A manual of rice seed health testing - IRRI books - International Rice ...

CHAPTER 13
Insect pests
J.A. Litsinger and A.T. Barrion
Several dozen insect pests feed on
rice seeds in storage. Although the
rice plant's tough husk is naturally
resistant to most insect pests, several
species can penetrate the seed. These
are called primary pests. Primary
pests are of greatest interest to quarantine.
Most species, however, are
secondary pests that cannot enter or
feed in whole grains. Nevertheless,
poor storage and handling practices
can create quarantine problems
where secondary pests have been
introduced from one country to another
in infested rice straw (e.g.,
stem borer and rice water weevil).
No field pests can be transferred in
whole grains.
The pests discussed here are pests
of stored grain. This group of pests
can present minimal quarantine risk
if the following procedures are followed:
Ship only whole seeds, eliminating
broken grain and detritus from seed
lots,
Do not dry seed in the sun as excessive
heat creates openings between
the lemma and palea, allowing
secondary pests to enter the
whole seed.
Do not stack seed as this creates
pressure that opens the lemma and
palea.
Fumigate seeds to kill all insects
that may be inside.
Rice moth
Scientific name: Corcyra cephalonica
(Stainton)
Common name: rice moth
Quarantine status: secondary pest
Stage of entrance or attachment to
seed: larva, egg
The adult's body is 12-15 mm long
and uniformly gray-brown. Diagnostic
features are the upper side of the
forewing without spots but with
moderately darkened veins; and
straight labial palps that are short
and inconspicuous in the male but
long and prominent in the female.
The moth lives for 1 wk.
Each female lays 100-300 eggs on
grain and in crevices. Larvae develop
in silken chambers that are attached
to milled rice. Pupal cocoons
are dense, white, tough, and occur in
clumps. Larvae are dirty white; the
first abdominal segment bears a
pigmented ring enclosing a membranous
area around the base of the
seta; abdominal spiracles have the
posterior rim prominently thicker
than the anterior part. The life cycle
of the rice moth is 5-7 wk.
The moth commonly attacks
rough rice and is rarely found in
flour mills.
Rusty red grain beetle
Scientific name: Cryptolestes ferrugineus
(Stephens)
Common name: rusty red grain beetle
Quarantine status: primary pest
Stage of entrance or attachment to
seed: larva
The adult's body is 1.5-2 mm long
and light reddish brown. The rusty
red grain beetle can be confused
with Cryptolestes pusillus Schönherr
(see figure on p. 70) or C. turcicus
Grouvelle. Its diagnostic features are
an extremely flat and rectangular
body;
V-shaped, threadlike antennae; and
a thorax with lateral ridges strongly
to moderately contracted posteriorly.
The beetle lives 6-9 mo.
Females lay an average of
423 eggs in cracks and crevices of the
grain, or loosely in farinaceous material,
in intergranular spaces, and in
grain dust. Many larvae are found
outside the grain kernel. Larvae spin
cocoons and prefer the embryo to
the endosperm. They complete their
development exclusively on some
species of seedborne fungi.
Larvae are white to straw-colored
with flat slender bodies; the posterior
end of the abdomen has two
dark slender horns. The life cycle
lasts 4-9 wk.