Ja. Bathgate et R. Loughman, Ascospores are a source of inoculum of Phaeosphaeria nodorum, P-avenaria f. sp avenaria and Mycosphaerella graminicola in Western Australia, AUSTRALAS P, 30(4), 2001, pp. 317-322
Ascospores of the wheat pathogens Phaeosphaeria nodorum (Muller) Hedjaroude
and Mycosphaerella graminicola (Fuckel) Schroeter were trapped above infec
ted wheat straw in 1990 in an area isolated from other possible sources. Re
lease of ascospores by P. nodorum and M. graminicola, and by the oat pathog
en P. avenaria f. sp. avenaria (Weber) Eriksson was monitored in the field
between April and September 1991 to determine the availability of ascospore
s as a source of primary inoculum. The major period of ascospore release of
P. nodorum and P. avenaria f. sp. avenaria was from mid-June to late Augus
t, which corresponded with the seedling to early flag emergence stage of cr
op development. The number of ascospores trapped was high, exceeding 4000 a
scospores/m(3) air/day for P. nodorum and 1000 ascospores/m(3) air/day for
P. avenaria f. sp. avenaria. The major release of ascospores of M. graminic
ola was from mid-May to late July, corresponding with the early seedling st
age of crop development. The numbers trapped, however, were low and did not
exceed 100 ascospores/m(3) air/day. P. nodorum was recognised as the predo
minant wheat leaf pathogen at the trapping site and this was reflected in l
arger numbers of ascospores of P. nodorum compared with those of M. gramini
cola.