The difference between weed and brush control and no injury to forage 

 species or severe injury to forage crops may often depend on a number of 

 conditions that are subject to the fluctuations of environment in localized 

 areas. 



General Considerations 



An attempt always should be made to apply the herbicide when weeds are 

 most susceptible and when desirable species are least likely to be injured. 

 These times of application are not always compatible. Frequently, desirable 

 species are susceptible at the same time weeds are most susceptible. In 

 these instances, the seriousness of weed infestation will influence the deci- 

 sion to use herbicides or not. 



Whenever possible, allow the weed canopy or companion- crop canopy to 

 develop so it will mask the spray from the forage species. 



The herbicides 2,4-D, 2,4,5-T, silvex, and MCPA are not poisonous to 

 livestock at the rates of application used to control w^eeds in forage crops, 

 pastures, and rangelands. If no poisonous plants are present in the treated 

 area, livestock need not be removed during or after application. 



If poisonous weeds or poisonous w^oody plants are known to occur in 

 pastures or on rangelands, remove the livestock from the area for at least 

 30 days after treatment. Several herbicides, including 2,4-D, 2,4,5-T, and 

 MCPA, are known to produce marked changes in the chemical composition 

 of treated plants. There also is evidence that some herbicides affect the 

 palatability of certain plants and that livestock will eat some treated species 

 that they normally would not eat. 



- 39 



