Pest control methods adopted for preservation of grain in Sri Lanka

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The use of pesticides for protection of grain is a common practice adopted by farmers of many countries. However, in Sri Lanka, the use of insecticides for protection of stored grain is restricted to a small farming population. Quantity of paddy stored by farmers for consumption, and as seed paddy is small, and they fear to mix insecticides with the grain meant for their consumption as they consider insecticides as highly toxic chemicals.

Cleaned, well dried paddy is stored by the farmers either in bags of in bulk, and by adopting good hygiene, the grain is kept insect free. In some cases, Margosa and Citrus leaves are kept in the 'Bins' or bags to repel the insects. Wood ash obtained from the kitchen is mixed with paddy by some farmers in addition to the use of leaves. Certain farmers resort to insecticidal sprays on the surface of bags and for that purpose the insecticide 'Actellic 50' is used. Besides the emulsifiable concentrate some farmers use BHC and actellic dust to protect bagged grain from insects.

Paddy stored in Central Warehouses of the Paddy Marketing Board is subjected to under mentioned treatments so as to minimize pest populations. Actellic 50% E.C. which contains the active ingredient, Pirimi-phosmethyl is applied ate dilution of 1: 150 as high volume sprays on the surface of bags and the entire warehouses. This treatment reduces the population of insects considerably. Spraying is done at least once in 3 weeks. In addition to spraying, warehouses are fogged with Actellic 50 EC at a dose of 120-240 nl. per 4 litres of diesel. If the insect population cannot be reduced by fogging, the grain is fumigated by using phosphine gas produced in situ by Magnesium Phosphide plates and Aluminium phosphide tablets. Fumigation is carried out under gas proof sheets when other pest control processes fail to achieve a reasonable level of pest control. 2-3 grams of phosphine gas per ton of grain is used as the standard dose for grain.

In the case of commodities like Rice, Maize, Cowpea, Green gram and Soyabeans the stocks are fumigated within a month of storage so as to prevent any major attack by pests. The stocks are fumigated when first signs of insect attack appear, so that the the quality is preserved.

Paddy Marketing Board,
No. 277, Union Place,
Colombo 2
Sri Lanka


Integrated Pest Management in Sri Lanka.

Sri Lanka is a developing country with an approximate population of around 16 million. The main food grains are sereals such as rice, maize and millet, and pulse grains such as cowpea, green grams, soya bean and black grams, and oil seeds such as ground nut.

Rice is the main food grain produce in Sri Lanka and it forms the staple diet of both rural and urban population of the country. Pulses also form an important protein source in the diets of Sri Lanka.

Sri Lanka is now on the threshold of self sufficiency in rice. Self sufficiency level is placed at around 110 kg per person per year. The deficit quantity between production and consumption is imported and made available by the Food Department.

Of the total paddy production, 50% is kept by the farmers for their own consumption, future sale and for seed purposes. The rest is sold soon after harvesting to the Paddy Marketing Board. This is the primary statutory grain marketing organization in Sri Lanka engaged in price stabilization and maintenance of food security reserves through procurement, storage processing, and distribution of a major portion of the country's paddy production. It purchases about 15% of the paddy made available for sale by farmers at the guaranteed price fixed by the Government.

Storage losses in paddy alone have been estimated to be 5% specially in countries like Sri Lanka with damp tropical climates favourable to the rapid development of agents of deterioration.

Rice, being structurally a delicate grain, has constantly posed difficulties in long time storage. Milled rice usually has a shelf-life up to one year when stored under the very best conditions. Under usual conditions it will not keep satisfactorily for a period of over 3 - 6 months.

The Food Department is the main operational arm of the government's procurement, storage, transport and distribution of rice, wheat and wheat flour. The department handles an average about 1.4 million metric tons of food commodities per year. It is responsible for the procurement of around 675,000 metric tons of wheat per year and for the distribution of around 500,000 metric tons of milled flour. The Department procures and distributes over 200,000 metric tons of rice per year. The cost of ali this is Rs. 6 billion a year.

