Seed storage is the maintenance of high seed germination and vigour from harvest until planting.
Importance of seed storage
Seed storage is important to get adequate plant stands in addition to healthy and vigorous plants.
Principles of storage
a. Seed storage conditions should be dry and cool
b. Effective storage pest control
c. Proper sanitation in seed stores
d. Before placing seeds into storage they should be dried to safe moisture limits.
e. Storing of high quality seed only i.e., well cleaned treated as well as of high
germination and vigour.
Stages of seed storage
1. Storage on plants (physiological maturity until harvest)
2. Harvest, until processed and stored in a warehouse
3. In storage's (ware houses)
4. In transit (rail, wagons, trucks, carts, railway shed etc.,)
5. In retail stores
6. On the user's farm
The seed quality can be considerably affected at any stage mentioned above unless sound principles involved in storage are practiced.
Factors affecting seed logevity in storage
1.Genetic factors The storage is influenced by the kind / vareity of seeds. Some kinds are naturally short lived (e.g) onion, soybeans, ground nut etc., Within a crop the storage period varies between varieties. Also the storage periods of hybrid and parent are differing.
II. Pre harvest factors
1.Effect of provenance
Seeds produced at Raichur/Ranebennur can be stored longer period compared to seeds produced at Chikkamagalur/Mangalore. This is due to different climatic conditions and soil types prevailing in different places.
2. Effect of weather
Fluctuating temperature during seed formation and maturity will affect seed storage. Pre-harvest rain may also affect the viability.
3. Pre harvest sanitation spray
In pulses, insect infestation comes from field (e.g.) bruchids.
III. Seed structures
IV. Intial quality of the seeds
Seed lot having vigorous, undeteriorated seeds store longer than deteriorated lots.
V. Environmental factors
1. Moisture content
The amount of moisture in the seeds is the most important factor influencing seed viability during storage.
Generally if the seed moisture content increases storage life decreases. If seeds are kept at high moisture content the losses could be very rapid due to mould growth very low moisture content below 4% may also damage seeds due to extreme desiccation or cause hard seededness in some crops.
Since the life of a seed largely revolves around its moisture content it is necessary to dry seeds to safe moisture contents.
2. Relative humidity and temperature during storage
Relative Humidity and temperature are the most important factors determining the storage life of seeds. If there is high RH resulted in increase in seed moisture contentment resulted in faster deterioration of seed quality. Usually at lower humidity seeds can store for longer period.
Equilibrium moisture content for a particular kind of seed at a given Relative Humidity tends to increase as temperature decreases.
Temperature also plays an imporant role in life of seed. Insects and moulds increase as temperature increases. The higher the moisture content of the seeds the more they are adversely affected by temperature. Decreasing temperature and seed moisture is an effective means of maintaining seed quality in storage.
The following thumb rules by Harrington are useful measures for assessing the effect of moisture and temperature on seed storage. These rules are as follows.
1. For every decrease of 1% seed moisture content the life of the seed doubles. This rule is applicable between moisture content of 5-14%.
2. For every decrease of 5oC in storage temperature the life of the seed doubles. This rules applies between 0oC to 50oC.
3. Good seed storage is achieved when the % of relative humidity in storage environment and the storage temperature in degrees Fahrenheit add upto one hundred but the contribution from temperature should not exceed 50 oF.
Nomograph : Roberts (1972) developed formulae to describe the relationship between temperature seed m.c.
4. Gas during storage
Increase in O2 pressure decrease the period of viability
N2 and CO2 atmosphere will increase the storage life of seeds.
5. Microflora, Insects and Mites
The activity of all these organisms can lead to damage resulting in loss of viability.The microflora activity is controlled by Relative Humidity temperature and Moisture Content of seed.
Treated seeds with fungicides can be stored for longer periods.
Fumigation to control insects will also help in longer period of stroage.
Fumigants - (e.g) methyl bromide, hydrogen cyanide, ethyline dichloride, carbon tetra chloride, carbon disulphide and napthalene and aluminimum phosphine.
VII. Types of packing materials
Thus the maintenance of seed moisture content during storage is a function of relative humidity and to a lesser extent of temperature. Moisture vapour proof contianers can help in longer stroage than the moisture previous containers.
VI. Seed treatment : Usually extends the storage life by preventing entry of storage microflora
VIII Use of desiccants
Desiccant like silicagel can maintain the m.c. in equilibrium with the Relative Humidity of 45%. It is kept @ 1 kg / 10 kg of seeds. When the silica gel turns to pink colour it should be dried at 175 oC in oven and then again placed in the container.
