Please go to www.ifca.com to see the guidance documents we have posted to help you determine if you need a NPDES permit to apply pesticides.  For normal row-crop applications a NPDES permit is not required.  However, any applications made to or near waters of the US, for mosquito control or wide-spread aerial spraying over forested areas will require a permit.  Anyone, whether they are a licensed applicator or not, who applies a registered pesticide to water, including ponds that have an overflow outlet that may drain to a water of the US, will need to get a permit in order to comply with this Clean Water Act regulation.