With the Government's abolition of the rationing and subsidy scheme and the liberalisation of the economy in 1979/80, the Food Department, which up to then had been vested with the responsibilities of managing subsidised food distribution scheme, had to operate as a commercial organization. In keeping with Government's food security strateg. The Food Department, in its new role, viz. rice and wheat flour, maintains adequate buffer stocks as well in order to be able to intervene in the market.

For purposes of food security, the Food Department is presently required to maintain the following buffer stocks of rice and wheat flour:


A total quantity of 150,000 metric tons, which is a six weeks' consumption requirement of the Country's population, to be maintained jointly by the Food Department and the Paddy Marketing Board.


A minimum of eight weeks' requirement, in the form of wheat flour and wheat grain - i.e. approximately 40,000 metric tons of wheat flour and 50,000 metric tons of wheat grain.

The Food Department purchases local rice only from the P.M.B. and its registered millers through the Network of stores in outstations. The Food Department, in consultation with the Ministry of Agriculture, the P.M.B. and the rice millers, formulated appropriate specifications for the procurement of local rice, taking into consideration the local methods of farming, threshing, milling, seed varieties and preference of the people.

With the commisioning of the Prima Mill in Trincomalee in October 1980, direct imports of wheat flour into the country had ceased, and the country's entire consumption requirement of wheat flour is now met by the Prima Mill. The Food Department imports and supplies the wheat grain required for milling by Prima, and wheat flour at an extraction rate of 74 percent is delivered to the Food Dept. by Prima. The Prima Mill is one of the largest and most modern flour mills in the world, and has a production capacity of around 2,000 metric tons per day. This makes it possible for the Food Department to make available to the consumer freshly milled good quality flour at all times. Since this allows for a quicker rotation of stocks, storage of flour is no longer a problem to the Department.

Farm Level Storage.

In new settlement schemes, grains kept by farmers are stored mainly in gunny bags. However, in old settlement schemes, farmers use indigenous storage bins to store their produce. A recent study completed by the Rice Processing Research & Development Centre (RPRDC) have shown that rectangular clay bins are not suitable for outdoor onfarm storage. This is because of high grain losses caused by insects and mold damage due to wetting of the walls during rain and exposure of greater surface area of the grain bulk to the atmosphere favouring insect multiplication. Straw walled outdoor bins did not afford any barrier against diffusion of water vapour and hence the grain moisture varied with ambient relative humidity changes making the grain susceptible to mold damage during wet weather. Therefore, straw walled bins are not suitable for outdoor on-farm storage. The elliptical clay bin performed best among the indigenous outdoor bins. After 180 days of storage the Clay bin averaged 2.6% less than the losses incurred in the other indigenous outdoor storage bins. The performance of the clay bins could be improved by providing rat guards and outlets for loading and unloading operations. It was found that total dry matter loss during the storage was due to insect infestation.

The cost of the storage indoor bins was, on the average, 2.0% higher than the outdoor bins. However, certain farmers prefer indoor bins over open outdoor structures since they found better security for their grains (palipane et. al 1986).

Commercial Level storage.

Paddy at commercial levels is stored for a period ranging from 3 to 12 months. In warehouses, even though grain is stored mainly in jute gunny bags, lowcost poly-propylene bags are becoming popular in the country.

Cross stacking is the main method of stacking because this method enables easy counting of bags for checking the stock. The normal size of a stack is 9 m. x 6 m. A 1 m. clearance is always between stacks and walls.

The main insect species which attack paddy grains during storage in Sri Lanka are Rhizopertha dominica, Sitrophilus orgzae, Sitotroga cerealella and the secondary insect pest Tribolium Spp.

Major insects attacking rice are Tribolium Spp., Rhizopertha dominica, Sitophilus oryzae, Sitotroga cerealella and Cocyra cephalonica. Mites and Ephestia cautella also appear seasonally in the rice store, but they are not a major problem. Trogoderma and Oryzeaphilus surinamensis sometimes appeared in imported rice but they are controlled before spreading further and presently, they are not seen in any of the stores.

Prevailing pest control practices.

