A systematic review of rodent pest research in Afro-Malagasy small-holder farming systems: Are we asking the right questions?

Rodent pests are especially problematic in terms of agriculture and public health since they can inflict considerable economic damage associated with their abundance, diversity, generalist feeding habits and high reproductive rates. To quantify rodent pest impacts and identify trends in rodent pest research impacting on small-holder agriculture in the Afro-Malagasy region we did a systematic review of research outputs from 1910 to 2015, by developing an a priori defined set of criteria to allow for replication of the review process. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We reviewed 162 publications, and while rodent pest research was spatially distributed across Africa (32 countries, including Madagascar), there was a disparity in number of studies per country with research biased towards four countries (Tanzania [25%], Nigeria [9%], Ethiopia [9%], Kenya [8%]) accounting for 51% of all rodent pest research in the Afro-Malagasy region. There was a disparity in the research themes addressed by Tanzanian publications compared to publications from the rest of the Afro-Malagasy region where research in Tanzania had a much more applied focus (50%) compared to a more basic research approach (92%) in the rest of the Afro-Malagasy region. We found that pest rodents have a significant negative effect on the Afro-Malagasy small-holder farming communities. Crop losses varied between cropping stages, storage and crops and the highest losses occurred during early cropping stages (46% median loss during seedling stage) and the mature stage (15% median loss). There was a scarcity of studies investigating the effectiveness of various management actions on rodent pest damage and population abundance. Our analysis highlights that there are inadequate empirical studies focused on developing sustainable control methods for rodent pests and rodent pests in the Africa-Malagasy context is generally ignored as a research topic

Impact of crop cycle on movement patterns of pest rodent species between fields and houses in Africa

Abstract Context. Rodent pests can have severe impacts on crop production in sub-Saharan Africa. In particular, the multimammate mouse Mastomys natalensis severely damages agricultural crops in southern and eastern Africa, leading to significant losses. Both its population ecology and breeding biology have been studied in agricultural and natural habitats. Population numbers erupt depending on the timing and amount of rainfall and may reach plague proportions, especially in agricultural settings, where it may become a serious pest. However, the ecology of this species, in particular its interactions with other species within the context of human settlement, is poorly understood. It may occasionally enter houses, but the degree to which it does so and the factors influencing this movement are not known. Aims. We investigated the relationship between Rattus spp. and M. natalensis entering buildings in an agro-ecological setting. We predicted that M. natalensis would enter houses more readily when food availability was lowest in the surrounding fields, and when the larger Rattus spp. were absent. Methods. We followed 40 individuals of M. natalensis in Swaziland and Namibia by radio-telemetry. Mice were captured in maize fields within 50 m of a homestead and fitted with radio-transmitters at three different times corresponding to different stages of crop development: pre-harvest, post-harvest and pre-planting. To corroborate the findings of the telemetry study, a non-toxic marker, rhodamine B, was mixed with standard bait and left at bait stations inside houses in 10 homesteads in Swaziland and Tanzania. Key results. Mice remained in the fields during the entire period of study in Swaziland, but entered buildings in Namibia during the post-harvest stage, which may represent a period of food shortage for these mice in the field. Rodents captured after baiting with rhodamine B demonstrated that Rattus spp. predominated within the houses. A small number of rhodamine B-marked M. natalensis were captured outside the houses, the proportion declining with distance away from the houses. Conclusions. These results suggest that in a typical rural African setting dominated by subsistence agriculture, Rattus spp. (when present) competitively exclude the smaller M. natalensis from entering houses. Implications. Interactions between rodent pest species may be important in determining which rodent species enter houses in rural African landscapes. Consideration of such interactions may play an important role when developing pest management strategies

Effect of synthetic hormones on reproduction in Mastomys natalensis

Rodent pest management traditionally relies on some form of lethal control. Developing effective fertility control for pest rodent species could be a major breakthrough particularly in the context of managing rodent population outbreaks. This laboratory-based study is the first to report on the effects of using fertility compounds on an outbreaking rodent pest species found throughout sub-Saharan Africa. Mastomys natalensis were fed bait containing the synthetic steroid hormones quinestrol and levonorgestrel, both singly and in combination, at three concentrations (10, 50, 100 ppm) for seven days. Consumption of the bait and animal body mass was mostly the same between treatments when analysed by sex, day and treatment. However, a repeated measures ANOVA indicated that quinestrol and quinestrol+levonorgestrel treatments reduced consumption by up to 45%, particularly at the higher concentrations of 50 and 100 ppm. Although there was no clear concentration effect on animal body mass, quinestrol and quinestrol+levonorgestrel lowered body mass by up to 20% compared to the untreated and levonorgestrel treatments. Quinestrol and quinestrol+levonorgestrel reduced the weight of male rat testes, epididymis and seminal vesicles by 60-80%, and sperm concentration and motility were reduced by more than 95%. No weight changes were observed to uterine and ovarian tissue; however, high uterine oedema was observed among all female rats consuming treated bait at 8 days and 40 days from trial start. Trials with mate pairing showed there were significant differences in the pregnancy rate with all treatments when compared to the untreated control group of rodents

Defects in Reinforced Concrete Due To Environmental Conditions and Concrete Treatment: A Case Study at The University Of Dar es Salaam

Abstrac

Effects in Reinforced Concrete Due To Environmental Conditions and Concrete Treatment: A Case Study at the University of Dar es Salaam

