Tanya Stathers

Resilience, power, culture, and climate: a case study from semi-arid Tanzania, and new research directions.

Rapid changes to the climate are predicted over the next few years, and these present challenges for womens empowerment and gender equality on a completely new scale. There is little evidence or research to provide a reliable basis for gender-sensitive approaches to agricultural adaptation to climate change. This article explores the gender dimensions of climate change, in relation to participation in decision-making, divisions of labour, access to resources, and knowledge systems. It draws on insights from recent research on agricultural adaptation to climate change in Tanzania. The article then explains why future gender-sensitive climate-adaptation efforts should draw upon insights from ‘resilience thinking’, ‘political ecology’, and environmental anthropology – as a way of embedding analysis of power struggles and cultural norms in the context of the overall socio-ecological system.

The efficacy and persistence of diatomaceous earths admixed with commodity against four tropical stored product beetle pests

The efficacy and persistence of two commercially available enhanced diatomaceous earth (DE) products (Dryacide® and Protect-It®) against four common tropical storage pests (Prostephanus truncatus, Sitophilus zeamais, Callosobruchus maculatus and Acanthoscelides obtectus) were studied when admixed with typical host commodities at different application rates and relative humidities. Persistence of the enhanced DE treatments was considered after 3 and 6 months storage by assessment of both adult mortality and F1 progeny emergence. Both DEs usually increased parental mortality and reduced progeny emergence of all four insect species in comparison with the untreated control at both 50% and 60% r.h., and at all storage periods. However, efficacy was inversely related to duration of storage and over time the host commodity also became less suitable for insect development. Each insect species differed in its susceptibility to the DE treatments, highlighting the need for field application rates to be based upon the entire spectrum of pest species likely to be present during storage.

Cashew nut production in Tanzania: Constraints and progress through integrated crop management

Cashew (Anacardium occidentale L.) is the fourth most valuable Tanzanian export crop after coffee, cotton and tea. Following a steady increase in production from the middle of this century, there was a dramatic decline from 145,000 t in 1973 to 16,500 t in 1986. This was caused by a complex of socio-economic (low producer prices, inefficient marketing, villagisation) and biological factors (cashew powdery mildew disease, low tree yields, overcrowding of trees). Recently, higher cashew prices and liberalised marketing have created favourable conditions that have encouraged farmers to tackle several of the biological constraints on production. As a result, cashew production has risen steadily from 16,500 t in 1986 to 70,320 t in 1994.

Activity of male pheromone of Melanesian rhinoceros beetle Scapanes australis

Laboratory and field investigations were carried out to investigate the nature and role of the male pheromone emitted by the Dynast beetle Scapanes australis and to develop a mass trapping technique against this major coconut pest in Papua New Guinea. We report the biological data obtained from natural and synthetic pheromone, previously described as an 84:12:4 (w/w) mixture of 2-butanol (1), 3-hydoxy-2-butanone (2), and 2,3-butanediol (3). EAG recordings from natural and synthetic pheromone and a pitfall olfactometer were poorly informative. In contrast, extensive field trapping trials with various synthetic pheromone mixtures and doses showed that 1 and 2 (formulated in polyethylene sachets in 90:5 v:v ratio) were necessary and sufficient for optimum long-range attraction. Beetles were captured in traps baited with racemic 1 plus 2, with or without a stereoisomer mixture of 3 (2.5- to 2500-mg/day doses). Plant pieces, either sugarcane or coconut, enhanced captures by the synthetic pheromone, which was active alone. Traps with the pheromone caught both sexes in a 3:2 female–male ratio. A pheromone-based mass trapping led to the capture of 2173 beetles in 14 traps surrounding 40 ha of a cocoa-coconut plantation. The captures followed a log-linear decrease during the 125-week trapping program. The role of the male pheromone and its potential for crop protection are discussed.

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.

Sweetpotato infestation by Cylas spp. in East Africa: I. Cultivar differences in field infestation and the role of plant factors

Sweetpotato weevils ( Cylas spp.) constitute a major constraint upon sweetpotato production and utilization world-wide. Attempts to breed for resistance to Cylas spp. have had limited success. However, there are reports of variation in the susceptibility to weevil attack in the field among cultivars in East Africa. Field trials were conducted at two sites (Ukiriguru and Kibaha) in Tanzania and at one site (Serere) in Uganda to determine the extent to which sweetpotato cultivars presently available in East Africa consistently differ in their susceptibility to field infestation by Cylas spp. and to identify the plant factors that determine the levels of susceptibility. Several methods to assess levels of field infestation were tested, and their relative merits are discussed. Significant cultivar differences in susceptibility to Cylas spp. infestation were observed for four out of six trials carried out over 2 years. The exceptions were cases where infestation levels were either very low or very high. Linear regression models of infestation suggest that the following plant characteristics are associated with low susceptibility to Cylas spp. infestation: increased distance of roots from the soil surface, fewer soil cracks, fewer exposed roots and a high foliage yield. Both the distance of the roots from the soil surface (shortest weevil distance) and foliage yield differ significantly between cultivars. The former cannot be approximated by measurement of root neck length, but must be measured in situ .

Sweetpotato infestation by Cylas spp. in East Africa: Ii. Investigating the role of root characteristics

The response of the sweetpotato weevil Cylas puncticollis (Coleoptera: Brentidae) to roots of different sweetpotato cvs was investigated as part of a project to examine the factors that affect susceptibility of sweetpotato cvs to weevil infestation in the field. Laboratory experiments were conducted at two sites (Ukiriguru and Kibaha) in Tanzania and at one site (Serere) in Uganda to determine if the harvested storage roots of sweetpotato cvs differed in their acceptability to C. puncticollis or if any root antibiosis towards C. puncticollis existed. For all experiments cultivar effects for the total number of emerging adults were significant to at least 10% and in most cases were much more significant. At Ukiriguru and Kibaha, the results showed reasonable consistency between years, and of the four cultivars used at both sites, fewer C. puncticollis adults emerged from roots of Sinia and Budagala than from SPN/0 and Mwanamonde on all occasions. A relationship between laboratory experiments and crown damage by Cylas spp. in the field suggests that cultivar differences in attraction/deterrence for Cylas spp. exist. However, correlations between adult emergence in laboratory antibiosis experiments and field infestation levels were generally not strong. Although this indicates that cultivar selection by laboratory experiments is not a useful strategy for reducing field infestation, there may be potential for using such techniques to select cultivars that are resistant to attack during long-term storage.

New aspects of the biology of the Melanesian rhinoceros beetle Scapanes australis (Col., Dynastidae) and evidence for field attraction to males.

Scapanes australis is a major coconut pest, endemic in Papua New Guinea. Early in the night, males placed singly into artificial galleries made in young coconut palms exhibited a sex specific calling behaviour for 1 to 1.5 h. Coming to the gallery entrance, they raised the abdomen and the hind legs, the head lowered inside the gallery, and emitted a liquid secretion, rhytmically smeared by crossing the legs. Females which did not behave so, were very mobile. The adult flying period coincided with the male calling behaviour. In field assays with caged insects on coconut palms, attraction of both sexes to males was evidenced when they were calling. Males fought for gallery possession at a male arrival. No aggression but mating was observed with arriving females, which proved not to have developed oocytes. The strong male attractionwas confirmed using automatic traps, baited with one lived male in a sugarcane piece. Male were assumed to release an aggregation pheromone. Further studies are underway to identify the putative pheromone.