21t) 



riVIC BIOLOQY 



late blight, or rot, and dry rot, or stem blight, of potato ; and crown gall 

 of grapes, berry bushes, and fruit trees. So, too, pear and apple blight 

 have often been scattered broadcast from nurseries because disinfec- 

 tion of j^runing tools was neglected. In general, disease shows \\\< 

 clearly in the nursery or field, while it would require bacteriological 

 and microscopic methods to find the germs within the seeds or stocks. 

 Go out and hunt over local nurseries or seed farms. Ask experts from 

 them to come in and demonstrate and discuss their methods. All wh.r) 



Fig. 103. Covn smwt {Ustilago zew) 



propose to distribute these important supplies to the puljlic ought to 

 know their business by this time. The best firms employ trained ex- 

 perts to see to it that stock is free from disease, and then they may 

 send it to branch farms, far away from any possible contamination, to 

 have it propagated for the market. 



2. If spores are alive on the seeds or tubers, ready to attack the 

 embryo plant when it germinates, kill them before planting. 



Scab of potatoes and smuts of grains are examples. Soak seed potatoes 

 for two hours in formalin solution (1 ounce to 2 gallons of water) or in 

 mercui'ic chloride (corrosive sublimate) solution (1 ounce to 8 gallons of 

 water). External spores of the smuts on wheat, oats, and barley are 

 killed by soaking for from ten to twenty minutes in formalin solution 

 (1 pint to 30 gallons of water) or by warming up the seed in water at 

 110°-120° and then holding it for ten minutes in water at 182°-133^ F. 



