Preface The 2nd revised edition of the book “Pests of Stored Grains and Their Management” covers syllabus as recommended by the 5th Deans Committee. The book covers updated information written in simple, lucid language, easily understandable by readers and summarizes the knowledge of insects and other pests of stored grains and grain products covering global scenario. Every chapter covers wider aspects of related work, storage requirement to prevent the losses of food grains at post harvest handling and at other levels too, different types of storage techniques and prevalent rural and improved storage structures and receptacles, storage pests (insects, mites, birds, rodents, microorganisms etc.), fumigants and their use, safety measures against poisoning, management of stored grain pests etc. The revised edition gives the readers the vast knowledge about the progress made in different aspects of storage entomology. The book will serve as the valuable source of information on the storage entomology and would be of great importance for its readers.

A series of efforts have been made to initiate the work on post-harvest grain technology in India. H.M. Lefroy, the 1st Imperial Entomologist appointed by the British Government in India in 1905 had given a tentative list of storage insects in 1906. This list of storage insects was further supplemented by T.B. Fletcher in 1914. The problems of grain storage were discussed at Pusa, Bihar at the Entomological meetings held during the years 1917, 1919 and 1923. The Department of Food was established in 1942 by the Government of India. The executive wing of the Food Department was responsible for the purchase, movement, transport and distribution of food grains. Central Food Technology Research Institute (CFTRI) at Mysore was established in 1950 with a mandate to train personnel and evolve technology relating to food processing and preservation. The Central Warehousing Corporation was set up on 2nd March, 1957 under Agricultural Produce (Warehousing and Development) Act 1956. On 1st January, 1965 Food Corporation of India was established. In 1958, the Department of Food started a centre at Hapur known as Grain Storage Research and Training Centre with the main objective to train the personnel of State Government engaged in food procurement, storage and distribution. This centre was upgraded during 1968-1973 with the technical and financial assistance of UNDP and this centre was redesignated as Indian Grain Storage Institute (IGSI). Two field stations at Ludhiana and Bapatla (later shifted to Hyderabad in March 1979) were established in 1968-69. Subsequently, three stations of IGSI at Jabalpur (October, 1980), Udaipur (February, 1981) and Jorhat (May, 1981) were also established. The overall objective was to minimize losses of food grains by development of modernized grain storage practices for the farmers, traders, cooperatives and large storage of food grains in the country and also to evolve the methodology to be adopted by the Save Grain Compaign which has its headquarters in the Department of Food.

Insect infestation occurs in stored grains and grain products to variable extent depending upon the storage conditions in developing countries. The losses of nutritional compounds are proportional to the extent of insect infestation, nature of insect feeding and distribution of nutritional chemicals in different seed components. 1. Sources of Insect Infestation There are many sources that leads to infestation in storage, viz., left over seed from bins or stores or spilled seeds under the stacks, cleanings, sweepings of storage structure, processing plants, old infested stores, old gunny bags, insect infested transport vehicles, storing insect infested seeds with fresh stock or vice-versa, entry of insects from neighbouring stores and carry over of field infestation

The damage to food grains in the storage may be caused due to insect attack, mould, fungi, bacteria, rodents, heat and moisture. The value of grain for milling purposes and human food is directly correlated with the amount of insect contamination present. The immature stages of rice and granary weevils, lesser grain borer, Angoumois grain moth and occasionally the flat grain beetle, cadelle, rust red flour beetle and saw toothed grain beetle live inside the kernels where they are hidden from view until they emerge. Grain from casual inspection appears to be in good condition but may contain enough internal infestation which render it unfit for human food or unfit for purchase for future sale as milling stock. In general, millers have found that wheat with more than 0.5 per cent of infested kernels is unfit for milling. The need for a rapid and accurate method of estimating insect contamination in grain offered for sale has become more and more important to both grain dealers and millers. Methods for Estimation of Damage In order to assess the damage caused to food grains due to any one or combination of various factors; physical, chemical and micro-analytical methods are employed according to the necessity and information required. Various methods have been employed by field workers as well as by laboratory technicians in estimating damaged grains in food grains with particular reference to detection of insect infestation which alone cause maximum damage. These methods have been described below.

