Granary Weevil
Sitophilus granarius
Granary Weevils are a significant pest in Australian grain storage facilities, causing economic losses by infesting and damaging stored grains.
For effective control and prevention, professional pest management is recommended.
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Granary Weevil At-A-Glance
Key facts and characteristics
Complete Granary Weevil Guide
Professional identification and control information
Identification
How to accurately identify Granary Weevil
Expert Tips
Look for dark brown weevils with a distinct snout and check for grain damage in storage facilities.
Confusion Species
Often confused with Rice Weevil; distinguish by the inability to fly and darker color.
Key Identification Features
Dark brown color, elongated snout, and inability to fly are key features for pest professionals.
Biology & Lifecycle
Understanding Granary Weevil biology and development
Anatomy
Granary Weevils have a hard exoskeleton, long snout, and six legs adapted for crawling within grains.
Genetics
Population genetics show limited variation, aiding in targeted pest management strategies.
Lifecycle Details
Egg Stage
Eggs are laid inside grain kernels and hatch within 5-7 days.
Adult Stage
Adults live for 3-8 months, continuously reproducing.
Pupal Stage
Not applicable; development occurs within the grain kernel.
Larval Stage
Larvae develop entirely within the grain kernel, feeding and growing.
Development Time
4-6 weeks under Australian summer conditions.
Reproduction Rate
Multiple generations per year, depending on temperature and food availability.
Habitat & Distribution
Where Granary Weevil lives and thrives
Preferred Habitats
- grain storage facilities
- silos
- warehouses
Nesting Behavior
Larvae develop entirely within grain kernels, making them difficult to detect.
Nesting Requirements
Requires whole grain kernels for larval development.
Temperature Preference
Thrives in temperatures between 20-30°C, typical of Australian grain storage.
Humidity Preference
Prefers moderate humidity levels found in grain storage environments.
Hiding Spots
- inside grain kernels
- grain storage bins
- silos
Distribution Patterns
Native Range
Not native to Australia; introduced through global trade.
Climate Zones
Found in temperate and subtropical grain-growing regions of Australia.
Urban Vs Rural
Primarily a rural pest, affecting grain storage facilities.
Introduced Range
Widespread in grain-growing regions across Australia.
Spread Mechanism
Spread through infested grain and human activity in grain trade.
Australian States
Found in all grain-growing states, including New South Wales, Victoria, and Queensland.
Establishment Factors
Thrives in grain storage environments with moderate humidity and temperature.
Behavior & Diet
Granary Weevil behavioral patterns and feeding habits
Activity Pattern
Nocturnal, with peak activity during cooler parts of the day.
Social Behavior
Solitary within grain kernels but can be found in large numbers in infested areas.
Territorial Behavior
Not territorial; multiple weevils can infest the same grain kernel.
Foraging Behavior
Limited to feeding within grain kernels; no external foraging.
Dispersal Behavior
Dispersal occurs through human activity, such as moving infested grain.
Dietary Preferences
Aphid Farming
Not applicable.
Feeding Habits
Larvae and adults feed exclusively on whole grains like wheat, barley, and rice.
Foraging Range
Limited to stored grain environments.
Feeding Patterns
Continuous feeding within grain kernels throughout their lifecycle.
Primary Food Sources
- wheat
- barley
- rice
Seasonal Diet Changes
No significant seasonal changes.
Health Risks
Health concerns associated with Granary Weevil
Always consult healthcare professionals for medical concerns related to pest exposure.
Allergens
None known.
Contamination Risk
High risk of grain contamination, leading to economic losses.
Disease Transmission
Not a known vector.
Economic Impact
Financial costs and economic effects of Granary Weevil
Economic impact information is being compiled.
Detection & Signs
Early warning signs of Granary Weevil presence
Detection information is being compiled.
Prevention
Proactive strategies to prevent Granary Weevil infestations
Prevention information is being compiled.
Control Methods
Effective treatment options for Granary Weevil control
Professional services information is being compiled.
Professional Services
Professional services information is being compiled.
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Seasonal Patterns
Granary Weevil seasonal activity and management timing
Autumn
Activity remains consistent in grain stores during autumn (March-May).
Legal Considerations
Legal requirements for Granary Weevil control in Australia
Legal considerations information is being compiled.
Frequently Asked Questions
Common questions about Granary Weevil
Are Granary Weevil dangerous?
Granary Weevils are not dangerous to humans but can cause significant damage to stored grains.
How do I identify Granary Weevil?
Identify by their dark brown color, elongated snout, and inability to fly.
How do I control Granary Weevil?
Control involves proper grain storage, fumigation, and regular monitoring of grain stores.
How do I identify a granary weevil in my home?
Adult granary weevils are small dark brown beetles 2-3.5 mm long with a characteristic long snout (rostrum) typical of true weevils. Unlike the similar rice weevil, granary weevils have no red spots and cannot fly. Look for tiny round exit holes (1-2 mm diameter) in flour, rice, pasta, cereals, or stored grains; this indicates larvae have completed development and emerged. Infested grain kernels appear lighter or hollowed out when cracked open. Fresh weevil droppings and webbing may also be visible in storage containers.
Are granary weevils dangerous in Australia?
Granary weevils do not bite, sting, or transmit disease and pose no direct health risk. They cause significant food safety and economic harm: infested grain and flour become unfit for consumption as larvae hollow out kernels and leave contaminated debris. Larval skins may trigger allergic reactions in sensitive individuals, particularly those with occupational exposure in bakeries or grain-handling facilities. For any health concerns related to consumption of infested products, contact the Australian Poisons Information Centre on 13 11 26.
How much does granary weevil control cost in Australia?
Home pantry control is low-cost: discarding infested products and freezing suspect items for 7 days at -18°C costs only replacement food. Professional pest control for warehouse or large grain storage varies based on facility size, infestation severity, storage infrastructure, and fumigation requirements. Phosphine fumigation in sealed silos requires licensed operatives and compliance with restricted-poison regulations. Preventative measures (cool storage, sealed containers) are far more cost-effective than remedial treatment. Obtain quotes from AEPMA-licensed pest control providers in your state for accurate pricing.
When are granary weevils most active in Australia?
Granary weevil activity is temperature-dependent: breeding occurs between 11-34°C, with development fastest at warmer temperatures and slowest approaching the lower threshold. At cooler temperatures development extends considerably; at 15°C or below breeding ceases entirely. In Australia's temperate southern states (Victoria, Tasmania, southern NSW) — where this species is most common — weevils are most active during warm months (November to March) when pantry and grain storage temperatures rise. In tropical and warm northern regions, activity may persist year-round in uncontrolled warm storage. Commercial grain coming direct from the paddock at elevated harvest temperatures is particularly vulnerable to rapid infestation.
Should I call a professional for granary weevils?
For home pantry infestations, professional pest control is rarely necessary. Discard infested items in sealed bags, freeze suspect products for 7 days at -18°C, clean shelves thoroughly, and store all grains and flour in airtight containers in cool conditions. Call an AEPMA-licensed pest control provider if: the infestation is severe and spreading to multiple pantry areas; you operate a commercial kitchen, bakery, restaurant, or food storage facility; you manage warehouse or grain silo operations; or if freezing and cleaning have not resolved the problem within 2 weeks. Contact your state Department of Primary Industries or the AEPMA for referrals to licensed operators in your region.
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Image Gallery
Visual identification guide for Granary Weevil
Images of Granary Weevil showing key identifying features: