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Crop Protection :: Storage insects and their management
  • In India, post-harvest losses caused by the unscientific storage, insects, rodents, micro-organisms etc., account for about 10 per cent of total food grains.
  • The major economic loss caused by grain infesting insects is not always the actual material they consume, but also the amount contaminated by them and their excreta which make food unfit for human consumption.
  • About 500 species of insects have been associated with stored grain products. Nearly 100 species of insect pests of stored products cause economic losses
 Storage insect pests are categorized into two types viz.,
  • Primary storage pests
  • Secondary storage pest

Primary storage pests: Insects that can damage sound grains are called as primary storage pests

    Common name Pest Host

Rice weevil

Sitophilus oryzae, S. zeamais, S. granarius

Rice, wheat, sorghum, barley, maize

Khapra beetle,

Trogoderma granarium

Cereals, groundnut and pulses

Angoumois grain moth

Rhyzopertha dominica

Paddy, maize and wheat

Lesser grain borer

Sitotroga cerealella

Rice, wheat and maize

Pulse beetle

Callosobruchus chinensis, C. maculatus

Pulses, bean and gram

Tamarind/Groundnut Bruchid

Caryedon serratus

Ground nut, tamarind and other legumes

Cigarette beetle

Lasioderma sericorne

Wheat flour, cereal bran, peanuts, cocoa beans, spices, turmeric, chillies, ginger, stored tobacco, cigarette

Drug store beetle

Stegobium paniceum

Turmeric, coriander, ginger, dry vegetable and animal matter

Sweet Potato weevil

Cylas formicarius

Sweet Potato

Potato tuber moth

Pthorimaea operculella

Potato

Secondary storage pest: Insects that damage broken or already damaged grains viz.,

Common name Pest Host

Red flour beetle

Tribolium castaneum
Tribolium confusum

Broken grains, damaged grains, milled products, machinery

Long headed flour beetle

Latheticus oryzae

 

Saw toothed grain beetle

Cryptolestus minutas, Laemophloeus pusillus

Dry fruits ,roce heat, maize,cereals andoil seeds

Rice moth

Corcyra cephalonica

Cereals, oilseeds nuts, dry fruits, rice and pulse

Fig moth or almond moth

Ephestia cautella

 

Indian meal moth

Plodia interpunctella

Maize, cereals, dry fruits, groundnut, and cereals products

Primary storage pests

 
1. Rice weevil: Sitophilus oryzae, S. zeamais, S. granarius
Host range: Wheat, rice, maize, jowar, paddy.
Symptoms of damage
  • Both grub and adults cause the damage.
  • Grains are hollowed out; kernels are reduced to mere powder. S. oryzae and S. zeamais starts its attack in field itself.
  • Adults cut circular holes. Heating takes place during heavy infestation, which is known as ‘dry heating’.

Identification of the pest

  • Egg - Translucent white, plugs the egg hole with gelatinous secretion, laid singly on grains.
  • Grub - White with yellowish brown head, apodous, fleshy, curved, remains within the grain
  • Pupa - Pupates inside the grain.
  • Adult - Small, reddish brown to chocolate coloured weevils has characteristic snout, and the elytra have four yellow spot
Larva Weevil
 
2. Khapra beetle: Trogoderma granarium

Host range: Wheat, maize, jowar, rice, pulses, oil seeds and their cakes.
Symptoms of damage

  • Adults are harmless. Grub damages the grain starting with germ portion, surface scratching and devouring the grain.
  • It reduces the grain into frass.
  • Excessive moulting results in loss of market value due to insanitation caused by the cast skin, frass and hair.
  • Crowding of larvae leads to unhygienic conditions in warehouses.
  • Damage is confined to peripheral layers of bags in bulk storage.

Identification of the pest

  • Egg - Eggs are laid on the grains or crevices.
  • Grub - Grub is straw coloured with dark brown hairy bands on each segment and typical posterior tuft forming a tail of long hairs. It is active, move and feed freely.
  • Pupa - Pupation takes place on the surface of the grain in bulk and overlapping edges of bags.  
  • Adult - Reddish brown, convex, oval in shape with practically no distinct division of head, thorax and abdomen. Abdomen size is comparatively larger.
Adult Grub
 
3. Lesser grain borer/Hooded grain borer/paddy borer beetle: Rhyzopertha dominica
Host range: Paddy, rice, wheat, maize. 
Symptoms of damage
  • Grubs and adults cause damage and are voracious feeders.
  • Adults reduce the grain kernels to mere frass.
  • Grubs eat their way into the grain or feed on the grain dust and are capable of attacking grain externally.

Identification of the pest

  • Egg - Eggs are laid on the surface or on the interstices of cereal grains singly or in clusters.
  • Grub - White, apodous with brown head, free living upto 3rd instar.
  • Pupa - Grub enters the grain after 3rd instar for pupation.
  • Adult - Brown to blackish beetle, head is deflexed down wards below prothorax to such an extent that it is almost hidden in a dorsal view. Antenna clubbed with large loose three segments.
Adult
 
4. Angoumois grain moth or Grain moth: Sitotroga cerealella
Host range: Paddy, maize, jowar, barley and wheat (rarely). 
Symptoms of damage
  • Larvae damage grains, adults being harmless.  
  • Grains are hollowed out.
  • It attacks both in fields and stores.
  • In stored bulk grain, infestation remains confined to upper 30 cms depth only.
  • Caterpillar enters the grain through crack or abrasion on grain.
  • It feeds inside and remains in a single grain only.