A number of insects infest seeds in storage. These insects infest seeds to fulfill their feed and shelter requirements, which result into qualitative as well as quantitative loss of seeds. Indian climate is very favourable for their multiplication and growth throughout the year. Storage pests move along with commercial products from one area to another and even to different countries in the world. Some adult insects are strong fliers and may spread from one to another place of storage or from source of infestation. Generally, all insects infesting seeds in storage belongs to insect order Coleoptera and Lepidoptera (Table 4.1). Some minor species belong to Pscoptera. These pests cause losses to man by destroying large quantities of grain, corn, legumes (beans, lentils and peas), milled cereal products, flour, bran, macaroni and other paste products, dried fruits, dried vegetables, cheese, nuts, candy and other food materials. They contaminate and thus eliminate for human consumption, far more food than they eat and either cause direct loss or transmit diseases to man and his domestic animals. These insects can be categorized as major or minor pests according to the loss of seeds caused by them. Similarly, on the basis of their feeding behavior, they can be grouped as follows:

There are several species in this cosmopolitan family that are of importance chiefly as pests of stored foods, flour, grain, seeds and bulbs, feeding on these products or the fungi that develop on them. These mites are mostly very minute, almost colourless, with the body bearing a few long setae, and with the legs terminating in one claw and usually a sucker. When very abundant the mites and their cast skins form a buff-colored dust and give rise to a characteristic odour. The living mites move slowly away from a source of light. An interesting characteristic of these mites is a nymphal resting stage (hypopus) during which they take no food but attach themselves to other mites, insects and humans by means of suckers and are thereby transported to other suitable places for development, where they drop off, moult, feed, and develop into adult stage. The hypopus may be resistant to fumigants. However, the cheese mites, Tyrophagus casei do not have a hypopial stage. Prolonged storage of products subject to infestation without cleaning of pantries and shelves where such materials are placed. These mites can subsist on organic debris in cracks, crevices and corners and are readily spread to other areas.

It is interesting to note that only 25 of about 1200 species of birds found in India have been reported to inflict damage to crops, vegetables and fruits. The exact ecological causes for population increase of individual species have yet to be studied. It would appear that, in general, the granivorous birds became abundant with the increase in area under grain crops and the subsequent storage of grain in godowns and bulk storage. The details of important bird pests are given below:

Economic Importance of Rodent Pests They consume and damage foods in the fields and in stores. In addition, they spoil it in store by urine and droppings reducing the sale values. Due to their gnawing and burrowing habit they destroy many articles (packing, clothes and furniture) and structures (floors, buildings, bridges, etc). By gnawing the electrical cables they can cause fires. They are responsible for transmitting diseases dangerous to human and domestic animals. Among many pests of agricultural crops and stored grain products, rodents are the major pests which do the great damage. Rodents including rats, mice and squirrels are gnawing animals having chisel like teeth. They have highly developed sense of smell, taste and hearing. They are omnivorous and feed on grains, vegetables, fruits, meat and other products in the houses or in the fields. Rats daily consume food equal to about 10 per cent of their body weight and the figure may go up to 30 per cent in case of mice. Rats are among the most destructive pests of paddy in the field causing about 5-10 percent damage. It is estimated that these animals destroy 30 per cent of the total world’s cereal production. In India, 10 million tonnes of food grains are lost every year. It is often said that if rodent ravages could be controlled, a huge amount of food grains can be saved. Of the 84 species of order Rodentia in India, 50 belong to family Muridae. The important ones belong to two sub-families, viz., Murinae and Gerbillinae. Murinae has 18 species of genus Rattus, 2 of Bandicota, 7 of Mus, 2 of Apodemus and a few each under eight other genera. The sub-family Gerbillinae has 2 species of Gerbillus, one each of Tatera and Meriones. Family Sciuridae has 10 species of flying squirrels and 13 species of tree squirrels in India.

As the name indicates, micro-organisms are very minute, cellular, living organisms which cannot be seen with the naked eyes (however, large colonies of fungi can be seen). Micro-organisms affecting stored grain can be divided into the following groups in order of their significance: Fungi Actinomycetes Yeast Bacteria Protozoa (not found in sound food grains) Fungi, bacteria and actinomycetes are grouped under the Thallophyta of the plant kingdom. The most important factors for their normal development are: (i) Nature of Food, (ii) Moisture, (iii) Oxygen and (iv) Temperature.

