Assessing storage insect pests and post-harvest loss of maize in major producing areas of Ethiopia

The survey was conducted for three years from 2018 to 2020 cropping seasons in four regions, Amahara, Oromia, SNNP and Benishangul Gumuz, to identify storage insect pests and to assess post-harvest loss of maize in major producing areas Ethiopia. All the collected data were analyzed by using the SPSS software and difference among means were also compared. A total of 280 farmers fi eld were surveyed. 98% of the surveyed farmers used traditional storage structures. Sitophilus zeamais was occurred with a dominant mean number 120, 115 & 116 in Asosa, west Gojam & Hawasa areas, respectively. High mean 31.84% of grains damaged was recorded in the sample collected from Hawasa whereas, low mean 6.03% in the sample collected from Buno Bedele areas. High mean 18.00% of weight losses was recorded in the samples collected from Hawasa. The majority 64% of the surveyed farmers stored their grains for more than eight months. The mean number of weevils, weight loss and grain damage showed an increasing trend as the storage periods increased because of most of the farmers stored their maize with husk and/or unshelled in the house; store with cobs in bare ground which favors moisture development and temperature increment in the store. From this survey, it can be concluded that most of the surveyed farmers used traditional storage structures, stored their grains either shelled or unshelled, heap with stalk in the fi eld for a longer period and used insecticides for the control maize weevils. These insecticides have harmful effect on the environment and human health. Therefore, uses of hermetic storage technology can be suggested to the farmers for, reducing weight loss, grains damage, use of insecticides and providing appropriate grains quality. Research Article Assessing storage insect pests and post-harvest loss of maize in major producing areas of Ethiopia Negasa Fufa*, Tekalign Zeleke, Dawit Melese and Teshale


Introduction
Maize (Zea mays L.) is one of the most important cereals crop in the world both as food for man and feed for animals.
It is also known as queen of cereals because of very high yield potential [1]. According to [2], the crop ranks fi rst in total production area and yield per hectare. it has been selected as one of the strategic commodities that satisfy the food selfsuffi ciency of the country to feed the fast-growing population [3]. However, maize production and yield in Ethiopia, in particular, and Africa, in general have been highly affected by an array of biotic and abiotic stresses [4]. [5] reported that insect pests are of the major challenging biotic constraints during storage. According to [6], reports lepidopterous stem borers and Coleopterous weevils are the most important fi eld and storage insect pests. While, [7] reports showed post-harvest insect pests are considered as the most important and cause huge of losses in the grains (30%-40%) .
Insect pests causes the losses up to 5-10% in the temperate zone and 20-30% in the tropical zone of stored grains and grain products (Nakakita, 1998). However [8] explained the post-harvest losses due to insect pest infestations was a major problem concerning among smallholder farmers who practice traditional storage structures. Likewise [9] explained that huge number of pathogenic mycofl ora infecting and infesting grain maize and caused a combined worldwide annual loss of 9.4%. To combat the problems of storage insect pest's, various strategies have been used [10,11], but chemical applications remain the key method for pest management with multiple side effects on non-target insects [12,13]. However, indiscriminate chemical applications boost population dynamics [14,15] and lead to insecticide resistance in insect pests [16,17] from farmers. The sample was collected from each of the agroecological areas through the administered questionaries.
Formal and local languages that were understood by the farmers were used. Questions asked included demographics, target crop production and storage practices, storage structures, loss incurred after storage, use of stored maize and marketing of the maize. 250 gm of grain maize was sampled from each of the sampling areas. The necessary data (GPS reading, temperature, RH, storage duration, storage method and pest conditions) was collected together with samples ( Figure 1). The research design used included observation, assessment and laboratory examination.

Data to be collected
Storage temperature and relative humidity: Th e temperature and relative humdity of the internal and external environment of the storage was measured at an interval of every week by using portable digital thermo-hygrometer (Hanna, HI8564) and measurement was done in the afternoon 3.00 p.m. in the day (to reduce variations) and at the time three data was taken and its average was recorded. Measurements were taken from the center, side and top portion of the storage according to [18].
Identifi cation of major insect pest: 250 g. of sample was taken from each of the storage for the laboratory insect identifi cation. The grain was sieved through 2 mm mesh sieve (to remove dead and alive insects from the sample taken and to left the grain on the sieve) as method used by [19]. The inspection, sampling and monitoring of grain stores provide baseline information that is useful in identifying and managing problems associated with grain storage, particularly insect pest infestations. Thus, generating of information from this research can be useful in assessing the absolute importance of loss-causing factors such as temperature, relative humidity, insect pests and the effect of storage structures on grains quality and quantity. Therefore, the objective of this research is: To assess storage insect pests, loss causing factors, effect storage structures and to assess post-harvest losses due to insect infestation.