For controlling insects in paddy and ether grains at farm level, farmers use wood ash and paddy husk ash. A study carried out by the Rice Processing Research and Development Centre has shown that paddy husk ash mixed with cowpea at levels of 4% by weight efficiently controls infestation and damage by the pulse beetle for a period of six months. Mixing of such dusts with the grains cause physical injuries to the insects, resulting in death due to deterioration of their bodies.

Another practice adopted is the use of citrus leaves and magosa which probably have insect repelling chemicals.

In commercial storage in the Paddy Marketing Board, a pest control programme is carried out where stored grains stock surfaces and buildings are sprayed with Primiphos methyl, at least once in three weeks to prevent cross infestation or reinfestation of grain. However, if an infestation sets in, the stocks are fumigated using Aluminium phosphide tablets or Magnesium phosphide plates. The extent of pest control work would vary depending on the duration of storage.

A study done by the Rice Processing Research and Development Centre to compare the efficency and toxicity of 7 insecticides have shown that the order of effectiveness of the tested insecticides against three insect species at the end of 28 days with significant difference at 95% confidence limit were;

Sitophilus oryzae: Methacrifos = Malathion = Phoxim, Pirimiphos-methyl, Permethrin, Thiodicarb, Cypermethrin.

Rhizopertha dominica: Pirimiphos-methyl, Malation = Methacrifos, Phoxim, Permethrin Thiodicarb, Cypermethrin

Sitotraga cerealella: Phoxim, Methacrifos Pirimiphos-methyl, Permethrin, Malathion, Cypermethrin, Thiodicarb

Pirimiphos methyl, Phoxim and Methacrifos showed greater initial toxicity against the three insect species than the others.

(The effecency and toxicity of seven insecticides against major storage insect pests of paddy and rice in Sri Lanka. Fernando M.D.: Navaratne S.B. (1988) Tropical Post Harvest Technologist vol:1 No:1)

In the Food Department, bagged rice and flour received into stores are stacked according to the stack plan on disinfested dunnage racks in a cross bag system for better ventilation during the storage. Regular inspections of the Department's store complexes are undertaken by trained personnel to check quality deterioration from insect infestation and rodents and micro-organism. As a pest control practice, fumigation is carried out by competent men using phosphine gas or methyl bromide in strict adherence to the limitaions regarding their use. In addition, fogging is the most common and sucessful spraying method which is used by the Food Department and Paddy Marketing Board in minimizing moth population in warehouses.

Strains of Rhizopertha dominica, Triboliumsp. and Sitophilus oryzae were collected from Flood Dept. stores and sent to ODNRI of U.K. to test the resistance for phosphine. None of these insects from Food Department stores survived the discriminating dose, so it may be assumed that none was resistant to phosphine. It is a result of the high technical standard of fumigation carried out by the Food Department Pest Control teams and the maintenance of a good storage practice.

With the continuous increase in paddy and other food grains it is envisaged that the problems of storage will become evermore serious with large quantities of grain to be handled and stored. Hence it is emphasised that cost effective intergrated pest control procedures are developed in the future to preserve food grains.


The Rice Processing Research and Development Centre is the main Institution engaged in research, training, extension and other development activities in post harvest technology of paddy and other food grains. An important area of activity of the Centre is the cost effective pest control practices to suit local conditions. A list of significant research publications of the Rice Processing Research and Development Centre is given in Annex 1. The projects that are presently being carried out by the Rice Processing Research and Development Centre in the area of storage are:

  1. The resistance of recently recommended rice varieties to damage by Rhizopertha dominica
  2. Storage loss assesment study.
  3. Identification of Insect pests of stored paddy and study of their population build-up patterns in different agroclimatic zones of Sri Lanka.

Apart from research, the Centre trains nearly 2000 personnel engaged in medium-to large-scale storage from both public and private sector organisations.

In addition, the Centre trains approximately 4000 farmers on improved Post Harvest Technologies.

