346 Landscape Gardening 



color they are often called the " white rusts " or mildews. 

 The spores germinate on the surface of the leaves, their 

 roots or feeding-parts (called myceUa) penetrate the leaf 

 through the stomata or breathing-pores, and after feeding 

 and developing for greater or less time, according to the 

 species or the condition of the weather, fruit (spores) is 

 produced on stalks or in masses on the surface of the leaf, 

 and scattered by the slightest breath of air. Of the true 

 rusts I shall mention only a few of the most important, with 

 the remedies most effective, but many others of a similar 

 character may be destroyed or prevented from doing harm 

 in the same manner. 



Poplar-rust* {Melanosporium populina), Rose-rust 

 (Phragmidium mucronatum), Hollyhock-rust (Puccinia 

 malvacearum) , Linden-rust {Cercospora microsora). — 

 The growth of all of these pests takes place under about the 

 same conditions, i.e., a weakened growth of the tree or plant 

 from any cause, and in close, moist, hot weather. Strong- 

 growing, healthy plants are less liable to attack than those 

 of a weak growth, though a too vigorous and soft. growth 

 may be produced by too much enrichment of the soil, and 

 is as much to be avoided as the other extreme. 



Remedy. — If copper in even minute quantities or lime- 

 sulphur solution is on the leaves and branches so that it will 

 be distributed over the surface whenever it rains or is wet 

 with dew, the spores cannot germinate, and the remedy to 

 apply is to spray the branches thoroughly with Bordeaux 

 mixture 4, 5, 50, before the leaves unfold, when all of 

 the earlier spores upon them will be destroyed The great 

 advantage of the Bordeaux mixture is that it holds the 

 copper firmly to the leaves and with every rain or 

 heavy dew minute quantities are dissolved and the spores 

 are prevented from germinating. The lime sulphur used for 

 the destruction of scale insects is also a fungicide, but can be 



