4. Pests Control

Barley is a host for numerous pathogens and insect pests attacking the plant at different stages of growth. The attacks at different stages would have various consequences on productivity but the degree of their impact on quantity and quality of the post harvest products may vary according to production, environment, crop husbandry and post harvest procedures. The biological factors affecting the stored grains are illustrated in the Fig. 4.1.

Figure 4.1. External and internal factors affecting storage quality of barley grains

The storage microorganisms and pests cause economical losses in stored grains in many parts of the world. The loss is higher especially in developing countries because the grain storage structures do not have adequate conservation properties. The post harvest loss of 5-10% for grains is usually considered inevitable at the village level in developing countries (Navarro et al., 1997) but this is likely to be higher for barley in rural areas of many developing countries.

4.1 Post harvest microorganisms

4.1.1 Field diseases with effect on post harvest procedures

Undoubtedly, the infection / infestation of harvested or stored grains by pathogens, saprophytes and insect pests directly reduce the quantity and quality of the grains. Occurrence of pests and diseases at vegetative stage and near the harvest time is, also important factors reducing the quantity and quality of the products. Although agents that attack the crop at earlier stages appear as less significant for the post harvest operations, they can reduce the quantity and quality of the products significantly under suitable conditions. For example, species of fungi producing mycotoxins and sunny bug injecting various enzymes could play very substantial role in quality of the stored grain. Thus, these agents and their relation with post harvest procedures are also described briefly.

The importance of field diseases is various parts of the world are depicted in Table 4.1.1. As seen in the table, diseases caused by Helminthosporium species seem to be the most widely occurring diseases. The common root rots, spot blotch and the seed borne leaf stripe are treated in this group. The smuts seem to be ranking 4^th in general following scald and yellow rust.

4.1.1.1 Root and foot rots:

The root and foot rots reduce the yield and quality of the barley crop through reducing tillering and amount and weight of the grains. These are caused by mainly soil borne pathogens, but some may also be transmitted through the seeds. Among the root infecting pathogens, Helminthosporium sativum is the most widely occurring species. The Fusarium species F. culmorum, F. graminearum and F. nivale can also infect the crowns and some even infect the leaves and heads later.

4.1.1.2 Foliar diseases:

There are a number of microbial agents causing different kinds of blotches and lesions on leaves of barley. Symptoms may be in the forms of spots, lesions, stripes or blotches. The most widely occurring fungal foliar diseases are scald (R. secalis), spot blotch (Helminthosporium sativum), Powdery mildew (Erysiphe graminis), Rusts (Puccinia spp.) and the barley leaf stripe (Pyrenophora graminea). The common characteristics of these symptoms are that they reduce the photosynthesis area. Often diseased plants have less ears and smaller and lighter grains.

Among the foliar diseases, the most important one is P. graminea (Fig. 4.1.1.2) which is wide spread disease in Mediterranean region including Morocco (Boulif, M., 1990; Lyamani, 1990; Arifi, 1990), Turkey (Cetin et al., 1995) and is also recorded in Korea (Lee, 1981). The disease is seed borne and infects the plant during germination process and develops systemically within the plant. The first symptoms appear at the seedling stage as pale, white stripes along the main leaf axil. This stripe develops and becomes easily visible and extended as the plant grows and finally leaves may be thorn apart as a result. Infected plants are stunted and produce no or few heads and the heads would have shriveled grains. Under moist conditions, sporulation takes place on the leaves and spores are spread by the wind to the ears of heads where the spores infect the floral parts which produce infected seeds. Infection of the floral parts is favored by cool and humid conditions. The infected seeds have to be treated with seed treatments if it is to be used as seeds.

Table 4.1.1: The Ranking of Importance of Main Pre-harvest Diseases of Barley in Different Parts of the World (1)
Region	Stem rust	Yellow rust	Leaf rust	Powdery mildew	Helm. spp.*2	Scald	Smuts
Middle east	6	3	5	1	2	5	4
South and Far East	5	1	6	3	2	7	4
North Africa	7	5	4	3	1	6	2
East Africa	7	4	3	5	2	1	5
Mediterranean Europe	7	3	6	2	1	5	4
South & Far east Asia	6	1	5	3	2	7	4
(1) Adapted from Srivastava (1977) and Kamel (1981); *2: Helminthosporium spp.

 

Figure 4.1.1.2. Severe infection of barley leaf stripe (Pyrenophora graminea)

4.1.2 Ear diseases

The smuts (Ustilago spp.) directly affect the yield and quality of the grains. This is because they replace the grains with their dark spore masses (Fig. 4.1.2 a, b). Three types of smuts may occur in barleys; loose smut, semi covered smut and covered smut. Their symptoms are similar and all produce dark spore masses in the place of grains in the ears and no grain is harvested from such plants. Their symptomatic differences are related to appearance of the spore balls. In loose smut (U. nuda), the seed coat is totally destroyed and spores can be freely flown away by the wind and only the axil of the heads may remain on the plant. In U. nigra,

Figure 4.1.2a. Covered smut of barley (Ustilago hordei)  

Figure 4.1.2b. Loose smut of barley (Ustilago nuda)

seed coat remains relatively intact and spore balls remain on the heads until late. However, towards the maturity the seed coat may be thorn apart and spores can be spread by the wind. In contrast, the seed coat of U. hordei is the strongest among the three smut species and remains intact until the harvest time. These structures are broken apart during harvest and spores are attached onto the clean seeds. The transmission of these three smut species is through infected or contaminated seeds. Loose smut spores infect the floral structures and as a result the fungus settles in the embryo of the floret. In contrast, the spores of U. nigra and U. hordei are carried on the seed coats to the next season. These spores infect the seedlings during germination and the fungus develops systemically up to the heads where they produce the spore balls in the place of grains. Apart from the smuts, Claviceps purpurea can also occur on barley heads as hard black horn like structures in the place of grains, if care is not taken.

The use of clean seeds or seed treatment is the most feasible means of control of the smuts. However despite this possibility, the smuts cause still significant yield losses in many developing countries, since seed treatment is not practiced properly. There are various reports indicating different levels of losses in various countries, resulting from the smuts. These are for U. nuda in Iraq (Hamdany et al., 1990), for U. hordei and U. nuda in Morocco (Lyamani, 1990), in India (Atyheya et al., 1981) and in Tunisia (El Ahmed et al., 1981) and for the three species of U.hordei, U.nigra and U. nuda in Turkey (Öğüt & Onan, 1995) and in Jordan (Mamluk, 1981).

