FUNGOUS DISEASES 83 



form of black or purplish spots, sometimes almost circular and 

 about one-fourth of an inch in diameter, or the spots will be ir- 

 regular in outline. The blotches are most distinct on the upper 

 side of the leaf. Although looking black to the naked eye, if 

 examined with a microscope, a delicate white cobweb will be 

 seen covering the patches and stretching toward the outside. 

 This, in time, develops into minute black specks, which is the 

 fruiting stage. It is easily spread around and soon defoliates 

 a house. 



The precautions necessary call for similar treatment to that 

 prescribed for keeping away mildew as regards air, cleanliness, 

 and water. Overwatering, sudden checks, drip in a house, and 

 all similar conditions, will induce its appearance. As a further 

 preventive, spraying with potassium sulphide, if commenced 

 early and continued every ten days, is good, or any of the regu- 

 lar copper solutions may be used. When the disease appears, all 

 affected leaves should be picked off and burned. There is little 

 use trying to check it by spraying when it becomes established, 

 as the infestation is simultaneous and not progressive. Spray- 

 ing is done to prevent rather than to cure black spot. Pick off 

 all affected leaves from the plants and also those which may 

 be on the ground, and keep the plants on the dry side until they 

 get a clean start. Sprinkle a little air-slaked lime around and 

 under the benches, and, with a bellows, apply air-slaked lime 

 mixed with an equal quantity of Grape Dust, on the foliage. 



ROSE RUST 



This form of rust is mostly troublesome on Roses outdoors, 

 on hardy hybrid varieties, but none is immune from it. All 

 affected leaves should be collected in the Fall and burned and 

 any affected wood cut away. Before growth commences in the 

 Spring, spraying with a copper solution should be started, and 

 kept up regularly until the growth has matured. 



