FUNGOUS AND BACTEK1AL DISEASES 217 



3. If living spores are continually sifting down from the air, we 

 must keep the surface of leaf or fruit covered with something that 

 will kill them as they germinate. If we wait till they get in, the crop 

 will be ruined. Various Bordeaux solutions and lime-sulfur washes are 

 effective for this purpose, and, naturally, while leaves are unfolding 

 rapidly or fruit is growing, we must spray every few days. 



4. If the spores are alive in the soil, there is nothing to do 

 but rotate. Plant something they cannot grow upon something that 

 will starve them out; there is no other way of killing them out of 

 the ground. 



5. Seek continually for resistant varieties and strains. AVith every- 

 body oil the lookout for these valuable variations, we may hope for 

 more rapid progress in the control of fungous diseases of plants. 



6. Observe general soil and plant hygiene. With the soil mellow and 

 well drained we may minimize danger from root rots and damping-off 

 fungi ; with plants well spaced to let in sunlight and allow free circu- 

 lation of air, or pruned with this in view, and with fruits thinned so as 

 not to touch, we may greatly reduce danger from air-borne spores. 



Every community organization, rural or suburban, ought 

 to have a committee on fungous diseases of plants and their 

 practical control. The local class in biology might well be 

 the laboratory right arm of such a committee. By working 

 out cooperative plans, thoroughly agreed upon, which might 

 spread from neighborhood to neighborhood as they were de- 

 veloped and perfected, many of our. worst fungus enemies 

 might be completely stamped out, No real estimate of the loss 

 caused by them has ever been even attempted. We do not 

 know enough about them. Duggar's guess of $500,000,000 

 a year is very low, and, while it might approximate the losses 

 to the large markets and channels of trade, we must certainly 

 add to this all the damage to the home garden and orchard, 

 with the labor and expense of fighting fungi in them. The 

 class in civic biology which gives us even a first attempt at 

 a detailed account of the expenses and losses chargeable to 

 fungous diseases of plants in any community will mark a 

 distinct forward move in this field. 



