Slug control with companion plants
Slug pressure on wheat is a major issue, particularly in Conservation Agriculture (ACS), where these pests are on average ten times more numerous than in conventional tilled systems[1]. They can cause significant damage to cereals from emergence by consuming the seedlings, leading to emergence gaps[2][3], especially if crops struggle to develop[1]. Slug activity is strongly influenced by climate, with mild and humid conditions particularly favorable for their development and reproduction, as egg hatching speed depends on soil temperature and moisture. Regular rainfall and mild weather, as in 2023, can allow activity almost year-round[1][2].
In this context, the interest of a trial with companion plants, or cover crops, is crucial as they can influence slug population dynamics[3][2]. Although farmers recognize that covers can feed and shelter slugs, potentially leading to proliferation, they also observe that starving slugs is not an effective solution as they become more voracious[1][3]. The objective is to manage the vegetation cover so that it acts as an alternative food source or a lure, such as rye before sunflower or rapeseed before corn or wheat[1][4], thus reducing pressure on the main crop[1]. A progressive destruction of the cover, allowing slugs to continue feeding on it, is considered an effective strategy to limit damage on the following crop[1][3].
It is recommended to favor rolling or a low-dose chemical herbicide rather than mowing, so that slugs can continue feeding on the cover[1][3]. Rapeseed is an interesting crop as it is very palatable to slugs and often present as a wheat predecessor[5]
Research question
- What is the effect of maintaining rapeseed regrowth on slug pressure during wheat emergence?
Contacts
Protocol
- Factor: Date of destruction of rapeseed regrowth
- Modality 1: Rapeseed regrowth destroyed 3 weeks before wheat sowing.
- Modality 2: Rapeseed regrowth destroyed the day before wheat sowing.
Technical itinerary
- Sowing: direct disc drill
- Seeding rate: 340 grains/m2
- Treatments: no anti-slug
Slug counting
4 cardboard slug traps of 50 cm per side were placed per modality.
- Trap installation: November 3, 2024
- Trap collection: November 8, 2024
Counting of attacked leaves
Defoliation percentage
Results
No significant differences appear between the two modalities regarding the number of slugs trapped.
The number of attacked leaves is higher in the modality with early destruction (3 weeks before) of rapeseed.
The defoliation percentage when slug attack is present does not seem to vary according to the two tested modalities.
Conclusion
In this trial, companion plants (Rapeseed) seem to tend to keep slug pressure on the companion plants and not on the cash crop. However, pressure in this plot remained low (around 20 slugs/m2). The question of the effectiveness of companion plants under much higher pressure can be raised.
This trial will be set up in multiple sites in the coming years to consolidate these results.
Sources and references
- ARVALIS - Institut du Végétal. (April 3, 2014). Should soil be worked? Paris Symposium.
- Eure Chamber of Agriculture. (September 26, 2011). Integrated Agriculture Messaging No. 2011 – 24: Rapeseed.
- De Sangosse. (June 2022). White paper on slug targeting 2022. (Source referenced as "Cultivar • June 2022")
- ADAMA France s.a.s. (August 2021). Good slug control practices 2021.
- Agroleague. (September 2022). Agroleague Technical Flash: Slugs.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 APAD (Association pour la Promotion de l'Agriculture Durable) - Technical Committee. (2023). Management of slugs in Conservation Agriculture: 2023 knowledge synthesis.
- ↑ 2.0 2.1 2.2 CETIOM, D. Lebourgeois – and Technical Institute of Beet. (n.d.).
- ↑ 3.0 3.1 3.2 3.3 3.4 Sauvage, Hélène. (June 2022). Contributes to several articles in "Cultivar - June 2022", notably "Slugs and cover crops get along well", "Anticipating the slug risk", "To reduce the IFT, you must trap slugs", "New regulation for metaldehyde", "Protecting the seed from sowing", "Benefit from the complementarity of the two active substances", "Iron phosphate: efficacy comparable to conventional products", "Innovate to gain efficiency", and "Slug control and beneficial fauna, the truth and myths".
- ↑ CHABERT, A. (ACTA). (2017, February 2). Slugs: biology, environmental influence and risk forecasting with lessons from the CasDAR RESOLIM project. APPO - Association for the Promotion of Legumes and Oilseeds, Gembloux Agro-Bio Tech - University of Liège.
- ↑ Agroscope - W. JOSSI et al., 2015 - Sensitivity of cover crops to slugs
