Gli Insetti rappresentano un flagello per i raccolti immagazzinati, che divorano direttamente; alcune specie si nutrono dell'endosperma delle granaglie, causandone una perdita di peso e di qualita'; altre attaccano il germe dei semi,  while other species feed on the germ, resulting in poor seed germination and less viability [Malek & Parveen, 1989; Santos et al., 1990]. Thus, due to damage done by insects, grains lose value for marketing, consumption and/or planting.
 

'..the tsetse fly puts about 100 million people and 60 million head of cattle at risk in sub-Saharian Africa due to the transmission of tripanosomiasis .' [ICIPE, 1997]

PEST accounted for pre-harvest losses of 42% of the potential value of crop [eight crops that together occupy half the world's cropland, with harvest wort $300 billion over 1988-1990], with 15% attributable to insects and 13% each to weeds and pathogens. An additional 10% of the potential value was lost post-harvest
[Oerke et al., 1994, 'Crop Production and Crop Protection',Elsevier, Amsterdam]
[American Phytopathological Society, www.scisoc.org/feature/FoodSecurity/Top.html]

'Herbivorous insects are said to be responsible for destroying one fifth of the world's total crop production annually.'   [www.fao.org/inpho/compend/text/ch02.htm]

Recent estimates of yield losses due to stemborers [Sesamia calamistis, Chilo orichalcociliellus, Busseola fusca] alone in sub-Saharian Africa are expected to be close of 20-40 percentage of the potential yield  [Youdeowei, A., 1989, 'Biological Control:a sustainable solution to crop pest problem in Africa', pp. 31-50; Seshu Reddy, K.V.  & Walker, P.T., 1990, Insect Sci. & its Applications 11, 563-569]

In Tanzania, maize losses of up to 35% may occur due to Prostephanus truncatus in 5-6 months [Mallya, G.A., 1992, Proc. of FAO/GTZ Coord. Meet., Lome, Togo] and up to 60 % after nine months storage [Keil, H., 1988, Proc. Workshop on Containment & Control of larger Grain Borer, Arush, Tanzania, pp.28-52].
Maize is the main staple food in sub-Saharian Africa. In the Kenyan highlands, total losses of maize due to pests were estimated at 57 percentage [Grisley, 1997] http://www.fao.org/inpho/compend/text/ch03.htm].

In Zimbabwe, grain damage of 92 % stored maize was reported due to insect pests [Mutiro et al., 1992, Zimbabwe J. of Agric. Res., 30(1), 49-58].

In Namibia, up to 30% losses in pearl millet production can take place due to the bush cricket Acanthopolus discoidalis[Wohlleber, B. et al.,  1996, Proc. SADC/ICRISAT Regional Sorghum & Pearl Millet Workshop, Gaborone, Bostwana].

In sub-Saharian Africa insect pests, in addition to fungal diseases, are responsible for 50 percentage damage in cassava [Yaninek, J.,1994, 'Proc. 5th Symp. Internat. Soc. for Tropical Root-Crop', Kampala, Uganda].
Infestations of stored cowpeas can be as high as 90 percentage in markets and in village stores [Alebeek, 1996] http://www.fao.org/inpho/compend/text/ch02.htm  ].

In Kenya, the National Food Policy Document reported up to 30 percentage destruction of harvested maize due to pests during storage and handling [Wongo, L., 1996, Post Harvest Technol., vol.11, p30 ].
In West Africa, up to 100 % damage to cowpeas may happen in a few months after storage due to infestation of Callosobruchus maculatus [Lienard, V. & Seck, D., 1994, Insect Sci. and its Application, 15(3), 301-311].

Post-Harvest losses of grains due to rodents is estimated to range between 2 and 12% on the average, rising up to 20-100% in some countries as Egypt, Belize, Sierra Leone, Korea, Ethiopia[Hopf et al., 1976,http://www.fao.org/inpho/compend/text/ch03.htm].

 LOCUSTS
Locusts can damage a wide variety of crops. The preferred food of locusts is green grass and cereals. However, once pasture have been eaten any green plant material is susceptible. Damage from locusts can be from immature locusts that arise from eggs laid in the vicinity or from locusts that fly into an area. Damage resulting from adult
locusts flying into an area can be sudden, unpredictable and devastating. Migrations of 500-600 km overnight are not uncommon and this behaviour can lead to the sudden appearence of large number of locusts in areas previously uninfested.
In 1984, during a major outbreak of the Australian plague locust, estimated crop loss was $5 million. Without control, losses would have been $103 million. The damage caused by an uncontrolled outbreak may reach up to $200 million; in 1990, locust damage in Australia totalled more than $20 million, after widespread spraying cropping
areas to control about 70% of locust population.   [www.agric.wa.gov.au:7000/locust/locust.html]
An extraordinarily huge swarm of these locusts was seen flying over the Red Sea; it was estimated to be 2,000 miles (3,000 kilometers) long.

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