In the past several insect pests had entered India and are causing economically perceptible damage to native crops. The Government of India, in line with the International Standards on Phytosanitary Measures (ISPM), notified ‘Plant Quarantine Order, 2003’ to reduce the risk of introduction of exotic insect pests in India. The storage insect pests of quarantine concern for India have been listed in Table 9.1.

Since commencement of the settlement of world, the search for food had been uppermost, thereby, practising the conservation of food is a basic need for ensuring its ample supply to human being. The problem of food storage is growing fast day by day with the increase in the population. The existing shortage of protein and caloric requirements will not only be solved by growing more food and resorting to family planning measures but also by saving the produce from deterioration and wastage, and its efficient allocation to meet the growing requirement of population. In countries with varied climatic conditions, it is a steady struggle of man with insects, mites, rodents and microbes in getting the food stuff. Need and Objectives of Storage Since times immemorial, man adopted a particular system of storage and certain produce storage standards. Some of the storage methods are still in use in several regions, in the capacity varying from one kg to several hundred quintals, like hollowed gourds, skin bags, mud bins, excavated stones, woven baskets, underground pits etc., particularly in the tropics. The problems of storage in developing countries are more acute than that in well developed countries and a considerable disparity seems to be there in food availability. All need a food supply that should be nutritious, clean; free from insects, rodents, birds, other animal filth and harmful chemical residues. There are two types of needs, one immediately after harvest and the other in off season. There is no need of storing the produce for immediate requirement but for the latter case, the need to conserve produce properly is inevitable. Further, the need for storage has always arisen for one reason to distribute commodity in deficit production areas and the other based on improved quality standards. In all the way, therefore; growers, processors, transporters and warehouse owner must assist to comply with these requirements.

A series of efforts have been made to initiate the work on post harvest grain technology in India. The history of post harvest grain technology in India goes back as early as 1888 when COATS published several papers from Calcutta related to biology of stored grain pests. The first professional was appointed in the year 1905, known as Imperial Entomologist, Harold Maxwell Lefroy adorned with this post. Lefroy (1906) for the first time gave a tentative list of storage insects, which was further supplemented by Fletcher (1914). The problems of grain storage were discussed at the entomological meetings held at Pusa, Bihar in the years 1917, 1919 and 1923. The first step towards establishing an Institute in India was in the year 1950 when Central Food Technology Research Institute (CFTRI) was established at Mysore (Karnataka) with a mandate to train personnel and evolve technology related to food processing and preservation. The Central Warehousing Corporation was set up on 2nd March 1957 under the Agricultural Produce (Warehousing and Development) Act 1956. The Food Corporation of India was established on 1st January 1965. In India, the farmers in traditional bulk and bag storage for food, feed and seed stored about 65-70 per cent of the total food grains and seed purposes till next harvest. Rest 30-35 per cent are procured and stored by food grain organizations, like Food Corporation of India (FCI), Central Warehousing Corporation (CWC), State Warehousing Corporations (SWCs), cooperatives, rural godowns and other state government agencies. In 1958, the Department of Food established a centre at Hapur known as Grain Storage Research and Training Centre (GSRTC) with the main objective to train the personnel of state government engaged in food procurement, storage and distribution. This centre was upgraded during 1968-1973 with the technical and financial assistance of UNDP and GSRTC and redesigned as Indian Grain Storage Institute (IGSI). The field stations at Ludhiana and Bapatla (later shifted to Hyderabad in March, 1979) were established in 1968-69. Subsequently, three stations were also established at Jabalpur (1980), Udaipur (1981) and Jorhat (1981).

Introduction The increase in agricultural production, particularly food grain is one of the major problems of national planners to achieve the target in the food production. Our farmers have been utilized more and more the modern methods of agriculture including the use of chemicals for protection of crop and stored products against the pests. A successful farmer knows that what pests to expect on his crops and stored products, when and under what conditions their attack will be possible. But due to insufficient knowledge of chemicals and their application, our farmers use them without care and injudicious manner, therefore, these chemicals not only give poor kill of insects but also cause the hazards to man and domestic animals. Success in pest control operations depends on many factors such as correct identification of pest, proper timing of insecticidal application, right choice of chemicals and their formulations, doses and method of application. Fumigants are still widely used for the control of insects and other pest organisms. Because of their unique characteristics and the great adaptability of fumigation technique, fumigants can often provide effective and economical control where other forms of pest control are not feasible. The development of light weight plastic sheets to enclose spaces or materials requiring fumigation has extended its use and made control procedures easier and much more adaptable. Among the fumigants, aluminum phosphide, ethylene dibromide (EDB), Ethylene dibromide- carbon tetrachloride (EDCT) etc. are most common in tropical and sub-tropical while methyl bromide is prevalent in temperate regions. Modern technology and research have also brought to notice certain problems with fumigants that are previously unknown. Among these, adverse effects on seed quality are most important. Thus, fumigants used in seed stores should not affect the viability of the seeds, should not be persistent, non-corrosive and highly diffusible.

