Albert Lea Seed House Oat Production Guide | Page 28

Appendix III
Principle Stored Grain Insects

PRINCIPAL STORED GRAIN INSECTS
Granary Weevil Sitophilus granarius
Length: Approximately 4 mm
Small, moderately polished, blackish or chestnut-brown beetle. The head extends into a long slender snout
with a pair of stout mandibles or jaws at the end. There are no wings under the wing covers, and the thorax
is well marked with longitudinal punctures, two characteristics that distinguish this insect from the closely
related rice weevil with which it is often found.
The adult live an average of 7 to 8 months. Each female lays 50 to 250 eggs during this period.
After mass infestation, the grain becomes warm and damp, this leading to the formation of mold.
rice Weevil Sitophilus oryzae
Length: Approximately 3 mm
Small snout beetle; varies from reddish brown to nearly black and is usually marked on the back with
four light-reddish or yellowish spots. It has fully developed wings beneath the wing covers. The thorax is
densely pitted with somewhat irregularly shaped punctures; except for a smooth narrow strip extending
down the middle of the upper (dorsal) side.
The adult live an average of 4 to 5 months, and each female lays 300 to 400 eggs during this period. The
early life stages are almost identical in habit and appearance to those of the granary weevil.
maize Weevil Sitophilus zeamais
Length: Approximately 5 mm
A small snout beetle. It varies from dull red-brown to nearly black and is usually marked on the back
with four light reddish or yellowish spots. It is slightly larger than the rice weevil and has more distinct
colored spots on the forewings.
The maize weevil has fully developed wings beneath its wing covers and can fly readily. The thorax is
densely pitted with somewhat irregularly shaped punctures, except for a smooth narrow strip
extending down the middle of the dorsal (top) side.
While developing, the larvae eat the internal contents of the maize; approximately 18 to 23 days.
cadelle Tenebroides mauritanicus
Length: Approximately 9 mm
An elongate, oblong, flattened, black or blackish beetle.
Both the larva and adult feed on grain and have the destructive habit of going from kernel to kernel
devouring the germs. Found in mills, granaries, and storehouses where it infests flour, meal, and grain.
It is one of longest lived of the insects that attack stored grain. Many of the adults live for more than 1
year and some of them for nearly 2 years. Both the larvae and adults can live in the woodwork of the
bin for a long time after the grain has been removed.
lesser Grain Borer Rhizopertha dominica
Length: Approximately 3 mm
Slender, cylindrical form and small size. Polished dark brown or black, with a somewhat roughened
surface. The head is turned down under the thorax and is armed with powerful jaws used for cutting
into wood.
Both the beetles and larvae cause serious damage in warm climates by attacking a great variety of
grains.
The eggs are deposited on the outside of the kernels. Badly infested wheat takes on a honey-like odor.
United StateS department of agricUltUre
grain inSpection
packerS and StockyardS
adminiStration

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national grain center
10383 n. ambaSSador drive
kanSaS city, miSSoUri 64153
[phone]