TNAU Agritech Portal :: Crop Protection

Crop Protection :: Grain Storage

Stored grains protection can be divided into two broad areas based on the type of intervention followed.

Preventive measures and
Curative measures

I. Preventive measures
Sanitation and handling of grains

Remove dirt, debris, mud balls, foreign particles, insects and infested grains from healthy grains that will reduce insect infestation.
Proper handling of grains and avoiding hooks on storage bags help minimize exposure to insects
Bags should be stacked on wooden dunnage 0.5 metre away from the wall
Bags should be stacked in rows having space of nearly 2 to 3 metre in-between height of a row should not be more than 15 bags leaving about 1/5thspace of total storage from the roof.
Likewise bulk storage structures should also be kept away from the ventilators or doors
Drying of grains Grains are harvested at a moisture content ranging from 20-28%
Moisture content should be brought to 12-13 percent
Sun drying and use of mechanical dryers can be opted to bring down moisture.
Improper drying of paddy grains during post harvest operations not only enhances the insect infestation but also enhances breakage during milling.
Staggered sun drying with short exposure to sun spread over large number of days (9-11 am for 8 days) reduces insect infestation.
Use of improved storage structures Gunny bags or jute bags with close weaves can reduce insect infestation.
Impregnation of gunny bags with insecticides can prevent entry of insects (Prakashet al., 1981).
Polythene lined gunny bags were suggested by Muthu and Pingale, 1955).
Polyester- polythene 400 gauge lined canvas was found to be resistant to all types if insect attack.
Improved storage structures namely aluminum bin, Pusa bin, Pusa cubicle PAU bin, IGSI domestic bin
TNAU insect removal bins have been found very effective for bulk storage and reducing insect damage.

Dis-infestation of stores/receptacles

Treatment of bulk and bag storage structures with insecticides is an important practice to avoid latent infestation in reused bags and bulk storage structure.
The insecticides commonly recommended are malathion and dichlorvos.
Legal method In India, the Destructive insects and Pests Act started in 1914.
Plant Quarantine Order 2003, govern the regulation or restriction of movement of insects through commodities into the country and among different areas within the country.
Grains or other commodities are thoroughly checked and treated at ports to avoid entry of insects.

II. Curative measures Physical control measures
1. Use of low and high Temperatures The insects can be controlled either by increasing or decreasing storage temperature.

Optimal temperature for most of the storage insects is between 25 and 33o C.
Temperatures between 13 and 25o C will slow development.
High temperatures of 35o C and above will stop development.
Refrigerated aeration of grains stored in bins gave results on par with insecticide treatment in Australia
USA and Israel in controlling storage pests (Navarro and Calderon, 1982).
High temperature disinfestations using heated air grain driers, fluidized beds, spouted beds, pneumatic conveyors, a counter flow heat exchanger, high frequency waves microwaves, infra red waves and solar radiations have been satisfactorily used for in disinfesting grains.

2. Mixing of inert dust

Inert dusts used in stored-product protection can be categorized into 4 groups.
The 1st group consists of clays, sand, paddy husk ash, volcanic ash and wood ash.
The 2nd group consists of a great number of minerals such as dolomite, magnesit copper oxy-chloride, rock phosphate, ground sulfur, lime limestone and common salt.
These minerals have been used at rates greater than 10 grams per kilogram of grain
The 3rd group consists of dusts that contain synthetic silica (silicon dioxide).
These materials are light and hygroscopic, and are produced by drying an aqueous solution of sodium silicate.
The 4th group consists of dusts that contain natural silica, such as diatomaceous earth (DE), which are made up fossilized skeletons of diatoms.
Many DE dusts are now commercially available and used in many developing countries for managing stored-product insects and mites, or to improve fumigation efficiency

3. Activated clay

Activated clay (kaolin) has been used in protecting grains from the attack of storage insects.
This method is very effective against most of the storage pests and nontoxic to higher animals.
The kaolinate clay after successive processes of activation with acid and heat can be used as physical poison.
The raw clay (kaolinate clay) having 45% silicondioxide and 38% alumina can be obtained from the Neyveli Lignite Corporation, Neyveli, Tamil Nadu