The changed role of the Food Department as a buffer stock holder and the resultant need for the maintenance of adequate stock of rice and wheat flour in storage for long periods has made it increasingly important in recent years to improve and enhance efficiency at the various levels of store management in order to minimize losses as well as ensure proper care over the health and hygiene of the food commodities kept in storage for distribution. The Food Department Training Centre and Quality Control Unit at Narahenpita which was established in 1980 and developed under the guidance of foreign experts from FAO and the ODNRI of the U.K. Government as an essential part of the Department programme to minimize food losses in storage, was further strengthened and new units opened. In its efforts to build up atrained cadre who would be competent in all aspects of grain handling and up-keep of warehouses, the Food Department Training Centre and Quality Control Unit has since conducted several initial and refresher courses on scientific methods of stock preservation, pest control, rodent control, quality control and store management for the benifit of the Department officers as well as personnel from other organizations such as the P.M.B., CARE, and the private sector.

In the context of Sri Lanka's rice production reaching near self-sufficiency levels, and with the prospect now very near for both thee Paddy Marketing Board and the Food Department to be carrying a national buffer comprising entirely of local rice, we of the Paddy Marketing Board and the Food Department have for sometime addressed our minds to the serious problems we may encounter in the matter of procurement, milling, processing and storing. Since the moisture content in local rice is high, such local rice stocks kept in long term storage as the national security buffer, could easily become susceptible to infestation by weevils and micro organisms, resulting in heavy storage losses.

The health and hygiene of grain and milled products thus kept in long term storage for distribution would require trained personnel possessing specialised knowledge in all aspects of store management. It is only by improving efficiency at the various levels of store management through appropriate academic and practical training that we could hope to check quality deterioration of food stocks in storage, and to minimise food losses.

We would indeed be very grateful for any FAO assistance to help overcome these problems by the introduction of scientific and more modern methods of stock preservation, as well as of more advance milling and processing techniques, and also by affording us suitable training opportunities to enable us to improve and enhance our efficiency levels in store management.

Rice processing research and development centre training course schedule January - June 1988


1. EVALUATION OF THE BISSA-AN INDIGENOUS STORAGE BIN. RPRDC Report 5/78, Rice Processing Research & Development Canter. Sri Lanka (1978)

2. PADDY HUSK ASH AS A PROTECTANT OF COWPEA AGAINST PULSE BEETLE. RPRDC Technical Note 11/84, Rice Processing Research & Development Centre. Sir Lanka (1984)

3. SUITABILITY OF METAL, BINS FOR INDOOR STORAGE OF PADDY. RPRDC Technical Note 12184, Rice Processing Research & Development Cenre. Sri Lanka (1984)

4. IMPROVEMENT OF FARM LEVEL STORAGE METHODS IN SRI LANKA. Proc. Grantees Seminar on Agriculture and Animal Husbandry, National Resources, Energy and Science Authority of Sri Larka (1986)

5. The Efficacy and toxicity of several insecticides against major insect pests of stored paddy and rice in sri lanka. (To be published in RPRDC Journal)


Activities of the post harvest technology working group on insect pest management research in grain storage in chiang mai university northern Thailand


Thailand is a constitutional monarchy encompassing an area of 513,520 square kilometers and located on the Indo Chinese Peninsula of Southeast Asia. Geographically it is divided into four regions: the southern peninsula, the central plains, the northeast and the north. The climate is tropical, with three distinct reasons: rainy (June-October), cool (November-February) and hot (March-May).

Northern Thailand is composed of 17 provinces divided into two parts: Upper North (9 provinces) with area approximately 10.51 million hectares and Lower North (8 provinces) with 6.72 million hectares. Three types of land are classified in the Upper North; highland (60%7, upland (30%) and lowland (10%).

The Chiang Mai Valley covers an area of 150,000 hectares (ha) situated approximately 700 kilometers from Bangkok at an elevation of 300 meters above sea level. It is the most intensively cropped area in the Upper North. Different cropping systems are utilized with either: one, two or three crops per year but two is the most common. The systems are specific to a particular location or combination of topographic, soil, water supply and socio-economic factors. The twocrops per year pattern is confined to irrigated area in the Valley, the sequence most commonly used being rice-tobacco, rice-garlic, rice-soybean, rice-peanut, rice-mungbean, rice-vegetable and etc. Monocropping such as rice, maize, soybean and etc. is confined to rainfed areas. Triple cropping includes planting sequences of rice-vegetable-vegetable, rice-soybeanvegetable, soybean-garlic-vegetable and etc.