4.1.3 Grain infecting field microorganisms

Many fungal species may be found in barley grains, but usually many of them would be unimportant. For example, Aktas (1999) have reported 23 fungal species in the barley grain flora in Eskisehir, Turkey and found the Alternaria alternata most frequently occurring species, but reported that the rest was at very low level of contamination levels, apart from U. nuda which was found in 44% of the 199 samples.

The main fungi infecting the heads and seeds of barley in the field belong to the genus Fusarium. The species infecting the barley heads include F. graminearum, F. poae, F. avenaceum, F. sporotrichoides (Salas et al., 1997), F. culmorum, F. moniliforme and F.nivale (Richardson, 1979).

The Fusarium species infect the grains and heads of barley in warm and humid areas especially if the wet and rainy periods coincide with the crop maturity. The occurrence of head blights have been stated in North West of Russia (Schipilova & Gagkaeva, 2000), in India (Paramjit et al., 2000), in Mexico (Gilchrist et al., 2000) and in Poland (Wisniewska et al., 1997). Those that have been reported to occur on barley seeds by Richardson (1979) include Fusarium culmorum, F. graminearum, F. moniliforme, F. nivale and F. poae. These species can also be involved in formation of leaf blotches and root/foot rots (Figure 4.1.3).

Apart from Fusarium spp., the species of Alternaria, Cladosporium and Dreschlera can infect the grains especially on the embryo side before harvest causing black points. These are common fungi that can be found world wide, but their frequency and severity may differ according to conditions. All grain infecting fungi reduce the quality of grains and could be the main cause of spoilage. They not only reduce the quality of grains, but also the toxins produced by some of the species may cause health concerns for livestock and men. The grains infected by such species are also more vulnerable to storage fungi such as Penicillium spp. and Aspergillus spp. Classification of the genera Fusarium, Alternaria, Helminthosporium, Penicillium, and Aspergillus which are the main post harvest micro organisms is illustrated in the Table 4.1.3.

Figure 4.1.3. Life cycle of Fusarium species (Parry, 1990)

Table 4.1.3: Classification of the Most Important Genera of Fungi Associated with Infection and Spoilage on Barley Grains (Kingdom:Mycota, Division:Eumycota)
Division	Sub-division	Class	Family	Genus
Eumycota
	Ascomycotina	Plectomycetes	Euroticeae	Aspergillus
				Penicillium
	Basidiomycotina	Teliomycetes	Ustilaginales	Ustilago
	Deuteromycotina	Hyphomycetes	Helminthosporiaceae	Helminthosporium
				Alternaria
	Deuteromycotina	Hyphomycetes	Tuberculariaceae	Fusarium

4.1.4 Storage microorganisms

Stored barley grains are subjected to infection by many species of micro organisms. Although there are a few species of bacteria and yeasts that can infect the stored barley grains, the main storage microorganisms are species of fungi.

The most important fungal species causing spoilage of barley in storage belong to the genus of Aspergillus and Penicillium. In general Aspergillus species can be adapted to conditions without free water and can grow at lower humidity R.H.70% (Dube, 1990) whereas Penicillium species are abundant mainly in grains with high moisture content stored at lower temperatures.  Similar to Penicillium spp., species of Rhizopus, Mucor and Nigrospora can also invade the high moisture grains before or during the storage (Sauer et al., 1992). There are many other less important species of fungi that can be isolated from barley grains stored under unfavorable conditions. For example Lacey (1988) isolated 65 different species of fungi from wheat and barley grains stored in underground pits or in buildings in Iran. However, only the species of Aspergillus, Penicillium and Alternaria were indicated to be significant.

The means and time of invasion of the grains by storage fungi are significant for the establishment of management strategies. In general, it is considered that the wet weather conditions near the harvest time would favor invasion of grains by storage fungi. However, Tuite & Christensen (1955) found no storage fungi growing from the surface sterilized barley seeds collected from barley fields of Minnesota in a wet and showery season. Sauer (1992) reviewed the studies on time of invasion of grains by storage fungi and indicated that the fungi causing damage to grains in storage do not invade the grains to any significant degree or extent before harvest. Therefore it may be concluded that the storage fungi contaminate the grains during or after harvest, as the conidia of Aspergillus and Penicillium species are present in the air. Here, the procedures and conditions during harvest, transportation and storage determine the extent of the invasion of grains by storage fungi.

Aspergillus and Penicillium species may be seen world wide, but Aspergillus spp. (Figure 4.1.4 a) is more of a problem in tropical countries while Penicillium spp. (Figure 4.1.4 b) species are more abundant in tropical countries (Dube, 1980). However, their occurrence on barley grains is not limited to geographical regions and they occur in all parts of the world providing the favorable storage conditions. The limiting factors for their occurrence and severity are mainly crop husbandry practices, quality and moisture of grains and characteristics of storage facilities.

Figure 4.1.4a,b. Life cycle of Aspergillus spp. (a,top) and Penicillium spp. (b, bottom) (Dube, 1990).

In developing countries, majority of the farmers lack the essential knowledge of good crop husbandry practices and much improvement is needed for availability and use of improved cultivars, field levelling and control of weeds, diseases and pests. Improper and inadequate crop husbandry practices result in production of low quality grains such as shriveled, smaller and broken grains. Although most farmers tend to wait until the crop is dry enough for harvest, they can not avoid adverse weather conditions such as rain during harvest time and threshing. Such grains are more vulnerable to invasion by storage fungi. All these factors help multiplication of storage fungi and increase the risk of spoilage.

In addition to crop husbandry practices and crop quality, the type, quality and conditions of the storage facilities are the major factor determining the occurrence and severity of the storage microorganisms on barley grains. Apart from the large scale professional barley producers and traders, majority of farmers in developing countries do not even have storage facilities. The small scale farmers store the grains mostly in sacks or as bulks in buildings made up of wood or bricks but with no control facilities. The larger farmers can store the bulk grains in underground or above ground pits, usually with a polyethylene liner and covered with polyethylene sheets and other coverings. Here, lack of atmosphere control facilities is the key factor which promotes development of storage fungi on the grain. In such storage facilities, it is impossible to keep the grain at a suitable temperature and dry enough to prevent the growth of storage fungi. As a result, the storage fungi develops steadily on grains using the available moisture deteriorating the grains. During growth, fungi increase the respiration and heating of the grains (Sauer et al., 1992). The grains invaded by the storage fungi loose their germination capacity and its normal color and may be decayed totally depending on the extent of the growth of fungi.

