Food security challenges in Sub-Saharan Africa: The potential contribution of postharvest skills, science and technology in closing the gap

More than half of global population growth between 2013 and 2050 is expected to occur in Africa and is projected to more than double from 1.1 billion to 2.4 billion people by 2050. Estimates suggest that globally, sustainable food production will need to increase by 70%. It is essential that postharvest loss (PHL) reduction occurs alongside this increase in sustainable food production and access to meet the enormous food demand. The paper examines the grain PHL levels in Sub-Saharan Africa (SSA) and their implications. The PHL reduction strategies, their merits and limitations are analysed in terms of appropriateness to smallholder farmers, who form the majority of the farming community in Africa. The paper further identifies emerging postharvest research and development issues and the implications at various levels. The need to consolidate the understanding, approaches and metrics of PHL is highlighted. This will enable losses to be measured more quickly, objectively and comparably across commodities and geographical locations in Africa and beyond, and to assist in decision-making and measuring the impact of different initiatives. That PHL reduction is now an aspiration of many high-level development plans across SSA is a significant step forward. However, the challenge still remains of converting this attention into meaningful practical actions and increased knowledge and skills at the scale required to enhance food security across the region

Insect infestation sources in stored maize grain; what is more important resident versus incoming infestation?

Most studies targeted pest control inside stores; incognisant of the population dynamics in the store vicinity; leading to product re-infestation. Distinction between storage insect pest source and sink grain patches is important for effective pest management strategies. We examined the role of resident versus incoming insect infestation in phosphine-fumigated closed or open and unfumigated closed or open maize farm stores. Grain quality measurements were recorded over 32 weeks for two storage seasons. Whether open or closed, fumigated grain had significantly lower (p < 0.001) grain damage and lower grain weight loss (p < 0.05) than unfumigated grain. Fumigated open stores had significantly higher (p= 0.004) grain damage and weight loss than closed ones. Grain damage was higher in unfumigated-closed than fumigated-open, evidence that resident infestation inflicted higher food loss than incoming infestation. Prostephanus truncatus, Cryptolestes ferrugineus and Tribolium castaneum had significantly higher populations (p < 0.001, p = 0.018 and p = 0.001; respectively) at bottom levels of unfumigated and fumigated grain (T. castaneum). Sitotroga cerealella and Sitophilus zeamais were significantly higher (p < 0.001) at the top of closed than open unfumigated compartments. Grain suffers less infestation and quality loss when it is a sink patch than when it is a source patch. Population build-up and ‘settling’ to inflict significant food loss takes longer for incoming compared to resident infestation. These results have ecological implications on postharvest IPM.Most studies targeted pest control inside stores; incognisant of the population dynamics in the store vicinity; leading to product re-infestation. Distinction between storage insect pest source and sink grain patches is important for effective pest management strategies. We examined the role of resident versus incoming insect infestation in phosphine-fumigated closed or open and unfumigated closed or open maize farm stores. Grain quality measurements were recorded over 32 weeks for two storage seasons. Whether open or closed, fumigated grain had significantly lower (p < 0.001) grain damage and lower grain weight loss (p < 0.05) than unfumigated grain. Fumigated open stores had significantly higher (p= 0.004) grain damage and weight loss than closed ones. Grain damage was higher in unfumigated-closed than fumigated-open, evidence that resident infestation inflicted higher food loss than incoming infestation. Prostephanus truncatus, Cryptolestes ferrugineus and Tribolium castaneum had significantly higher populations (p < 0.001, p = 0.018 and p = 0.001; respectively) at bottom levels of unfumigated and fumigated grain (T. castaneum). Sitotroga cerealella and Sitophilus zeamais were significantly higher (p < 0.001) at the top of closed than open unfumigated compartments. Grain suffers less infestation and quality loss when it is a sink patch than when it is a source patch. Population build-up and ‘settling’ to inflict significant food loss takes longer for incoming compared to resident infestation. These results have ecological implications on postharvest IPM

Sitotroga cerealella (Olivier) resilience to extreme temperature and desiccation may explain its increasing pest status in changing climates: Poster