Post harvest grain losses have assumed increasing importance in recent years in Thailand. There is an awareness amongst both policy makers and technicians that reducting post harvest losses could lead to the achievement of food security ensuring adequate food supples for the increasing population of national level. The Thai government realized the importance of these losses when it ranked as high priority the needs of post harvest technology in the Sixth Five Year Plan (1987-1991). In response to this policy, the Faculty of Agriculture, Chiang Mai University has formed a Post Harvest Technology Working Group since 1984. The Working Group is composed of staff members from various Departments within the Faculty, with staff from other Faculties when considered appropriate. The 18 members of the group are from Agricultural Engineering, Agronomy, Entomology, Pathology, Food Science and Technology, Horticulture, Animal Husbandry, Economics and Agric. Extension. The Group was formed for research, curriculum development and counselling in Post Harvest Technology in the Faculty of Agriculture. Curriculum development from the M.S. Degree and research in post harvest technology is progressing.

The farmers in the north are similar to those of other parts of the country., They normally sell 70-80% of their grains immediately after harvest and some are sold before or during harvest. The rest of the grain is stored mainly for consumption and seed purposes. The amount is usually less than one ton and storage periods up to six months until the next harvest are common. They do nothing to protect their grains from insect damage compared with intensive pest management done in the field. The grains are commonly stored in commercial warehouses of silos for a short period of time before transporting to the market in Bangkok, and exported. Because of lack of understanding or knowledge on methods of pest control and proper commodity management strategies, problems associated with pests such as damage and loss have been increasing significantly in recent years. Entomologists in the Post Harvest Technology Working Group, Faculty of Agriculture, Chiang Mai University realized this importance and commenced experiments on stored insect pests in recent years with emphasis on Integrated Pest Management (IPM).



Among the various stored insect pests, those most commonly encountered and considered as being most important in term of losses and damage to stored grains in N. Thailand are as follows:

  1. Rice weevil, Sitophilus oryzae (rice)
  2. Maize weevil, Sitophilus zeamais (rice, maize)
  3. Lesser grain borer, Rhyzopertha dominica (rice, wheat)
  4. Cowpea weevil, Callosobruchus chinensis (pulses)
  5. Southern cowpea weevil, Callosobruchus maculatus (pulses)
  6. Cigarette beetle, Lasioderma serricorne (tobacco)
  7. Sawtoothed grain beetle. Oryzaephilus surinamensis (rice, wheat)
  8. Red flour beetle, Tribolium castaneum (rice, wheat)
  9. Confused flour beetle, Tribolium confusum (rice, wheat)
  10. Angounmois grain moth, Sitotroga cerealella (rice, wheat, barley)
  11. Rice moth, Cocyra cephalonica (rice)
  12. Tropical warehouse moth, Ephestia cautella (puIses)



Entomologists in the Post Harvest working Group has commenced research experiments on stored insect pests which consider both pre and post- harvest handling because it will influence subsequent quality deterioration and insect damage after harvest. At present, some of the experiments being implemented are as follows:

1. Harvesting time affecting species and numbers of stored grain insects in wheat.

2. Identification of insect pests associated with stored wheat.

3. Life table studies of Sitophilus spp.

4. Wheat losses caused by Sitophilus spp. in laboratory trials.

5. Type of containers and their affect on Sitophilus spp. infestation.

6. Varietal susceptability/tolerance to Sitophi /us spp. infestation in wheat.

7. Chemical control of Sitophilus spp. on wheat.

7.1 Admixture

7.2 Dipping of jute sacks

8. Observation of non-chemical control of Sitophilus spp

9. Observation of natural enemies of Sitophilus spp. on wheat.

10. Harvesting time affecting stored soybean insect infestation.



It is envisaged that efforts to reduce losses in stored grain will continue to depend on the use of Integrated Pest Management. Research should consider as an immediate priority, pesticide usage which is a fast and reliable means of pest control, but it must be employed within an established IPM framework. A long term research need should encompass other components of IPM such as biological, physical and mechanical control. Economic important commodities will be mainly rice, maize, soyben, mungbean, peanut and wheat. The research needs for insect pests of these commodities are as follows:

