The literature of the ecological and agricultural aspects
of take-all disease caused by Gaeumannomyces graminis var tritioi is reviewed.
Assessment of the disease in a long-term spring barley
trial from its 3rd to 12th years revealed that^although it developed
in the accepted take-all decline pattern^the onset of decline was
delayed. Incidence was low until the 9th season, rose to a maximum
of 80% in the 11th and decreased to about 45% in the 12th year.
Applications of 50, 100 and 150 kg/ha of nitrogen fertiliser decreased
incidence but different methods of ploughing had more variable results:
until the 6th year in barley take-all was less prevalent in the deepand
unploughed compared with the shallow- and chisel-ploughed treatments,
but subsequently only direct-drilling suppressed disease. At the peak
of infection there was no difference in incidence between cultivation
treatments. Severity of infection increased slightly from the 3rd
to 12th crops but was always low.
A technique was devised to predict the development of
disease in different soil types. When soil from the long-term barley
trial was assayed the occurrence of infection was similar in some ways
to the field pattern. An experiment using the technique compared
infection in four soils: a sand, a sandy loam, a clay loam and a clay,
each at four cropping histories. Although infection patterns peaked
and declined in all soils their disease development differed with time
and cropping history. Inoculation increased level of infection but
did not change the pattern. Assaying field soil samples collected
in 1975 and 1976 revealed a wide range of disease patterns.
Evolvement of a technique to assess the virulence of field
populations of the take-all fungus showed that virulence was not
correlated with soil texture or cereal history but might be affected
by previous cultivation technique.
The theory and practical problems of the assay techniques
and their relevance to contemporary agriculture are discussed.
Incidence of the take-all fungus was found to be wide¬
spread in the soils of South-East Scotland yet loss of grain yield from
infection appeared to be small unless other adverse predisposing
factors were present.