206 REPORT OF THE No. 3 



IV. Hyalopsora Fern Rust of Balsam. 



The foliage of the balsam is subject to the attacks of many rust fungi, — 

 species of five or six well-marked genera. All of them are known to parasitize 

 an alternate host, and, indeed, infection is never from balsam to balsam, but 

 from alternate host to balsam. These hosts, depending on the particular kind 

 of rust, include the willow, fireweed, chickweed, blueberry and the ferns. The 

 chickweed rust causes the "witches' brooms" common enough in some areas, 

 but the others with one partial exception affect the needles only, and especially 

 of seedlings and small trees. Injuries to the crown may at times be serious 

 enough to cause a killing of young trees; this applies particularly to the fern 

 rusts, although conditions during the past summer were so favourable to the 

 fireweed rust in certain localities that pure natural stands of young balsams up 

 to two feet in height were 100 per cent, affected and extremely heavily so. It 

 is obvious that these rusts take a heavy toll at times and are a factor of con- 

 sequence in reproduction. 



The revealing of the course of the life history of the balsam rusts has resulted 

 from the persistent experimentation of several distinguished students of plant 

 diseases. Robert Hartig, whose work on the diseases of forest trees laid solid 

 foundations for the science of Forest Pathology, discovered the connection 

 between a rust on the balsam and blueberry rust in 1880; though the two are 

 so unlike in appearance yet they were proved by cross-inoculations to be but 

 phases of the same rust, and its continuance is dependent on the association of 

 the two hosts. Klebahn discovered the fireweed balsam combination in 1898, 

 Fischer the chickweed balsam combination in 1901, Eraser the willow balsam 

 combination in 1911, and Eraser a fern balsam combination in 1912. All of 

 these connections were established by careful, repeated cross-inoculations under 

 controlled conditions. 



A new rust on balsam has now been found in Ontario and Quebec and its 

 connection with a long-known group of perplexing fern rusts {Hyalopsora) has 

 been determined. 



An immature stage of this rust was observed in the Timagami Forest 

 Reserve by the writer in the summer of 1920, and the mature condition found 

 by H. P. Bell in the same locality in the spring of 1922. It was found to be not 

 infrequent in Timagami during the past summer, and fairly abundant in the 

 eastern forests of Quebec. Unlike the majority of balsam rusts it is not evident 

 on the needles of the current season; an immature stage (pycnial) shows on two- 

 year-old needles, and the mature stage (aecial) on needles beginning their third 

 year. Professor Bell named the phase on the balsam Peridermium pycnocon- 

 spicuum and made a few partially successful inoculation tests in 1922 that led 

 him to tentatively recognize its connection with the Hyalopsora fern rust referred 

 to above {Hyalopsora aspidiotus) on the oak leaf fern {Phegopteris dryopteris). 



The Hyalopsora rusts on ferns in Europe were described as far back as 1801, 

 though they were not proved to be rusts until 1895. In 1916 Klebahn, one of 

 the foremost European rust experts, inoculated balsam and spruce with the 

 Hyalopsora rust of the oak fern, without effect on the spruce, and with indeter- 

 minate results on the balsam. 



As there was an abundant supply of the newly-discovered rust on the 

 balsam in Timagami in June, 1923, inoculations were made, with the help of 

 Mr. G. D. Darker, from the balsam to the oak fern and with complete success. 

 Twenty fronds in all were inoculated under perfectly-controlled conditions, and 

 thirty fronds placed under the same conditions were kept as controls. Every 

 inoculated frond showed lesions indicating infection (249 lesions in all), most of 



