Assessing and controlling bio-deterioration of maize in Tanzania

Agriculture is the backbone of the Tanzanian economy. It accounts for about one-third of the gross domestic product (GDP), provides 85 percent of all exports and serves as a livelihood to over 80 percent of the total population. Maize or corn (Zea mays L.) is the primary staple crop; it’s grown in nearly all agro-ecological zones in the country. Tanzania is a major maize producer in Sub-Saharan Africa. In the last four decades, Tanzania has ranked among the top 25 maize producing countries in the world. Despite the steady production of maize over the past three decades, post-harvest losses of maize remained significantly high, especially for small-holder farmers. Post-harvest handling, poor infrastructure, and weather variability, bio-deterioration brought about by pest organisms such as insects, molds, and fungi, rodent, bacteria, pathogens, and viruses often aggravate such losses. In tropical countries, a large proportion of the maize is harvested and stored under humid and warm climatic conditions, which subsequently results in rapid deterioration of the grains, mainly because of growth of molds and pests. Deterioration of maize is mainly affected by moisture content, temperature (grain and air), relative humidity, storage conditions, fungal growth, and insect pests. Fungal growth, especially Aspergillus flavus and Fusarium sp in maize, facilitated by hot and humid conditions, poses a major health risk through the production of mycotoxins. Mycotoxins are toxic secondary metabolites of fungi that frequently contaminate the maize in the field and/or during storage. The most important mycotoxins in maize are the aflatoxins, Fumonisins, deoxynivalenol, and ochratoxin. In order to maintain high-quality maize for both short- and long-term storage, maize must be protected from weather, the growth of microorganisms, and insect pests. Stored product pests such as Sitophilus zeamais (Motschulsky), the maize weevil, are serious pests of economic importance in stored products in tropical and subtropical countries. Infestation often starts in the field, but serious damage is done during maize storage. This study determined the resistance of flint corn and dent corn to infestation by S. zeamais. Improved King Philip hybrid flint corn and Fontanelle 6T-510 hybrid dent corn were used. Two temperature conditions (10 and 27úC) and two storage times (15 and 30 days) were used. Results showed flint corn was more resistant to insect damage than dent corn at 27úC and 30 days storage time. After 30 d storage time and 27úC, the death rate of the weevls was significantly higher in flint corn (R2 = 0.945) compared to dent corn (R2 = 0.634). Likewise, the damaged seed was 10% higher in dent corn than in flint corn at 27úC and 30 days. However, no significant difference was observed for seed weight loss between flint corn and dent corn at the same storage conditions. Further, the study evaluated S. zeamais infestation on seven varieties of maize. Seven commercial maize varieties (white dent, yellow dent, orange flint, Indian flint, white and yellow popcorn, and sweet corn), two temperature conditions (10 and 27 ðC) and three storage times (30, 60, and 90 days) were used. The moisture contents of all maize samples were adjusted to 15.5 ñ 0.5% (wet basis) prior to initiating storage trials. Numbers of live weevils, seed damage, weight loss, and weight of powder produced were assessed at the end of each storage time. As expected, severe damage was observed at 27úC and 90 d for all maize varieties. Exponential growth rates of S. zeamais were observed in almost all maize varieties. Among seven varieties evaluated, orange flint corn, yellow, and white popcorn show resistance to S. zeamais. Sweet and dent corn were most susceptible to maize weevil infestation. Higher numbers of live S. zeamais were observed on Indian flint corn and sweet corn. Consequently, there was a higher seed weight damage and weight loss. In addition, seed damaged, percentage seed weight loss and weight of powder produced was significantly and positively correlated with a number of live S. zeamais (r = 0.91, P\u3c0.05), (r = 0.88, P\u3c0.05), and (r = 0.89, P\u3c0.05) respectively. Thus, some varieties of flint corn and popcorn can be considered as potential maize varieties to be used to reduce the postharvest loss of maize in tropical countries due to their natural resistance to S. zeamais infestation. Moreover, the study also determined the techno-economic analysis (TEA) and life cycle analysis (LCA) of maize storage for middle-class farmers in developing countries. Maize is the most widely cultivated cereal crop worldwide. It is produced on a seasonal basis, usually harvested once per year. To maintain a constant supply throughout the year, maize should be properly stored. But this entails high cost and high-energy consumption, which can contribute