WEED POISONS 227 



Northwest, sodium arsenite (U pounds sodium arsenite in 50 gallons 

 water) is given first rank. Salt is probably the most efifective to destroy 

 dandelion and some other weeds. Iron sulfate is very satisfactory to 

 kill mustard weeds, ragweed, white-top, yarrow, and we believe a great 

 many other broad-leaved weeds. Neither the salt nor the iron sulfate 

 is regarded as offering any risk of application to pastures in which stock 

 is running. Sodium arsenite is a very active poison, and rather dan- 

 gerous for that reason. Calcium chlorid (of same strength as common 

 salt solution) has done very well where tested, but appears to be slightly 

 inferior to salt. Copper sulfate solutions may be used in grain fields 

 for mustards, especially, but owing to the poisonous nature of the 

 copper sulfate, it has a very narrow range of application. 



Experiments by the Cornell Station gave the following general con- 

 clusions : Wild mustard growing with cereals or peas can be destroyed 

 with a solution of copper sidfate, without injury to the crop. A 3 per 

 cent solution (about 10 pounds to the barrel, or 40 gallons of water), at 

 the rate of 40 to 50 gallons per acre, gives very satisfactory results. 



The following notes on the effect of the copper sulfate solution on 

 different plants are from observations and reports from various sources: 



" Plants reported killed by copper sulfate solutions : wild mustard, 

 wild radish, wild barley, penny-grass (if young), shepherd's purse, wild 

 buckwheat, lamb's quarters, ragweed, sow-thistle, hemp-nettle, bind- 

 weed, dock, dodder. 



"Plants reported severely injured; curly dock, black bindweed, 

 dandelion, sow-thistle, and senecio. 



" Plants reported as not injured : wild rose, poppies, pigweed, 

 spurge, corn-flower, field-thistles, chamomile, couch-grass, bent-grass, 

 and horsetails. 



" Crops that may safely be sprayed : all cereals, as wheat, rye, bar- 

 ley, and corn ; the grasses ; peas ; sugar beets. 



" Crops that are killed or severely injured by the copper sulfate 

 solution: beans, potatoes, turnips, rape." 



Charlock, known also as kale or wild mustard (Brassica Sinapistrutn), 

 is easily destroj^ed in oat-, wheat-, or other grain-fields by spraying with 

 a solution of 1 pound of copper sulfate in 4 to 6 gallons of water (2 to 3 

 per cent solution). A force pump should be used, supplied with fine 