Identification of the pest

  • Egg - White eggs on the surface of damp grains in stores or fields, which soon become red.
  • Larva - White with yellow head.
  • Pupa - Pupates in cocoon inside the grain.
  • Adult - Dirty yellowish brown with narrow pointed wings completely folded over back in a sloping manner.
Larva Adult
 
5. Pulse beetle: Callosobruchus chinensis, C. maculatus

Host range: All whole pulses, beans and grams. 
Symptoms of damage

  • Grubs eat up the grain kernel and make a cavity.
  • Adults come out making exit holes.

Identification of the pest

  • Egg - Laid singly, glued to the surface of the pod (in fields) or on grains (in stores). Fresh eggs are translucent, orange cream in colour, changing to greyish white with age.
  • Grub - Fleshy, curved, creamy white in colour with black mouth parts.
  • Pupa - Pupation takes place in a pupal cell prepared beneath the seed coat.  
Adult
  • Brownish grey beetle with characteristic elevated ivory like spots near the middle of the dorsal side.
  • It is small, short, and active with long conspicuous serrate antenna.
  • Elytra do not cover the abdomen completely, which is called as pygidium.
  • Adults are short lived, it is harmless and do not feed on storage produce at all
Egg Pupa Adult
 
6. Tamarind/Peanut bruchid: Caryedon serratus 
Symptoms of damage
  • Grub causes the damage.
  • Circular hole on fruits and seeds of tamarind both in tree and storage.
Identification of the pest
  • Adult: Small grey coloured beetle.

Identification of the pest

  • Egg - Laid singly, glued to the surface of the pod (in fields) or on grains (in stores). Fresh eggs are translucent, orange cream in colour, changing to greyish white with age.
  • Grub - Fleshy, curved, creamy white in colour with black mouth parts.
  • Pupa - Pupation takes place in a pupal cell prepared beneath the seed coat.  
Adult
  • Brownish grey beetle with characteristic elevated ivory like spots near the middle of the dorsal side.
  • It is small, short, and active with long conspicuous serrate antenna.
  • Elytra do not cover the abdomen completely, which is called as pygidium.
  • Adults are short lived, it is harmless and do not feed on storage produce at all
Egg Pupa Larva Adult
 
7. Cigarette beetle: Lasioderma sericorne
Host range: Wheat flour, cereal bran, peanuts, cocoa beans, cottonseed, spices and even
insecticides containing pyrethrum, meat and fishmeal, ginger, turmeric and chillies.
Symptoms of damage
  • Grub causes the damage which made circular, pinhead sized bore holes on processed tobacco.

Identification of the pest

  • Grub: White, fleshy and hairy grub.
  • Adult: Small, robust, oval, light brown round beetle with its thorax and head bent downward gives the insect a humped appearance. Elytra have minute hairs on them and are not striated.
Grub Adult Infected Cigarette
 
8. Drug store beetle: Stegobium paniceum

Host range: Turmeric, coriander, ginger, dry vegetable and animal matter.
Symptoms of damage

  • Circular pinhead sized bore holes, caused by grubs
Identification of the pest
  • Grub: Similar to cigarette beetle but not hairy.  
  • Adult: Reddish brown round beetle with striated elytra and clubbed antenna.
Grub Adult
 
9. Sweet Potato weevil: Cylas formicarius 

Host range: Sweet Potato: Potato
Symptoms of damage

  • Grubs and adults bore into tubers, field and storage.
  • Adult weevils feed on vines,  leaves
 

Identification of the pest

  • Egg - laid in cavities on vines or tubers
  • Pupate inside vine or tuber inside tuber
  • Adult- - Slender, antlike with long snout, shiny black with reddish brown thorax and leg
Larva Weevil
 
10. Potato tuber moth: Pthorimaea operculella 

Host range: Potato: Potato
Symptoms of damage

  • Larvae mine into leaves or bore into tender shoots and developing tubers.
  • Rotting and foul smelling of damaged tubers
 

Identification of the pest

  • Egg-laid singly on under surface of leaves and exposed tubers   
  • Larvae - Pale greenish
  • Pupa - silken cocoon among trash or ground or bags...
  • Adult - small dark brown moth with fringed wings; forewings grey brown with dark spots and hind wings dirty white.

 

Larva Adult
 Secondary storage pests
 
11. Rust red flour beetle: Tribolium castaneum

Confused flour beetle: Tribolium confusum, 
Host range: Broken grains/ mechanically damaged grains, germ portion and milled products. Heavy infestation causes stinking odour in flour, adversely affecting the dough quality. It is an important pest for mill machinery.