A. Biology and Ecology

B. Physical Control

C. Non-chemical Control

D. Cultural Control

E. Chemical Control

Table 1. Production of Principal crops grown in Northern Thailand (1983/1984)



% Production from the North
  Country (t) North (t)  
Rice 19,047.000 5,068,000 26.60%
Maize 3,552,000 1,745,000 49.12%
Mungbean 288,337 233,381 80.94%
Soybean 179,126 154,101 86.02%
Peanut 146,550 96,067 65.55%

Source: Center for Agricultural Statistics Office of Agricultural Economics, Ministry of Agriculture and Cooperatives. Agricultural Statistics No. 213 1983/1984


Survey of stored insect in rice field before harvest



Survey of stored insect in rice field before harvest was conducted at 2 rice experiment stations for 2 year study. The result of the first year showed that Sitotroga cerealella Olivier was the only insect species found. The number of eggs laid on the panicle were not examined but the adult emerged from the panicle keeping for 30 days after picking was examined and it was 1.16 and 6.9 insects per 10 panicles in RD 7 and Hom Om respectively. In the second year, the result confirmed that S. cerealella Olivier was the only insect found and laying eggs in the field. The number of adult insects found by sweeping had an average of 2.7, 0.9, 1.18 and 2.4 insects per 50 x 50 metre per day in RD 7, RD 15, Kao Dok Mali 105 and Hom Om respectively. The number of adult emerged from the panicles was 3.6, 3, 2.7 and 4.8 per 10 panicles in RD 7, RD 15, Kao Dok Mali 105 and Hom Om respectively.

The need to know whether stored insects lay the eggs in rice field before harvest or not is quite necessary. Since this may cause a serious insect infestation in the storage bin after some time. It is already known that some stored insects lay the in eggs in the field before harvesting time. But does it need any protection before harvest is a problem. If this condition occurs it is possible that protection of agricultural produce may commence in the field before harvest. This may be appropiate of some crops in some countries but in general, it is practice should be discouraged. This is because protection of insect infestation by farmers in Thailand is still dependent on insecticides in the field and if more were to be applied it will add more toxic substances to man and environment unnecessarily. Therefore, this experiment was conducted so as to know the kinds of insect present in the field before harvest and whether the es,gs were laid in the field in large enough number that serious insect infestation would occur in the storage bin there-after.

The insects to be searched for were Sitotroga cerealella Olivier which is the most important insect pest of paddy during storage, Rhyzopertha dominica Hbst. and Sitophilus species.

Materials and Methods

The research was conducted at 2 rice experiment stations in the first year and 1 in the second year during November to December 1982 and 1983. In the first year, 5 rice varieties from Bangkhen and Chainat experiment stations were tested and in the second year 4 varieties were tested at Chainat. The experiment consisted of rice plot of 50 x 50 metre and each plot contained only one rice variety. The plot was divided into 4 parts in which 10 panicles were randomly picking everyday for 15 days before harvesting time of each variety. After picking, the panicles were put in the paper bag and were dried in the room at ordinary temperature for 2 - 3 days because some panicles were still wet and might cause a fungul growth. Then the panicles were put in the glass jar and cover with muslin cloth. Examination of first adult appeared in the jar was recorded until 30 days after each picking. During picking the panicles, the adult insects were also collected by sweeping net to see the kinds and number of insects present in the field.

Results and Discussion

Result of the first year and second year were as followed.

First year

The result showed that Sitotroga cerealella Olivier was the only insect found in the field. But whether it had laid the eggs in the field was still indoubt. This was because the panicles were dried in the room near to the room where the insects had already infested. So, it was possible that insect might lay the eggs during this time. Therefore, the data showed the number of adult S. cerealella emerged from the jar was more in some variety such as Hom Om and RD 7 (see Tabel I). It should be noted that the nearer the harvesting time the more the number of insects emerge from the jar. As it could be seen in Table I in which the data was from Chainat showed that adult S. cerealella laid the eggs in every rice variety. In sweeping, S. cerealella adult was found in every variety. (See Table II). At Bangkhen very few insects were found and the data is not shown here.

