Seasonal Concentrations of Airborne Pyricularia grisea Conidia.
John Kaminski III, University of Connecticut, 1376 Storrs Road, 1376 Storrs Road, Storrs, CT 06269, United States of America and Peter H. Dernoeden, Univ. of Maryland, Dept of Natural Resource Sci & LA, 1112 H.J. Patterson Hall, College Park, MD 20742.
leaf spot (Pyricularia grisea [Cooke]
Sacc.) is a major disease of perennial ryegrass (Loliumperenne L.)
turf in the United States. Conidia
are an important source of primary and secondary inoculum for gray leaf spot;
however, their seasonal airborne distribution patterns are unknown. Estimated
concentrations of airborne P. grisea
conidia were determined in the field between May and October from 2000 to 2004
in Maryland. Conidia were monitored using a 7-day
volumetric spore sampler in 0.6 m3 of air hr-1 through a
14 by 2 mm orifice located 45 cm above the ground. Total conidia collected each day and
cumulative seasonal concentrations were determined. Conidia
of P. grisea were observed within air
samples as early as 4 June. Greatest airborne
concentrations of P. grisea conidia
generally were detected between mid-August and September. During peak disease activity in adjacent
stands of perennial ryegrass, as many as 5500 conidia were collected in a
single day. Disease severity in perennial
ryegrass was not correlated with the total number of conidia collected in each season. In all years, conidia concentrations declined
between late September and mid-October. Relatively
large numbers of conidia, however, were collected in July (2002) and October (2002
and 2004), and conidia were detected as late as 31 October.