Conditions at sowing in 2023 provided ideal conditions for high slug pressure in the south-west region. High soil moisture levels and slug population increases over recent years indicated that crop establishment may be at risk. Canola is often more susceptible to slug damage in comparison to cereals due to its growing point being above the surface. If the growing point is damaged during establishment the plant will likely not survive.

With the high slug pressure, extensive baiting programs and management systems were implemented throughout the region. However, they were not always effective in high pressure conditions and can be quite expensive. When a crop suffers high levels of damage from slugs it leaves growers with a difficult decision in whether to wear the costs of re-sowing.

Canola trials conducted by Southern Farming Systems (SFS) in 2023 aimed to investigate Canola’s ability to compensate after damage events and at what level of damage is resowing necessary.  Four different target plant populations were used to simulate damage events in which 0%, 25%, 50% and 75% of the crop had been damaged by slugs. Two trials were set up at SFS Streatham trial site to look at how different Clearfield and Triazine Tolerant varieties responded to the different levels of damage and the financial implications were calculated.

In season assessments found that the lower the plant density, plants would grow more branches and have deeper podding depths indicating an ability to compensate and grow into the space left by the damaged plants. Yield results from the trials showed despite the different levels of plant damage, all treatments yielded 3.9 t/ha or above and returned positive gross margins. Lower simulated damage like 25% often yielded similar to the 0% damage treatment due to the plants ability to compensate.

The results show that there are alternative options to re-sowing and that canola can compensate when slug damage occurs. Alternatively, canola’s ability to compensate could provide options for growers to reduce seed costs and use lower sowing rates and not suffer significant yield reductions. A full report of these trials can be found in the Southern Farming Systems 2023 Results Book