SEED STORAGE    

 

• Seed storage is the maintenance of high seed germination and vigour from harvest until planting.

 

Introduction         

The ability of seed to tolerate moisture loss allows the seed to maintain the viability in dry state.

Storage starts in the mother plant itself when it attains physiological maturity.

After harvesting the seeds are either stored in ware houses or in transit or in retail shops.

During the old age days , the farmers were used farm saved seeds, in little quantity,

but introduction of high yielding varieties and hybrids and modernization of agriculture necessitated

the development of storage techniques to preserve the seeds.

The practice of storing the seeds starts from the ancient days itself, following simple and cheap techniques

e.g. Placing the seeds in salt, red earth treatment to red gram etc.

But the same practices are not hold good for the present day agriculture, because

• large quantity to be stored

• exchange of varieties and species

•  The type of material to be stored decides the techniques to be followed for safe storage. Now a day’s storage technique changed from ordinary go-down storage to cryogenic tank storage and even gene storage.

• exchange of genes

 

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.

 

3. Temperature

• 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.

eg. polyethylene bags of >7000 gauge thickness, aluminium foil pouches, rigid plastics etc.,

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

2. Threshing

3. Seed processing

4. Drying

5. Seed treatment

6. Packaging

 

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

Pest Scientific Name Order Crops Nature of Damage

1. Rice weevil

 

Rice black weevil

 

 

Maize weevil /

Ganary weevil Sitophilus oryzae (L.)

S. zeamais (Motsch)

 

 

S. granaries (L.) Coleoptera Wheat, rice, maize, jowar and paddy Both 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

2. Lesser Grain Borer /Paddy Borer Beetle/ Hood  Grain Borer,

Rhyzopertha dominica (Fab) Coleoptera Paddy, rice, wheat and maize Irregular 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.

Coleoptera Most of the pulses Larvae eat up the seeds and make a cavity. Adults are short lived,   harmless and do not feed on seeds.

4. Angoumois grain mouth Sitotroga cerealella (Oliver) Lepidoptera Paddy, maize, jowar, barley and wheat Only 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

Caryedon serratus

C.fuscus (Goeze), C.gonagra (Fab) Coleoptera Tamarind pods. “Groundnut pods” wild tree legumes like Cassia, Acacia, Bauhinia Larvae 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

Pest Scientific Name Order Crops Nature of Damage

1.Khapra beetle Trogoderma granarium Coleoptera Wheat, maize, jowar, rice, pulses, oilseeds It 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 beetle Tribolium castaneum (Herbst.) Coleoptera Broken seeds/mechanically damaged seeds Both 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 beetle Oryzaephilus surinamensis Coleoptera Rice, wheat, maize, cereal products, oilseeds Adults 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.

4.Warehouse  moth Ephestia cautella Lepidoptera Wheat, rice, maize, jowar, groundnut, spices

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 moth Plodia interpunctella Lepidoptera Maize, cereals, dry fruits, groundnuts Primary 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 moth Corcyra cephalonica Lepidoptera Rice, 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

1.Preventive measures

2. Curative measures

 

I . 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.

 

II. Curative measures

1.   Non-chemical control measures

2.  Chemical control measures

 

Non-chemical control measures

A. Ecological control measures

i. Temperature

ii. Moisture content of Seed

iii. Availability of oxygen

i. Temperature

✽ 200C to 400 C accelerate the development.

✽ >420C and <140C retards reproduction and

development

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 traps

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.

Pheromone traps

Ephestia cautella, Sitotroga cerealella, Corcyra cephalonica, Rhyzopertha dominica, Tribolium casteneum, Oryzaephilus surinamensis and Trogoderma granarium.

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.

 

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

• Aspergillus Spp

• Rhizopus Spp

• Penicillium Spp

Control: Dry the seeds to safe moisture level

Treat seeds with thiram/capton/Metalaxyl @2g/kg of seeds