NEEDLERUSH 33 



CONTROL 



Studies on needlerush control have yielded encouraging results, 

 but much remains to be learned about best methods to use in dif- 

 ferent places and about prospects for suitable replacement. In- 

 dications are that the plants cannot spread or reestablish as 

 readily in sites flooded most of the time as compared with better- 

 drained locations. The most vulnerable period is in the spring, 

 during flowering and early stages of fruiting. 



Different results have been obtained in different places with 

 similar control treatments, as indicated in the three main areas of 

 needlerush study : North Carolina, Florida, and Maryland. The 

 variations in susceptibility appear to depend on both regional and 

 localized factors. Another peculiarity in the response of needle- 

 rush to chemicals is the fact that herbicidal concentrations have 

 to be increased when applying a large gallonage per unit area, 

 as with power sprayers. This contrasts with the usual situation 

 with marsh plants in that ordinarily the requirements for pound- 

 age of herbicides per unit area remain the same regardless of 

 carrier volume. 



In North Carolina, 27 pounds acid equivalent of 2,4-D isopropyl 

 ester per acre were required for effective control (Barber, 1952). 

 At the Chassahowitzka Refuge in northern Florida, 95% to 99% 

 elimination of needlerush resulted from airplane treatment using 

 16.7 pounds acid equivalent of 2,4-D ester in 5 gallons per acre 

 (Myers, 1955). In Maryland, both salt and ester formulations 

 of 2,4-D have yielded over 95% control at rates as low as 14 

 pounds acid equivalent per acre in 200 gallons of carrier (either 

 water or oil) when applied during the vulnerable period (Steenis, 

 Webster, Nicholson, 1954). 



The Maryland tests involved use of hand-pressure cylinder 

 sprayers. Treatments at other than the vulnerable period gave 

 erratic results. Slightly superior results were noted with 2,4-D 

 esters in oil, probably owing to better coverage plus some herbi- 

 cidal effect of the oil. TCA alone was not satisfactory for needle- 

 rush control but with a combination of 2,4-D at 8 pounds acid 

 equivalent per acre and 25 pounds of TCA the results were bet- 

 ter than with 2,4-D alone. In treatments with 2,4-D alone by 

 power-sprayer equipment, using over 400 gallons of water per 

 acre, it was found necessary to increase the herbicidal concentra- 

 tion to 27 pounds per acre. Also in mixed treatments with a 

 power sprayer, it was necessary to increase the concentration of 

 2,4-D to 14 pounds per acre and TCA to 50. Monuron, acting 

 as a soil sterilant, was used successfully at 20 pounds active per 