Table I - Data showed average number of Sitotroga cerealella emerged from the jar after 30 days of picking panicles at Chainat and Bangkhen during November to December 1982

Table II - Data showed the number of S. cerealella found by sweeping in different rice variety 50 x 50 m rice plot at Chainat during November to December 1982

Sampling day RD1 Morning Afternoon RD5 Morning Afternoon Hom Om Morning Afternoon
15 - - - - 0 0
14 - - - - 0 0
13 - - - - 2 2
12 - - - - 1 0
11 - - - - 1 2
10 - - - - 2 1
9 - - - - 1 0
8 0 1 - - 0 0
7 2 1 - - 1 -
6 1 1 - - 0 0
5 1 0 - - 1 0
4 1 1 0 1 1 0
3 2 1 2 3 1 0
2 0 1 1 4 2 1
1 1 0 2 3 2 1

- = No panicle picking

The average number of s. cerealella adult per day which was obtained from the number of adult insects emerged from the jar after keeping for 30 days was very high in Hom Om being 6.8 insects per day at Chainat while other varietes were much less. At Bangkhen, the adult insect emerged was very few and it was 0.14 in RD7, none in Neo San Pa Tong, 0.06 in RD21 none in Kao Dok Mali 105. See table III.

Table III - Data showed average number of adult S. cerealella emerged from jar of each rice variety per day at Chainat and Bangkhen during November to December 1982


Avg. no of S. cerealella per day

Rice variety Chainat Bangkhen
RD1 1.18 -
RD11 0.29 -
RD7 1.16 0.14
Hom Om 6.68  
RD5 1.65 -
RD15 - -
NSPT - 0
RD21 - 0.06
KDML - 0

NSPT = Neo San Pa tong
KDML = Kao Dok Mali 105

Second year

Only S. Cerealella was found by sweeping. No other insect such as Sitophilus oryzae Linn. or other Sitophilus species found at all. The adult moth laid the eggs in the field but the number of the adult insect emerged were so small as compared to the number of seed keeping in the jar. As it could be when that the number of insects emerged from the glass jar were 3.6 insects in RD7, 3 in RD15, 2.7 in Kao Dok Mali 105 and 4.8 in Hom Om per 10 panicles per day. The number of insect caught by sweeping averaged per day per 50 x 50 metre was 2.7, 0.9, 1.18 and 2.4 in RD7, RD15, Kao Kok Mali 105 and Hom Om respectively. See table IV.

From the result of year 2 study it can be concluded that Sitotroga cerealella was the only insect species found and it laid the eggs in the rice field before harvest. But the eggs emerged into adults in very small numbers, and they should not cause serious insect infestation when harvest and stored in the storage bin. Therefore, it is concluded from this study that any insecticidal treatments prior to harvest would not be warranted, and that subsequent drying storage management and treatment, if necessary, in the storage system would prove more cost-effective.

Table IV - Data showed average number of S. cerealella obtained by sweeping and from panicles after keeping for 30 days in 4 rice variety at Chainat during November to December 1983

Rice variety

Avg. no of insect per day

  from sweeping from panicles
RD7 2.7 3.6
RD15 0.9 3.0
Kao Dok Mali 105 1.18 2.7
Hom Om 2.4 4.8



Hinton, H.E. and A.S. Corbett. 1972. Common Insect Pests of Stored Food Products. British Museum Economic Series No 15. 62 p.

Kusuma, N.1978. Life history of Sitotroga cerealella (Olivier). Annual Report of Entomol. and Zool. Div., Dept. of Agri. Bangkok. 177-179.


Present situation and experience in the socialist republic of Vietnam on pest management

Prepared by Eng. VU QUOC TRUNG

I - Foodgrain Production

Vietnam is one of the agricultural countries in South East Asia. It has a population of about 62 million. About 20% of the land is cultivated and arable (6 million hectare).

For Vietnam, rice and rice products are the major food grain. About 80% of the arable land is utilized for rice cultivation.