All due precautions have to be exercised in handling pesticides because many of these leave toxic residues on treated food materials and plants which accumulate in higher concentrations in animals which consume these. General Precautions Read the precautions given by the manufacturer of the pesticides carefully. Store the pesticides under lock and key; prevent access of children to these; empty containers must be disposed off safely. Blood and skin contaminations must be avoided. The godown for fumigation must be made airtight by closing the doors, windows, ventilators, crevices etc. In case of fumigation, the operator must use a suitable gas mask. It is a face-piece connected to a canister containing an absorbent material for the vapours of the fumigants by means of a flexible non-kinking breathing tube and provided with valves so that all air inhaled by the user passes through the canister and the exhausted air passes directly to the outside atmosphere through a non-return valve. The absorbent canister carries instructions indicating the number of hours for which it is effective in an atmosphere charged with the fumigant. After the required exposure period, aerate the godown thoroughly. First open the entrance door, keep it open for 6-7 hours, then only enter and open other doors or windows.

Insecticide resistance to both fumigants and contact insecticides is an increasing problem in controlling stored grain and grain product insects throughout the world (Table 14.1). Hence, persons engaged in food commodity storage and preservation world over are concerned about the resistance of stored product insects to contact insecticides and fumigants. It is, therefore, necessary to work out strategies to delay or minimize the probability of resistance evolution. Resistance to pesticides is the ability of a strain of insects to tolerate doses of toxicants which would prove lethal to a normal population of insects of the same species. Resistance results when occasional resistant individuals arise in a population and survive the pesticidal treatment. These survivors then reproduce and confer the resistance to their offspring in succeeding generations. Resistance is the ability of a population (of insects) to survive a dose (of insecticide) that would normally kill 100 per cent of a susceptible population. Insecticide resistance is a dynamic phenomenon dependent on biochemical, physiological, genetic and ecological factors. The chances of development of insecticide resistance in stored grain insect pest are more because of their life style, i.e., to remain confined in limited area. This results in more common inbreeding of the homozygous resistant strain resulting into homozygous resistant progeny. At the same time their management, once detected, can be easily achieved with the application of sufficiently acceptable sufficiently higher dose of the most appropriate insecticide to eliminate all the resistant survivors The insect pest of stored grains can be conveniently divided into two groups, i.e., coleopterous and lepidopterous, therefore, the subject on these two groups has been pooled accordingly.

The produced food grains have to be stored either for short or long duration for utilization in the coming times for food, feed and seed. In storage, these undergo 9.33 per cent losses due to various agencies such as rodents, insects and mites, microorganism and moisture in India, whereas, in other developing countries, the losses are as high as 30 to 50 per cent. Therefore, with an urge to produce more, there is still urgent need to protect the produce in the storage to meet the challenge. As a result of improved storage technology, the losses in Government Warehouses could be reduced to minimum but at farmers’ level, where 60-70 per cent of the produce is retained, the losses are still too high. The management of insects in stored products is in transition from a dependence on regular applications of chemical insecticides to the use of integrated pest management (IPM). IPM involves understanding interactions between stored product environment and insects associated with stored products, and replacing all or most of the chemical applications with cost effective non chemical alternatives. The increased emphasis in adopting IPM strategies for stored product insects is primarily due to consumers’ demand for food free from pesticide residues. The transition from a heavy reliance on chemicals to little or no chemical input and increased use of non chemical approaches requires a thorough understanding of stored product insects, their identification, monitoring, biology, ecology and response to chemical and non chemical management options. The current scenario of stored grain protection in India depends totally and judicious use of IPM strategies. For safe storage of food grains, both the preventive and curative measures are required:

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