A manual of rice seed health testing - IRRI books - International Rice ...
A manual of rice seed health testing - IRRI books - International Rice ...
A manual of rice seed health testing - IRRI books - International Rice ...
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Cryptolestes pusillus Schonherr<br />
The rusty red grain beetle thrives<br />
in hot moist grain. Larvae are coldhardy,<br />
tolerant <strong>of</strong> low relative humidity,<br />
and have a climatic plasticity<br />
index <strong>of</strong> 570. The adult is a strong<br />
flier.<br />
Saw-toothed grain beetle<br />
Scientific name: Oryzaephilus<br />
surinamensis (Linnaeus)<br />
Common name: saw-toothed grain beetle<br />
Quarantine status: primary pest<br />
Stage <strong>of</strong> entrance or attachment to<br />
<strong>seed</strong>: none<br />
The adult’s body is 2.5-3.5 mm long<br />
and dark brown. Although the sawtoothed<br />
beetle can be confused with<br />
the merchant grain beetle<br />
( O. mercator ), O. surinamensis has<br />
smaller eyes and longer rounded<br />
checks behind the eyes. Diagnostic<br />
features include a flat body and the<br />
prothorax bears six prominent teeth<br />
along each side and three longitudinal<br />
ridges on the dorsal side. The<br />
adult usually lives 6-10 mo, but may<br />
survive as long as 3 yr.<br />
Each adult female lays 50-<br />
400 eggs loose among grains. Larvae<br />
feed on the external parts <strong>of</strong> broken<br />
grains. They have long white bodies,<br />
brown heads, and three pairs <strong>of</strong> distinct<br />
legs behind the head; and the<br />
abdomen tapers posteriorly. The larvae<br />
form a protective chamber by<br />
sticking small food particles together.<br />
The life cycle is 4-5 wk.<br />
The saw-toothed grain beetle can<br />
tolerate high moisture content in<br />
grain. Undamaged <strong>seed</strong>s or kernels<br />
are immune to attack, unless they<br />
are moist and s<strong>of</strong>t. The beetle is coldhardy,<br />
tolerant <strong>of</strong> low relative humidity,<br />
and has a climate plasticity<br />
index <strong>of</strong> 500. Scarring and roughing<br />
<strong>of</strong> the food or grain surface indicates<br />
feeding damage <strong>of</strong> this beetle. The<br />
adult is very active but rarely flies.<br />
Indian meal moth<br />
Scientific name: Plodia interpunctella<br />
(Hubner)<br />
Common name: Indian meal moth or<br />
dried fruit moth<br />
Quarantine status: primary pest<br />
Stage <strong>of</strong> entrance or attachment to<br />
<strong>seed</strong>: larva, egg<br />
The adult’s body is 16 mm long and<br />
reddish brown. It may be confused<br />
with the <strong>rice</strong> moth Corcyra<br />
cephalonica. Diagnostic features are<br />
the basal half <strong>of</strong> the forewing is pale<br />
yellow to whitish gray with occasional<br />
dark spots; the rest <strong>of</strong> the<br />
body is reddish brown with a coppery<br />
luster and pale to dark transverse,<br />
irregular, leaden gray stripes.<br />
At rest, the wings are folded closely<br />
together like a ro<strong>of</strong> along the<br />
bodyline and antennae lie flat on the<br />
wings. Mutant forms are common—<br />
e.g., forms without normal color patterns<br />
or with uniformly dark<br />
forewings. The adult lives 14 d.<br />
Each female lays 40-400 eggs on<br />
grain. Larvae feed on both external<br />
and internal parts <strong>of</strong> the <strong>rice</strong>. They<br />
prefer the embryo. Larval color depends<br />
on the food consumed. Larvae<br />
spin silk to bind grains together and<br />
then spin a web over the grains.<br />
Larvae have dirty white legs<br />
(3 pairs on the thorax and 4 on the<br />
abdomen) along a hairy body. Each<br />
side <strong>of</strong> the head has 5-6 eye spots.<br />
The front <strong>of</strong> the head extends<br />
slightly more than two-thirds into a<br />
vertical triangle. The life cycle is<br />
3-8 wk.<br />
70 <strong>Rice</strong> <strong>seed</strong> <strong>health</strong> <strong>testing</strong> <strong>manual</strong>