26 GIANT CUTGRASS 



CONTROL 

 Giant cutgrass is difficult to kill, and no fully satisfactory, eco- 

 nomical way has been found to control it despite nearly a decade 

 of experimentation at Reelfoot Lake and elsewhere. Within lim- 

 ited areas, complete elimination is possible, but generally it is 

 difficult and costly. Methods of control used and the extent of 

 their effectiveness depend considerably upon whether standing 

 water is present. Degree of success also depends on whether 

 treatment is made during the most vulnerable stage, which is in 

 late summer or early fall, during maximum runner growth. This 

 susceptible stage occurs about 2 months after the main period of 

 flowering. 



CONTROL ON DRAINED AREAS 



Growing on land, giant cutgrass can be reduced or largely elimi- 

 nated by disking, grazing, or by herbicides. Winter freezing kills 

 the plants, particularly if preceded by dewatering and burning. 



On drained sites, dalapon seems superior to TCA, Polybor- 

 chlorate, Chlorax Liquid, silvex, 2,4,5-T and several other herbi- 

 cides tested. At rates of 70 to 199 pounds acid equivalent per 

 acre, dalapon applied during the vulnerable period has given good 

 to excellent control. Monuron at the rate of 100 pounds active 

 per acre has been effective in controlling giant cutgrass on moist 

 land not subject to moving water. 



CONTROL IN FLOODED AREAS 



At Reelfoot Lake complete foliage coverage by Ammate at the 

 rate of 170 pounds active or by Polybor-chlorate at 200 to 300 

 pounds per acre during the vulnerable period has yielded good to 

 excellent control. Of the newer herbicides, dalapon applied at 

 the rate of 140 pounds acid equivalent per acre proved effective. 

 The results from treatments with silvex and certain other herbi- 

 cides have been inconclusive. 



Underwater cutting can, under favorable circumstances, yield 

 at least a 90% kill, but the method has practical limitations for 

 extensive application. For best results, the cutting must be done 

 in the vulnerable period and should be in at least 6 inches of water. 

 A commercial underwater mower tested for this purpose proved 

 impractical since it could not operate in water less than 16 

 inches deep and was unable to cut the tough stems of plants over 

 30 inches tall. Allowing cut stems to remain where they fall 

 appears to increase the percentage of kill. Mowing at other than 

 the vulnerable stage is comparatively ineffective. 



REFERENCES 

 1955. A Report on Experimental Control of Giant Cutgrass (Zizaniopsis miliacea), 

 i 1950-54. Charles K. Rawls, Jr. Mimeo report SE Assoc. Game and Fish 

 . Commissioners Conf., Daytona Beach. 