The Vietnamese farmers are very industrious and the applications of modern technical and scientific progress in agriculture has always been increasing in recent years, due to these technological improvements.

II - Foodgrain Storage

In the surplus areas about 75-80% of foodgrain production is stored at the farm level. The government handles about 4 million tons of foodgrain, mainly rice and maize.

At the farmers' level the foodgrain is stored in different shapes and sizes of jars, make-shift baskets or wooden boxes.

In cooperatives foodgrain storage is carried out in ventilated brick stores with 20-30 ton capacity.

State-run stores are considered more suitable domed-roof stores are considered the best in Vietnam, then Al stores are also common.

Foodgrain after drying are ventilated, subjected to quality control, and put into stores.

In north Vietnam 100% of the foodgrain is stored in bulk, where as in the south it is stored in bags.

The duration of storage is about 6 months.

"Place prevention first and pay due attention to both prevention and cure" is the policy for foodgrain storage in Vietnam. Comprehensive methods are being used to make stored food grain safe through hygienic control, maintenance of the physical machinery and application of suitable chemical treatments.

Foodgrain delivered to the State by the farmer should be dry and clean. National standards for quality for all staple foodgrain in different areas have been set up.

For many years Vietnam has adopted the practice of keeping "four-free foodgrain stores", i.e. stores should be free from insects, molds, birds and rodents. This has brought about effective results of foodgrain storage.


Production of Foodgrain in million ton

Year Rice Maize Root and other cereals Total
1985 14.7 0.5 1.8 17.4
1986 15.9 0.6 1.9 18.4
1987 16.0 0.7 1.9 18.4
1988 16.2 0.8 2.0 19.0
1989 17.0 0.9 2.1 20.0
1990 18.0 1.0 2.0 21.0

With conventional methods of storage annual losses of foodgrain constitute 8-10% of the total production.


III Pest Management

The climate in Vietnam is tropical and humid. The average temperature of the year is more than 20C, the relative humidity (RH) is 80%, thus providing ideal environments for the development and subsequent damage by pests.

The Hanoi Institute of Post-harvest Technology has shown that in VN nearly 50 species of pests are in stores. The following are the most abundant 15 species:

Alphitobius piceus O
Araecerus fasciculatus D Sitophilus zeamais L
Carpophilus dimidiatus F
Lacmophloeus pusillus K Lophocaters pusillus K
Oryzaephilus surinamensis L Rhizopertha dominica F
Sitophilus oryzae L
Tenebroides mauritanicus L
Tribolium castaneum H
Tenebrio molitor L
Aglossa dimidiata H
Corcyra cephalonica S
Polodia interpunctella H
Sitotroga cerealella H

Two insect species: Sitophilus granarius and Tribolium confusum are prohibited to be imported into Vietnam.

Investigations have pointd out that in VN 26 species of rodents are available in foodgrain stores and the most common ones are Rattus flavipectrs (chuot dan) Mus musculus (chuot nhat), Rattus norvegicus (chuut cong).

Scientific and technical progress has been made in pest management. However, the most economical and important measure has been storage hygiene. All foodgrain stores should be carefully cleaned, and sprayed with insecticide. malathion, dipterex and DDVP are very popular in VN. Home-made insecticides extracted from poison containing plants is also used effectively. These plants are:

Kaolin powder (a mixture of Kaolin soil and acid sulfuric) is very effective and suitable under present conditions for the prevention of insects during a period of 6-12 months.

When the density of insects is high fumigation is applied. Aluminum phosphide, the most common fumkgatant chemical in VN, can now be manufactured locally. To enhance its toxic effect stores are kept closed for 96 hours after fumigation, and more CO2 added.

For rodent control bait pies made from Warfarin mixed with tasty food is widely used together with other traditional methods

We are now making furthur research into and applying up-to-date technological achievements to foodgrain storage and pest management, with a view to reducing 50% of present losses, i.e. 45% of total production. This is of great significance, as it helps increase social products, develop the economy and improve people's living-standards.

Finally, I would like to express my sincere thanks to the host country and RAS/86/189 project for giving me this opportunity. Thank you for your attention.

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