Abstrac

Winning the fight against rodent pests: Recent developments in Tanzania

Rodent management programs in Tanzania have been reactive and did not consider the population ecology of the target species. The strategies used to manage rodents were probably most suited to managing low-density rodent populations and were selected to solve localised rodent problems in certain areas. These included bounty schemes, burning of homes and vegetation, trapping and poisoning. In recent years, new developments in rodent pest management include a system designed to provide early warning of potent damage. An understanding of the population processes that give rise to rodent pest's problems provides the framework for evaluating the causes and solutions. Population models for predicting outbreaks have been developed. These have incorporated simulations and aspects of economics in the implementation of control strategies. Simulation based on Bioeconomics models have shown that the most economically rewarding strategies differ significantly from current practices of symptomatic treatment when severe rodent damage is noticed in the fields. Therefore, shifting from symptomatic practices and controlling rodents on a calendar basis can substantially improve the economic conditions for the majority of maize products in Tanzania

Effect of Seedbed Type on Yield and Yield Components of Common bean (Phaseolus vulgaris L.) Commercial Cultivars

Journal of Agronomy, 2006; 5 (4): 583-588Two experiments were conducted, one in 1997 during the long rain season (April-July) and another in 2004 during dry season (September - December) at Sokoine University of Agriculture plots, Morogoro, Tanzania to evaluate the effect of seedbed types on crop performance of beans of different growth types. Treatments were laid out in a split plot arrangement in a Randomized Complete Block Design (RCBD) with three replications. In 1997, the main plots consisted of four common bean cultivars namely SUA 90, Canadian wonder, Kablanketi and Glory. Three seedbed types constituted the sub-plots namely ridge cultivation, flat cultivation and ngolo cultivation. In 2004, the main plots consisted of two bean cultivars namely SUA 90 and Kablanketi. Four seedbed types constituted the sub-plots viz., ridge cultivation, flat cultivation, ngolo cultivation and fipa mound seedbed. The data recorded included number of harvested plants m-2, number of branches plant-1, pods plant-1, pod length, seeds pod-1, grain yield plant-1, yield ha-1 and 100 seed weight. Results showed that bean cultivars differed in yield components and determinate cultivars showed consistently higher seed yield per plant while indeterminate showed consistely higher 100 seed weight. Ridge seedbed showed superiority on number of pods per plant, pod length and yield per plant only during dry season. However, flat seedbeds showed consistently good performance for many variables investigated. Increased grain yield in flat seedbeds, therefore, at both cropping seasons was reflected in increased production of pods per plant, longer pods and yield per plant. Therefore, flat seedbed type is recommended for bean production in the studied location

Effect of Seedbed Type on Yield and Yield Components of Common bean (Phaseolus vulgaris L.) Commercial Cultivars

Journal of Agronomy, 2006; 5 (4): 583-588Two experiments were conducted, one in 1997 during the long rain season (April-July) and another in 2004 during dry season (September - December) at Sokoine University of Agriculture plots, Morogoro, Tanzania to evaluate the effect of seedbed types on crop performance of beans of different growth types. Treatments were laid out in a split plot arrangement in a Randomized Complete Block Design (RCBD) with three replications. In 1997, the main plots consisted of four common bean cultivars namely SUA 90, Canadian wonder, Kablanketi and Glory. Three seedbed types constituted the sub-plots namely ridge cultivation, flat cultivation and ngolo cultivation. In 2004, the main plots consisted of two bean cultivars namely SUA 90 and Kablanketi. Four seedbed types constituted the sub-plots viz., ridge cultivation, flat cultivation, ngolo cultivation and fipa mound seedbed. The data recorded included number of harvested plants m-2, number of branches plant-1, pods plant-1, pod length, seeds pod-1, grain yield plant-1, yield ha-1 and 100 seed weight. Results showed that bean cultivars differed in yield components and determinate cultivars showed consistently higher seed yield per plant while indeterminate showed consistely higher 100 seed weight. Ridge seedbed showed superiority on number of pods per plant, pod length and yield per plant only during dry season. However, flat seedbeds showed consistently good performance for many variables investigated. Increased grain yield in flat seedbeds, therefore, at both cropping seasons was reflected in increased production of pods per plant, longer pods and yield per plant. Therefore, flat seedbed type is recommended for bean production in the studied location

Land use determinants of small mammal abundance and distribution in a plague endemic area of Lushoto District, Tanzania

Small mammals are considered to be involved in the transmission cycle of bubonic plague, still occurring in different parts of the world, including the Lushoto District in Tanzania. The objective of this study was to determine the relationship between land use types and practices and small mammal abundance and distribution. A field survey was used to collect data in three landscapes differing in plague incidences. Data collection was done both in the wet season (April-June 2012) and dry season (August- October 2012). Analysis of variance and Boosted Regression Trees (BRT) modelling technique were used to establish the relationship between land use and small mammal abundance and distribution. Significant variations (p ≤ 0.05) of small mammal abundance among land use types were identified. Plantation forest with farming, natural forest and fallow had higher populations of small mammals than the other aggregated land use types. The influence of individual land use types on small mammal abundance level showed that, in both dry and wet seasons, miraba and fallow tended to favour small mammals’ habitation whereas land tillage practices had the opposite effect. In addition, during the wet season crop types such as potato and maize appeared to positively influence the distribution and abundance of small mammals which was attributed to both shelter and food availability. Based on the findings from this study it is recommended that future efforts to predict and map spatial and temporal human plague infection risk at fine scale should consider the role played by land use and associated human activities on small mammal abundance and distribution