Fertilizer can be applied easily in granular form to turfgrass, but most post-emergence herbicides are more effective if sprayed as liquids.
This has led many commercial turf applicators to use liquids for everything; however, uniform spray application to lawns can be difficult. There are good boom sprayers available for spraying larger, open turf areas like golf courses, sod farms and sports fields, but boom sprayers are usually impractical for lawns regardless of whether the lawn is to be treated by a homeowner or a commercial applicator.
Commercial applicators usually use gun sprayers on a hose, and homeowners are usually restricted to either a pump-up sprayer or a hose-end sprayer on a garden hose. These methods are not inherently accurate or easy to use. With practice, a commercial applicator can learn to apply herbicide at a reasonably uniform rate, but the results are very subjective. Also, these methods require transporting and applying large volumes of water – typically 4 gal/1,000 ft2 (or 174 gal/acre).
An Easy Alternative
An excellent alternative is to apply fertilizers in granular form and then use the Herbi sprayer imported from Micron Sprayers, Ltd., Great Britain (Figure 1) to apply liquid herbicides when needed. This sprayer can apply relatively uniform droplets of herbicide spray (called Controlled Droplet Application or CDA) in a uniform 4-foot swath at low rates. It is light and easy to carry. It is extremely maneuverable for working around obstacles in lawns. Testing for many years has shown this sprayer to be very effective.
How the Sprayer Works
This sprayer consists of a hand-held wand with a small bottle on the upper end and an electric motor with a spinning cup on the lower end. The cup has a serrated lip and spins at high speed. Spray solution flows by gravity through a metering orifice into the cup and is then spun out (Figure 2). As the liquid leaves the cup, the serrations on the lip of the cup cause the liquid to form “ligaments” or individual streams of liquid. These streams then break up into relatively uniform droplets of about 250 microns. This is an excellent droplet size for herbicide efficacy and for minimization of drift. Since few smaller droplets are formed, the drift potential is further reduced. The unit is held with the head about a foot above the ground and the spray is discharged almost horizontally and then falls to the ground in a full circle. The effective swath width is about 4 feet. The sprayer is powered by D-cell batteries in the shaft.
In addition to the uniform, relatively large droplet size, this sprayer offers the advantage of low spray rate. Total spray rate is typically only 0.8 – 2.3 gal/acre; there is some evidence indicating that the rate of active ingredient can be reduced because the uniform droplets are so efficacious. Maneuverability is another strong advantage. The sprayer is easy to carry and easy to maneuver around obstacles in the lawn (Figure 3).
As noted, the droplet size and uniformity minimize drift, but it is still important to take precautions. This sprayer is not shielded; any wind will cause drift. Also, the spray pattern is relatively wide. You must be careful to avoid spraying non-target areas.
Several options are available for the Herbi sprayer. One version offers two heads to provide a 7-foot swath width. Another option is a backpack tank for increased capacity and fewer fill-ups. A neck strap to help support the wand is available. All of these options may appeal to professional applicators, but they are not needed for homeowners. A shield for the spray head is offered as an option, but its use almost completely negates the CDA effect since the droplets impinge on the shield and either coalesce or break up.
In summary, the Herbi CDA sprayer offers both homeowners and professionals a simple and effective way of applying liquid herbicides to complement granular fertilizer programs.