In our previous seasons, we’ve had mildew on primarily squash and cucumber leaves, although last season it was sufficiently bad that is spread to other plants. This year, we’re trying an early start to suppressing mildew, applying a preventative even before we see any mildew.
Last season, we used a mix of sodium bicarbonate (baking soda) and soybean oil (vegetable oil), a couple tablespoons of each per gallon of water. The active preventative is the sodium bicarbonate; the soybean oil makes it stick to the leaves.
This season we’re using potassium bicarbonate instead, which is a little more expensive, as one of our garden experts was concerned about adding sodium to our soil. The instructions for the potassium bicarbonate fungicide said only to mix it with water, and not combine it with anything else, so we didn’t combine it with soybean oil. We’ll check later to see how that works out. It was also noted that the oil gummed up our sprayer.
As an experiment, we applied this fungicide to the sunflower and turnip leaves, which were terribly munched upon. In theory, this shouldn’t help, because we suspect the culprit is some insect (although we didn’t see any on the leaves). However, maybe that particular insect won’t like the new taste.