The genera of Aspergillus and Penicillium are taxonomically placed in the Euroticeae family of the class Plectomycetes in Ascomycotina subdivision of Eumycota division in the fungal kingdom. Since sexual stages of some of the species are identified, the genera of Aspergillus and Penicillium are studied in the sub division of ascomycotina. However they extensively reproduce asexually through conidia and in fact, in many species sexual stage is absent or unidentified. They over winter as mycelia or conidia, but the species with asexual stages can also use the cleistothocia which contain the asci carrying the sexual ascospores as over wintering organ. The conidia are produced on conidiophores which are produced on the foot cells of the somatic hyphae which is hyaline, septate. The hypha is branched and multinucleate in Aspergillus (Fig. 4.1.4a) while it is highly branched and uninucleate in Pencillium (Fig. 4.1.4b). The color of the conidia such as blue, green, black or yellow gives the colony color and is a useful tool for the identification of species. The conidia resemble the glass beads and are produced as chains on phialide which is produced by metula on vesicle at the end of the conidiophores. The number and shapes of these reproduction structures are the major differences between the species of Aspergillus and Penicillium.

4.1.5 Mycotoxins in barley grains

The most important biological risk factor in the barley grains is the mycotoxins produced by various fungi that invade barley grains before or during storage. These fungi can be grouped in two groups. Some fungal species infecting the grains before harvest may produce mycotoxins in barley grains. These include the species of Claviceps spp. and Fusarium spp. The second group includes the storage fungi Aspergillus spp. and Penicillium spp.

The most known field infecting toxigenic fungus is the ergot Claviceps purpuea (Fr.) Tul. It may infect 38 gramineaceous species including barley Jones & Clifford, 1978). The fungus infects the florets during anthesis and sclerotia (known as ergot) is formed in place of the grains and these contain various alkaloids which may be hazardous to animals and humans. The fungus is more common in grass species and less frequent in barley (Gair et al., 1987) but it has been reported from India (Richardson, 1979). During harvest and threshing, the ergots formed in heads of barley or grasses in the field are mixed with the harvested grain trough breakage. The ergotism in livestock results from grazing eating diseased grains in pastures but it may also result from eating stored barley grains containing ergots.

There are a number of Fusarium species that can produce mycotoxins. Those that have been reported to occur on barley seeds by Richardson (1979) include Fusarium culmorum, F. graminearum, F. moniliforme, F. nivale and F. poae. These species can also be involved in formation of leaf blotches and root/foot rots. The Fusarium species have been shown to produce various mycotoxins such as Trichothecenes, zearalenone (ZEN), moniliformin, fumonosins and fusarins (Wilson & Abramson, 1992). So far, more than 70 individual trichothecenes have been identified but only the deoxynivalenol (Vomitoxin-DON) and nivalenol have been found to have significance on naturally infected commodities (Shepherd & Gilbert, 1986). Salas et al. (1997) reported that some toxins are specific for some Fusarium species. In his study barley infecting Fusarium species produced 10 different mycotoxins and DON and 15-DON was specific for F. graminearum, T-2, HT-2 and T-2 TET for Fusarium sporotrichioides and presence of NIV somewhat specific for F. poae.

In general, infection of the seeds by Fusarium species is favored by humid and rainy periods at generative periods.

Further fungal growth is promoted by moist storage conditions. However, if the grain is dried, the growth of the grain micro flora would be retarded.

Apart from the Fusarium species the storage fungi Aspergillus and Penicillium species are also responsible for production of a number of mycotoxins in storage. Wilson & Abramson (1992) reported production of 17 different mycotoxins or potential mycotoxins by Aspergillus species and 14 by Penicillium species, some being produced by both. The most well known mycotoxins produced by Aspergillus species are aflatoxins and those produced by Penicillium species are naphthoquinones. The general mycotoxin problems in stored grains are reviewed by Wilson & Abramson (1992), Fusarium mycotoxins by Shepherd & Gilbert (1986) and mycotoxins of mould species in cereal grains and animal feedstuffs by Buckle, A.E. (1986), Scudamore et al. (1986) and Paterson & Kozakiewicz (1997).

Although the mycotoxins are identified academically, there are few documents, most being in developed countries, indicating the extent of the toxicological problems in practice. Gilbert et al.(1983) found deoxynivalenol (Vomitoxin-DON) at insignificant concentration levels (<0.02 mg/kg) in feeding and malting barleys in England and Scotland. Similarly, the ADAS microbiologists found Ochratoxin A, Sterigmatocystin and citrinin in only 6, 3, and 1 barley samples respectively in 108 barley stores in England and Wales (Buckle, 1986).

However, the severity of occurrence of mycotoxin on livestocks was considered to be insignificant. In contrast, Ehling et al. (1997) indicated that WHO (1993) reported a relatively high mean DON concentration in food/feeds in South America, Africa and Southern China, the individual results varied considerably between 0.01 - 92 ppm. Scudamore et al. (1986) summarized the reports of outbreaks of mycotoxic porcine nephropathy linked with the ochratoxin A in feedstuff in livestock in a number of European countries including Denmark, Sweden, Netherlands, Hungary and Yugoslavia. The extent of Mycotoxin problem has been investigated in a number of developing countries by various workers. Lacey (1988) surveyed the wheat and barley stores in high oesophageal cancer area of Iran for toxigenic fungi and mycotoxins to study the linkage between the grain microflora and cancer incidence. The study concluded that despite the poor storage facilities, serious deterioration of the grains and detection of aflatoxins and ochratoxins, the cancer incidence and severity could not be linked with the mycoflora and mycotoxins of the wheat and barley grains in the area. However, it is clear that the storage facilities in the area need to be improved significantly to ensure better preservation of the quality of the grains. Similarly, Karacan et al. (2000) surveyed the grains from the regions of Marmara, Aegea, Black Sea, Mediterranean, Central Anatolia and Southeast Anatolia for microbial flora and mycotoxins such as aflatoxin, Ochratoxin A, DON, ZEN, T-2, HT-2 and tenuazonic acid. They found that the predominant fungi in black point formations were Alternaria sp., Penicillium spp. and Aspergillus spp. and the toxin concentrations were at ignorable levels. However, Gagkaeva and Levitin (1997) detected high level of toxigenic potential in F. graminearum Schwabe populations from wheat and high level mycotoxin contamination risk in the grains in South European part of Russia, although there was no such record for the far east parts. Bacha et al. (1988) indicated that mycotoxins are involved in the death of many cattle, horses and poultry died in Tunisia in 1970s and studied the mycotoxins of Tunisian cereals in 1988. The conclusion was that the Aflatoxins B1, B2, G1 and G2 all produced by Aspergillus flavus Link were detected especially in humid areas. Citrinin was encountered only in stores with hygene problems and ochratoxin A was absent in locally produced cereals.