Survey areas and sample collection methods
The survey areas were including the selected regions, zones, woredas and kebele's depend on their potential in maize production and selection of farmers was made together with woreda agricultural experts. Its coverers four major maize producing regional states; namely, Amhara, South Nations, Nationalities and Peoples (SNNP), Oromia and Tigray regions.  Both live and dead insect were isolated by using hand lens magnifi cation methods, counted and removed using procedure outlined by entomology department, Bako National Maize Research Center.
Assessment of grain damaged: Insect damage was recorded by the count and weighing method. Each fi ve hundred (500g) grains were taken from initial to last storage periods and from each of the storage types and the number of insect damaged and un-damaged grain were obtained using a hand lens by searching for the presence of hole on the seeds. The percentage of insect damaged grains was calculated according to the methods used by [20] as follows: Number of insect damaged grain Insect damaged grain (%) = ×100 Total number of grain Grain weight loss: Weight loss was determined by using a known volume of measuring container and initially the grain was fi lled into the container and the weight was recorded.
The grains were fi lled till over fl ow its edge and leveled with scraper. Then grain weight loss was determined through each period of data collection during the study. The weight loss was determined by subtracting from initial period weight at each successive two months interval of sample taken according to the methods used by [21]. Then, the percentage weight loss was calculated as follows: Initial weight-weight of sample taken at any time Weight loss (%) = ×100 Initial weight Germination Test: Standard germination tests for control and treated seeds were carried out according to the International Seed Testing Association [22] procedures to evaluate the effect of each treatment on seed germination capacity. 30 seeds were kept in petri-dishes lined on fi lter paper moistened with distilled water until it was moistened and done in three replications (30 seeds per petri-dishes) and incubated at room temperature (25 o c) for 5 to 7 days. The germinated seeds were counted visually up on appearance of radicle and/or plumule and percentage germination was calculated as follows: -

 
No. of germinated seeds Germination % X1 00 Total No. of seeds soaked in each petri dish  

Demography of the respondent and methods of grains threshing/shelling
The majority of the respondent's farmers were male A number of pathogenic fungi also infecting the grains when the stored grains moisture content was above recommended and some of these pathogens producing mycotoxins that can be harmful to humans and animals.

Maize storage in Ethiopia
Almost all, 98% of the surveyed farmers used traditional storage structures. These traditional storages structures are gombisa (gotera), gumbi, polythene sacks with different size (50 and 100 kg), woven sacks and a few hangs over the tree.
The farmers stored their grain maize in shelled and unshelled with cobs. A few of them heap with stalk for two to four months without shelling (Figure 2 B). According to [23], survey data in Ethiopia, farmers store their grain maize in polypropylene or jute bags of 50 or 100 kg capacity after shelling and winnowing.
Although Gotera is normally made from wood and plastered with mud and cow dung, farmers in Alamata woreda use stones to build their gotera. However [24] reports different forms of traditional storage structures, generally made of locally available materials such as bamboo split, wooden walls, mud, and thatched grass roofs. In different parts of Africa smallholder farmers uses different storage structure to store their grain.
Likewise [25] indicated that the majority of farmers in Jimma zone (more than 97%) stored their grain in traditional storage that couldn't protect the stored grain from deterioration. damaged of the grains at the fi elds and in storage (Figure 4).
Similarly, the maize stored with cobs were infested by termites.
Not only for the infestation of insect pests but also favors the development mould which develop mycotoxin in the grains and cause a harmful healthy problem and reduces quality and quantity and made grains unfi t for consumptions.

Length of storage of grains
In average , 64% (n = 280) of the respondents stored their grains for 1 to 8 months, 20% of them stored for nine to ten months and 13.33% for eleven to twelve months [26] repocrted that the small-scale farmers retain 60 to 90% of the total grain produced for subsistence and store it for 6 to 12 months in Ethiopia. Since the maize grains have low angle of repose it develops temperature and moistures as stored on over heaped for longer periods and imposes the farmer a second-round insecticides application for the control weevils as the weevils newly developed after the application of three months. This costs to the farmers, reduces quality, increases weight losses, grains damage and also leave the residual effect on the grains which was a healthy problem to the human beings after eating [27] explained that grain is often not stored for more than eight months due to poor storage techniques, and inadequate pest management systems in Ethiopia [28] reports showed in Ethiopia, most of the farmers store their grain in traditional methods; which is poorly constructed with locally available materials and cannot protect stored grains from abiotic and biotic agents such as insect pests and fungal diseases.
Furthermore, the poor hygiene of traditional grain storage in Ethiopia favors infestation of insect pests and rodents.

Identifi cat ion of storage insect pests
Seven (7)

Control met hods used by the farmers
The farmer s used cultural and chemical control methods.
Cultural control methods are cleaning two to three times their storage per a year, sanitation, dry the grains properly and kept aerated the storage. Few 7% of the farmers used smoke by hanging the cobs on the roof for the seeds. Likewise [33] reported that in Nigeria, between 3.6 and 12% of the farmers used smoke to protect their maize and affl ation levels decreased when smoke was used to protect maize. Similarly [34] reported that effectiveness of hanging maize above fi re against insect damage and diseases. Almost 80% of the farmers in the surveyed areas used celphox and phosphotoxin fumigants insecticides. A few of them 10 to 13% used emulsion malathion and malathion dust and mographos fumigants tablets in their storage.

Damaged grains, weight loss, germination and farmer's perception of losses
The survey data indicated that high mean 31.84% of grains damaged was recorded in the sample collected from in Hawasa whereas, low mean 6.03% in the sample collected from Buno Bedele areas, respectively. Also, maximum weight loss 18% was recorded in the sample collected from Hawasa. According to visual score during the survey heavy infestation of insect pest grain damage was up to 30 to 100% in sever causes when the farmers not used insecticides and store for three to four months ( Figure 4). This is due to heavy infestation of the insect pests in the areas because of the farmers of in the area were   stored their maize with husk either in sack or without sack in the house. Also [35] reported that 0.2%-11.8% weight loss due to insect infestation in maize after 6 months of storage in traditional granaries in Togo and 3.

Conclusion and recommendation
Most of the surveyed farmers 98% were used traditional storage structures made of local materials which was not protect their grain from insect infestation. Seven weevil species were identifi ed from the collected samples.