significant amounts of greenhouse gas emissions. Three storage capacities (25,000 bu, 250,000 bu, and 2,500,000 bu) per year were evaluated for economic analysis and environmental impact. The result shows the total storage cost per kilogram decreased as storage capacity increased (3.69$/bu, 1.89$/bu, and 0.42$/bu). Likewise, energy consumption (electricity, diesel, and liquid propane) increased as storage capacity increased. Consequently, more greenhouse gas emissions (CO2, CH4, and NOX) were emitted to the environment. Thus, to obtain an optimal balance between economics and the environment, it is important for the farmers to understand the concepts of techno-economic analysis and life cycle assessment. Furthermore, the study also determined the measured and predicted temperature of maize under hermetic conditions. Three different storage conditions (room at 25ðC, cooling at 4ðC, and freezing at -20ðC) were investigated. Yellow dent corn variety Blue River 571136 from Iowa, harvested in 2011 was used. Maize was stored in two hermetically sealed bins (50-cm diameter x 76-cm height). Five logger sensors were installed inside the bin to measure temperature and relative humidity of the air and maize grain. The sensors were located at the top, center, bottom, left and right at about 12 centimeters apart. After placing each barrel into storage, temperature and relative humidity values were measured every minute for 9 days throughout the duration of the experiment. Model validation was carried out by comparing predicted with measured maize grain temperature data in the radial and vertical directions. The temperature in the hermetically sealed cylindrical bins varied, mostly in the radial direction and very little in the axial vertical directions. No noticeable change in temperature was observed in the room condition. Moreover, the temperature in the grain changed more rapidly in the freezing conditions than in the room temperature and cooling conditions. Furthermore, the lag time between the center temperature and the side (right, left, top, and bottom) was greater in the radial direction compared to in the vertical direction. The maximum difference between predicted and measured temperature was ñ1.5ðC. The predicted and measured values of maize grain temperature at radial and vertical directions were found to be in good agreement. The model shows a good potential application to predict the temperature of maize grain stored at the room, cooling and freezing conditions under hermetic storage. In addition, the study determined the impact of moisture content and S. zeamais on maize quality during hermetic and non-hermetic storage conditions. Commercially commingled maize kernels were conditioned to target moistures 14, 16, 18, and 20% moisture content (wet basis), and then three replications of 300 grams of maize grain were stored in glass jars or triple Ziplocî slider 66 μm (2.6-mil) polyethylene bags at four conditions: hermetic with weevils, hermetic no-weevils, non-hermetic with weevils, non-hermetic no-weevils. All jars and bags were stored in an environmental chamber at 27ðC and 70% relative humidity for either 30 or 60 days. At the end of each storage period, jars and bags were assessed for visual mold growth, mycotoxin levels, CO2 and O2 concentrations, pH level, the numbers of live and dead S. zeamais, and maize moisture content. The maize stored in non-hermetic conditions with weevils at 18 and 20% exhibited high levels of mold growth and aflatoxin contamination (\u3e150 ppb). Although mold growth was observed, there were no aflatoxins detected in maize stored in hermetic conditions. The CO2 and O2 concentrations were directly related to the maize moisture contents and storage times. In general, CO2 increased and O2 gradually decreased as storage time increased. No significant difference in pH was observed in any storage conditions (P\u3c0.05). Total mortality (100%) of S. zeamais was observed in all hermetically stored samples at the end of 60 days storage. The number of S. zeamais linearly increased with storage time for maize stored in non-hermetic conditions. Moisture content for hermetically stored maize was relatively constant. Moreover, a positive correlation between moisture content and storage time was observed for maize stored in non-hermetic conditions with weevils (r = 0.96, P\u3c0.05). The results indicate that moisture content and the number of S. zeamais play a significant role in maize storage, both under hermetic and non-hermetic conditions. The study also determined whether there is a synergistic interaction between P. truncatus and S. zeamais during storage. The interaction between the two insects was evaluated in terms of the numbers of the live population, percent damaged grain, the weight of powder (flour) produced, and percentage seed weight loss. Higher damage was observed in non-hermetic storage with P. truncatus and in mixed treatments (P. truncatus and S. zeamais). A significant difference (P\u3c0.05) and positive correlation were observed between the number of live population, percentage grain damage, the weight of powder produced, and percentage seed weight loss on infestation by P. truncates, S. zeamais, and mixed treatments. S. zeamais dominate populations in the early stage but were outnumbered by P. truncatus after 60 d of storage in the individual species as well as in mixed treatments. The high percentage grain damage was observed in non-hermetic storage after 60 days in P. truncatus (58%) and mixed treatments (54%). The weight of powder produced ranged from 0-30 grams per 250 grams of maize. Percentage seed weight loss decreased after 60 days for P. truncatus and mixed treatments, but increased onward for S. zeamais, a low synergistic interaction between P. truncatus and S. zeamais was observed. However, P. truncatus plays a significant role when two insects coexist and cause more severe damage than S. zeamais in maize under non-hermetic storage conditions. Furthermore, the study determined the practicability of periodic physical disturbance on S. zeamais mortality and adaptation by smallholder farmers in developing countries. S. zeamais is the most widely occurring and important cosmopolitan postharvest insect pest of stored maize in tropic and sub-tropical regions. Preventing infestation of this pest without using chemicals remains a huge challenge for smallholder farmers in the developing countries. Physical control methods are effective and attractive alternative methods to prevent, and control stored product pests in grain handling and storage facilities. Physical techniques are based on the application of some kind of force to manipulate the storage environments. They can provide unfavorable conditions for insect pests to multiply or damage to the grain. In this experiment, disturbed and stationary/control treatments were arranged in a Completely Randomized Design (CRD) with three replications and three-storage times (30, 60, and 90 days) in three regions of Tanzania. A total of 108 clean 20L (L284 x W234 x H391) millimeter plastic containers were each loaded with 10 kilograms of fresh white dent corn and 0.50 kilograms of maize infested with S. zeamais. The initial numbers of S. zeamais were determined. For the turned treatment, containers were disturbed or turned twice a day, whereas, for the controls, the containers were not disturbed until the end of storage. The overall percent mortality after 30, 60, and 90 days of storage were 88, 96, and 98% respectively. A statistically significant difference (P\u3c0.05) was observed for the number of live S. zeamais in the control treatments. While the number of live S. zeamais in the turned treatment significantly decreased as storage time increased. The study shows the potential of a feasible, simple, affordable, safe and effective method of protecting maize grain for small-holder farmers in developing countries without using chemicals. Lastly, the study assessed the postharvest practices and awareness of mycotoxins contamination in maize grain. Maize is a major cereal crop in Tanzania and it is grown in diverse agro-ecological zones. Like other sub-Saharan countries, postharvest losses of maize during storage in Tanzania remain significantly high, especially for smallholder farmers. Unpredictable weather and poor postharvest practice contribute significantly to rapid deterioration of grain and mold contamination, and subsequent production of mycotoxins. The purpose of this study was to assess the postharvest practices and awareness and knowledge of mycotoxin contamination in maize grain in three agro-ecological zones (Eastern, Central, and Northern) of Tanzania between November 2015 and February 2016. A survey using semi-structured questionnaires was administered to farmers, traders, and consumers of maize. A total of 90 people (30 from each zone) were surveyed with a response rate of was 96% (87). In addition, several samples of maize were collected and analyzed for aflatoxin, fumonisin, and Zearalenone contamination to validate the awareness and knowledge of mycotoxin contamination of maize. The result shows a high level of postharvest losses of maize mainly through insect infestation. Moreover, over 80% of the farmers, traders, and consumers of maize were unaware of mycotoxins contamination. All maize samples collected contained detected levels of mycotoxins. The maximum concentration of aflatoxins, fumonisin, and Zearalenone in maize samples was 19.20 ppb, 7.60 ppm, and 189.90 ppb respectively. Education intervention is necessary to decrease the disconnect observed between actual mycotoxin contamination and the awareness and knowledge of farmers, traders, and consumers of maize in Tanzania. Enhancing awareness and knowledge provide the opportunity to educate on post-harvest practices that reduce postharvest losses of maize in Tanzania

