Plant- Diseases . 51 



Grape (Powdery Mildew), continued. 



hot pipes. Any of the sprays of copper compounds are 

 specifics. 

 Ripe-Rot {Glososporium fructigenum, Berk.). — See under Apple- 

 The treatment for black-rot is efficacious for this. 

 Hollyhock. Rust {Puccinia Malvacearum, Mont. ) . — Appears upon 

 leaves of hollyhocks and a few related plants in small, light 

 brown patches. Introduced from Europe, and becoming com- 

 mon in this country. 



Remedies. — To destroy the plants is the only general method 

 yet employed to prevent the spread of the disease, but some 

 of the copper fungicides may be used. 

 Lettuce. Mildew {Peronospora gangliformis, DeBary). — A deli- 

 cate mildew, attacking lettuce-leaves and causing yellow or 

 brown spots, and finally killing the leaf. 



Preventives. (According to Maynard.) — Grow at a low 

 temperature (35° to 40° at night, 50° to 70° during day) ; give 

 abundance of plant-food; give abundance of water, but 

 apply it in morning and bright days only; avoid sudden 

 extreme changes of temperature. 



Remedy.— Ymnes of sulphur. 

 Maple. Leaf-Spot (Phyllosticta acej-icola, C. & E.). — Attacks the 

 leaves of red, silver, and striped maples in spring, causing 

 them to become spotted and unsightly, and lessening the 

 vigor of the tree. 



Remedies.— Rake and burn the leaves in autumn. When 

 the leaves are two -thirds gi-own spray with sulphide of 

 potassium or copper fungicides, and repeat every three or 

 four weeks as long as necessary. 

 Onion. Rust {Pero)iospora Schleidejiiana, linger). — The leaves 

 turn yellow about the time the onions begin to bottom, or a 

 little later, and wilt and die. 



Remedies.— Grow on land not infected, and destroy all af- 

 fected onions. Spray early with copper fungicides. 

 Smut (UrocysUs cepulce, Frost). — Attacks the first leaf or 

 leaves of seedling onions, producing dark irregular spots, 

 and killing or weakening the plants. 



Remedy.— The sulphur and lime mixture drilled into the 

 ground with the seed ; about an ounce of the mixture to 50 

 feet of drill. 



