Application of Coniothyrium minitans against Sclerotinia of oilseed rape

CONTANS WG is a biological plant protection product containing spores of Coniothyrium minitans. It is a mycoparasite that causes the destruction of hyphae and sclerotia of Sclerotinia sclerotiorum, S. minor and S. trifoliorum present in the soil.

How does it work?

When in contact with a sclerotium, the spores of Coniothyrium minitans germinate and produce mycelial hyphae that invade the sclerotia, then enzymes degrade their cellular structures. Thus altered, the sclerotia become unable to emit mycelial filaments or apothecia carrying ascospores and are finally destroyed within a few months depending on soil and climatic conditions. The sclerotinia cycle is thus broken.

Three application periods are possible:

In pre-sowing of oilseed rape at 2 kg/ha, preferably incorporated, targeting superficial sclerotia, thus reducing the inoculum pressure, notably the amount of ascospores that contaminate petals.
By spraying at 2 kg/ha post-emergence, up to the 4-6 leaf stage of oilseed rape. This method, less effective than incorporation at pre-sowing, should only be considered before heavy rainfall (or irrigation). Water is indeed necessary to ensure the penetration of Coniothyrium minitans spores into the sclerotia.
By spraying on infected crops residues at 1 to 2 kg/ha depending on the amount of sclerotia present. This aims to reduce the stock of viable sclerotia returned to the soil and thus reduce the inoculum quantity.

The application of CONTANS WG increases the percentage of altered sclerotia compared to the untreated control. This is even more true as time passes. The effectiveness on sclerotia alteration varies depending on the timing of CONTANS WG application: pre-sowing application provides the best results.

Conditions of high Sclerotinia pressure

In cases of severe sclerotinia attacks (average of 51% of plants affected), a single application of CONTANS at 2 kg/ha was as effective as a DMI-based fungicide applied at the G1 stage of first petal fall. The combination of CONTANS WG at 2 kg/ha pre-sowing with a DMI fungicide provides an efficacy gain of about 30% compared to foliar fungicide alone. Combined with a more effective fungicide (Pictor Pro), 2 kg/ha of CONTANS WG pre-sowing also provides a more modest efficacy gain of about 10%. In terms of yield, single treatments with CONTANS WG or fungicides lead to yield gains of 6 to 10 q/ha compared to untreated controls. Incorporation of CONTANS WG pre-sowing followed by a fungicide at the G1 stage provides an additional gain.

Benefits

No known danger to the user
No known environmental impact
No known impact on soil life
Long-lasting effect (12 to 18 months)
No IFT

Limitations

Demanding storage conditions (sensitive to high temperatures and light)
Effectiveness dependent on application conditions (soil temperature and humidity)

Advisor's opinion

An application of CONTANS pre-sowing significantly reduces sclerotinia attacks. However, the use of Coniothyrium minitans must be part of a long-term and more comprehensive control strategy. Indeed, a single application does not destroy 100% of sclerotia, especially in cases of short rotations, sensitive crops, or significant and recent attacks. The duration of action of CONTANS WG being about 12 to 18 months, it is advisable to renew the application each year to reduce the soil infectious potential in the medium term. Trials have also shown that the efficacy tends to increase with successive applications.

Cost

€26 - 32/ha

Sources

This article was written based on the document The fields of possibility in biological control of arable crops jointly authored by François DUMOULIN, Hélène BAUDET, Gilles SALITOT and Inma TINOCO from the Chamber of Agriculture of Oise.

Appendices

Est complémentaire des leviers

S'applique aux cultures suivantes

Oilseed rape

Défavorise les bioagresseurs suivants

Sclerotinia on oilseed rape