Air-assist nozzles that use pneumatic energy to help atomize the spray liquid were reviewed. These nozzles use larger orifices than conventional hydraulic nozzles for low-volume applications. By changing the air pressure, various droplet sizes can be produced without changing nozzle tips. Several systems use air to transport the atomized spray to specific target sites. Various air volumes and velocities have been evaluated in these systems. Preliminary research indicated that air can improve canopy penetration and can cover the entire plant more uniformly. Undersides of leaves can be treated easier with air-assist systems compared to conventional applications with hydraulic nozzles.

Contact, induction, and corona electrostatic charging systems for pesticide spraying are reviewed and are compared with uncharged spraying systems. When uncharged sprays are poorly intercepted by plants, charging significantly increases deposition, drawing from the reservoir normally deposited on the soil. Post-emergent herbicide spraying is the one area where the benefits of electrostatic charging are identified least easily. For insecticides and fungicides where the young crop is the ‘general’ target, increased capture of charged spray may permit reducing doses with economic and environmental benefits. While charging may not increase total capture where uncharged spray interception is good, it does alter spray distribution throughout the crop canopy. The biological consequences of modifying spray distribution depend upon the ‘real’ pesticide target. In situations where the crop acts as an electrical shield limiting spray penetraton, air assistance is necessary to augment charged spray deposition within the crop canopy. Drift of charged spray clouds should be related to drop spectra, velocities and trajectories and requires further study as do protocols for spray charge measurement and definition. In addition to biological performance, the transfer of electrostatic technology to farms is limited because of financial, legal, and practical factors. Identifying specific major crop/pest problems will help to introduce electrostatic spraying, which will complement, rather than replace, traditional spray systems.

In the late 1930s, European engineers discovered that, for very low flow rates, rotary disk atomizers produced a more definable range of droplet sizes than hydraulic atomizers. In the late 1970s, a cup-like spinning atomizer was developed to apply herbicides at low and ultra-low volumes. Rotary atomizers distribute droplets in a pattern similar to hollow cone nozzles. The droplet trajectory could affect deposits adversely since droplets released horizontally are exposed to wind and other environmental effects longer than hydraulic spray nozzles. Propellers and fans were used to enhance downward movement of droplets without considering that droplet impingement velocity was critical for efficient deposition. In the early 1980s, rotary atomizers were promoted to reduce herbicide rates, but the claims were products of unconfirmed testing. Herbicide efficacy in confirmed research was not influenced by application with the rotary atomizer, but lower carrier rates reduced the amount of water handled during the spraying operation. The cost of the atomizer, more maintenance, and greater care during operation with no decrease in herbicide rates discourage continued use.

Crabgrasses (Digitaria spp.), the first cultivated grains, were grown for food thousands of years before they were considered weeds. Digitaria, a genus of about 60 species, grows in the world's temperate and tropical regions. Many of the species are good forage grasses. Thirteen weedy Digitaria species infest the United States, but large crabgrass (D. sanguinalis # DIGSA) and smooth crabgrass (D. ischaemum # DIGIS) are the most common.