16 BIOLOGICAL CONTROL 



burning after treatment was beneficial provided it was delayed 

 until fall. Burning preliminary to herbicidal treatment of re- 

 growth is practiced in California on dense growth such as phrag- 

 mites and cattails. In tidal marshes, burning at intervals of 1 to 

 3 years has been found beneficial in controlling bushy growths. 



BIOLOGICAL CONTROL 



The only instances of man-arranged biological control in marshes 

 occur where muskrats, nutria, or livestock have been allowed to 

 reduce undesirable stands of plants. Cattail is plagued by stem 

 borers, lotus by leaf beetles, and other weeds by their special para- 

 sites, but at present man has not developed methods of capitalizing 

 on the usefulness of these minute control agents for marsh man- 

 agement. 



