Rice Weevil (Sitophilus oryzae)
Pheromone Traps used to Monitor Rice Weevils
Rice Weevil Description
Rice Weevil Adults: Adults are 2-3 mm (0.125 inches) long, dull reddish-brown to black, having the prothorax pitted with deep, round punctures and with four light spots on the wing covers.
Rice Weevil Eggs: Female Rice weevils will chew a hole into a grain kernel and deposit a single egg.
Rice Weevil Larvae: Larva fully develops inside the whole kernel of grain or dried pasta, eating it away as it grows. By the time it is ready for pupation, the entire inside of the kernel has been eaten away, usually leaving only a thin seed cover.
Rice Weevil Pupae: Pupation also occurs within the kernel of grain.
Life Cycle of the Rice Weevil
In the Rice weevil life cycle, the female will eat out a cavity in the grain large enough for an egg. She will then use her ovipositor at the tip of her abdomen to lay a single egg in each kernel of grain. After depositing the egg, she will seal off the hole, making detection difficult.
The Rice weevil egg will hatch in about 3 days. The larval stage will take, on average, about 18 days and pupation will take 4 days. The adults will live about 110 days and are strong fliers.
Damage & Detection from Rice weevils
The larvae do the greatest amount of damage as they eat the inside of grains and seeds, leaving only a husk behind. The adults also have strong chewing mouthparts and will cause damage as well. Detection can be difficult in grains that have recently had eggs laid in them.
After some time, the damage becomes evident as the grains become so light and hollow, that you can easily break them into dust with your fingertips. In heavy infestations, chewing can sometimes be heard.
Fun Facts about Rice weevils
Similar species include granary weevil (Sitophilus granaries) and maize weevil (Sitophilus zeamais).
Other common names include lesser grain weevil.
Rice weevil is an internal feeder, meaning that larvae can burrow into a grain kernel where they feed and remain until they emerge as an adult.
Rice weevil initiates flight at temperatures above 20°C (68°F).
The pheromone that attracts rice weevil also attracts similar species including:
Granary weevil (Sitophilus granaries)
Maize weevil (Sitophilus zeamais)
Bearded weevil (Rhinostomus barbirostris)
Monitoring Tips & Tricks for Rice Weevil
Rice Weevil Monitoring Guidelines
Lure
BULLET LURE Contains aggregation pheromone to attract male beetles.
PANTRY PATROL Pheromone /oil dispenser. Contains grain-based food attractants and aggregation pheromones to attract males and female Rice Weevil.
STORED PRODUCT BEETLE Lures are food bait and pheromone lures that was specifically designed to make the Pantry Patrol gel into a tablet form.
ALL BEETLE TRAP READY-TO-USE TRAY is a preloaded accessory of the ALL BEETLE TRAP that contains either the PANTRY PATROL Pheromone/oil dispenser or the STORED PRODUCT BEETLE LURE and glueboard.
Lure Storage
Keep unopened BULLET LURES, PANTRY PATROL pheromone /oil dispensers, READY-TO-USE TRAYS, and STORED PRODUCT BEETLE LURES in cool storage for 12 Months or in refrigeration for up to 24 months before using or discarding.
Trap Designs Used with Lure
ALL BEETLE TRAP consists of three parts: A clear lid, blue base, and snap in tray. This device can be paired with many different types of attractants available by Insects Limited depending on the insect you are monitoring.
PANTRY PATROL “CORNER” pitfall traps contain a triangular pit to receive a full dispenser of pheromone /oil. Dust cover is incorporated into cardboard packaging.
Pheromone Traps used to Monitor Rice weevil
Trap Placement & Use
Trap Placement Techniques
Pheromone traps can be placed year-round but are especially recommended when temperatures exceed 12.5°C (55°F). Floor pheromone traps like the All Beetle Trap and Flat Trap are more effective at capturing rice weevil compared to hanging pheromone traps. In areas such as a pantry or home, place one or two pheromone traps per room.
In commercial areas such as warehouses or retail stores, place pheromone traps 2-5 m (5–15 feet) apart to determine the presence or absence of Rice weevil. Keep pheromone traps 7.5 m (25 feet) away from exterior doors. Rice weevil pheromone traps are best utilized in areas that store dried goods such as food, grains, seeds, nuts, animal feed, or pet food.
Trap and Lure Maintenance
Replace traps when glue is filled with insects or becomes dusty. Replace pheromone lures every 90 days. Replace all pheromone lures in a location at the same time. Do not cut the cap off the bullet lure. Do not stagger lure replacement over several weeks. Record date and number of catches to identify trending information.
Rice Weevil Information
Rice Weevil Behavior
Rice Weevil FAQs
What do rice weevils look like?
Adult rice weevil are 2-3 mm (0.125 inches) long with a long snout protruding from their head, dull reddish-brown to black in color, having their prothorax (area behind the head) is pitted with deep, round punctures and they have four light spots on the wing covers. Female Rice weevils will chew a hole into a grain kernel and deposit a single egg.
The eggs are never seen unless a grain kernel is carefully broken open and inspected with a microscope. The larva fully develops inside the whole kernel of grain or dried pasta, eating it away as it grows. By the time it is ready for pupation, the entire inside of the kernel has been eaten away, usually leaving only a thin seed cover. Pupation also occurs within the kernel of grain.
How do I get rid of weevils?
The use of pheromone traps for rice weevils can indicate their presence as well as where the beetles are coming from. Insect light traps are also an excellent indicator of the presence of rice weevil adults.
A visual inspection of whole grains or seeds in the vicinity of the pheromone traps containing the most beetles can reveal specific grain stores containing the beetles. Once an infestation is found, the infested materials should be sealed up and discarded or treated to kill the weevils.
Treatment options for weevils includes freezing rice weevils for one week or having a certified pest management specialist perform an anoxic treatment or a gas fumigation on the infested materials.
What do rice weevils eat?
Rice weevils are internal feeders of whole grains and seeds. This means that they eat the inside of the grain kernels from the inside out, often leaving an empty husk behind.
The female will eat out a cavity large enough for an egg. She will then use her ovipositor at the tip of her abdomen to lay a single egg in each kernel of grain. After depositing the egg, she will seal off the hole, making detection difficult.
The egg hatches and the larva starts to feed until the entire inside of the grain kernel has been consumed.
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