The mechanisms underlying Sitotroga cerealella survival under variable and increasing mean thermal and desiccation environments typical under global change is currently unknown. To understand how S. cerealella survives extreme abiotic stressors typical of stored-grain environments, we measured S. cerealella tolerance temperature and desiccation. The results showed that to survive desiccating grain storage environments, S. cerealella relied more on high body water content (BWC) (70.2 ± 3.72%) compared to lipid reserves (9.8± 0.81%). In desiccating environment, S. cerealella showed a reduced water loss rate (0.056mg/h) (equivalent of 1.81% of body water/hour) which would require 19.31 h to reduce the insect body water to its critical minimum (35.23% body water content at death), which is 50.20% of normal initial body water. Similarly S. cerealella exhibited high basal heat tolerance with critical thermal maximum of 46.09 ± 1.042°C and a heat knockdown time of 7.97 ± 1.64 minutes. Basal cold tolerance was relatively compromised (critical thermal minima of 4.52 ± 1.06°C and chill coma recovery time of 5.80 ±1.17 minutes), following 1h at 0°C. We found no significant correlation (P > 0.001) between BWC and the measured thermal tolerance traits. Low water loss rates reported here may be an evolutionary resistance mechanism for desiccation tolerance. Observed abiotic stress tolerance may explain the ubiquitous distribution of S. cerealella in Africa which is likely to enhance its survival and increase its pest status under global change.The mechanisms underlying Sitotroga cerealella survival under variable and increasing mean thermal and desiccation environments typical under global change is currently unknown. To understand how S. cerealella survives extreme abiotic stressors typical of stored-grain environments, we measured S. cerealella tolerance temperature and desiccation. The results showed that to survive desiccating grain storage environments, S. cerealella relied more on high body water content (BWC) (70.2 ± 3.72%) compared to lipid reserves (9.8± 0.81%). In desiccating environment, S. cerealella showed a reduced water loss rate (0.056mg/h) (equivalent of 1.81% of body water/hour) which would require 19.31 h to reduce the insect body water to its critical minimum (35.23% body water content at death), which is 50.20% of normal initial body water. Similarly S. cerealella exhibited high basal heat tolerance with critical thermal maximum of 46.09 ± 1.042°C and a heat knockdown time of 7.97 ± 1.64 minutes. Basal cold tolerance was relatively compromised (critical thermal minima of 4.52 ± 1.06°C and chill coma recovery time of 5.80 ±1.17 minutes), following 1h at 0°C. We found no significant correlation (P > 0.001) between BWC and the measured thermal tolerance traits. Low water loss rates reported here may be an evolutionary resistance mechanism for desiccation tolerance. Observed abiotic stress tolerance may explain the ubiquitous distribution of S. cerealella in Africa which is likely to enhance its survival and increase its pest status under global change

Ergonomic evaluation of manually-operated peanut butter mills

A JASSA evaluation of manually-operated peanut butter mills in Zimbabwe.Previous studies showed that the manually-operated peanut butter mills available on the market had technical problems related to the design and operation of the machines. One such problem was that the mills were too heavy for women to operate, resulting in limited operational time and ultimately, low total output. An ergonomic study of the original and modified versions of the mills was conducted at the University of Zimbabwe to verify the previously identified problems and develop appropriate and lighter mills for manual operation. A body discomfort assessment and heart rate measurement were used to determine stress endured by 12 women, as a result of operating the mills. Medium to high levels of discomfort were experienced in the lower back, neck, chest, lower arm, upper arm and shoulder. The heart rate readings showed that the mills currently available on the market were highly stressful (138 beats/minute), exceeding guidelines for safe manual operations. The modified mills, incorporating variable feed control devices, can be adjusted to ensure that stress levels are within recommended levels. The ergonomic study also established that for feed rates of 1.1 and . 1.5kg/hour, the mills produce peanut butter of acceptable fineness to the subjects, in one pass without over stressing the operator. In a separate field experiment using the same subjects, extremely high stress levels ( 150 beats/minute) were recorded with the traditional stone-mill

Field efficacy of hermetic and other maize grain storage options under smallholder farmer management