4.2 Post harvest pests

Barley is a host for more than 100 species of insect pests. Various groups of insect pests attack the barley crop at different stages, reducing the yield and quality. The feeding of insects on barley crops results in loss of yields or grain quality. Yield loss usually occur through killing of plants or reduction in number of tillers, heads or grains as a result of feeding, injection of various toxins or acting as vectors for various microbial disease agents like barley Yellow Dwarf Virus (BYDV). The loss of grain quality occurs through shriveling, reduced weight and biochemical changes in the grains. Especially the effects of insects on grain quality have much relation with the post harvest operations. The shriveled and low quality grains are more vulnerable the spoilage by the storage microorganisms and storage insects. The low quality grains are broken apart more easily during harvest and threshing and provide better nutrition for the storage microorganisms and insect pests. Therefore, the insects infesting the crop in the field would also have a significant effect on deterioration of the grains in storage.

Many of the insect pests of barley are polyphagous feeding also on other cereals and grass weeds. No barley crop would be free from the insect pests, but just a few of the insects become key pests causing significant losses in various parts of the world. Majority of the pests have secondary importance and they cause economical losses occasionally only if the agro ecological conditions become suitable.

The insect pests of barley may be studied in 6 different groups considering their feeding habits and the type of damage they cause: 1) Soil borne insects; 2) Sap feeding insects; 3) Chewing insects; 4) Borers; 5) Storage pests; 6) Nematodes 7) Moluscae, Rodents and Birds. The insect pests of barley, infesting the crop in field are reviewed by Starks & Webster (1985) and Gair et al. (1987) and those in stored cereals are reviewed by Wilkin & Hurlock (1986).

4.2.1 Preharvest insects

4.2.1.1 Soil insects:

This group of insects mostly cause damage to the underground parts of the plants. The most important insects in this group include wire worms and false wire worms, the common species being Agriotes lineatus, A. mancus, A. obscura, A. sputator, Athous haemorhoidalis and Ctenicera spp. The adults of these insects feed on maturing cereals and grasses including barley, but the major damage are caused by the larvae which passes through the summers and winters deeper in the soil. As a consequence of larval feeding, the plants are totally killed or the established tillers produce shriveled grains. In addition to wire worms, there are a number of other species feeding on underground parts of barley. Among these, the white grubs in the genus Phyllophaga, many ants (formicididae), webworms (Crambus spp.) and Billbugs (Sphenophorus spp.) were reported to feed on underground parts of barleys in North America  (Starks & Webster, 1985). Briggs (1978) reported that the larvae of Crane flies caused about 0.2% loss in barleys of Great Britain.

4.2.1.2 Sap feeding insects:

This group of insects includes mostly the arthropods which feed on leaves and stems. During feeding they may inject various toxins and transmit various diseases. They multiply rapidly giving 10 generations in a season. The aphids are in this category. Although the predominant species may vary from country to country, the aphids occur in all continents (Vickerman and Wratten, 1979). The English grain aphid (Sitobion avenae (Fabricius)) infects other cereals, transmits BYDV and is a pest of barley in Europe, Asia as well as North and South America. Among the aphids, the Russian wheat aphid (Diuraphis noxia) is the most known cereal aphid and reported to occur in wide range of geography including North America, Latin America, South Africa, North Africa, Central and West Asia (Elmalı, 1999). They are small and have soft bodies with various colors such as whitish gray, green and black and sucking mouthparts. They over winter on weeds and infest almost all species of graminea. They suck the nutrients from the green parts of the plants, inject various toxins and also transmit important cereal diseases such as Barley Yellow Dwarf Virus (BYDV) and as a result reduce tillering and grain quality. The extent of damage varies depending on the species, population density and time of infestation. Total devastation of cereal crops in Konya province, Turkey due to Russian wheat aphid is reported (Elmalı, 1999). The control measures include development and use of resistant cultivars Starks and Webster (1985), early sowing, removal of alternative hosts and insecticide sprays. Other sap feeding insects include Chinch bug (Blissus leucupterus (Say)), leafhoppers (Family Cicadellidae), planthoppers (Fulgoridae) and mites such as Aceria spp., Petrobia spp., Penthaleus spp. and Oligonychus spp. Some mite species can also be found in cereal stores. For example, flour mite (Acarus siro) can feed on broken pieces of grains in cereal stores.

Among the sap feeding insects in developing countries include the sunny pest and cereal bugs. The most known species are Eurygaster integriceps and Aelia rostrata respectively. Various species can also be present in different countries. These include E. Maura, E. Austrica, A. acuminata, A. syriaca, A. furcula, A. melanota, A. turanica, A. virgata, A. albovittata and A. sibirica. The sunny pest and cereal bug species over winter in high forestry areas and move to cereal fields including barleys in the spring. The nimphs and adults suck the vegetative parts starting from seedling stage causing drying out of plants, reduced tillering and white heads. Later in the season the nymphs and adults feed on the maturing grains causing production of empty or shriveled grains. The infested grains loose their quality as a result of shriveling and also due to the enzymes injected. Such grains would also act as a host for the spoilage microorganisms and storage insects. The grains that have 2% or more sucked grains are considered to be of low quality. The sunny pests and cereal bugs are among the most serious insect pests of cereals in many countries in Asia, Africa and Eastern Europe and cause significant economical losses. In Turkey alone approximately 12 million USD is spent for the control of these insects and despite this, significant damage still occurs. They are predominant pests in West Asia and North Africa. Individual reports of importance have been made for Iran (Anonymous, 1967) and Turkey (Ozkan et al., 1999). Control of these insects is very difficult and requires integrated approach such as development and protection of biological control agents, establishment of green belts, use of efficient fungicide applications and improvement of tolerant/resistant cultivars.

4.2.1.3 Chewing insects:

The most important species of insects with chewing mouth parts is the Cereal leaf beetle (Oulema melanopus L.) which feeds on the epidermis opening narrow channels, consequently reducing the photosynthesis area and reduced grain weight. Other species include the widely occurring armyworms (Pseudaletia unipuncta), cutworms (Euxoa auxiliaris, Agrotis orthogonia), grasshoppers and other minor insects such as Mormon cricket (Anabrus simplex), blister beetles (Epicauta spp.), (Starks and Webster, 1985). These species generally feed on leaves and stems of barley as well as other cereals. The symptoms that the species cause include defoliation of the plants, blotching and streaks on the leaves, breakage of the stalks and damage on florets and grains.

