Development of methods improving precision of risk assessment of Sclerotinia stem rot in oilseed rape

摘要

The disease forcasting of Sclerotinia Stem Rot in oilseed rape available for Swedish farmers today is a regional risk assessment, based on local climate and field data. Precision in risk assessment can be improved by determining whether the pathogen is present in the field. In a study carried out in 1998 and 1999 three different methods were evaluated. Identification of inoculum on petals was performed by two serological kits available on the market, Alert(R)-On-Site detection kit (Neogen corporation, Lansing MI 48 912, USA) and IDENTIKITTM (Adgen LTD. Auchincruve, AYR, KA6 5 HW, UK) and was compared with the petal test on agar (Turkington et. al., 1988). Altogehter 119 fields of spring oilseed rape, spring oilseed turnip rape and winter oilseed rape were tested. The results of the Alert- test and the Identikit did not correspond reliably with the results of the agar petal test. With the Agar test a quantitative measure was achieved indicating the future disease risk. In areas where humidity was high during flowering a relationship between percentage of infected petals and disease incidence in the field was found. At the level of 20 % infected petals disease incidence exceeded 20 %, the damage threshold, in several fields. In areas where dry weather prevailed during flowering low disease incidence was found also at high levels of infected petals.