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Ascosporenflug, Blattbefall und Unterschiede im Pathogenitätsspektrum als Kriterien zur Vorhersage der Schadwirkung von Leptosphaeria maculans an Winterraps
Author(s) -
Thürwächter F.,
Garbe V.,
Hoppe H. H.
Publication year - 1999
Publication title -
journal of phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 60
eISSN - 1439-0434
pISSN - 0931-1785
DOI - 10.1046/j.1439-0434.1999.147004215.x
Subject(s) - blackleg , leptosphaeria maculans , biology , ascospore , canker , infestation , horticulture , agronomy , botany , spore , brassica
The aim of this investigation was to evaluate criteria for the forecast and targeted control of basal stem canker (blackleg) caused by Leptosphaeria maculans on oilseed rape. Ascospore discharge, ratio of aggressive and non‐aggressive isolates and leaf and stem infestations were determined during 1991/92–1993/94 at 6–10 sites in Northern Germany. On a 1–9 scale, blackleg intensity varied from 2.3 to 6.3 at BBCH 81 between different sites and years. Ascospore discharge started in September or October, and reached maxima 1 or 2 months later, without an apparent relationship to blackleg or leaf infestation. There was a positive relationship between leaf infestation and blackleg. However, correlation coefficients were too low to be used as a basis for forecasting. On plant residues from the stem base, aggressive isolates were dominant (>80%) on all sites. From higher parts of the stem and from leaves also, non‐aggressive isolates were isolated with higher frequencies on some locations, but the proportion of aggressive isolates was not related to the blackleg intensity. Taken all together, the three criteria alone seem to be insufficient for the development of a system of blackleg forecasting and targeted control. Further factors (e.g. climatic factors, seed‐and soilborne inoculum, cultural practices) have to be included in models for forecasting the impact of blackleg on oilseed rape.