4.2.1.4 Borers:

The insects in this group usually grow through the stems of barley. The species include barley joint worm (Harmolita hordei), wheat stem maggot (Meromyxa spp.), fritfly (Oscinella frit) and lesser cornstalk borer (Elasmopalpus lignosellus). The species of sawflies are the major hymenopterous pests of small grains in North America, Europe, North America and East Asia. The saw fly species include Trachelus tabidus, T. libanensis, Cephus pygmaeus and C. cinctus (Starks & Webster, 1985). The symptoms include stunting or death of plants, formation of shrunken or prematurely whitened heads, shriveling of grains and cutting of stems as in saw flies.

4.2.1.5 Nematodes:

There are a few nematodes that may be recorded on barley. The seed gal nematode (Anguina tritici) is mainly a pest of wheat but it may sometimes be observed on barley. This causes stunting of plants, deformation of leaves and produces galls on heads in place of grains. The contaminated grains are not suitable for use as seeds, food or feed.

Apart from the seed gal nematode, Cereal cyst nematodes infect the roots and produce pin head like cysts on roots. The most widely occurring cereal cyst nematode agent is Heterodera avena but species of H. filipjevi, H. mani, H.bifenestra, H.iri, H. hordecalis and H. latipons are among the causal agents. Other nematodes infecting the barley roots include meloidogyne spp. producing knots and Pratylenchus spp. producing brown lesions on the roots. Other nematodes of minor importance include stunt nematode (Tylenchorhynchus spp.), sheath nematodes (Hemicycliophora spp.) and pin nematodes (Paratylenchus spp.).

The nematodes in barleys reduce the water and nutrient uptake resulting in retarded plant growth, reduced tillering and grain weight, producing symptoms like similar to nutrient deficiencies. The effect of majority of nematodes on barley is not well known, but yield losses of up to 50 % has been reported due to cereal root knot nematode and yield gain of 21% as a result of control of Root lesion nematode of P. pallax in Wales (Gair et al., 1987).

4.2.2 Storage pests

The main cereal storage pests are from the various families of the orders of Coleoptera (Beetles) and Lepidoptera (Butterflies and moths) and also include mites (Table 4.2.2). The species of Coleoptera have hardened front wings and chewing mouth parts, while the adults of Lepidoptera have loose wings and siphoning mouth parts, larvae having chewing mouth parts. Both order have complete metamorphosis, egg - larva - pupa - adult (beetle) for Coleoptera (Fig. 4.2.2) and egg - Larva (or caterpillar) - Pupa - Adult (Butterfly or moth) for Lepidoptera (Morril, W.L., 1995).

The storage insects feed on many food sources that can be found in stores, although some have preferences. Therefore, it is impossible to separate them on the bases of commodities. However, here, the insects causing economically important damage to cereals, barley in particular, are explained. The storage pests of cereals can be studied in four different groups: 1) Primary storage insects, 2) Secondary storage insects, 3) Storage mites, 4) Birds and rodents.

4.2.2.1 The primary storage insects:

This group of insects constitutes the most damaging storage insects. This is so because they feed internally within the grains and without careful examination it is difficult to observe them until the damage is very obvious at which time the degree of damage becomes irrecoverable. The adults chew a hole in the grain and the females lay their eggs in these holes after mating. The larva passes through the larval instars within the grain transforming to pupa and then into an adult weevil. The larva, with its chewing mouth parts feeds on the endosperm but some portions of embryo can also be consumed. These insects prefer drier grains for feeding and can feed on grains with moisture content of 2%.

Table 4.2.2: Important insect pests of barley stores
Order	Family	Species	Common name	Type*1
Coleoptera	Dermestidae	Trogoderma granarium	Khapra Beetle	***
	Ostomatidae	Tenebrioides mauritanicus	Cadelle	*
	Bostrychidae	Rhyzopherta dominica	Lesser grain borer	***
	Silvanidae	Oryzaephilus surinamensis	Sawtoothed grain beetle	*
	Silvanidae	Oryzaephilus mecator	Merchant grain beetle	*
	Tenebrioidae	Tribolium castaneum	Red flour beetle	*
	Tenebrioidae	Tribolium confusum	Red flour beetle	*
	Tenebrioidae	Tribolium molitor	Red flour beetle	*
	Tenebrioidae	Gnathocerus cornutus	Broad horned flour beetle	*
	Curculionidae	Sitophilus granaries	Granary weevil	***
	Curculionidae	Sitophilus oryzae	Rice weevil	***
	Curculionidae	Sitophilus zeamais	Maize weevil	***
	Cucujidae	Leomophloeus(Cryptolestes)ferrugineus	Red grain beetle	*
	Cucujidae	Ahasverus advena	Foreign grain beetle	*
Lepidoptera	Gelechiidae	Sitotroga cerealella	Angoumois grain	***
	Pyralidae	Anagasta (Ephestia) kuehniella	Mediterranean flour moth	*
	Galleriidae	Ephestia cautella	Tropical warehouse moth	*
	Galleriidae	Ephestia eutella	Tobacco moth	*
	Galleriidae	Ephestia figuliella	Raisin moth	*
	Galleriidae	Pyralis farinalis	Meal moth	*
	Galleriidae	Plodia interpunctella	Indian meal moth	*
Acarina	Acaridae	Acarus siro	Grain mite	*
*1: ***: Primary grain pest; *: Secondary grain pest

Figure 4.2.2. Life cycle of Trogoderma granarium, a member of Coleoptera (Adapted from Yasar, 1996 and Akan, 2003).

Economically, the most important species in this group are the grain weevil species (Sitophilus spp.), namely rice weevil (S. oryzae), maize weevil (S. zeamais) and granary weevil (S. granarius). The adults are dark brown, the egg, larva and adult stages all take place in the grain and adults can fly to fields to re-infest the crops. They occur worldwide and can cause significant losses in cereals in Turkey (Dörtbudak et al., 1988).

Other economically important species in this group include Lesser borer (Rhyzopertha dominica (Fabricus)). This species is cylindrical, 3 mm long, strong flier and favor dust particles and broken grain particles. The less damaging primary storage insect is the Lepidopter Angoumois grain moth (Sitotroga cerealella). The adult moth of this species is 5-8 mm long and can not feed on whole grains with its sucking type of mouth parts. The females lay their eggs among the grains and the larva feeds into the grains, feeds there, pupates and then transforms into adults. This species favors feeding on broken grain pieces and grain dust.

