Aerobiology ofSclerotinia sclerotiorumandBotrytis cinereaspores in New Zealand tobacco crops

Abstract

The seasonal abundance of ascos'pore~of Sclerotinia sclerotiorum (Lib.) de Bary m the au depended~n ramfall rnotstenmg the soil sufficiently for apothecia to devt:l~p. No otherclimatic factors were found to be related to the trapping pattern.Conidia of Botrytis ctnerea Pers, ex Fr. were released in large numbers if the preVIOUS day was calm and the night wal"Ill;, or when rain was falling. Few conidia wer~released~t night unless ram was falhng. Ascospores of S. sclerotiorum and conidia of B. ctnerea both showed markedly diurnal distribution patterns.

Spread of Sclerotinia stem rot of soybean from area and point sources of apothecial inoculum

“…Our results are in agreement with those of Hartill (1980) and Suzui and Kobayashi (1972a), who found that the majority of ascospores of S. sclerotiorum were deposited within a few metres of the source (apothecia). Our results imply that Sclerotinia stem rot of soybean results mainly from ascospores produced within the field.…”

“…Hartill (1980) found that ascospores of S. sclerotiorum were trapped in large numbers when apothecia were found near the trap. In sporetrapping studies in sunflower (Helianthus annuus) fields artificially infested with sclerotia of S. sclerotiorum, McCartney and Lacey (1991) concluded that disease severity may be related to the concentration of ascospores during the infection period.…”

“…Ascospore dispersal is important for dissemination and survival of the pathogen. Previous studies (Hartill 1980;McCartney and Lacey 1991;Suzui and Kobayashi 1972a) have shown that the majority of ascospores of S. sclerotiorum are deposited within a few metres of the source. Boland and Hall (1988) found that apothecia of S. sclerotiorum and Sclerotinia stem rot of soybean were spatially aggregated, and numbers of apothecia and disease incidence were correlated.…”

The relationship between the release of ascospores ofSclerotinia sclerotiorum, infection and disease in sunflower plots in the United Kingdom

“…Ascospore production was more or less confined to the middle of the day with few spores being released ;it night or in the early morning, a pattern similar to that found by Harthill (1980) in tobacco crops. Thc mechanisms of ascospore release in S. sclerotioririii are not \\.ell known, but changes in humidity i d light have been implicated in XCOSpore discharge in other ascomycetes (Ingold 1971).…”

“…1 and 4): in 1988 there were about 450 ascospores m-3 in the air, averaged over 24 h, for every 100 apothecia in the plot, in 1989 the relationship between apothccia and ascospores was less clear but more ascospores per apothecia appeared to have been produced. Harthill (1980) found little relationship be- tween ti,eilther variables and ascospore concentration above tobacco crops in New Zealand as long as there was sufficient rain to moisten the soil and promote apothccia formation.…”