New Zealand Journal of Agricultural Research abstracts

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Survival and germination of shallow-buried sclerotia of
Sclerotinia sclerotiorum in pastures in Canterbury

I. C. HARVEY
L. M. FOLEY
D. J. SAVILLE

AgResearch
P. O. Box 60
Lincoln, New Zealand

Abstract  Laboratory-produced Sclerotinia sclerotiorum sclerotia of two size ranges (< 4 and > 4 mm diam.) were buried in mesh bags in sheltered or exposed positions in the A horizon under two pastures in Canterbury in June. This emulated sclerotia entering a heavy and a light soil after mycoherbicide application to Californian thistle in pasture. The bags, each containing 20 sclerotia were lifted 3, 5, and 7 months after burial. Large sclerotia survived better than small sclerotia. The percentage of sclerotia producing mycelium in culture was less after 5 months burial than after 3 months, but was then greater after 7 months than after 5 months. Carpogenic germination was greater in exposed than in sheltered locations especially at the site with heavy soil, and was not influenced by sclerotium size. The number of intact exhumed sclerotia yielding micro-organisms was greater after 5 months than after 3 months, but less after 7 months than after 5 months, which contrasted with the changes in ability of exhumed sclerotia to produce mycelium in culture. More micro-organisms were isolated from large than small sclerotia, but the position within the paddock did not appear to influence the number of micro-organisms isolated. One fungus, Chrysosporium luteum, is recorded as a possible mycoparasite of sclerotia of S. sclerotiorum for the first time. Several other genera, including Fusarium and Mucor spp., and bacteria were associated with sclerotia that failed to produce mycelium in culture. The results of this study have assisted not only in assessing the risk to subsequent crops or neighbouring crops through ascospore spread and through sclerotia of S. sclerotiorum that remain in the soil after the pathogen is used as a mycoherbicide in pastures, but also in developing a longer-term sclerotium burial experiment.

Keywords Sclerotinia sclerotiorum; sclerotium survival; mycoherbicide; mycoparasites

New Zealand Journal of Agricultural Research, 1995, Vol. 38: 279-284

0028-8233/95/3802-0279 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (536K); (scanned from paper original: notes about this process)

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