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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This cold-hardy species has a climatic<br />
plasticity index <strong>of</strong> 330. It feeds<br />
not only on cereals but also on nuts,<br />
dried fruits, and other dry foods inside<br />
groceries and households.<br />
It prefers the germ, bran, and<br />
endosperm (in that order), and can<br />
overwinter in unheated granaries in<br />
temperate countries.<br />
Lesser grain borer<br />
Scientific name: Rhizopertha dominica<br />
Fabricus<br />
Common name: lesser grain borer or<br />
Capucine beetle<br />
Quarantine status: primary pest<br />
Stage <strong>of</strong> entrance to <strong>seed</strong>: larva<br />
The adult's body is 2.5-3 mm long<br />
and dark brown. Diagnostic features<br />
include a cylindrical body with rows<br />
<strong>of</strong> round punctures on the hard wing<br />
cover; deflexed head, hidden by a<br />
prothorax which has a coarsely tuberculate<br />
anterior margin; and antennae<br />
with large and distinctly<br />
separated 3-segmented club. It lives<br />
1 yr.<br />
Each female lays 300-600 eggs<br />
loose among the grains. Larvae feed<br />
on inner and outer parts <strong>of</strong> the grain.<br />
They prefer the endosperm and can<br />
tolerate grain moisture as low as 8%.<br />
The larvae are grublike and have<br />
front legs. The head is withdrawn<br />
into the-curved body. The life cycle<br />
is 4-5 wk.<br />
The adult is a strong flier. The<br />
presence <strong>of</strong> flour dust inside a warehouse<br />
indicates heavy infestation by<br />
the lesser grain borer. The insect is<br />
voracious but does not attack leguminous<br />
and sunflower <strong>seed</strong>s.<br />
Granary weevil<br />
Scientific name: Sitophilus granarius<br />
(Linnaeus)<br />
Common name: granary weevil<br />
Quarantine status: primary pest;<br />
unable to fly and thus can only infest<br />
grains in storage<br />
Stage <strong>of</strong> entrance or attachment to<br />
<strong>seed</strong>: egg, larva, pupa, adult<br />
The body <strong>of</strong> the adult is 2.5-4.7 mm<br />
long and shiny reddish brown to<br />
black brown with no spots on the<br />
wings. It may be confused with the<br />
<strong>rice</strong> and maize weevils. The granary<br />
weevil’s diagnostic features include<br />
sparse oblong-oval or elongated<br />
punctures on the thorax, and a head<br />
telescoped into a distinct snoutlike<br />
structure. The adult lives 3-8 mo.<br />
The adult cannot fly because <strong>of</strong> its<br />
poorly developed hindwings.<br />
Each female lays 50-400 eggs singly<br />
in a hole chewed in a <strong>rice</strong> <strong>seed</strong>.<br />
Each larva hollows out its <strong>seed</strong>. The<br />
larva is grublike, white, legless, has a<br />
brown head, and the lower side <strong>of</strong> its<br />
body is straight. The life cycle is<br />
4-8 wk. If physically disturbed, larvae<br />
do not successfully complete development.<br />
The granary weevil is a coldhardy<br />
species with a climatic plasticity<br />
index value <strong>of</strong> 173. The adult<br />
feeds on whole stored cereals and<br />
leaves small holes on damaged<br />
<strong>seed</strong>s. When disturbed, the adult<br />
feigns death, as does S. oryzae. The<br />
granary weevil does not develop on<br />
millet, oil <strong>seed</strong>s, and pulses except<br />
chickpeas.<br />
Insect pests 71