Lesson 2: Bollworm

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Lesson 2 Bollworm
The moth is large and, brown or gray with specks
that form a V-shaped mark on the fore wings. The
hind wings are dull-colored, with a black border
(Fig.).
Bollworm moth
The female moth lays spherical yellowish eggs in
singles on the young sorghum heads (Fig.).
Egg of Bollworm
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Lesson 2 Bollworm
The young larvae are whitish-green. Fully-grown
larvae vary from almost black, brown or green to
pale yellow or pink with light and dark stripes.
Fully-grown larvae are about 40 mm long (Fig.).
The larval period lasts from 18 to 25 days when
the sorghum heads are damaged.
Bollworm larva
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Lesson 2 Bollworm
Crop damage Bollworms infest both whorls of
leaves and earheads of sorghum. Infestation of
earheads is more serious than infestation of
whorls. Larvae that hatch from eggs feed on
tender, folded leaves in the whorl, before
earheads are available for them to
infest. Damage to leaves usually does not affect
yield.
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Lesson 2 Bollworm
Crop damage Infestation of sorghum earheads is
of concern because Bollworm larvae feed on
developing seeds. Small larvae at first feed on
florets, then hollow out developing seeds.
About 80 damage is caused by grownup larvae.
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Lesson 2 Bollworm
Crop damage Larval excrement or frass is common
in infested heads and may be seen on the tops of
upper leaves or on the ground under
plants. Under certain conditions, seeds of
infested earheads may develop mold fungus.
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Lesson 2 Bollworm
Management Natural mortality, predators,
parasites, pathogens, and cannibalism among
larvae suppress abundance of Bollworms in sorghum
whorls and panicles.
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Lesson 2 Bollworm
Management An important management tactic is to
use cultivars with loose or open panicles. Larvae
on open panicles are exposed to predaceous
insects and birds.