352 Diseases of Economic Plants 



causal fungus, which are abundant upon the dead straw, 

 find lodgment upon the seed, especially if it be moist. 



To prevent carrying the disease to land yet uninfested, 

 all seed should be disinfected in the following manner: 



Use formaldehyde at the rate of 1 pound to 40 or 45 gallons 

 of water. Spread the seed upon a tight floor or upon a canvas 

 and sprinkle or spray upon it a small amount of the liquid. 

 Shovel, hoe, or rake the grain over rajiidly. Repeat this 

 spraying, shoveling, and raking until all of the seeds are 

 evenly moistened, yet not wet enough to mat or gum to- 

 gether. Continue to stir the grain, so that the mass may 

 become dry as soon as possible. Avoid any excess of moisture. 

 If flax seeds are dipped in the solution or are allowed to be- 

 come wet enough to soften the coats so that they stick to- 

 gether, they are liable to be considerably injured or even 

 killed. 



The solution recommended is strong enough to kill all 

 seeds if they are thoroughly saturated or are allowed to re- 

 main damp for some hours. Less than one-half gallon of 

 solution is required to treat one bushel of seed. It is well, 

 also, to burn all the infested straw and to avoid too deep 

 planting. 



By continued selection of seed from resistant plants 

 Bolley has developed a variety which is resistant to the 

 wilt. 



Damping-off of young plants may be caused by Alternaria 

 or CoUetotrichum. 



Rust {Melampsora lirii (DC.) Tub). ^ — ^Characteristic 

 rust sori are in evidence and in the early season the leaves 

 are yellow or orange. Later black sori appear, chiefly upon 

 the stems. Badly affected plants turn ])rown and die earher 

 than plants not rusted. Large injury is not usual, though in 

 1904 and 1905 considerable damage was reported from North 

 Dakota. 



Dodder {Cuscuta epilimim Weihe) is similar to the dodder 

 of legumes. See alfalfa. 