Is Flint Corn Naturally Resistant to Maize Weevil Infestation?

Sitophilus zeamais (maize weevil) is one of the most destructive pests of maize stored in tropical and subtropical regions. This study determined the resistance of flint corn and dent corn to infestation by S. zeamais (Motschulsky), the maize weevil. Improved King Philip hybrid flint corn and Fontanelle 6T-510 hybrid dent corn were used in this experiment. Two temperature conditions (10 °C and 27 °C) and two storage times (15 days and 30 days) were used. Results showed that flint corn was more resistant to insect damage than dent corn at 27 °C and 30 day storage time. After 30 days storage time and 27 ºC death rate was significantly higher in flint corn (R2 = 0.945) compared to (R2 = 0.634) in dent corn. Damaged seed was 10% higher in dent corn then in flint corn at 27 ºC and 30 days. However, no significant difference was observed for seed weight loss between flint corn and dent corn at the same storage conditions. Both dent and flint corn are extensively cultivated in developing countries. It appears that storage of flint corn may be one promising solution to reducing corn damage and infestation problems in the tropics and in developing countries, but more research is needed

Current Maize Production, Postharvest Losses and the Risk of Mycotoxins Contamination in Tanzania

Agriculture is the backbone of Tanzanian economy. It accounts for about one-third of the gross domestic product (GDP), provides 85 percent of all exports and saves as a livelihood to over 80 percent of the total population. Maize is the primary staple crop; it’s grown in nearly all agro-ecological zones in the country. Tanzania is a major maize producer in Sub-Saharan Africa. In the last four decades, Tanzania has ranked among the top 25 maize producing countries in the world. In the 2013/14 growing seasons Tanzania produced over half billion metric tons of maize of these maize smallholder farmers produced around 85%. Despite the steady production of maize over the past three decades, post-harvest losses of maize remained significant, up to 30-40 % in some rural areas. Post-harvest handling, poor infrastructure, weather variability, biotic factors such as insects and pests, bacteria, pathogens, viruses, and fungi, often aggravate such losses. Mycotoxin producing fungi pose a major risk. Mycotoxins are toxic secondary metabolites of fungi that frequently contaminate the maize in the field and/or during storage. Mycotoxin contamination of maize poses a health risk to humans and animals if not properly managed. The most important mycotoxins in Tanzania are the aflatoxins, fumonisins and Ochratoxin. The objective of this paper was to review current literature on the production trends, consumption, post-harvest losses, and mycotoxins contamination of maize and to provide strategies to control and prevent postharvest losses and mycotoxins contamination in Tanzania

Techno-economic analysis (TEA) and life cycle assessment (LCA) of maize storage for small and middle sized farmers

Maize is the most widely cultivated cereal crop worldwide, currently ranked the third most important crop globally after wheat and rice. It is a key staple food in many developing countries. However, maize is produced on a seasonal basis, usually harvest once per year. To maintain a constant supply throughout the year, maize should be properly stored. But this may entail high cost and high-energy consumption, which can contribute significant amounts of greenhouse gas emissions. In this study, three storage capacities (25,000 bu, 250,000 bu and 2,500,000 bu) of maize were evaluated for economic analysis and environmental impact. The results show that the total storage cost per bushel decreased as storage capacity increased (3.68$/bu, 1.89$/bu, and 0.40$/bu). Likewise, energy consumption (electricity, diesel and liquid propane) increased as storage capacity increased. Consequently, more greenhouse gas emissions (CO2, CH4, and NOX) were emitted to the environment as storage scale increased. Thus, to obtain an optimal balance between economics and the environment, it is important for small and middle-sized farms to understand the concepts of techno-economic analysis (TEA) and life cycle assessment (LCA)

