. Canadian journal of agricultural science. Agricultural Institute of Canada; Agriculture. :Marth. 1922. scir-:xTiFic agriculture 235 Life History of the Organism. Selerotia remain donnant in the soil until early summer when they may germ- inate giving rise to apotheeia bearing as- cospores. The aseopores are discharged and infect the older leaves of the stem in the lowest axils. The selerotia may also live over winter in the soil and germinate by mycelium which can infect the plants. In England and Ireland the organism is tnown as Selerotinia sclerotiorum but for the selerotinia found by Lach
. Canadian journal of agricultural science. Agricultural Institute of Canada; Agriculture. :Marth. 1922. scir-:xTiFic agriculture 235 Life History of the Organism. Selerotia remain donnant in the soil until early summer when they may germ- inate giving rise to apotheeia bearing as- cospores. The aseopores are discharged and infect the older leaves of the stem in the lowest axils. The selerotia may also live over winter in the soil and germinate by mycelium which can infect the plants. In England and Ireland the organism is tnown as Selerotinia sclerotiorum but for the selerotinia found by Lachaine in New Brunswick no definite name can yet be given although it appears to be 8. liber- tiana. Control. The only satisfactory means of control ^re crop rotation so that susceptible plants are not available to the fungus and careful removal and destruction of diseased plant parts. In England, Cotton finds that late plant- ing has proved successful since fewer old leaves are available at the time of spore discharge. Group 6. Disease Caused by a Basidiomycete. Dry Stem-Rot and Black Scurf This disease is known under a variety of common names of which the chief are:— dry stem-rot, black scurf, black scab, rus- set scab. Rhizoctonia disease, little potato, aerial potato, rosette, black speck sdab and collar fungus. The first description of Rhizoctonia was given by Duhamel in 1728 as causing a disease of saffron in France. De Candolle in 1815 gave the fungus the name Rhizoc- tonia when he discovered a similar disease on lucerne. In the Tulasne brothers classified all the then known rhizoctonias as R. violacea but Kuhn in 1858 described a species on potato which he named R. so- lani. Webber (1890) first reported the fungus in America and in 1901 Duggar and Stewart (Bull. 186. ) gave a list of hos'^s attacked by Rhizoctonia. It is now known to occur generally in the Ignited States and Canada and is reported from the West Indies, India. Australia and S"outh America.
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