Application of Bacillus Pumilus against Sclerotinia of Rapeseed
Bacillus pumilus is a bacterium naturally present in the soil and produces metabolites active against sclerotinia on oilseed rape.
This bacterium is found in various commercial solutions, find them here and there.
How does it work?
Bacillus pumilus secretes active metabolites which have the effect of inhibiting the germination of ascospores and reducing the mycelial growth of Sclerotinia sclerotiorum. The secreted metabolites lyse cell membranes, affecting cell integrity and thus causing the death of the pathogenic fungus. The action is therefore preventive like synthetic fungicides. Ballad and Rhapsody are recommended in combination with a synthetic fungicide and are even marketed as a pack.
Low Sclerotinia pressure conditions
In 3 trials by Terres-Inovia under low attack conditions (10% of plants affected by sclerotinia), Ballad (Bacillus pumilus strain QST 208), applied alone at 2 l/ha at the first petal fall stage, provided an average efficacy level of 36%, but extremely variable. Rhapsody at 2 l/ha reached 56% efficacy, more consistent but without reaching, even up to 4 l/ha, the 86% of Propulse applied at 0.8 l/ha.
High Sclerotinia pressure conditions
In situations of high attacks with 25% of plants affected in 2 trials, the efficacy of products at 2 l/ha was 32 and 27%, far behind Propulse at 0.8 l/ha which provided 95% efficacy. Doubling the dose of Rhapsody to 4 l/ha brought no improvement and efficacy still plateaued at 39% with 2 applications at 4 l/ha. Finally, in 3 trials under high attack conditions with 38% of plants affected, the efficacy of Propulse at 0.8 l/ha was 86%, and 77% at 0.5 l/ha confirming a dose effect. The combination of 2 l/ha of Rhapsody with 0.5 l/ha of Propulse brought almost no benefit considering the additional cost and does not compensate for the reduction of 0.3 l/ha of Propulse.
Benefits
- No known environmental impact
- Reduction of the IFT
- Positioning identical to a synthetic fungicide
- Prevention of the risk of resistant strains to certain synthetic fungicides due to the combination of two different modes of action
Limitations
- Living organism with variable efficacy
- Higher cost than a conventional fungicide strategy
- Efficacy not demonstrated on other diseases of oilseed rape (powdery mildew and alternaria)
Advisor's opinion
The performance of Ballad/Rhapsody applied alone is very modest and very variable. When combined with a conventional fungicide, efficacy gains are very small. Thus, the Rhapsody pack 2 l/ha + Propulse 0.5 l/ha does not provide a significant efficacy gain compared to Propulse alone at 0.5 l/ha. Given the pack cost of about €44, the interest therefore seems very limited. The use of Ballad/Rhapsody alone should be limited to low pressure sclerotinia situations with an objective of IFT reduction or in organic systems. It will then be essential to reduce the sclerotinia risk beforehand with known agronomic levers: crop rotation with extended return intervals considering other sensitive crops, use of Contans WG, airy varieties to limit dew presence, controlled density and fertilization nitrogen management...
Cost
€39/ha in pack at 1l/ha + averdyn 0.5 l/ha
Sources
- This article was written based on the document The fields of possibility in biological control in arable crops jointly written 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
Défavorise les bioagresseurs suivants
