Parasitic Attack on "Eucalyptus Globulus." 85.3 



Stereuvi hirsutum is very widely distributed and is one of our 

 commonest saprophytic fungi. Its fruiting- bodies or sporopliores 

 may usually be found growing in bracket-like fashion on dead 

 trunks, stumps, etc., though occasionally and, in fact, usually in 

 the early stages of growth it forms a yellow crust on the wood on 

 which it develops. As a rule these sporophores are produced in large 

 numbers forming successions of brackets one above the other, close 

 together, but seldom overlapping (Plate I). Each individual fructi- 

 fication consists of a thin but firm leathery structure with a lobed 

 margin. Its upper surface is dingy ochraceous to grey in colour, 

 faintly zoned, and covered with fine grey hairs, while the under- 

 surface, the region which produces the spores or reproductive bodies 

 of the fungus, is smooth and bright ochraceous in colour. Under 

 moist conditions the fungus is expanded at right angles to its point 

 of attachment, but on drying it contracts and curls over. 



The fungus under discussion is one of a very large number of 

 fungi belonging to the genus Stereum. With the exception of a few 

 which grow on humus, the members of this group occur on wood and 

 are generally considered to be saprophytic, i.e. depend for their 

 existence on dead organic matter. Some few, however, though 

 usually saprophytic are known at times to be active parasites, and 

 as such cause a considerable amount of damage, though even in these 

 cases it is very probable that the fungus starts as a saprophyte on 

 dead wood, such as is found in dead branches and wounds, and 

 spreading from this to living wood eventually becomes parasitic on the 

 latter. Amongst the best known of those parasitic Stereums which 

 are of economic importance, are S. jxurpureuvi — said to be the cause of 

 " silver-leaf " disease in the plum, peach, apricot, etc. — *S'. rugosum 

 which parasitises the cherry laurel to such an extent in some parts as 

 to preclude its cultivation — S. frustulosuvi which attacks oaks in 

 Germany, causing a rot known as "partridge wood " — and lastly the 

 fungus under discussion, >S'. hirsuturrv, the well-known cause of 

 " white-piped " and " yellow-piped " wood in oaks in Europe. 



It has been suspected for some time that S. liirsutuvi was respon- 

 sible in this country for damage to various trees other than oaks, 

 e.g. peach trees, but no clear proof of its parasitism has been forth- 

 coming. Eecently, however, this fungus has been found growing on 

 the living stem tissues of Eucalyptus globulus, the ordinary blue-gum, 

 in plantations on the farm Cliffendale, near Eoodepoort, Witwaters- 

 rand. So far, however, the fungus has not been found on living tissues 

 except at Cliffendale, though careful examination has been made of it 

 in gum plantations on the farms The Willows, District Pretoria, and 

 Lions Glen, near Amsterdam, District Ermelo, where it is abundantly 

 present as a saprophyte. 



The following observations were made on the attack at the three 

 places mentioned : — 



Cliffendale. 



The plantation is situated in a sheltered valley, about five miles 

 north of Eoodepoort, on gently sloping ground with a north aspect, 

 sheltered from the south wind, and at an elevation of between 

 4600 feet and 5000 feet. The soil is a red sandj' loam of good depth, 

 probably resting on shale or quartzite. The rainfall is estimated at 

 between 30 and 33 inches, and the situation is hot in summer with cold 