Household grain storage continues to be of paramount importance in improving food security in sub-Saharan Africa (SSA) where maize postharvest losses of 10-20 % are reported. On-farm trials to compare alternative solutions for reducing household maize storage losses were conducted in the 2014/15 and 2015/16 storage seasons in two contrasting agro-ecological zones in Hwedza district of Zimbabwe. A wide range of treatments including a commercial synthetic pesticide (Shumba super dust®1), unregistered but commonly used botanical pesticides (Aloe ash, Colophospermum mopane leaves, Eleusine coracana (rapoko) chaff, and Ocimum gratissimum), hermetic storage facilities (metal silos, GrainPro Super Grain Bags (SGB) IVR™, Purdue Improved Crop Storage (PICS) bags), and storage bags with pesticide incorporated into their fabric (ZeroFly® bags), were evaluated. The results demonstrated the superiority of hermetic storage facilities (PICS bags, SGBs, and metal silos) in suppressing insect pest build up, insect grain damage and weight loss in stored maize grain. A newly introduced synthetic pesticide on the Zimbabwean market, Actellic gold dust®, was also evaluated in the 2015/16 season and was found to be highly effective. The following grain storage technologies; hermetic metal silos, SGB bags, PICS bags, and Actellic gold dust® pesticide are therefore recommended for smallholder farmer use to reduce stored grain losses due to insect pests

Farmers’ ethno-ecological knowledge of vegetable pests and pesticidal plant use in Malawi and Zambia

While pests are a major constraint in vegetable production in many parts of Southern Africa, little is known about farmers’ knowledge and management practices. A survey was conducted among 168 and 91 vegetable farmers in Northern Malawi and Eastern Zambia, respectively, to evaluate their knowledge, attitudes and traditional management practices in tomato and crucifers (brassica). All respondents in Malawi and Zambia reported pest damage on tomato and crucifers, and 75% had used synthetic pesticides. The use of pesticidal plants, cultural practices and resistant varieties constituted a smaller portion of the pest control options in both crucifers and tomato. Over 70% of the respondents were aware of pesticidal plants, and more female (75%) than male (55%) respondents reported using them. While over 20 different plant species were mentioned by respondents, Tephrosia vogelii accounted for 61 and 53% of the pesticidal species known to respondents in Malawi and Zambia, respectively. Farmers with small landholdings were more inclined to use pesticidal plants than those with medium and large landholding highlighting the importance of this management alternative for poor farmers. Most respondents were willing to cultivate pesticidal plants, which indicate that farmers understand the potential value of these plants in pest management

Postharvest orange losses and small-scale farmers’ perceptions on the loss causes in the fruit value chain: a case study of Rusitu Valley, Zimbabwe

Surveys were conducted in Rusitu Valley , Chimanimani district of Zimbabwe between 2011 and 2012 to determine orange losses and farmers’ perceptions on the sweet orange (Citrus sinensis) supply value chain. The following data were collected using interviewer-administered Likert type questionnaires and informal interviews: orchard management practices, pest infestation, fruit handling activities, and marketing practices through. The study sample of 240 respondents was derived from two randomly selected villages in each of the four administrative wards with significant sweet orange production. The study revealed that on average a small-scale farmer in Rusitu Valley owns about 4047 m2 (one acre) orchard with an average of 55 orange trees and that a farmer harvested 1 200 kg of oranges per tree which converts to a total of 66 000 kg of orange produce per season. The study revealed that on average a farmer lost 480 kg of oranges per tree which converts to 26 400 kg per farmer or 40% loss per farmer during the season. Based on the total number of orange farmers in Rusitu Valley, the total loss translates to 89,529,600 kg. About 54% of respondents perceived that the major postharvest losses were a result of fruit fly attack while 36% linked these losses to red weaver ants (Oecophylla spp.). Trapping using a mixture of methyl eugenol and malathion during the same season positively identified the African invader fly, Bactrocera invadens. Unavailability of appropriate storage and transport facilities were the contributing factors to major postharvest losses. Citrus production extension package with an emphasis on the control of insect pests and sustainable postharvest management should be developed to improve the capacity of the small-scale farmers in Rusitu Valley. Keywords: Small-scale farmers, postharvest losses, pests and diseases, fruit value chai

Effectiveness of grain storage facilities and protectants in controlling stored-maize insect pests in a climate-risk prone area of Shire Valley, southern Malawi

