FRIENDS AND ENEMIES OF PLANTS m 



Some of the most common forms are the fire blight of the pear 

 and apple, smut, rust, rot, wilt, potato scab, potato blight, peach 

 leaf curl, apple scab, club root, black knot, and other kindred 

 diseases. 



Fire Blight. Frequently we find twigs on our apple or 'pear 

 trees which look black as if they had been charred by fire and the 

 leaves upon these twigs also are blackened and withered. This 

 disease is caused by the presence of bacteria in the juicy part of 

 the stem between the bark and the hard wood. These bacteria are 

 carried from tree to tree at blossoming time by insects as they flit 

 from flower to flower. As soon as the diseased twigs are discovered 

 they should be cut off and burned without delay. It is best to cut 

 the twig off about ten or twelve inches below the affected part, and 

 as an additional precaution the pruned stub should be thoroughly 

 disinfected by swabbing with a sponge soaked in a dilute solution 

 of corrosive sublimate, one part in one thousand of water. 



Smut infests cereals and is especially noticeable on oats and 

 wheat. The smuts of these two plants, however, are entirely dis- 

 tinct. The spores of the oat smut fungus are lodged under the 

 seed coat and infect the young oat seedling when two or three days 

 old. This disease may be controlled by soaking the seed oats for an 

 hour with formalin diluted at the rate of one pint in fifty gallons 

 of water. The wheat smut fungus gains entrance to the seed at the 

 blossoming time and lies dormant in the kernel over winter. With 

 the growth of the plant the fungus causes a smut of the head. 

 Formalin is not effective except in strengths which would kill the 

 germ of the grain. A hot-water method of treatment has been 

 devised. 



Rust. One of the most common forms of this disease is what 

 is known as apple rust. This fungus uses the red cedar as its 

 winter host and causes the so-called cedar apple. In wet weather 

 jellylike tentacles or arms form on these cedar apples which 

 contain millions and millions of spores. In dry weather they 

 float off in the form of a dust or powder through the air and lodge 

 on the foliage of the apple tree. In a short time the leaves become 

 covered with orange-colored spots and wither away. The only 

 satisfactory remedy is to remove all cedar trees from the vicinity 

 of the orchard. 