4. Irradiation

Low dose irradiation completely kills or sterilizes the common grain pests, and even the eggs deposited inside the grains.
Only a single radiation exposure of grains is sufficient for disinfestations.
Ideally suited for large-scale operations, thereby offering substantial economic benefits.
Effective process for disinfestations of certain pre-packed cereal products.
Low dose applications (Less Than 1kGy) has been found useful for Insect disinfestationin stored grain, pulses and products (Tilton et al. 1974)

5. Use of controlled atmosphere

The normal storage atmosphere (or earth’s atmosphere) contains 78% Nitrogen (N2), 21% Oxygen (O2) and 0.03% carbon dioxide (CO2).
In grain storage, insects can be controlled by decreasing O2 or increasing CO2 or N2 concentration in the atmosphere thereby interfering with the normal respiration of insects.
This is achieved by modified atmospheric storage, controlled atmospheric storage or airtight storage

Mechanical control measures

Several mechanical devices have been developed both for monitoring and mass trapping stored product insects.
Entoleters are used primarily in flour mills.
Kernels infested with primary feeders such as Sitophilus sp. R. dominica break apart and are separated from intact kernels.
Other traps: Probe trap, Pulse Beetle Trap, Light traps, Sticky traps, Bait traps, Pheromone traps and TNAU Automatic Insect Removal Bin.

Use of plant products

Neem leaf powder, Nochi leaf powder, turmeric powder, Sweet Flag (Vasambu) Rhizome powder all at 10g /kg have been found to be effective against storage pests.
Experimental results show that the fresh leaves of Nochi mixed with paddy at the rate of 2% w/w protected the grains from insect attack for 9 months.
Garlic extract is yet another plant product which is nontoxic and was found to be grain protectant.
The water extract (0.02%)of bulbs mixed with the grains at the rate of 2 litres/ 100 kg grains can give good protection to paddy grains against insect attack.

Management of stored product pests in Warehouses

Maintain store house hygiene brushing the cracks, crevices and corners, removing all debris and cleaning the entire godown before storing the grains
Reduce moisture content below 10 %
Dry all the bags, bins etc in the sun
Eliminate conditions which favour storage pests sieving and removing all broken grains, stitching all torn bags before filling
Maintain good storage conditions by providing dunnage leaving gangway or alleyway of 0.75 to 1 m all around for aeration inspection prevention of moisture seepage and for fumigation and chemical spraying. Treat the walls, dunnage materials and ceilings of empty godown with Malathion50 EC 10 ml/l or DDVP 76 WSC 7 ml/l at 3 l spray solution per 100 sq m.
Air charge or treat alleyways and gangways with Malathion50 EC 10 ml/l or DDVP 76 WSC 7 m (1 litre of spray fluid /270u.m)
Apply stack spraying over the bags with Malathion50 EC 10 ml/l @ 3litre of spray fluid /100 sq.m

Fumigation

Decide the need for shed fumigation (entire store house or godown) or cover fumigation (only selected blocks of bags).
Check the store house/godown and the black polythene sheets or rubberized aluminium covers for holes and get them ready for fumigation
Choose the fumigant and work out the requirement based on the following guidelines.
Aluminium Phosphide For cover fumigation: 3 tablets of 3 g each per tonne of grain.
For shed fumigation: 21 tablets of 3 g each for 28 cubic metres.
Period of fumigation: 5 days,
In case of cover fumigation Keep ready sand-snakes.
Insert the required number of aluminum phosphide tablets in between the bags in different layers.
Cover the bags immediately with fumigation cover
Plaster the edges of cover all round with wet red earth or clay plaster or
Use sand-snakes to make leak proof.
Keep the bags for a period of 5 -7 days under fumigation
Remove the mud plaster after specified fumigation period and
Lift cover in the corner to allow the residual gas to escape.
Allow aeration and lift cover after a few hours.
Follow similar steps in case of shed fumigation also

Prophylactic treatment of grains/seeds:

If the produce is meant for seed purpose, mix 1 kg of activated kaolin or 1 kg of lindane1.3 D or 1 kg of malathion 5 D for every 100 kg of seed and store/pack in gunny or polythene lined bags
If the produce is meant for grain purpose, Mix 1 kg of activated kaolin for every 100 kg of grain and store.
To protect the pulse grains, Mix activated kaolin at the above dosage or any one of the edible oils at 1 kg for every 100 kg of grains or Mix 1 kg of neem seed kernel powder for every 100 kg of cereal or pulse and store.

NOTE: Never mix synthetic insecticides with grains meant for consumption