Symptoms of damage

  • Grubs feed on milled products.
  • Flour beetles are secondary pests of all grains and primary pests of flour and other milled products.
  • In grains, embryo or germ portion is preferred.
  • They construct tunnels as they move through flour and other granular food products.
  • In addition they release gaseous quinines to the medium, which may produce a readily identifiable acid odour in heavy infestations.

Identification of the pest

Egg - White, translucent, sticky, slender and cylindrical. 
Grub - Worm like, whitish cream colour, faint stripes, two spines like appendages at the end segment. 
Pupa - Pupa remains loosely lying in the grain and is naked. 
Adult - Oblong, flat, brown in colour. In T. confusum, the compound eyes are completely notched and antennae are not gradually thickened whereas in T.castaneum, the notch is not complete and antennae have a clear 3-segmented club.

Grub Adult
 
12. Long headed flour beetle: Latheticus oryzae

Host range: Cereal flours, packaged food, rice and rice products, grains with excessive dust, dockage and broken grains with high moisture contents preferred.

Symptom of damage : Both grubs and adults feed. 

Identification

Egg - White, smooth, cylindrical eggs at random in grain and seams of the bags. 
Grub - Active grub feeds voraciously. 
Pupa - Pupa is naked. 
Adult - Light brown with elongated body, resembles Tribolium sp. Antennae shorter than head, 11 segmented with 5 clubbed apical segments.

Grub Adult
 
13. Flat grain beetle: Cryptolestus minutas, Laemophloeus pusillus

Host range: Rice, maize, wheat with excessive brokens, different flours, groundnut particularly with high moisture and mouldy grain.

Symptoms of damage
  • Both adults and grubs feed on stored products and are important pests of mills.
  • Grubs feed on germ portion and even on dead insects.
  • Adults are only scavengers, cause heating in grain and flour in case of heavy infestation.
Identification of the pest

Egg: White eggs are laid loosely in flour, grain or crevices. 
Grub: Cigar like, yellowish white with two reddish brown spines at anal segment. 
Pupa: Matured larvae pupate in a gelatinous cocoon covered with dust particles. 
Adult: Tiny, light to dark reddish brown beetle with filiform antennae.

Adult
 
14. Saw toothed grain beetle: Oryzaephilus surinamensis
Host range: Rice, wheat, maize, cereal products, oil seeds and dry fruits.
Nature of damage 
Adults and grub cause roughening of grain surface and off odour in grain. 
Grains with higher percentage of broken, dockage and foreign matter sustain heavy infestation, which leads to heating of grain.

Identification of the pest

Egg: Whitish eggs laid loosely in cracks of storage receptacles or godowns. 
Grub: Grub is slender, pale cream with two slightly darker patches on each segment. 
Pupa: Full grown grub makes protective cocoon like covering with sticky secretion. 
Adult:: Narrow, flattened, thorax having six teeth like serrations on each side. Antenna clubbed. Elytra cover abdomen completely.

Grub Adult
 
15. Rice moth: Corcyra cephalonica 

Host range: Rice, jowar, other millets, whole cereals, cereal products, pulses, processed products of cereals, pulses, oil seeds, nuts, dry fruits and milled spices.

Symptoms of damage

Larva is only responsible for damage.
It contaminates food grains with frass, moults and dense webbing. 
In whole grains, kernels are bound into lumps upto 2 kg

Identification of the pest

Egg: Small, oval, elliptical laid on wall, bags or on grain.

Larva: Creamy white has prothoracic shield.

Pupa: It webs silken shelter before pupation. In case of heavy infestation cocoons may be seen sticking to the grain bags. Cocoon dense white and tough.

Adult: Pale buff brown colour, forewings pale yellowish green and grey white hind wings.

Larva Adult
 
16. Fig or Almond or Warehouse moth: Ephestia cautella

Host range: Wheat, rice, maize, jowar, groundnuts, spices.

Symptoms of damage

Larva feeds on germ portion leaving the rest of the kernel undamaged. 
In bulk infestation its damage is limited to peripheral top layers only. 
Web formation covers the bags, floor-space and mill machinery thereby leading to clogging in mills.

Identification of the pest

Egg: Eggs are laid in grains exposed at the sampling tube spots in jute bags.

Larva: Greyish white, hairy with dark brown head with 2 dark areas on the first segment behind the head.

Pupa: Spins silken cocoon at the time of pupation.

Adult: Dirty white to greyish in colour with indistinct black bands
Larva Adult
 
17. Indian meal moth: Plodia interpunctella

Host range: Maize, cereals, dry fruits, groundnuts and cereal products.

Symptoms of damage
  • Larva causes serious damage to ear and grain of maize; contaminates the grain with excreta, cast skins, webbings, dead individuals and cocoons; prefers to eat the germ portion and hence grains lose viability.
  • It feeds superficially but may construct more than one silken tunnel.

Identification of the pest

Egg: Greyish white with granular surface, laid indiscriminately at night.

Larva: Transparent, dirty white, skin is granular with hairy body.

Pupa: Straw coloured, changes colour to greyish with age, in silken cocoon.

Adult: Forewing basal half silver white or greyish, outer 2/3 portion is reddish copper bronze lustre with irregular bands

Larva Pupa Adult
Updated on April 2, 2014


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