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Signs of grain beetles
See how to identify signs of a problem
Common Stored Product Insect species
Stored product insects (SPI) not only damage foodstuff and raw materials but can also contaminate finished products, hence making them unfit for use. Understanding the appearance, habits and life cycles of SPIs can help to identify the most effective SPI control for your property.
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Lesser grain borer
(Rhyzopertha dominica)
Appearance
- Adult is 2–3 mm in length.
- Ranges from red-brown to black-brown in colour.
Lifecycle
- Female produces 200–500 eggs.
- At ideal temperature of 34°C and 70% Relative Humidity (RH), pupation takes up to 3 days.
- At ideal temperature (34°C and 70% RH), life cycle last around 3—4 weeks.
Habits
- Eggs are laid in crevices or on the rough surfaces of a seed.
- Larva will bore inside the grain to continue growing.
- Larva develops faster on whole grain compared to flour.
- Adult mate as soon as they emerge.
- Commonly found in warehouse and store.
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Drugstore beetle/Biscuit beetle
(Stegobium paniceum)
Appearance
- Adult is 2–3.5 mm in length.
- Light brown in colour and oval in shape.
- Antennas end with 3–segmented club.
Lifecycle
- Female produces 20–100 eggs.
- Eggs take around 60–210 days to develop into adults, with 1–4 generations per year depending on the temperature.
- Adult lives for about 13–65 days
Habits
- Adults are active fliers, especially during afternoon to evening time.
- Commonly found infesting processed goods such as chocolate, confectionery and biscuits. Also often found on dried food product such as dried herbs and spices.
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Cigarette beetle
(Lasioderma serricorne)
Appearance
- Adult is 2–3 mm in length.
- Light brown to reddish brown in colour.
- Antennas are about half of its body length and are shaped serrated (saw-like).
Lifecycle
- Female produces up to 30–42 eggs.
- Eggs take 30–90 days to develop, with 3–6 overlapping generations per year.
- Adult lives 23–28 days.
Habits
- Larva produces a cell of food fragments and waste materials to pupate.
- Adults are active fliers, especially during afternoon to evening time.
- Adult do not feed while the larva is the one doing the damage.
- Feeds off tobacco, dry stored food products, spices, seeds, grains and dried plant material.
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Rusty grain beetle
(Cryptolestes ferrugineus)
Appearance
- Adult is 1.5 – 2.5 mm in length.
- Red-brown in colour with flat body.
Lifecycle
- Female produces up to 200 eggs.
- In ideal temperature conditions, the life cycle is about 23 days.
Habits
- Adults walk with a characteristic swaying movement.
- Adults are winged but rarely fly.
- Feeds on cereals, dates, dried fruits and other materials.
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Saw toothed grain beetle
(Oryzaephilus surinamensis)
Appearance
- Adult is about 2.5–3 mm in length.
- 6 sawlike teeth on each side of prothorax
Lifecycle
- Female produces 45–285 eggs.
- Life cycle takes about 30–50 days.
Habits
- Larvae feed within mass produce.
- Adults are winged but do not fly.
- Often wander from food into cracks, crevices and roof spaces to hide.
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Khapra beetle
(Trogoderma granarium)
Appearance
- Adult is 2 – 3 mm in length.
- Dark brown in colour with light brown pattern on wing covers.
- Oval in shape.
Lifecycle
- Female can lay up to 35 eggs.
- It takes about a month to complete life cycle.
Habits
- Larvae make the most damage on stored products by shedding cast skin and feeding on materials.
- It can survive up to 9 months without food.
- Commonly found infesting grains, cereals and pulses.
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Copra beetle/Red legged ham beetle
(Necrobia rufipes)
Appearance
- Adult is around 3.5–7 mm in length.
- Shiny green to bluish green in colour with red legs.
Lifecycle
- Female lays up to 30 eggs per day in cracks or crevices of cured fish.
- Adult lives up to 14 months.
Habits
- Commonly feeds on dried copra and other insects that are attracted to mouldy food.
- Infest areas such as palm kernels, oilseeds, spices, dried fish and other meat products.
- Adults are slow fliers and will bite human when disturbed.
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Granary weevil
(Sitophilus granarius)
Appearance
- Adult is 2.5–3.5 mm in length.
- Brown to black in colour with reddish spots on the back of the abdomen.
- Has a long slender snout.
Lifecycle
- Female lays 300–400 eggs.
- It takes as short as 32 days to complete life cycle.
- Adult lives up to 3–6 months.
Habits
- Female drills a tiny hole in the grain kernel to lay egg in the cavity.
- Grows, feeds and pupates within a grain kernel.
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Rice weevil
(Sitophilus oryzae)
Appearance
- Adult is about 2.5–3 mm in length.
- 6 sawlike teeth on each side of prothorax
Lifecycle
- Female produces 45–285 eggs.
- Life cycle takes about 30–50 days.
Habits
- Larvae feed within mass produce.
- Adults are winged but do not fly.
- Often wander from food into cracks, crevices and roof spaces to hide.
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Flour beetle
(Tribolium castaneum)
Appearance
- Adult is 3–4 mm in length.
- Reddish brown in colour.
Lifecycle
- Under optimal conditions, it takes 20 days to develop from egg to adult.
Habits
- Larva and adult feed on wide range of durable commodities such as groundnuts, nuts, spices, coffee, cereals, dried fruits and animal feed.
- Disperses by flying and does not depend on humans' movement of food products.
Grain beetles facts
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