25. 



sublimate are strong poisons. The copper sulphate is also poison- 

 ous but less so than the other solutions. Sodium arsenite will de- 

 stroy Canada thistle and many other weeds. It may be used 

 at the rate of l 1 /^ pounds to 52 gallons of water. Stock must 

 be kept away when the thistles are treated. The treatment must 

 be repeated as often as thistles appear. Corrosive sublimate was 

 found to be efficient in killing many weeds, but is not to be recom- 

 mended on account of its very poisonous nature. Salt, when ap- 

 plied in sufficient amount is efficacious, but it is expensive when 

 used in this way and can only be used as I have indicated for 

 Canada thistle and Horse nettle. Iron sulphate, which is a by- 

 product in the manufacture of wire is cheap, costing in 100 pound 

 bags, 92 cents per hundred pounds F. O. B. from several Iowa 

 points. If bought in 200 pound bags it costs 5 cents less per 

 hundred pounds. It comes in granulated form, is readily soluble 

 in water and may be made in various strengths of solution. For 

 most plants it is used at the rate of 100 pounds to a barrel of 

 water. The solution cannot stand over night. It may be applied 

 with a hand or traction sprayer. I have found it efficacious for 

 the following plants: Mustard, ragweed or kinghead, smart- 

 weed, dandelion, artichoke, velvet weed, small ragweed, lamb's 

 quarter, may weed, hedge mustard, pigweed, boot jack, etc. In 

 fact the majority of weeds found in grain fields readily yield to 

 the application of this spray. 



WEEDS OF SPECIAL CROPS. 



Small Grain. It is well known that certain weeds occur with 

 certain crops since the very earliest times ; such weeds as common 

 mustard, darnel, corncockle, vetch and bindweed or wild buck- 

 wheat have been found with small grain. These weeds are as 

 common in Europe as in the United States. They are found 

 wherever small grain is cultivated. Formerly it was difficult to 

 remove these weed seeds from the grain, but with modern me- 

 thods of screening has made it possible to remove most of the 

 weed seeds. 



Corn. Locality sometimes determines the kind of weeds found 

 in the field; in southern Iowa cocklebur, horse nettle, arc com- 

 mon. In northern Iowa quack grass and artichoke occurs. The 

 smartweeds, fox tail pigeon grass, crab grass, shoestring, milk- 

 weed, pigweed and morning glory are common in all parts of 

 the state. In early spring northern nut grass may appear; 

 easily recognized by the yellowish appearance of the field. The 

 plant has grass-like leaves and spreads by its "roots." Rag- 

 weeds are also common in all parts of the state; velvet weed is 

 common and in western Iowa marsh elder and sunflower are 

 abundant. 