4.2.2.2 The secondary storage insects:

The insects that feed on parts of the grain such as broken grains or particles of grains, dusts or flours are considered in this group. The species in this group feed on the outside of the grains and prefer embryos. The adults are 3-4 mm long, brown or reddish - brown in color. The best known species in this group are flour beetles (Tribolium spp.). There are slight differences between the T. confusum and T. castaneum especially in the structure of antennas and eyes. The females lay their eggs among the grains and the compaction of dusts and grain particles are very favorable for the flour beetles to survive. The adults can live up to 5 years and when the environment becomes unfavorable they secrete quinons which turns the flour into pink color.

The saw-toothed grain beetle (Oryzaephilus spp.) and merchant beetle (O. mercator) are among the common storage grain infesting species. Development from egg to adult takes place in 25 days. The eggs are laid singly or as groups on the feed sources. The larva is pale yellow with dark segments on thorax and the adults are black, 2.5-3 mm long. Larvae can not damage the whole grains but can feed on broken grain pieces, dusts and flour. The grain beetles (Cryptolestes spp.) group also has three species namely flat grain beetle (C.pusillus), rusty grain beetle (C. ferrugineus) and flour beetle (C. turcicus). These can feed externally on the grains consuming embryo as well as broken grain pieces, dust and flours.

In addition, a number of dermestids such as Trogoderma variable, T. glabrum and most importantly the Khapra beetle (T. granarium) cause significant damages in cereal stores. The adults of khapra beetle have a very short life span of about 1-3 weeks, the larvae can remain alive for several months without food and can tolerate to adverse conditions such as 2% moisture and 44 °C o temperature (Pedersen, 1992). All this makes the Khapra beetle one of the most significant storage pests of cereal grains and difficult to eradicate. The Khapra beetle is the most damaging dermestid in countries of India, Pakistan and arid regions of Africa (Pedersen, 1992). Ring (1965) reported the records of total loss of 300 tones of barley in USA, 30 tones of grains in southeastern Turkey and average grain loss of around 20-30% in Turkey due to Khapra beetle. The occurrence and importance of Khapra beetle in grain stores are reported for Afghanistan, Iran, Iraq, Jordan, Kuwait, Libya, Pakistan, Saudi Arabia, Sudan and U.A.R. (Anonymous, 1967) and in Saudi Arabia (Rostom, 1993).

Additional insects that may cause damage to stored cereals include Catedelle (Tenebroides mauritanicus L.), Cigarette beetle (Lasioderma serricorne) and drugstore beetle (Stegobium paniceum L.), Indian moth (Plodia interpunctella), the almond moth (Cadra cautella), tobacco moth (Ephestia elutella) and Mediterranean flour moth (Anagasta kuehniella) (Pedersen, 1992).

In addition to the insects that favor drier grains and those feeding on broken grain pieces, dusts and flour, there are a number of insect species feeding on moist grains under damp and moldy conditions. These are more of a problem especially in humid areas and with storages without sufficient drying and aeration facilities. These include foreign grain beetle (Ahasverus advena), hairy fungus beetle (Typhaea stercorea L.), Mealworms (Tenebrio molitor, T.obscurus, Alphitobius diaperinus), psocids - booklice (Liposcelis spp.) and mites (Acarus spp.).

4.2.2.4 Storage mites:

Apart from the members of the coleoptera and diptera, the mites (Acaridae family in Arthropoda) are studied together with the insect pests due to the nature of their behaviour and damage. Although many mite species are predators of many insect pests and also feed on moulds, some species are also pests of stored grains especially in temperate climates (Wilkin, 1975). The mites can also feed on the embryos of the grains. The most important mite species causing damage to barleys in storage is the Acarus siro L. which favors damp grains and conditions. Favorable conditions are 23 -25 °C and 75 - 85 % R.H. (Pedersen, 1992). It is reported to be a significant problem in barley stores in tropical and subtropical countries but it may be present in where ever the conditions are suitable. A. siro has been significant problem in cereal stores in UK (Wilkin & Hurlock, 1986) and in souteastern part of Turkey (Yildirim, et al.,1997). Together with A. siro, Lepidoglyphus destructor and Cheyletus eruditus have been reported to be important pests of cereal grains in Turkey (Emekçi and Toros, 1999). Some other species have also been reported in various countries. For example, Acaropsis sollers is reported in Saudi Arabia (Rostom, 1993), and together with this Tyrophagus sp., Calogyphus berlesi, Rhizoglyphus sp. and Oribatula sp. in Iraq (Mahmood, 1992).

4.2.2.5 Birds and rodents:

Barleys, as well as many other crops are subject to damage by birds and rodents. They can cause damage both in the field and in storage. Birds can pick up the seeds following sowing if especially shallow seeding practiced. The birds can pick the grains from the heads near the harvest time causing significant losses for example in south east Anatolia of Turkey (Akın, 1973) as well as in many other locations. In addition, the birds can also enter the unprotected grain stores and eat the grains. Among the most important bird species causing such damage are crows (Corvus spp.) and sparrows (Passer domesticus, Sturnus vulgaris).

Rodents can also cause important losses in field and stores. The Microtus spp. and Microtus arvalis are common problems especially in fields. These can eat the seeds and seedlings in the field after sowing. Their control in field is difficult but application of LPG gas into the tunnels or placement of seeds treated with Zinc phosphide near the open end of the tunnels are practiced by some farmers for this purpose. The rodents are also among the major problems in storage. The rodents are capable of passing through very small holes and can be real problems in barley stores in developing countries. The major species that infest barley stores as well as many other commodities include Mus musculus and Rattus rattus. These are present almost in all developing countries. They are reported to cause damage in stores in all parts of Turkey (Yildirim et al., 1997) and in Pakistan, Sudan and other parts of the Near East region (Anonymous, 1967).

4.3 Control of post harvest microorganisms and pests

In order to minimize the losses due to post harvest losses caused by microorganisms, insects or other pests, application of appropriate control measures is necessary. These procedures include better crop production practices, control of diseases and pests in field, better harvest technology, controlling the storage atmosphere and use of pesticides at various stages such as in field, on seeds or in storage effectively. The control measures for post harvest diseases and pests and their status in developing countries are as follows.

4.3.1 Better crop husbandry practices

Since the post harvest diseases and pests favor low quality, shriveled and broken grains, the production of better quality grains is the first stage for management of post harvest pests. The procedures to achieve this include selection of right cultivars, use of quality seeds, practicing good soil tillage, appropriate fertilization and other crop production practices.

