The rice weevil is a small beetle that infests grain products like rice and wheat. The adult is 1/8 inch long with reddish-brown or black coloring and four spots on its wings. It lays eggs in grains, and the legless white larvae feed within the grains. The full lifecycle from egg to adult can take as little as 26 days in warm conditions. Rice weevils damage grain by eating into it and reducing its quality. Control methods include inspecting for infestation, discarding heavily infected material, freezing food below 0°F for 3 days or heating to 140°F for 15 minutes to kill all life stages.

1. RICE WEEVIL
By
Dr. S N Bhalerao

2. Kingdom : Animalia
Phylum : Arthropoda
Class : Insecta
Order : Coleoptera
Family : Curculionidae
Genus : Sitophilus
Species : Oryzae
CLASSIFICATION

3. • Adults are about 1/8 inch long, reddish brown to black
with four reddish or yellowish spots on the wing covers
(elytra).
• The head bears a slender snout and
shield behind the head (pronotum)
has course round punctures.
• The elytra have deep lines
(striae) and course punctures.
• Larvae are legless, white and rotund with a distinct
head capsule.
• The granary weevil has elongated punctures on the
pronotum and is wingless.
Identification Marks

4. LIFE CYCLE OF RICE WEEVIL
ADULT
LARVA INSTARS
EGGS
ADULT

5. Life Cycle
• The female lives 4 to 5 months, and lays a total of
300 to 400 eggs.
• Like the granary weevil, she bores a small hole in
the kernel with her mandibles, lays an egg in it,
and covers the hole with a gelatinous fluid.
• The small, white, legless larva, with a brownish-
black head, has 3-4 instars. In warm weather, the
combined stages from egg to pupa may take as
few as 26 days.
• After emergence, the adult stays in the kernel for 3
or 4 days, hardening and maturing, then bores its
way out.

6. • This weevil is basically a grain pest, but has been
reared from solidified farinaceous products stitch
as macaroni or caked flour.
• The most favorable temperatures for development
are 27 to 30° C.
• Approximately below 7° C, the beetle is dormant.
• It usually dies after 2 weeks of freezing
temperatures, or after an hour at 49° C.

7. • The adults bore into the grain and lay their eggs in
the grain.
• The larva feeds inside a kernel of grain in which
both larva and pupa completes their development.
• Both larvae and adults eat similar food.
NATURE OF DAMAGE

8. • The adult can crawl or fly about and feed
on various products.
• They have been reported to occur on
beans, nuts, cereals wheat products,
and grapes and damage them.
• They have also been observed sucking
the juice from apples and pears,
gradually forming cavities in which they
concealed themselves.

9. Control Measures
• Control of these insects involves inspection and
removal of infested food products.
• Discarding the heavily infested material, repackaging
material in new containers, and vacuuming kitchen
cabinets.
• Rice weevils in all stages of development can be
killed by freezing infected food below 0o
F for a period
of three or more days.
• These Rice weevils can also be removed by heating
to 140o
F for a period of 15 minutes.
…

10. Control Measures
• Control of these insects involves inspection and
removal of infested food products.
• Discarding the heavily infested material, repackaging
material in new containers, and vacuuming kitchen
cabinets.
• Rice weevils in all stages of development can be
killed by freezing infected food below 0o
F for a period
of three or more days.
• These Rice weevils can also be removed by heating
to 140o
F for a period of 15 minutes.
…