Shire Valley is one of Malawi's most vulnerable areas to climate change (CC). In addition to other impacts, CC is expected to affect storage insect pest status, and the efficacy of grain storage facilities and protectants. On-farm grain storage trials were therefore conducted in Shire Valley to assess the performance of storage facilities and grain protectants against storage insect pests. Eight smallholder farmers hosted the trials in Thyolo and Chikwawa districts. Seven grain storage treatments were evaluated for 32 weeks during two storage seasons: Neem leaf powder (NM), Actellic Super dust (ASD), ZeroFly® bag (ZFB), Purdue Improved Crop Storage bag (PICS), Super Grain Bag (SGB), hermetic metal silo (MS) and untreated grain in a polypropylene bag (PP). Insect pest populations and grain damage increased with storage duration and differed significantly between treatments (p 75%) at both sites. The hermetic MS, ZFB bags, ASD and NM treatments did not effectively protect grain from insect damage. High in-store mean temperature (35.6 C) and high initial grain moisture content (13.7%) may have negatively affected efficacy of some treatments and seed germination. Tribolium castaneum survival in the MS requires further investigation. The hermetic storage bags (PICS, SGB) can be recommended for long-term maize grain storage (>32 weeks) by smallholder farmers in Shire Valley and other similar climate change-prone areas in sub-Saharan Africa

Predicting Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations and associated grain damage in smallholder farmers’ maize stores: a machine learning approach

Prostephanus truncatus is a notorious pest of stored-maize grain and its spread throughout sub-Saharan Africa has led to increased levels of grain storage losses. The current study developed models to predict the level of P. truncatus infestation and associated damage of maize grain in smallholder farmer stores. Data were gathered from grain storage trials conducted in Hwedza and Mbire districts of Zimbabwe and collated with weather data for each of the sites. Insect counts of P. truncatus and other common stored grain insect pests had a strong correlation with time of year with highest recorded numbers from January to May. Correlation analysis showed insect-generated grain dust from boring and feeding activity to be the best indicator of P. truncatus presence in stores (r = 0.70), while a moderate correlation (r = 0.48) was found between P. truncatus numbers and storage insect parasitic wasps, and grain damage levels significantly correlated with the presence of Tribolium castaneum (r = 0.60). Models were developed for predicting P. truncatus infestation and grain damage using parameter selection algorithms and decision-tree machine learning algorithms with 10-fold cross-validation. The P. truncatus population size prediction model performance was weak (r = 0.43) due to the complicated sampling and detection of the pest and eight-week long period between sampling events. The grain damage prediction model had a stronger correlation coefficient (r = 0.93) and is a good estimator for in situ stored grain insect damage. The models were developed for use under southern Africa climatic conditions and can be improved with more input data for greater precision models to build decision-support tools for maize-based production systems

Field evaluation of hermetic and synthetic pesticide-based technologies in smallholder sorghum grain storage in hot and arid climates

Field evaluation of six grain storage technologies under hot and arid conditions (32–42 oC; rainfall < 450 mm/year) in two locations in Zimbabwe were conducted over two storage seasons. The treatments included three hermetic technologies (Purdue Improved Crop Storage bags, GrainPro Super Grainbags, metal silos); three synthetic pesticide-based treatments; and an untreated control, all using threshed sorghum grain. Sampling was at eight-week intervals for 32 weeks. Highly significant differences (p<0.01) occurred between hermetic and non-hermetic treatments regarding grain damage, weight loss, insect pest populations, and grain moisture content; with the hermetic containers exhibiting superior grain protection. Weight losses were low (<3%) in hermetic treatments compared to pesticide-based treatments (3.7 to 14.2%). Tribolium castaneum developed in metal silos, deltamethrin-incorporated polypropylene bags and a pesticide treatment containing deltamethrin 0.13% and fenitrothion 1% while Sitotroga cerealella developed in a pesticide treatment containing pirimiphos-methyl 0.16% + thiamethoxam 0.036%. Mechanisms of survival and development of these pests in the tested treatments and under similar climatic conditions need further elucidation. These hermetic technologies can be successfully used by smallholder farmers in developing countries as alternatives to synthetic pesticides for protecting stored-sorghum grain under hot and arid climatic conditions to attain household food security. To our knowledge, this is the first published study on modern hermetic storage of sorghum grain under typical smallholder storage conditions and involving stakeholders