4.3.2 Preharvest control of diseases and pests in field

Control of field diseases and pests is necessary for production of good quality grains. Moreover, many post harvest diseases and pests originate from field infection/infestation. Grain infecting fungi such as Fusarium spp., Alternaria spp. and Helminthosporium spp. infect the grains in the field before harvest and continue their spoilage in storage under appropriate conditions. Similarly grain veewils (Sitophilus spp.) can infest the grains in the field and then be transported to the storage together with the grains. Therefore their control in the field would help in preventing, or at least minimize, initial infestation of the grains before storage. The pre harvest control measures include use of resistant cultivars, seed treatments for seed borne diseases such as smuts (Ustilago spp.), barley leaf stripe (P. graminea) and wire worms, fungicidal sprays for foliar diseases which lower the grain quality such as Scald (R. secalis) and powdery mildew (Erysyphe graminis) and insecticidal sprays for sunny pest (Eurygaster integriceps) and cereal bugs (Aelia spp.). However despite the recommendations, control measures are not taken adequately in most of the developing countries. This is because most of the farmers are not aware of the importance of the diseases and pests and control technology or their financial status does not allow them to focus on this. As a result, the barley grains produced are of lower quality than the potential, which are vulnerable to storage diseases and pests. However in some countries, state agricultural organizations may execute the protection programs for pests causing economical losses in wide areas. For example, the survey and insecticide spray for the control of sunny pest and cereal bug in Turkey have been carried out by the institutions of Ministry of Agriculture until recently. However, there is a growing debate as to the efficiency and feasibility of this approach. In order to achieve the control of diseases and pests, practical integrated strategies need to be developed and the technologies should be transferred to the farmers.

4.3.3 Appropriate harvest procedures

Harvest procedures not only affect the direct grain losses but also affect the grain quality and as a result the losses due to post harvest diseases and pests. To minimize this effect, the harvest should be done at right time as the moist grains are more vulnerable not only to storage micro organisms such as Penicillium spp. and Aspergillus spp. but also to a number of storage pests such as A. advena, T. stercorea L., T. molitor and Liposcelis spp. The efficiency of threshing procedures can also affect the grain quality.

The portion of broken grains may increase if harvest delayed and thresher adjustments and procedures are not done properly (Demirci, 1982). In such situation there would be higher risk of microbial spoilage and insect damage in stores as such grains would provide more nutrient sources for many post harvest insects, especially secondary storage insects such as flour beetles (Tribolium spp.) and saw-toothed grain beetle (Oryzaephilus spp.) which feed on broken grain pieces, dusts and flour.

In very rural areas of most developing countries the small farmers harvest the crop by hand and leave the crop outside until threshing time. The threshing may also be done with rather primitive methods which would result in higher portion of broken grains. Similarly, even with the medium size farmers who harvest the crop with combines, the harvest procedures are not appropriate to minimize the grain loss and breakage, due to inadequate training of the operators. To improve this, efficient extension activities are needed for the training of farmers and combine operators.

4.3.4 Drying the grains

Many post harvest diseases and pests favor moist grains in storage. These include microorganisms such as Penicillium spp. and Aspergillus spp. and insect pests such as foreign grain beetle (A. advena), hairy fungus beetle (T. stercorea L.), mealworms (T.enebrio spp.), booklice (Liposcelis spp.) and mites (Acarus spp.). In order to avoid the spoilage by these agents, the grains may have to be dried if the moisture content is too high at harvest time. The efficiency of grain drying has been reported for the control of Acarus spp. (Wilkin, 1975). The moisture content of the grains must not be over 13-14% in order to avoid infestation by these microorganisms and insect pests. The large producers and traders may have drying facilities but the small and medium size farms do not. However some farmers dry the grains in the open air before placing them in storage

4.3.5 Building of better storage facilities and control of storage atmosphere

The characteristics of the storage facilities and atmosphere in them are the major factors determining the extent of development of storage microorganisms, pests on barley grains and resulting damage. Therefore, ideally the storage facilities should have sufficient isolations and controllable atmosphere to create the most adverse conditions for the development and multiplication of microorganisms and pests. There are many storage types with different degrees of sophistication and facilities, described in previous sections of this title. The better quality storage facilities are present only for large companies and organizations in the developing countries. The majority of small and medium size barley producers in developing countries do not even have storage facilities and they store their grains either as bags in buildings, or as bulk in wood or concrete stores. The medium and large size farmers may also store the grains in underground or above ground pits. In most cases these would be covered polyethylene sheets and have almost no atmosphere control facilities.

The grains in these primitive storage facilities would have almost no protection against the storage microorganisms and insect pests other then the covering. In fact if the covering is of good quality and properly placed, the grain could be protected at least for a season. However in many cases the grains in such pits are exposed to moisture, internal and external heating problems and s a result become vulnerable to storage microorganisms and pests. 65 different species of microorganisms have been reported from such storages in Iran (Lacey, 1988) and 16 species of mites in Iraq (Mahmood, 1992). Of course the storage environment in better storage facilities would be more suitable for the grains for protection against the storage grains and pests, but their costs would be too high for the ordinary farmers in developing countries. Therefore, in most cases these farmers keep the grains for domestic use only and sell the rest as soon as they harvest. However, the farmers with primitive storage facilities can improve the quality of their storage by not leaving any opening or cracks in the walls of the stores or covering properly to minimize the entry of outside moisture or organisms into the stored grains.

In order to promote safer and more effective storage of cereal grains, alternative storage methods suitable for the small farmers in developing countries are needed. For this purpose hermetic storage method which is based on storing the grains in totally sealed small PVC containers and keeping the grain quality through allowing consumption of the all O₂ by the present organisms to produce CO². With this method, Populations of R. dominica and T. castaneum, Cryptolestes sp. were reduced significantly (Ferizli and Emekçi, 1999). The method is also recommended for the tropical and sub tropical countries (Navarro et al., 1994).

4.3.6 Use of Pesticides

4.3.6.1 Rodenticides:

Despite the care taken not to leave any holes or cracks on the walls of storage, the rodents can find their way to the stored grains. The rodents are important problems especially in developing countries because the store structures are not properly constructed. In the very rural areas and small farms the rats are caught with mechanical traps on which attractive foods, such as cheese, are placed. However, medium size farmers tend to use rodenticides in various formulations. For example in Turkey, the rodents are chemically controlled through placement of pellets (such as Difenacum 0.05%), grains treated with the poisonous rodenticides (Coumatetraly 0.75, Brodifacoum 0.05%, Zinc phosphide, 80-95%) or tablets (aluminium phosphide 56-57%, 1 tablet for 1m³) in the grain stores. The use of zinc phosphide treated grains as baits is reported for Sudan (Anonymous, 1967) as well.

