268 GARDEN FOES, 



Chrysanthemum Leaf Rust— This is a pest 

 wliich lias only manifested itself of recent years. At one 

 time it threatened to practically exterminate the chrysan- 

 themum, so virulent did it become all over the country. 

 Thanks, however, to the united and vigorous efforts of 

 growers, the Kust was greatly checked in its course, and 

 now we only hear of it occasionally. It is scientifically 

 known as Puccinia hieracii, and is a near relative of the 

 Hollyhock Fungus. This fungus is not confined to the 

 chrysanthemum only ; it is prevalent on our native hawk- 

 weeds, thistles, groundsels, burdock, and knapweeds ; con- 

 sequently, wherever these weeds abound, there is always 

 risk of the fungus finding its way, either by the agency 

 of winds, birds, insects, or human beings, to the chrysan- 

 themums. 



The life history of this pest is, briefly, as follows: It is 

 propagated by what are known as summer or winter 

 spores. The former, technically called uredo-spores, con- 

 sist of the brownish or snuff-coloured spots found on leaves 

 infected with the fungus. The spots may be dispersed 

 singly about the surface of the leaf, or congregated in 

 masses thereon. In any case, there are myriads of them, 

 and these are distributed about by one or more of the 

 agencies previously mentioned. When a spore alights on 

 a leaf, and the conditions are congenial, it develops in 

 eight to ten days, and gradually takes possession of the 

 leaf, finally causing its ill-health and ultimate death. The 

 winter spore, technically called the telutospore, differs 

 from the summer spore in not germinating the same sea- 

 son. It either remains on the leaves or falls on the soil, 

 and remains inactive till the following spring, when it 

 develops, and begins to again spread the disease among 

 the plants. It will thus be seen that the Leaf Kust may 

 make its appearance on plants in early summer through 

 the summer spores being conveyed to the foliage by in- 

 sects, birds, winds, or the clothing of persons who have 

 previously been in contact with weeds or with chrysan- 

 themums infected with the disease. Or some of the 