Techno-economic Analysis (TEA) of Extruded Aquafeeds

The worldwide decline and overexploitation of ocean fisheries stocks had provided an incentive for the rapid growth of aquaculture. The aquaculture industry has been recognized as the fastest-growing food production system globally, with a 10% increase in production per year and is one of the most reliable and sustainable growth markets for manufactured feeds. Extrusion technology has been extensively used in the modern aquatic feed manufacturing, due to nutritional, physical properties improvements and cost effectiveness of feeds. Cost related to aquatic feed remains the biggest challenge, especially for small-scale producers. In order to understand costs and potential breakeven points, a single screw extruder and three different production scenarios (0.2, 2 and 20 t/day) throughput were used to develop techno-economic models for small-scale producers of extruded aquatic feeds. The results show annualized capital costs decreased as production capacity increased. Thus, aquatic feed producers could use this tool to evaluate annual costs and benefits to determine processing economics. Producers will have to consider the ingredients used, though, as raw ingredients constitute the greatest cost for the production of feeds

Effects of Deterioration Parameters on Storage of Maize: A Review

Maize (Zea mays L), commonly known as corn in the United States, is the third most important cereal grain worldwide, after wheat and rice. It is a basic staple grain for large groups of people in Africa, Latin America, and Asia. In tropical countries, a large proportion of the maize is harvested and stored under humid and warm climatic conditions, which subsequently results in rapid deterioration of the grains, mainly because of growth of molds and pests. This study reviewed the main factors that lead to deterioration of maize in tropical countries and suggests ways of preventing the identified causes. This paper also reviews world production, varieties, climatic and storage conditions of maize. Deterioration of maize is mainly affected by moisture content, temperature (grain and air), relative humidity, storage conditions, fungal growth, and insect pests. Fungal growth, especially Aspergillus flavus and Fusarium sp in maize, facilitated by hot and humid conditions, poses a major risk through production of mycotoxins. In order to maintain high quality maize for both short- and long-term storage, maize must be protected from weather, growth of microorganisms, and pests. Keywords: Maize, corn, relative humidity, temperature, fungal growth, storage

Influence of Effective Microorganisms on Qualities of Tomatoes (Lycopersicon esculentum) Grown on Tropical Loam Soil

The use of Effective Microorganism (EM) consortium along with compost may overcome the harmful effects caused by chemical fertilizer while improving the nutritional quality of crops. The study aimed to determining the influence of compost inoculated with EM on the nutritional qualities of tomatoes (Lycopersicon esculentum) grown in tropical loam soil.  Four sets of treated loamy soils was experimented. The treatments were the compost without EM (C); compost containing effective microorganisms (EM); compost containing effective microorganisms with chicken manure (CEM) and urea as mineral fertilizer (M). Tomatoes were harvested randomly after matured and kept in plastic bag and immediately transferred to the laboratory for analysis of beta-carotene, vitamin C and brix contents.  The results shows that tomatoes planted with EM inoculated compost have relatively higher level of β-Carotene (7.76µg/100g), Brix (4.9%), and vitamin C (77.55mg/100g) compared with those from mineral 4.01µg/100g, 4.8%, and 3.83mg/100g respectively. This is likely reflect the efficiency of organic nature decomposition of EM compost over mineral fertilizers. We may therefore conclude that EM compost can be applied to supersede chemical fertilizer to promote sustainable and environmentally friendly tomatoes agriculture. Keywords: Beta-carotene, Brix, Compost, Effective microorganisms, Vitamin C

Periodic Physical Disturbance: An Alternative Method for Controlling Sitophilus zeamais (Maize Weevil) Infestation

Sitophilus zeamais Motschulsky is the most important insect pest of stored maize in tropical regions. The objective of this study was to determine the practicality of periodic physical disturbance on S. zeamaismortality and its adoption by smallholder farmers in developing countries. In this experiment, treatments and control were arranged in a randomized block design with three replications and three storage times in three regions of Tanzania. Region was used as the blocking variable. A total of 108 clean 20-L plastic containers were each loaded with 10 kg of fresh white dent corn and 0.50 kg of maize infested with S. zeamais. For the treatment, containers were disturbed twice a day, whereas for the controls the containers were not disturbed until the end of storage. The overall mortality rate (%) after 30, 60, and 90 days of storage were 88%, 96%, and 98%, respectively. A statistically significant difference (p \u3c 0.05) was observed for the number of live S. zeamais between the control and experimental treatments. Additionally, the number of live S. zeamais in the treatment significantly decreased as storage time increased. This study shows the potential of a feasible, simple, affordable, and effective method of protecting maize grain for small-holder farmers in developing countries without using chemicals