Brighton M. Mvumi

Farmers' insect pest management practices and pesticidal plant use in the protection of stored maize and beans in Southern Africa

Storage losses due to pests threaten livelihoods of farmers across Africa. Synthetic pesticides provide effective control when used correctly but resource-poor farmers cannot afford them. A survey of farmer ethno-ecological knowledge of pests of stored maize and bean, and their pest management practices including pesticidal plant use, was conducted in eastern Zambia and northern Malawi. Almost all respondents reported serious pest damage, with bruchids (Callosobruchus maculatus) and grain weevils (Sitophilus spp.) being major pests in beans and maize, respectively. The larger grain borer (Prostephanus truncatus) was reported more widely in Malawi. In Zambia, 50% of farmers used synthetic pesticides during storage, while nearly all did so in Malawi. Despite differences in storage methods between Malawi and Zambia, farmers in both countries were familiar with pesticidal plants, where Tephrosia vogelii was the most frequently reported. Surprisingly few farmers actually used pesticidal plants, highlighting a promotion opportunity. Our results provide a foundation for optimizing the use of pesticidal plants and enhancing their value to resource-poor farmers, across Africa.

Botanical pesticide production, trade and regulatory mechanisms in sub-Saharan Africa: making a case for plant-based pesticidal products

Pesticides are the major technology used in the management of field and postharvest losses due to pests. There is growing demand for effective alternatives that present low health risks and conserve ecosystems and biological diversity. Pesticidal plants are increasingly used as alternatives where synthetic products are unaffordable, have limited availability or are ineffective. Plant materials, however, are often used inefficiently and their effective use requires optimisation. In Africa wide-scale uptake of pesticidal plants remains limited despite the success of pyrethrum in some countries and other pesticidal plant products in China and India. This is mainly due to lack of data on efficacy and safety, inconsistent efficacy of plant products, the prohibitive cost of registration, and an inadequately developed conventional pesticides sector. Globally, the demand for botanicals is poised to grow due to an increasing shift in consumer demand for safe food, increasing organic farming, lobbying by environmentalists and the increasing pressure from new regulations on internationally traded foods in Europe. These demands can only be met by formalising production, marketing and use of pesticidal plants. This has to be supported by friendly registration procedures, sustainable forest management, propagation and cultivation of pesticidal plants. This paper presents a critical review of the enabling environment required for wide-scale adoption and commercialisation of botanical pesticides in sub-Saharan Africa. We conclude that regulations and protocols for production, marketing and trade need to be reviewed to facilitate the development of the botanicals sector in Africa.

Postharvest agriculture in changing climates: its importance to African smallholder farmers

Climate change and variability affect not only the field stages and yields of crops, but also what happens to them after harvest. There has been little discussion of the impacts of climate change on postharvest agriculture, and still less on these impacts in developing countries. Many studies have focused on potential crop yield and pre-harvest implications of different climatic projections, but have omitted an analysis of the need and ability to then protect this increasingly valuable harvest as a vital aspect of food security. Postharvest systems will be affected by changes in temperature, rainfall, humidity, extreme events and the natural and human responses to climate change and variability. This study describes typical grain postharvest systems in east and southern Africa and discusses the likely impacts of different climate change trends on postharvest activities, assets and human well-being outcomes. Adaptation opportunities for creating more climate resilient postharvest agricultural systems and associated livelihoods are identified. Many of these adaptation opportunities are already known and understood by postharvest service providers, highlighting the significant challenge of getting postharvest knowledge into use at a larger scale. A discussion is presented on the factors influencing attempts to strengthen the adaptive capacity of postharvest systems, such as its invisibility, its omission from training curricula, innovation system challenges, the policy bias towards pre-harvest agricultural spending, limited understanding of gender and diversity aspects of postharvest roles, and the dominance of maize in the food system. The study recognises the crucial role of postharvest agriculture in helping communities adapt and cope with change.

