Abstract: The invention is a filtering device for the drilled passage in on-off control valves used in aircraft liquid crop spraying systems. The device is mounted within the on-off control valve in the spray boom supply line at the opening of the drilled passage which connects the low pressure area of the suck back venturi to the spray boom supply line. In the "two-part" and "four-part" configuration of the device, it is composed of a small gauge wire mesh sleeve inside a perforated cylinder with raised collars on both ends. The collars secure and align the device in the on-off control valve assembly. The collars may be machined in one piece with the perforated cylinder (the "two-part" configuration) or machined separately and fitted onto the ends of the perforated cylinder (the "four-part" configuration).