Seed packaging materials
Classification of packaging materials or containers
1.Moisture and vapour previous containers
These containers allow entry of water in the form of vapour and liquid.
(eg) cloth bags, gunny bags, paper bags etc.,
2.Moisture impervious but vapour previous containers
These allow entry of water in the form of vapourand not in liquid.
(e.g) polythene bags of <100 guage thickness and urea bags.
3. Moisture and vapour proof containers
These containers will not allow entry of moisture in the form of liquid or vapour.
Certified seeds of cereals, pulses and oil seeds are normally packed either in gunny bags or cloth bags. However, paper bag, aluminium foil pouches and polyethylene bags are used for packing flower and vegetable seeds
Storage Pests and Their Management
Post harvest handling of seeds 1. Before harvesting
3. Seed processing
5. Seed treatment
Storage Pests and Management
There are heavy losses in the course of grain storage. Importance of the additional grain that can be made available for human consumption by pest free / pest controlled storage is intensely felt during unfavorable agricultural years. Surplus grains produced in the country only aggravate storage problems.
More than 65 percent of the total grain produced is retained and stored by the farmers for food, feed and seed purposes till the next harvest. It is estimated that about 5-8% of grains are retained for seed, about 20% is hand-pounded and the rest is milled.
Source of infestation of stored product insects
i. Field infestation
ii. Infestation by migration
iii. Infestation through conveyance
iv. Storage building or structures, birds, bird
nests and ants, rodent burrows, etc.
A. Internal Feeders
PestScientific NameOrderCropsNature of Damage
1. Rice weevil
Rice black weevil
Maize weevil /
Ganary weevilSitophilus oryzae (L.)
S. zeamais (Motsch)
S. granaries (L.)ColeopteraWheat, rice, maize, jowar and paddyBoth grubs adults cause the damage. Seeds are hollowed out. Kernels are reduced to mere powder, Sitophilus oryzae and S. zeamais are known to attack seeds in fields too. Adults cut circular holes. Heating takes place during heavy infestation
Rhyzopertha dominica (Fab)ColeopteraPaddy, rice, wheat and maizeIrregular holes in bagged storage, irregular messy waste flour spots indicate infestation of this pest. Heating is very common. Localized infestation is almost a rule. Both adults and larvae cause damage and are voracious feeders.
3. Pulse beetle
Callosobruchus maculates (Fab)
C. chinensis L.
ColeopteraMost of the pulsesLarvae eat up the seeds and make a cavity. Adults are short lived, harmless and do not feed on seeds.
4. Angoumois grain mouthSitotroga cerealella (Oliver)LepidopteraPaddy, maize, jowar, barley and wheatOnly larvae damage seeds, adults being harmless. Seeds are hollowed out. It attacks in field and stores too. In stored bulk seeds, infestation remains confined to upper 30cms, depth only. Hole is circular with characteristic ‘flap’ or ‘trap door’.
5. Tamarind beetle
C.fuscus (Goeze), C.gonagra (Fab)ColeopteraTamarind pods. “Groundnut pods” wild tree legumes like Cassia, Acacia, BauhiniaLarvae bore into the groundnut shell and feed on the seed. They usually leave the pod to pupate. Infestation of groundnut is revealed by larval emergence holes and the presence of cocoons outside the pods. Feeding damage to the seeds can be seen when infested pods are split open.
B. External Feeders
PestScientific NameOrderCropsNature of Damage
1.Khapra beetleTrogoderma granarium ColeopteraWheat, maize, jowar, rice, pulses, oilseedsIt damages the seed starting with germ portion, surface scratching and devouring the seed. Actually it reduces seed into frass. Crowding of larvae leads to unhygienic conditions in warehouses. Damage is confined to peripheral layers of bags or 5 to 30 cms in bulk storage
2.Red flour beetleTribolium castaneum (Herbst.)ColeopteraBroken seeds/mechanically damaged seedsBoth adults and larvae feeds on seeds & are secondary pests of all seeds and primary pests of flour and other milled products. In seeds, embryo or germ portion is preferred for feeding.
3.Saw toothed grain beetleOryzaephilus surinamensisColeopteraRice, wheat, maize, cereal products, oilseedsAdults and larvae cause roughening of seed surface and off odour in seed. Seed with higher percentage of brokens, dockage and foreign matter sustain heavy infestation, which leads to heating of seed.
Only larval stage is harmful. It mainly feeds on germ portion leaving the rest of the seed undamaged. In bulk infestation, its damage is limited to peripheral top layers only.
