PESTS AND DISEASES. 
91 
Leaf Rust. — This is a pest which has only manifested 
itself of recent years. At one time it threatened to practically 
exterminate the chrysanthemum, so virulent did it become all 
over the country. Thanks, however, to the united and 
vigorous efforts of growers, the Rust 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 hawkweeds, 
thistles, groundsels, burdock, and knapweeds, consequently 
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 chrysanthemums. 
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, consist 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, oi 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 con- 
genial, 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 
season. 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 Rust may make its appearance 
on plants in early summer through the summer spores being 
conveyed to the foliage by insects, birds, winds, or the clothing 
of persons who have previously been in contact with weeds or 
with chrysanthemums infected with the disease. Or some of 
the winter spores may be present in the soil used for striking 
the cuttings, or on the leaves of the cuttings, and these have 
given birth to the Rust. The worst of pests of this kind is, 
their presence is not discovered until too late to prevent them 
injuring the foliage. The spores, when germinating, penetrate 
the delicate leaf tissues with their mycelium, rupture the cells. 
