Impact of stubble management on small conical snail mortality

Overall Objective

• Provide growers with a clear percentage of the effect of three stubble management techniques (cabling, stubble crunching and speed tillage) on small conical snail mortality.
• Introduce more ‘tools’ into growers’ repertoire to control snails and reduce the current reliance on snail baiting.
• Demonstrate ‘GrainCam’ ’s effectiveness in identifying snail hot spots in paddocks and map their distribution for targeted management.

Project Synopsis

This project aimed to assess the impact of summer stubble management to control small conical snail populations in the Albany Port Zone (APZ) of Western Australia. Small conical snails have become a serious problem in WA over the last 20 years, causing damage to grain crops, pasture and downgrading grain quality. Current snail management techniques involve burning windrows, removing green bridges, and baiting during the growing season. The best option for removing small conical snails from grain is to put the grain through a specially designed snail rolling machine before delivering to bulk handling depots.

The project idea was based on management practices utilised in South Australia, where snails are knocked onto the ground from stubble on hot days (>35 degrees) to dehydrate and die. This project aimed to test cabling, stubble crunching, and speed tilling because these methods are widely available options to growers within the APZ. Growers have very few low-cost snail control options, and this trial wanted to address that need.

Researchers collected three separate datasets from the treatment effects on small conical snail numbers. These were:

1. Physical small conical snail counts before and after the treatments were applied in Match 2020 (pre-sowing of the wheat crop)
2. The physical collection of 166-grain samples while harvesting the trial and then counting the snails in the grain samples later in the laboratory. (December 2020)
3. Analysis of 3,486 photo images taken by GrainCam while harvesting the farm-scale trial plots by artificial intelligence software. (February-March 2021)

The physical snail counts from the harvested grain sample were used to validate the results obtained from the GrainCam imagery and subsequent analysis using artificial intelligence software. The correlation between the snails counted in samples and snails detected by artificial intelligence (GrainCam) was 0.55, which is significant at p<0.05. The three data sets showed no short or long-term reduction of small conical snail numbers from the stubble management techniques used in this trial.

On a positive note, the trial demonstrated a successful application of the GrainCam concept designed by DPIRD researcher John Moore. The DPIRD report states that the snails in 2020 were much smaller than average, and the images used to train the artificial intelligence (AI) software. Providing more images or ‘training’ for the AI software would likely improve the correlation between the snails detected by GrainCam and the actual counts.

Counting snails manually is not a viable option for grain growers or even researchers doing trial work due to being very labour intensive.  The use of the GrainCam to estimate snail density is, therefore, a valuable system for detecting pests in grain samples. GrainCam could easily be deployed to test for other grain contaminants such as bedstraw, skeleton weed, insects etc.

John Moore believes it would be possible to utilise the camera systems already used in modern harvesters to ‘run’ GrainCam for detecting snails (or other contaminants) rather than a mobile phone as was used in this trial. The concept needs considerable resources and funding to take the idea from the prototype stage to the market application.

The snail mortality results from the stubble treatments are disappointing because we hoped to find an alternative solution to controlling small conical and conical snails that would complement baiting. Stubble management is relatively cheap and is also completed for other agronomic benefits. The main industry benefit from the project is communicating what we tried and that it was not an effective small conical snail control method for use in the Albany Port Zone.