Small-scale farmer perceptions of diatomaceous earth products as potential stored grain protectants in Zimbabwe

Abstract Farmers repeated prioritisation of the need for improved methods of controlling insect damage to stored commodities in Zimbabwe led to the search for alternative grain protectants to the locally available organophosphate-based pesticides. In field trials the diatomaceous earth (DE) products, Protect-It ® and Dryacide ® , gave good protection to threshed maize, sorghum and cowpea from insect attack during 8 months storage, enabling households to increase both their food security and control over grain sales. However the initial trials, although on-farm, were researcher-managed and only evaluated by farmers at the end of the storage period. No information existed on how effective DEs were under real farmer management. At the start of the 1999/2000 storage season, farmers in Buhera and Binga districts set up trials in their own granaries using their own maize and sorghum grain, respectively. During a 7 months storage period they evaluated the application of 0.1% w/w Protect-It ® compared to their typical grain protection methods. At 5 and 7 months storage, farmers compared the treatments using the parameters they view as important such as insect damage, expected ‘sadza’ yield and quality and sale price. The DE treatments outscored other practices for all parameters and farmers were keen to purchase DEs to protect their future harvests. Grain samples from the same trial were also analysed in the laboratory at 5 and 7 months for insect populations, damage and moisture content. Although grain damage and insect numbers were higher in the typical grain protection treatment than the DE treatment, the differences were not statistically significant.

Field assessment of the efficacy and persistence of diatomaceous earths in protecting stored grain on small-scale farms in Zimbabwe

Abstract Farmers and grain traders in sub-Saharan Africa are forced to sell stored produce prematurely because of deterioration due mostly to insect damage. Producers expressed a need for a relatively cheap and safe method of insect control. Diatomaceous earths (DE) offer safer alternatives to synthetic chemicals, but information on their efficacy under tropical small-scale farming conditions is lacking. Two commercially available DE products, Protect-It ® and Dryacide ® , were tested against the major post-harvest insect pests of grains and pulses. On-farm field trials in Zimbabwe showed that both inert dusts gave significant protection against insect damage when admixed with farm stored maize, sorghum and cowpeas for periods of 40 weeks. However, efficacy of these DEs is closely linked to the application rates and differs between commodities, locations and insect pests. An admixture application rate of 0.1% w/w of Protect-It ® or Dryacide ® can be recommended to protect both maize and cowpea grain that is to be stored for 4 months or longer in Zimbabwe. However, Dryacide ® was not effective in preventing damage to sorghum grain by the bostrichid Rhyzopertha dominica unless applied at a higher rate of 0.2% w/w.

Acute mammalian toxicity of four pesticidal plants

Many plant species show potential as alternatives to synthetic pesticides but little is known about their acute mammalian toxicity. The single-dose acute oral toxicities of crude aqueous extracts of Strychnos spinosa and Bobgunnia madagascariensis fruits and the foliage of Vernonia amygdalina and Cissus quadrangularis (plant species that are commonly used as pesticides in Southern Africa) were evaluated in BALB/c mice. Plant extracts (up to 75% w/v or v/v) were orally administered to sexually mature mice. Behavioural changes, clinical signs and mortality were monitored for 4 days. Mice that received S. spinosa had generalized tonic muscle spasms and a high mortality of 83%. Those that received B. madagascariensis exhibited signs of buccal and nasal irritation with occasional sneezes during administration and a high mortality of 75% was recorded. C. quadrangularis consumption resulted in much lower mortality of 21% while no clinical signs of toxicity were evident on mice administered V. amygdalina. Chemical analysis showed the presence of secoiridoids in the seedless pulp of S. spinosa. These results indicate that aqueous extracts of S. spinosa and B. madagascariensis fruits and foliage of C. quadrangularis may have deleterious health implications on humans and animals; hence, advice on their safety should accompany promotion of their use.