4.3.6.2 Sanitation of stores before storage:

In order to protect the grains in store from the storage microorganisms and insect pests, the stores should be cleaned and sanitized before the grain is placed. Otherwise small amount of microorganism or insects can grow and develop in time after storage and cause extensive damage, if the environmental conditions are suitable for them.

Some farmers do apply lime to the walls of ordinary building stores to eliminate the microorganisms before storage. The insect pests existing in the store can be destroyed before the grain is stored with the use of Malathion, Bromophos, Chlorpyrifos-Methyl and Primiphos methyl. For the application, WP or EC formulation of the insecticides must be used and all surface area must be sprayed.

However, majority of small scale farmers ignore to do this and the losses are encountered frequently resulting from the existing micro organisms and pests in stores.

4.3.6.3 Use of grain protectants:

The protection of grains from spoilage fungi such as Penicillium spp. and Aspergillus spp. is more difficult in developing countries. Although application of propionic acid as sprays is widely used in many developed countries for this purpose (Sauer et al., 1992) especially the smaller farmers in developing countries do not practice this. Use of protectants is an efficient way of protecting grains especially from contamination of the storage insects. The major objectives for application of grain protectants are to kill the most important insects in the grain and prevent them from establishing an infestation after the storage. One protectant application may be sufficient during only one storage season (Harein & Davis, 1992).

The earlier protectant insecticide studies in the USA, India and Kenya are reviewed by Harein and Davis (1992) and included diatomaceous earths, silica aero gels, magnesium oxide, aluminium oxide and activated clays in the form of inert dust acting as toxic and repellent insecticide. Although the inert dusts have residue problems they still seem to interest the producers in developing countries (Mittal & Wrightman, 1989). The insecticides that have been developed as effective grain protectants include Malathion, Pyrethrins, Dichlorvos, Chlorpyrifos-Methyl and Pirimoiphos - Methyl against many important storage insects such as A. advena, Sitophilus spp., Oryzaephilus spp., Cryptolestes spp., Trogoderma spp. and Tribolium spp. at various degrees. Although the small size farms in developing countries ignore use of protectant fungicides, the medium size farms use these protectant fungicides as this is more suitable for their loosely built stores which are unsuitable for fumigation. Recommendations for application of insecticides in cereal storage in Turkey are summarized in Table 4.3.6 as an example. Care should be taken to minimize and monitor the development of insect resistance against these insecticides.

The grain protectants are applied either as dust to the grains such as (Malathion, Pyrethrins, Chlorpyrifos-Methyl and Pirimoiphos - Methyl or some may be more effective if applied as sprays as in the case of dichlorvos which acts as semi fumigant dissolving in the store atmosphere but not being able to penetrate into the depth of bulk grain.

4.3.6.4 Fumigation:

Despite every effort that is made, it may not be possible to achieve complete isolation of the grain stores from their environment, control the atmosphere and destroy the storage microorganisms and pests in the grain that is placed in the store. In such cases the microorganisms and pests can grow and multiply in time at various speed depending on the atmosphere conditions and their requirements. Then it may be necessary to fumigate the stores to destroy them or decrease their population.

Various fumigation agents have been developed but only two are widely used currently, methyl bromide and phosphin. These are available in most developing countries, but only the medium and large scale farmers, traders and industry apply fumigation in their barley grain in stores in the developing countries. Methyl bromide is currently considered hazardous and its use is limited in developed countries, but it is still used widely in grain stores in developing countries as it is cheaper and more widely available. The more advanced phosphin group of fumigants (Aluminium phosphide, Magnesium phosphide) are costly and not widely used by the small farmers, but medium and large scale farmers use the phosphins in different forms.

However, some developing countries are also considering removal of methyl bromide from use. For example Turkey is planning to ban the use of methyl bromide from use in stores in 2005 and in other areas in 2008. Therefore alternative fumigants are gaining importance in similar countries.

Various fumigation technology is available for all kinds of storage facilities including the sophisticated atmosphere controlled silos, underground or above ground pits under polythene covering, wood or concrete stores. The principle of phosphin fumigation is based on release of the gas into the stored grain atmosphere and keeping it as long as possible. Here, the most critical factor is the efficiency of covering of the stored grain. Therefore special care needs to be taken to cover the grains especially in the pits which are common practices of grain storage (Fig. 4.3.6.4.). The farmers need to have sufficient experience and knowledge of the technology for effective application of fumigation.

In order to achieve maximum benefit from fumigation and reduce fumigant use following steps must be taken are necessary:

 

Table 4.3.6: Recommendations for Use of Insecticides and Fumigants in Grain Stores in Turkey (1)
Insecticide	Formulation	Recommended dose (Preparation) for
		100 m2	1 ton grain	1 m3 (Vol.)
Malathion %25 W/W	WP	500 g
Malathion 190 g/l	EC	650 ml
Malathion 650 g/l	EC	200  ml
Bromophos 360 g/l	EC	250 ml
Primiphos-methyl 500 g/l	EC	300 ml
Methacrifos 500 g/l	EC	200 ml	20 ml	In 1 lt water
Chlorpyiphos-Methyl	EC	425 ml
Malathion %2 W/W	Dust		500 g
Fenitrothion %3 W/W	Dust		133,2 g
Fenitrothion %1 W/W	Dust		400 g
Aluminium phosphide %57	Tablet		9-30 g	3-12 g
Aluminium phosphide %57	Granule sack			8,5 g
Methyl bromide %98	Liquid gas			25 g
Dichorvos 550 g/l (DDVP)	EC			0,150 ml (in 10 ml water)
Dichorvos 1000 g/l (DDVP	EC			In 1 lt. water at 25 °C or over
(1) Adapted from Yasar (1996); Yildirim et al., (1997)

Figure 4.3.6.4. Storage of a covered pit and application of phosphine tablet for developing countries (Akan, 2003).

- selection of the most appropriate fumigation method,

- insuring that the store is isolated from the outside environment by filling in any wholes, cracks and openings,

- application of the fumigants according to the recommendations,

- revision of dosage rates to avoid overdosing;

- reducing the frequency of treatments by preventing or reducing reinvasion of pests subsequent to fumigation.

Ideal fumigation techniques are known only by professional grain producers, traders or industrialists in the developing countries. Majority of the small scale farmers are unaware of these techniques. Even in the medium - large size farms, the efficiency of fumigation is generally low and still significant losses occur due to storage diseases and pests. The main reason for inefficient grain preservation in smaller farms in developing countries is the inadequacy of technical knowledge and unsuitability of present storage systems for their conditions as well as financial resources for establishment of better storage facilities.