Lake Okeechobee, FL.

ERDC TN-DOER-C20

March 2001

all demonstration plots. The bagasse and N-Viro biosolids plots showed the least amount of

undesirable vegetation and the best growth of planted desirable vegetation (Figure 10). After 2

years of herbicide wiping, Spanish needle continued to reestablish from the massive seed bank

collected over the years (Figures 11 and 12). However, perennial peanut became established on the

bagasse and N-Viro plots despite the continuous regrowth of Spanish needle (Figure 13).

Vegetation management changes in mowing height for the entire dike system were implemented in

1995. Mowing height was increased to 152-203 mm (6-8 in.) above the ground, which allowed the

desired grass to compete more effectively with undesired weedy vegetation. Innovative technolo-

gies were applied to control the undesirable vegetation. A weed wiper applicator (Figure 14) was

used to control the taller undesirable napier grass and Spanish needle. The glyphosate herbicide

Round-Up was applied at a rate of 2.3 102 mR/ha (32 oz/acre) as full-strength liquid to the wiper

that was set at 305 mm (12 in.) above the ground at a tractor speed of 4.8 km/hr (3 miles/hr) (Figure 15).

Round-Up is registered by the U.S. Environmental Protection Agency for use in noncrop sites to

control undesirable grasses.

The initial wiper was constructed of an aluminum panel measuring 102 mm by 203 mm by 3 m (4 in.

by 8 in. by 10 ft) long covered with coarse sand grit comparable to coarse sandpaper. The herbicide

was applied to the gritted surface by plastic tubes and micropumps. The panel became wet with

herbicide. As the wiper came into contact with the undesirable plant leaf, the grit surface scratched

the leaf surface and applied herbicide in the wound. The herbicide entered the plant leaf immediately

and was translocated to the plant root, resulting in total plant kill. This innovative technique can be

used when herbicide spraying cannot be used because of windy conditions or other adverse weather

conditions. The wiper technique used approximately one-quarter of the herbicide used by typical

sprayers to kill undesirable vegetation and does not injure nontarget (desirable) vegetation that might

come in contact with spray drift.

The wiper applicator was improved by covering the aluminum panel with an AstroturfTM type carpet

material. Plant leaves are chafed by the brace chains ahead of the panels and scraped by the

AstroturfTM carpet material. The improved panel works as well as the grit panel and provides for

more even distribution of herbicide solution through a series of check valves installed to prevent

gravitational flow within the panel while working at acute angles on the side of the levee. Additional

improvements were made by applying a 7.01 103 mR/ha (96-oz/acre) solution of glyphosate

chemical and water. Mixing rates have been 9.46 102 mR (32 oz) chemical/18.92 102 mR (64 oz) of

water or 710 mR (24 oz) chemical/2,129 mR (72 oz) of water. The water reduces the viscosity of the

herbicide, thus making it easier for the plant to absorb and translocate. The diluted herbicide solution

also disperses on the plants better than the pure chemical.

In areas of predominately napier grass, four wipings (Figures 16 and 17) were required to almost

eliminate that plant. However, as soon as the napier grass disappeared, Spanish needle covered the

area (Figure 18). Two additional wipings of 2.3 102 mR/ha (32 oz/acre) of Round-Up herbicide

were required to control the Spanish needle vegetation. A combination of wiping and mowing over

2 years was required to control napier grass and Spanish needle vegetation and allow the Bermuda

grass and Bahia grass to reestablish on the area. The wiper applicator also successfully controlled

undesirable weeds on all of the RSMT demonstration plots established on the dike.