Nozzle type and application pressure govern droplet size (see Nozzles: Selection and Sizing, Virginia Cooperative Extension publication 442-032), which in turn affects system output (application rate), target deposition, uniformity, efficacy, and the risk of drift. Off-target movement in the form of spray drift is a major concern because it diverts the chemical from the intended target, reduces efficacy, and deposits pesticide where it is not needed or wanted. When a pesticide drifts, it may cause both environmental and economic damage, including exposure to people and property, injury to susceptible vegetation, harm to wildlife, deposition of illegal residues on crops, and contamination of water supplies.

The people of Virginia use nearly 400 million gallons of groundwater each day to meet industrial, agricultural, public, and private water demands. One-third of Virginia's citizens rely on groundwater as their primary source of fresh drinking water, and 80 percent of Virginians use groundwater to supply some or all of their daily water needs. Groundwater is an important resource, but it is a hidden one and, therefore, is often forgotten. In fact, until recent incidents of groundwater contamination, little attention was paid to the need to protect Virginia's groundwater.

This fact sheet covers nozzle description, recommended use for common nozzle types, and orifice sizing for agricultural and turf sprayers. Proper selection of a nozzle type and size is essential for correct and accurate pesticide application. The nozzle is a major factor in determining the amount of spray applied to an area, uniformity of application, coverage obtained on the target surface, and amount of potential drift.