Global loss in stored products, caused by insects, have been estimated to be between five and ten percent. In the tropics it may reach upto 30%. Insects not only cause direct loss through consumption of kernels but also indirect losses which includes accumulation of frass, exuviae, webbing and insect cadavers. High levels of this insect detritus may result in grain that is unfit for human consumption. Storage insect pests are categorized into two types viz.,

 

1. Primary storage pests are those capable of penetrating and infesting intact kernels of grain, and have immature stages that can readily develop within a kernel of grain. 

Insect

Family : order

Damaging stage

Damage symptom

Images

Rice weevil

Sitophilus oryzae

Curculionidae: Coloeoptera

Grubs and adults

Grubs feed inside, grains are hollowed out and in some cases the kernels are reduced to powder. Adults make irregular holes on the grains.

Adult weevil 

Adult weevil

Khapra beetle

Trogoderma granarium

Dermestidae:Coleoptera

Grubs

Grubs mainly attacks the grains of wheat, maize, sorghum, pulses and oil seeds. Grubs remain on the top few layers of the bulk grains

 

 Grub

Pulse beetles

Callosobruchus chinensis

C. maculatus

C. analis

Bruchidae: Coleoptera

Grubs

Individual eggs are laid on pulses by adult beetle and the emerging  grubs feed on the inner contents and pupates inside the grain

 Egg and Adult

Cigarette beetle

Lasioderma serricorne

Anobiidae:Coleoptera

Grubs and adults

Grubs and adults feed on stored tobacco, turmeric, chillies and ginger

 Adult

Angoumois Grain Moth

Sitotroga cerealella

 

Gelechidae Lepidoptera

Larvae

Infestation confined only to upper 30 cms depth. Larvae makes hole and feeds the internal content. Pupation takes place inside the grain. Adult emerge out by circular 'flap ' or 'trap door '.

Adult

2. Secondary storage pests cannot infest sound grain but feed on broken kernels, debris and grain damaged by primary insect pests. In general, the immature stages of these species are found external to the grain. 

Insect

Family : Order

Damaging stage

Damage symptom

Images

 Rust Red flour beetle

Tribolium castaneum
T. confusum

Tenebrionidae: Coloeoptera

Grubs and adults

Grubs and adults feed on milled products but  can also attack broken grains

 

Adult

Almond moth

Ephestia  cautella

Phyctidae:Lepidoptera

Larvae

The larvae webs the grains and feed on germ portion leaving the rest of the kernel undamaged

 

Larvae

Rice moth

Corcyra cephalonica

Galleridae:Lepidoptera

Larvae

Larvae pollutes food grains with frass, moults and dense webbing

 

Larvae

Indian meal moth

Plodia interpunctella

Phyctidae:Lepidoptera

Larvae

Insect prefers to feed on the germ portion, hence the grains lose viability.Larvae contaminates the grain with excrement, webbings, dead individuals and Exuviae.   

 

 

Saw toothed grain beetle

Oryzaephilus surinamensis

Cucjidae:Coleoptera

Grubs and adults 

Grubs and adults feeds grains which are already damaged by primary pests

 

Flat grain beetle

Cryptolestes minutus

Cucjidae: Coleoptera

Grubs and adults 

Grubs attacks only broken grains

 

Long headed flour beetle

Latheticus oryzae

Tenebrionidae:  Coleoptera

Grubs and adults 

Grubs attacks only broken grains

 

The integrated pest management (IPM) approach for stored grain includes:

  1. Sanitation:
  • It should be maintained at both field and storage godowns.
  • Undergo clean harvest.
  • Both harvesting and threshing machines need to be thoroughly cleaned prior to use.
  • Never store a new crop along with the old grain.
  • Cracks and crevices should be properly sealed
  • Remove spilled grain outside the storage structure.
  • Rat burrows to be closed with a mixture of broken glass pieces and plastered with cement.
  • For additional protection, the inside and outside surfaces, foundations and floor of a storage facility should be treated with a residual insecticide, four to six weeks prior to harvest.
  • The grain is monitored every 2-3 weeks during throughout storage period
  • careful monitoring should  be done on the following parameters:Aeration is used to dry and cool the newly stored grain there by prevent the development of hotspots. It is also used to prevent moisture migration when ambient temperatures drop below that of the grain temperature.
    • Grain quality
    • Grain temperature
    • Insects and insect density
    • Hot spots
    • Mould growth
    • Any “off odor”
  1. Frequent monitoring: Pest monitoring is an important component in the post-harvest IPM practice for stored grain
  1. Aeration
  1. Pesticide treatments

Infestation develops due to hidden or cross infestation, which could be effectively managed by using the following insecticides and fumigants.

Grain protectants: it is not advisable to mix the chemical dust along with food grains as it is meant for human consumption. However, they can be mixed with the grains meant for seed purposes only. Pyrethrum dust, Spinosad dust etc. are normally used as seed protectants.

Fumigants: Properly conducted fumigation will stop insect infestation and effectively reduce the pest populations.

Aluminum phosphide: This is a most widely used fumigant in India and available in the market under trade name Celphos of 3 gm tablets. The phosphide pellets or tablets release phosphine gas as they are exposed to moisture in the air. The recommended dose is 3tablets/tonne of grains.

Reference:

TnauAgritech Poratal - http://agritech.tnau.ac.in/index.html

David¸B.V and Ramamurthy, V.V. 2012. Elements of economic entomology. Book Chapter: Insect pests of Stored grain Products.


Authors:

Guru Pirasanna Pandi G., Soumia P.S. and Thava Prakasa Pandian R.

Ph D Scholars, Indian Agricultural Research Institute, New Delhi.