pH is a measure of water alkalinity represented on a logarithmic scale of 0 to 14. Water with pH greater than 7.0 is considered alkaline while water less than 7.0 pH is described as acidic. Some pesticides, mostly insecticides, miticides and fungicides, are broken down chemically by high pH water. This degradation is called alkaline hydrolysis. Some pesticides are sensitive to loss in low pH water; this degradation is called acid hydrolysis. Accordingly, it is important to have a general understanding of the spray water pH and the sensitivity of pesticides to it. In general, a pH of 5.0 to 6.5 (slightly acidic) is optimum for most spray applications.