Occurrence and distribution of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in Zimbabwe

The study sought to confirm reports by farmers and agricultural extension personnel of Prostephanus truncatus (Horn) attacking harvested maize in Mashonaland West and Mashonaland Central provinces of Zimbabwe and to map out, using pheromone trap catch data, the distribution of the pest in the country. A survey of 296 respondents confirmed the presence of P. truncatus in five districts of the provinces. Some respondents reported that the first few sightings of the pest were in 2005 or earlier, while the majority mentioned the 2006/2007 storage season. The map showed a more concentrated distribution of P. truncatus in the northern part of the country moving further inland towards the central and eastern parts of Zimbabwe, indicating possible spread of the pest from the neighbouring countries Zambia and Mozambique. The results of the study indicate legitimate concerns over food security with respect to stored maize grain and seed. The occurrence of P. truncatus in the country has serious implications on training of extension agents and packaging of extension messages that need to be disseminated to the farming community to reduce the impact of the pest. This is the first evidence-based and official documented report of P. truncatus occurrence in Zimbabwe.

Penetration of Sitophilus zeamais (Coleoptera: Curculionidae) through diatomaceous earth-treated bulk maize grain

The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26 ± 2°C and 70 ± 10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant (P < 0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live + dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It®, indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.RésuméLa pénétration des adultes de Sitophilus zeamais Motschulsky dans des stocks de 0,75 m de profondeur de grains de maïs, traités avec du Protect-Itw, un sol à diatomées (DE) aux doses de 0, 0,05, 0,1 et 0,2% (w /w) a été déterminée 12 semaines apre`s que les charancçons aient été lâchés à la surface des grains. Le maïs était stocké dans des colonnes constituées par des tuyaux de chloride de polyvinyle (PVC), en conditions contrôlées à 26,28C et 70 10% HR. Les échantillons de grains ont été prélevés à différentes profondeurs préalablement déterminées et les charancçons dénombrés. Le nombre d’insectes étaient tre`s significativement différent entre traitement et selon la profondeur (P < 0,001). La partie inférieure (entre 0,65 et 0,75 m) héberge significativement plus d’insectes que les parties supérieures quelque soit le traitement. Les cadavres de charancçons ont été trouvés à la partie inférieure des stocks traités au Protect-Itw, indiquant que les insectes ont pu pénétrer les stocks traités avant de mourir. Il n’a pas été possible de montrer que les stocks traités limitaient les déplacements des charancçons.

Natural postharvest aflatoxin occurrence in food legumes in the smallholder farming sector of Zimbabwe

ABSTRACT Aflatoxins, mainly produced by Aspergillus flavus and Aspergillus parasiticus, are highly toxic and may lead to health problems such as liver cancer. Exposure to aflatoxins may result from ingestion of contaminated foods. Levels of AFB1, AFB2, AFG1 and AFG2 in samples of groundnuts (Arachis hypogaea), beans (Phaseolus vulgaris), cowpeas (Vigna unguiculata) and bambara nuts (Vigna subterranean) grown by smallholder farmers in Shamva and Makoni districts, Zimbabwe, were determined at harvesting, using high performance liquid chromatography after immunoaffinity clean-up. Aflatoxins were detected in 12.5% of groundnut samples with concentrations ranging up to 175.9 µg/kg. Aflatoxins were present in 4.3% of the cowpea samples with concentrations ranging from 1.4 to 103.4 µg/kg. Due to alarming levels of aflatoxins detected in legumes versus maximum permissible levels, there is a need to assist smallholder farmers to develop harvest control strategies to reduce contamination of aflatoxins in legumes.

The banana postharvest value chain analysis in Zimbabwe

Purpose – The purpose of this paper is to evaluate the banana industry in Zimbabwe focusing on postharvest losses along the value chain (VC). Design/methodology/approach – The study evaluated the banana industry in Zimbabwe focusing on postharvest losses along the VC. Findings – Total postharvest losses for 2011-2012 were estimated to be 24-27 per cent of total production with a minimum economic loss of USD69,983/annum/firm, and a total loss of more than USD500,000/annum between the VCs analysed. The bulk of the losses occurred at farm level during handling and transportation. The major factors contributing to banana postharvest losses were: unreliable transport, poor communication and coordination between producers and processors; lack of or inefficient temperature management and poor sanitation. Practical implications – The study identified production capacity, quality and branding as opportunities and challenges in the banana industry. Currently, there is a 40 per cent unmet local demand for bananas an...