Sclerotinia in oilseed rape: towards a stabilisation of the observation of SDHI resistance?
Sclerotinia in oilseed rape: towards a stabilisation of the observation of SDHI resistance?
Nuisibility and frequency of attack: reminders
Sclerotinia is the main disease of oilseed rape if we consider that the control of phoma is primarily a genetic control. Although the frequency of attack is considered to be low, with an attack observed one to two years out of ten on a national scale (variability at regional level to be taken into account), the harmfulness of Sclerotinia sclerotiorum is significant from 10% of the main stems affected. From this threshold, 1 to 1.5 quintals of damage per hectare are observed for each additional 10% of main stems affected. Attacks on branches are rarely harmful except in the case of very heavy attacks, i.e. from 50% of branches affected.
Let us recall that the factors favourable to the development of the disease are, beyond the contamination phase, mild temperatures and a high relative humidity. The inoculum is rarely the limiting factor for the development of the disease as shown by the results of the petal kits carried out at the scale of the regional BSV (see the BSV publications in your region).
Due to the need for preventive intervention against this disease (no curative solution available), the difficulty of predicting the development of the disease other than by setting up petal kits, and depending on the plot context (type of rotation, history of sclerotinia pressure, etc.), an intervention at the BBCH 69 stage (G1 stage) may be necessary.
More information: Article « Sclerotinia, is it necessary to carry out a fungicide treatment? ».
Sclerotinia management at BBCH 69 (G1 stage)
From the point of view of available fungicide solutions, apart from biocontrol solutions (considered insufficient in case of harmful attack), since the 2022 campaign, a fourth mode of action has enriched the possible choices for action at G1 stage (BBCH 69).
More information: 2022 webinar « spring diseases and pests ».
Management of sclerotinia resistance to SDHI: update on the situation
The joint note from ANSES, INRAe, and Terres Inovia provides an update on the situation in 2022 regarding the resistance of Sclerotinia sclerotiorum strains to fungicides and more particularly to SDHI. Since 2020, the number of sclerotia samples taken during the season for analysis has decreased significantly, in connection with low field pressures. Nevertheless, the inoculum is still present in the plots (cf. results of the petal kits in your region) and vigilance regarding the acquisition of resistance to the available modes of action remains necessary.
Note: With the introduction of the fludioxonil-based solution, the number of available modes of action for sclerotinia control is increased to four. With the growing range of products on offer and the application of the recommendations, the sustainability of sclerotinia management is secured.