Stored grain pests_bd4edbe7a273cbe1ca0817aec7836311

Overview of Stored Grain Pests

  • In India, post-harvest losses due to pests account for about 10% of total food grains.

  • Economic losses from grain-infesting insects arise not just from consumption but also from contamination.

  • Approximately 500 species of insects are associated with stored grains, with nearly 100 species causing significant economic damage.

Types of Storage Insect Pests

  • Primary Storage Pests: Insects that damage sound grains.

    • Internal Feeders: Damage occurs within the grain.

    • External Feeders: Feed on the surface or damaged grains.

  • Secondary Storage Pests: Attack already damaged grains.

Primary Storage Pests (Internal Feeders)

1. Rice Weevil

  • Scientific Name: Sitophilus oryzae

  • Family: Curculionidae

  • Order: Coleoptera

  • Description: Reddish-brown beetle, approx. 3 mm long with elongated rostrum.

  • Bionomics: Active from April to October, lays ~400 eggs on grains. Larval stage in grain.

  • Damage: Creates holes (~1.5 mm diameter); causes significant loss of grain integrity.

2. Lesser Grain Borer

  • Scientific Name: Rhyzopertha dominica

  • Family: Bostrychidae

  • Order: Coleoptera

  • Description: Small, dark brown cylindrical beetle (~3 mm long).

  • Bionomics: Breeds from March to November; lays 300-400 eggs.

  • Damage: Destroys grain down to shells, produces a lot of frass.

3. Angoumois Grain Moth

  • Scientific Name: Sitotroga cerealella

  • Family: Gelechiidae

  • Order: Lepidoptera

  • Description: Buff to greyish-brown moth with narrow wings.

  • Bionomics: Overwinters as a larva; lays ~150 eggs.

  • Damage: Feeds on grain kernels, leaving exit holes and pellets of excreta.

4. Pulse Beetle

  • Scientific Name: Callosobruchus chinensis, C. maculatus

  • Family: Bruchidae

  • Order: Coleoptera

  • Description: Oval, chocolate-brown beetle (~3-4 mm long).

  • Bionomics: Breeds actively from March to November; 7-8 overlapping generations/year.

  • Damage: Makes small holes in grains and lays eggs on surfaces.

5. Cigarette Beetle

  • Scientific Name: Lasioderma serricorne

  • Family: Anobiidae

  • Order: Coleoptera

  • Description: Light brown, humped appearance; measures ~3 mm.

  • Damage: Attacks tobacco products; leaves circular pin-sized holes.

Secondary Storage Pests

1. Saw Toothed Grain Beetle

  • Scientific Name: Oryzaephilus surinamensis

  • Family: Silvanidae

  • Order: Coleoptera

  • Damage: Scavenges on grains, creating surface holes.

2. Long Headed Flour Beetle

  • Scientific Name: Latheticus oryzae

  • Family: Tenebrionidae

  • Order: Coleoptera

  • Damage: Attacks milled products and flour, feeding on grains.

3. Flat Grain Beetle

  • Scientific Name: Cryptolestes minutus

  • Family: Cucujidae

  • Order: Coleoptera

  • Damage: Infests flour, rice, and other grains, causing spoilage.

Management of Storage Pests

Preventive Measures

  • Proper drying of grains before storage.

  • Clean storage areas and seal cracks to prevent pest entry.

  • Maintain cleanliness to eliminate hiding places.

Curative Measures

  • Ecological Control: Manage temperature and moisture to create unfavorable conditions for pests.

  • Fumigation: Use ethylene dichloride and carbon tetrachloride for grain storage.

  • Chemical Treatments: Apply malathion at recommended rates for seed treatment and storage disinfestation.

Storage Recommendations

  • Use insect-proof storage bins (e.g., metal or reinforced structures) to protect stored grains.

Key Identification Points

  1. Rice Weevil - Irregular holes on grains.

  2. Lesser Grain Borer - Dark brown beetle with a unique head shape.

  3. Pulse Beetle - Circular exit holes in grains.

  4. Cigarette Beetle - Pin-sized holes in tobacco products.

  5. Sweet Potato Weevil - Ant-like appearance with a long snout.

Quiz Questions (Sample)

  1. The presence of 1.5 mm diameter holes in grains indicates damage by the Rice Weevil.

  2. The lesser grain borer is identified by a deflexed head and is known for its migration capabilities.

  3. Damage by the Potato Tuber Moth occurs in both fields and storage.

  4. Khapra Beetle can be effectively collected by placing bags on heaps of grain to trap them.