HERBICIDAL CONTROL 7 



vented serious weed problems but has also provided good nesting 

 conditions adjacent to excellent food supplies. In the Southeast, 

 where control of one kind of weed sometimes simply clears the way 

 for a worse one, wild millet, browntop millet, corn, soybeans, and 

 other useful species are commonly planted in dewatered marsh 

 areas that have been cleared of weeds and prepared for seeding 

 by farm machinery. 



Timing of water-level adjustments is especially important in 

 drawdowns involving production of native (noncultivated) plants. 

 The more rapid growth of desirable annuals, as compared with 

 most perennial weed seedlings, frequently makes it possible to 

 destroy unwanted plants and spare the good ones. At the Thousand- 

 Acre Marsh in Delaware, thousands of seedlings of phragmites, 

 hibiscus, swamp dock, pickerelweed, and arrow-arum have been 

 drowned while permitting survival of young plants of wild millet, 

 smartweeds, rice cutgrass, and fall panicum. If the timing of 

 water-level change is wrong, however, more harm than good is 

 likely to result. Excessive duration of a drawdown risks estab- 

 lishment of perennial-weed seedlings and serious spread of runner- 

 producing plants such as phragmites and giant cutgrass. 



Temporary drainage has been found advantageous for control 

 of some weedy marsh and aquatic growths. Draining of beds of 

 alligatorweed or waterprimrose allows more thorough spraying 

 and better kill of the plants. Draining also facilitates mechanical 

 control and enables the burning of old dead stalks of phragmites 

 or needlerush prior to spraying. In some places, winter drainage 

 followed by freezing of the marsh floor has helped get rid of unde- 

 sirable plants. Flooding, following cutting or herbicidal control, 

 is frequently helpful in eliminating plants such as needlerush, hibis- 

 cus, and buttonbush. 



HERBICIDAL CONTROL 



The use of herbicides in marsh management has increased rap- 

 idly during the past decade, and it will probably continue to grow 

 as new and better chemicals become available. Several valuable 

 new herbicides released within the past few years have given fresh 

 impetus to work in this field. 



DANGERS 



Spraying marsh weeds with herbicides usually poses no direct 

 danger to man, livestock, fish, or wildlife. In this regard, plant- 

 control agents are much safer than other pesticides such as insecti- 

 cides or rodenticides. Formerly, dangerous substances such as 