5. Indian meal mothPlodia interpunctellaLepidopteraMaize, cereals, dry fruits, groundnutsPrimary pest, cause serious damage to ear and seed of maize, contaminates the seed with excrement, cast skins, webbing, dead individuals and cocoons; prefers to eat germ portion and hence seed lose viability.
6.Rice mothCorcyra cephalonicaLepidopteraRice, jowar, other millets, pulses, oil seeds, nuts
Larva is only responsible for damage. It pollutes seeds with frass, moults and dense webbing. In case of whole grains, kernels are bound into lumps upto 2 kgs
Management of insect pests of Seeds
Control of Insect pests
2. Curative measures
1. Preventive measures
A. Hygiene or sanitation
a.Threshing floor/yard should be clean, free from insect infestation and away from the vicinity of villages/granaries.
b.Clean the harvesting and the threshing machines before their use.
c.Trucks, trolleys or bullock carts which are used for transportation seeds should be made free from insect infestation.
d.Clean the storage structure / godowns before storage of newly harvested crop.
All dirt, rubbish, sweepings and webbings should be removed from the stores and disposed / destroyed.
f. All the cracks, crevices, holes existing in the floors, ceiling should be plastered with mud or cement permanently.
g. All the rat burrows should be closed with a mixture of broken glass pieces and mud and then plastered with mud/cement.
h. White wash the store rooms before storage of seeds
i. Seeds should be kept in stores which are rat & moisture proof.
j. Proper stacking of bags also helps in seed protection.
B. Disinfestations of stores / receptacles
Before the use, the receptacles / store rooms should be disinfested with approved residual insecticides preferably by spraying Malathion 50% EC3 ml/ L or dichlorovas 100%EC @ 1ml/lit.
C. Legal method
Entry of an insect which is not found in the particular area can be prevented by the imposition of Destructive Insect Pests Act, 1914.
1. Non-chemical control measures
2. Chemical control measures
Non-chemical control measures
A. Ecological control measures
ii. Moisture content of Seed
iii. Availability of oxygen
✽ 200C to 400 C accelerate the development.
✽ >420C and <140C retards reproduction and
ii. Moisture content of seed
✽ Moisture is the critical factor in safe storage of seeds.
✽ Around 10% moisture content escape from the attack of
insects (except kapra beetle)
iii. Availability of oxygen
O2 level will reduce below 1% and CO2 level will automatically increase which will be lethal to all the stages of insects.
B. Probe Traps
✽ New method of detecting insects in bulk stored seed
✽ The traps are simple to use, helps in continuous monitoring of stored product insects.
✽ Insects like Sitophilus oryzae, Rhyzopertha dominica, Tribolium castaneum, Oryzaephilus surinamensis and Sitotroga cerealella can effectively be trapped and monitored by traps.
Pulse beetle trap : Designed for pulse beetle.
Pitfall traps : Soil-inhabiting insects. These traps can logically be used in bulk stored seeds for capturing insects active on the seed surface.
Light traps : Green light -Lepidopterans.
UV light. Lesser grain borer, Rhyzopertha dominica, Red flour beetle, Tribolium castaneum, Cigarette beetle, Lasioderma serricorne, etc.
UV light traps can be used in mass trapping and for population monitoring of beetles in paddy buffer stock warehouses, as majority of the beetles attacking paddy are attracted in large numbers to UV light. Significant among them are Rhyzopertha and Tribolium casteneum.
Sticky boards, screens, paper strips, hollow tubes and large wing traps have been used to trap stored product moths. However, sticky traps are generally used with pheromones.
But fortunately, in major families of stored product beetles, the adult males release chemicals commonly termed as aggregation pheromones to which both females and males get attracted. Examples for this include, Tribolium castaneum, T. confusum, Rhyzopertha dominica and Oryzaephilus surinamensis.
C. Storage container for automatic removal of insects from seeds
Recently storage container model of 2 kg, 25 kg and 500 kg capacity, which can remove insect automatically, has been designed. Bruchids damage can be prevented by storing the pulses in containers along with a layer of sand above and sealing the lid of the container.
II Chemical control measures
Treat the seeds of cereals or pulses used for seed purpose with deltamethrin 40mg/kg of seed or bifenthrin 20mg/kg of seed and store the seeds by packing them in polylined gunny bags. Oilseeds can be treated with melathion 4 % dust @ 50mg/kg of pods or seeds.
Fumigate seeds @7 tablates per ton of seeds for a period of one week in air tight condition by Aluminium Phosphide tablates
Seed Storage Fungi
Control: Dry the seeds to safe moisture level
Treat seeds with thiram/capton/Metalaxyl @2g/kg of seeds