PestFacts November (no. 2) 2022
Spring and summer management of snails
The most effective management of pest snails requires a year-round systems approach. In spring, growers should determine if snails will be a problem during harvest, then implement strategies to deliver clean grain and start controlling snail numbers for next season. For spring management read the SARDI produced Paddock Practices: Snail management is a critical part of harvest preparation.
Summer management
Snails are vulnerable to dehydration and require refuges to survive hot and dry summer conditions and high soil surface temperatures. They over-summer above or below the soil surface on stubble, weeds, fence posts, rocks or other objects that provide cool, moist refuges.
Several cultural control methods exploit these vulnerabilities and can significantly reduce populations by removing available refuges and directly killing snails. They can be used repeatedly or in combination. However, decisions to employ these tactics need to balance the trade-offs between managing snails and the benefits of retaining stubble.
For a full overview read Bash'em Burn'em Bait'em: Integrated snail management in crops and pastures. Updated guidance is expected by the end of 2022.
Summer weed control
Reducing summer weeds is key for over-summering for many pest species. It is an important tactic to control snail populations and should be done before using other cultural controls. When summer weeds are present other control techniques are less effective. Weed control should also occur in late autumn prior to baiting to reduce alternative food sources for snails.
Bash 'em by rolling, cabling and slashing
These tactics flatten stubble to reduce vertical refuges, knock snails onto the soil surface, where many will dehydrate, and crush some snails.
Stubble bashing is most effective on hot sunny days with maximum temperatures above 35°C (ideally 40°C, when ground temperature is about 55°C), followed by more hot days, but fire risk needs to be carefully managed. Repeat operations may be more effective in coastal areas with milder temperatures.
Grazing also flattens stubble, crushes snails and assists with weed control, and can be implemented any time between spring and autumn.
Bait 'em
While snails may become active on the soil surface after summer rainfall, recent research has shown they do not always actively feed. Sample baiting after rainfall can be used to determine the extent of snail feeding and where to apply baits effectively.
The effectiveness of metaldehyde baits is also affected by temperature as they degrade in temperatures above 40°C. Where possible, we recommend storing bait pellets in cool conditions over summer and avoiding hot sheds.
More information
- Bash 'em Burn 'em Bait 'em: Integrated snail management in crops and pastures
- Snail management
- Snail bait application
- Snail identification and control: The back pocket guide
- PestNotes: Conical or pointed snail ()
- PestNotes: Small pointed snail ()
- PestNotes: Vineyard snail ()
- PestNotes: White Italian Snail ()
Stored grain insect management
Stored grain insect pests pose a serious threat to grain quality, and there is a nil tolerance for live insects at grain receival sites. Therefore, an integrated approach to insect control, including careful management of the storage environment, is critical.
Managing storage pests
When managing storage pests, prevention is always better than cure. Most problems can be overcome by effective farm hygiene, well-managed aeration cooling and correct fumigation. We recommend the following:
- Remove grain residues from in and around empty storage and grain handling equipment before reuse.
- Reduce introduction of insect pests to your property by thoroughly cleaning equipment and farm machinery.
- After cleaning, consider treating storage and equipment with a structural treatment, such as an inert dust. Be aware of market requirements and withholding periods before selecting a treatment.
- Install aeration cooling fans and an aeration controller in storages to reduce grain temperature, slow insect development and maintain grain quality. Aim for temperatures below 20°C.
- Monitor stored grain monthly for insect pests, mould, grain temperature and grain moisture content.
Grain stored for more than six weeks should generally be fumigated for insect pests. All fumigation must be conducted in pressure-tested sealable gas-tight silos. The widespread use of phosphine has resulted in high levels of phosphine resistance in several stored grain insect pests. Surveillance conducted across South Australia in 2021 detected several populations of lesser grain borer (Rhyzopertha dominica) with resistance, and surveillance will continue this summer.
To help manage resistance, ensure that phosphine is only used when necessary and that fumigation is always conducted correctly within well-maintained gas-tight storages. Phosphine should be held at lethal concentrations for 7 to 10 days to ensure effective control of all insect life stages. Poor fumigation often results in a partial kill and selects for further resistance. Under phosphine label regulations, a ‘fumigation in progress’ warning sign must be displayed. A phosphine warning sign (850 KB PDF) can be downloaded from the Farm Biosecurity website.
When insect pests are discovered, correct identification allows for more targeted control options and avoids control failures due to insecticide resistance. Read the Grain storage fact sheet: Stored grain pests identification for help. The SARDI insect diagnostic service is free and available over summer; specimens can be posted in a non-crushable container, or images can be sent to @PestFactsSARDI on Twitter or email rebecca.hamdorf@sa.gov.au.
Look out for biosecurity
Look out for unusual pests/diseases in stored grain, such as the khapra beetle (Trogoderma granarium) and karnal bunt (Tilletia indica), which are high priority biosecurity threats for the Australian grains industry. Submit any unusual specimens for diagnosis by either:
- sending photos or specimens to PestFacts SA
- contacting Biosecurity SA Grains Officer Shafiya Hussein (shafiya.hussein@sa.gov.au)
- calling the Exotic Plant Pest Hotline on 1800 084 881.
More information
The latest information for growers and advisors on the activity and management of pests in all broadacre crops during the winter growing season.
