50 



THE MONTHLY BULLETIN. 



Eradication. 



Ideas differ materially regarding the possi- 

 bility of eradicating such pests as Canada 

 thistle, but there is no doubt that if the 

 proper methods are used it can be done. 

 .Many other states have wrestled with the 

 Canada thistle problem with success where 

 the cooperation of the farmers was secured. 

 Since it occurs in only a few places in Cali- 

 seeds of Canada fornia there is little doubt that it can be 

 Thistle. Oiraium arvensis. successfully combatted. The following reeom- 



The seeds are light brown, •* ° 



slightly curved and fiat- mendations are selected from the experiences 



tened, J-inch long, apex cup- „ , . - . * . . 



shaped with tubercle in cen- ot other states, altered to apply to our local 



ter, tapering slightly to j 



rounded base. (Original.) -uceu&. 



1. Plow shallow and harrow as soon as possible after harvesting what- 

 ever field crop is grown. The exact location of the infested spots should 

 have been previously marked so that the spot can be harrowed with a 

 springtooth or a light cultivator during the summer and fall. After 

 the first fall rains plow deep and turn all roots to the air, removing 

 as many as possible. Allow the land to lie thus through the winter, 

 lu the following spring, plowing and harrowing before the grain is 

 put in, will finish the job. 



It must be understood that the idea of such frequent plowings is to 

 keep all green leaves out of sight. The roots will continue to send up 

 shoots until their stock of food is exhausted, when they will die. It is 

 the green leaves which give them new life. 



2. If the infestation is very bad hoe-crops should be planted in the 

 spring instead of grain. The careful cultivation required to bring 

 these to maturity will eliminate what thistles still retain life after the 

 treatment outlined above. 



3. A good stand of alfalfa planted in a thoroughly prepared seed bed 

 will kill out Canada thistle in the second year. The land should, how- 

 ever, be thoroughly worked over and any thistles which appear should 

 be cut below the surface of the ground. Thistles growing along the 

 fences and roadsides should not be allowed to remain, because the plants 

 spread from the underground roots. 



4. Chemical weed killers such as salt solution, arsenite of soda (3 

 pounds to 100 gallons water), iron sulphate (100 pounds to 100 gallons 

 water), and crude oil can be used to eradicate small patches of Canada 

 thistle. These liquids should be applied directly to the plant roots 

 after the tops have been removed. The action of chemicals under Cali- 

 fornia conditions is still in doubt and the use of them is, therefore, not 

 recommended except as an experiment. Upon application to this office 

 we will gladly supply what information we have in regard to their use. 



The following extract on the eradication of Canada thistles on grazing 

 lands is taken from the New Zealand Department of Agriculture 

 "Leaflets for Farmers." 



