As a general rule of thumb, the ideal pH for water used in spraying
pesticides is slightly acidic (pH 4 -6). However, there are always
exceptions. Make sure to read the label of the pesticide you intend to use
as there are always some exceptions. For example, some herbicides have been
known to break down in a sprayer tank when the pH is too acidic (pH less
than 7). The sulfonylureas such as Ally, Escort, Amber, Harmony Extra,
Express, and Accent may inactivate if left in the sprayer tank mixed in
acidic water. Higher temperatures will also cause these herbicides to
inactivate at a higher rate.
Insecticides and fungicides, on the other hand, have been shown to break
down in water that has a high pH (alkaline). This means that an insecticide
begins to break down once mixed with high pH water in the sprayer tank.
Fungicides such as Benlate, Bravo and Captan can also inactivate quickly if
left in the spray tank in an alkaline water source
This might explain why some folks get very different results than others
when using the same product. I never paid attention to the labels to see the
part about the ph of water. Did you?
Rodney Eveland
Northeast Wyoming
[NAFEX] Ph of water used in spraying,
Rodney, 02/15/2006