Aphid Control 1 cup chopped onions or shallots 1 cup water Purée the chopped onion or shallots in a blender until they are a fine mush. Add water, a little at a time. Continue blending, scraping down the sides if necessary. Label and store in a glass jar, tightly sealed, in the refrigerator for up to 6 weeks. To use, pour into a spray container and spritz the liquid over the plant, even under the blossoms. It is best to spray in the early morning, after the dew has dried, or in the late afternoon when the sun is not too hot.