The material works only while wet, and the slower drying conditions in early morning favor better control. Compatibility with other pesticides and fertilizers. Insecticidal soap is compatible with many other kinds of pesticides, but should not be mixed with rotenone-based insecticides, Manzate, Dithane, lime sulfur, copper sulfate or copper fungicides such as Bordeaux mixture. It should also not be combined with concentrated mineral fertilizers for spraying on foliage. Compatibility with hard water.
Soft water is best for diluting to the proper strength.
Soap combines with and is precipitated by certain minerals in hard water, especially calcium, iron and magnesium. Test for compatibility by allowing a quart of the prepared spray solution to stand for 15 minutes. The solution should normally be a light, milky color. This publication contains pesticide recommendations. Changes in pesticide regulations occur constantly and human errors are still possible.