Insect of the Month: Rice Weevil
What do Red Rice Weevils look like?
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.
Eggs: Female Rice weevils will chew a hole into a grain kernel and deposit a single egg.
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.
Pupae: Pupation also occurs within the kernel of grain.
What is the Rice Weevil Life Cycle?
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.
Rice Weevil Damage & Detection:
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.
Rice Weevil Facts:
Similar species include granary weevil (Sitophilus granaries) and maize weevil (Sitophilus zeamais).
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 red flour beetle also attracts similar species including:
- Granary weevil (Sitophilus granaries)
- Maize weevil (Sitophilus zeamais)
- Bearded weevil (Rhinostomus barbirostris)
Recommended monitoring systems & treatment for the Rice Weevil:
- Hanging NoSurvivor Trap with PTL Multi-Species Bullet Lure (IL-408)
- Dragnet Dust
