CONCLUSIONS AND RECOMMENDATIONS

ERDC TN-DOER-C20

March 2001

was sought to manage the plant tops. After 6 months, the compost was used as cellulose in a

manufactured topsoil according to RSMT. On May 23, 2000, the new regrowth of the Phragmites

was wiped with a wiper panel on two separate demonstration plots (each 6 by 30 m (20 by 100 ft))

with the glyphosate herbicide Round-Up at a rate of 2.3 102 mR/ha (32 oz/acre) once (Figures 24-27)

and then a second time after 4 days. Two similar size control (untreated) plots were established for

comparison. The plant height was approximately 0.6 m (2 ft) high each time wiping was performed.

Effects of the wiping were observed on 24 Jun 2000 (32 days) (Figures 28 and 29). On 5 Jul 2000

(44 days), some new regrowth was observed (Figures 30 and 31). A gallon of ready-to-use

Round-Up was applied by hand spray to spot-spray the green leaves present on each demonstration

plot. The concentration of glyphosate was 0.96 percent as the isopropylamine salt. Observations

(Figures 32 and 33) were made on 22 Jul 2000 (60 days after the initial wiping and 14 days after

hand spot-spray application). Control plots that were not wiped with herbicide were covered with

Phragmites and other undesirable weeds (Figures 34 and 35). It is expected that the roots/rhizomes

of Phragmites in these plots will be dead allowing material from that area to be used for RSMT

manufactured topsoil or other uses without the interferences caused by Phragmites.

CONCLUSIONS AND RECOMMENDATIONS: Based on the results of these demonstrations,

the following procedures for controlling undesirable vegetation such as napier grass and Phragmites

on dredged material are recommended:

After mowing or cutting and removal of plant tops, allow undesirable vegetation to regrow

to between 0.3 and 0.6 m (1 and 2 ft) tall.

With wiping equipment set at 0.3 m (1 ft) above the surface of the ground, wipe plant tops

with glyphosate (Round-Up, Gly-flow or equivalent) at a rate of 2.3 102 mR/ha (32 oz/acre).

Repeat this procedure after 2 weeks.

After 3 weeks, mow vegetation at a height of 152-203 mm (6-8 in.).

When undesirable vegetation grows to 0.6 m (2 ft) in height, set the wiping equipment at 0.3 m

(1 ft) and rewipe as before.

Repeat the wiping at 2 weeks.

After 3 weeks, mow vegetation at a height of 152-203 mm (6-8 in.).

When undesirable vegetation grows to 0.6 m (2 ft) in height, set the wiping equipment at 0.3 m

(1 ft) and rewipe as before.

Repeat the wiping at 2 weeks.

After 3 weeks, mow vegetation at a height of 152-203 mm (6-8 in.).

Spot-wipe as required when undesirable weeds grow to a height of 0.6 m (2 ft) above the

desirable vegetation.

ACKNOWLEDGMENTS: This research was supported by the U.S. Army Engineer District,

Jacksonville, Mr. Pete Milam, Resident Engineer, and Mr. Jimmy Owens, Project Manager of the

South Florida Field Office at Clewiston, FL. The demonstration was conducted in cooperation with

Monsanto Company, represented by Dr. Jorge Cuarezma and Mr. Ross Hake, Regional Managers;