fungi (when it gets wet or ends up in the soil), or attract other plant-eating bugs?

joanie, flour is another of the ground up grains that goes into organic fertilizers. It doesn't clog anything because the microbes in the soil (both bacteria and beneficial fungi) decompose it quickly. On a plant there are microbes, too, which eventually will decompose flour but not as quickly.

You can squish a few thousand aphids with your fingers about as fast as you can dust the foliage (carefully so as not to get on any flowers) with flour. Sometimes (maybe always?) it jsut makes sense to 'keep it simple'.

Thanks, guys. I've squished as many as I could find since the plants first leafed out. I think the ants finally got the hint and stopped bringing the green ones up the pear trees, but now my pom has the black ones again. As I said, when my plants have reached full size, they'll be too big for fleapicking unless it's all I do, so I'll need something easy to apply. I've seen how flour behaves in the air, so I might try it if the infestation gets out of hand.

Did I mention that the ants ate the flowers off one of my pear trees? I wouldn't have believed it if I hadn't seen it; I thought it was some kind of rotting disease at first. Maybe I should move this discussion to Pests.

If you have ants tending to the aphids for their sugary secretions, you might be able to confuse the ants by spraying everything in sight with diluted molasses. I would add milk to that in equal proportions.

I think healthy plants discourage infestations by insects. I have roses that have not had more than a dozen aphids total in the past 8 years since I went organic. All I do is fertilize with corn meal, and I'm not very good about being regular about that. I would like to do it monthly but I'm more like seasonally.

dchall,

You said, "All I do is fertilize with corn meal." Expand, please.

When do you fertilize?
How often, or just "seasonally?"
Does that mean four times a year, once a season?
At the beginning of each season?
Do you just sprinkle cornmeal around the plants in the garden?
How thickly? Just broadcasting with your hand or using a measuring tool?
Do you reapply after rain or watering?
Just regular cornmeal used in cooking, as in corn bread?

I find this very interesting. Always looking for cheap, organic, common sense gardening tips that work.

Thanks,
Barbara in Virginia (frequent reader, infrequent poster)