Trap Barrier System (TBS) as a New Tool for Rodent Pest Management in Irrigated Rice in Africa

Rodent infestation poses a serious threat to smallholder farmers in both developed and developing countries where a large proportion of potential crop yield is lost. In Tanzania, the average annual yield loss of rice is estimated to be around 5–12%. Management of rodent pests in Africa relies mostly on the use of rodenticides which, however, are often applied only when damage has already occurred rather than routinely. Rodenticides used in this way are rarely economically and ecologically sustainable for managing rodents in irrigated rice. A “community-based Trap-Barrier-System (cTBS)” provides an alternative novel rodent control approach for controlling rodents in rice fields. This is basically a system where rodents are trapped in a rice field that is planted a short period earlier than the surrounding fields and therefore attracting rodents from a much wider area than the field itself. The system has proved very successful in irrigated rice fields in Tanzania, increasing rice yields in the intervention fields by 40.91%. A single cTBS can confer protection in up to 16 ha of irrigated rice field. Therefore, if scaled up and used widely, TBS has a great potential for managing rodent pests and improving yield in irrigated rice fields

Impact of spatio-temporal simulations of rat damage on yield of rice (Oryza sativa L.) and implications for rodent pest management

Rodents often damage crops throughout the growing season, from germination to harvest, thus making it difficult to understand the cumulative effects of rodent damage for crops such as rice that are able to partially compensate for damage. Compensation can make it difficult to understand the impact of variable rodent damage in terms of when the damage occurs, its severity and thus when, whether and how rodent pests should be controlled. The compensatory responses of rice to simulated rat damage carried out at different growth stages and at different spatial levels of severity showed that higher yield was recorded during the wet season in comparison to the dry season. However, yield loss was observed during all cropping stages for all levels of simulated damage for wet and dry season crops, with significant compensation noted at the transplanting [14 days after sowing (DAS)] and vegetative (45 DAS) stages. Only damage at the maturity (110 DAS) stage resulted in significant reductions in rice crop yield. Seasonal differences suggest water availability was an important factor that perhaps enhanced rice production. The ability of rice to compensate for early rodent damage could potentially reduce a farmer's perception of damage. However, failing to control rodents at these earlier crop growth stages could lead to increased rodent populations at the time of maturity when compensatory effects are limited

Population dynamics and breeding patterns of Mastomys natalensis Smith 1932 in irrigated rice in eastern Tanzania

Mulungu, L.S., Ngowo, V., Mdangi, M., Katakweba, A.S., Tesha, P., Mrosso, F.P., Mchomvu, M

The Ecorat project: development of ecologically-based rodent management for the southern African region

Mulungu, L.S., Belmain, S.R., Dlamini, N., Eiseb, S., Kirsten, F., Mahlaba, T., Makundi, R., Malebane, P., Von Maltitz, E., Massawe, A., Monadjem, A., Taylor, P., Tutjavi, V

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

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

Control of rodent pests in maize cultivation: the case of Africa

Rodents cause serious problems to human communities in Africa as a result of their involvement in the spread of diseases (Katakweba et al. 2012) and in the losses of crops through direct consumption (Mulungu et al. 2003; Bekele et al. 2003) and spoilage (Mdangi et al. 2013). For example, Taylor (1968) reported 20% damage to maize crop after the outbreak of rodents in Western Kenya. Earlier reports (Taylor 1968) on economic losses due to rodents in Kenya indicated 20–30% damage to maize crops, and a 34–100% loss during rodent outbreaks. In Ethiopia, it has been estimated that rodents consume up to 26.4% of maize crop in most years (Bekele et al. 2003). In Northern Ethiopia, surveyed farmers estimated 9–44% pre-harvest yield losses in annual production of cereal crops due to rodent attacks (Meheretu et al. 2010), while Central Ethiopia showed 26.4% loss of yield in maize (Bekele et al. 2003). In Tanzania, rodents are estimated to cause on average 15% yield loss (Makundi et al. 1991), which would mean the loss of around 382 673 tonnes per year of the actual yield (FAO statistics 2014). This amount of maize, with an estimated value of US$42.5 million (at US$11.1 per 100 kg bag of maize), would be enough to feed 2.1 million people for a whole year (at about 0.5 kg/day/person). However, in many parts of Africa, this figure has risen dramatically over the last few years, most noticeably in places where rodent outbreaks occur (Mwanjabe et al. 2002; Taylor and Green 1968, 1976). Toda

Control of rodent pests in maize cultivation: the case of Africa

Rodents cause serious problems to human communities in Africa as a result of their involvement in the spread of diseases (Katakweba et al. 2012) and in the losses of crops through direct consumption (Mulungu et al. 2003; Bekele et al. 2003) and spoilage (Mdangi et al. 2013). For example, Taylor (1968) reported 20% damage to maize crop after the outbreak of rodents in Western Kenya. Earlier reports (Taylor 1968) on economic losses due to rodents in Kenya indicated 20–30% damage to maize crops, and a 34–100% loss during rodent outbreaks. In Ethiopia, it has been estimated that rodents consume up to 26.4% of maize crop in most years (Bekele et al. 2003). In Northern Ethiopia, surveyed farmers estimated 9–44% pre-harvest yield losses in annual production of cereal crops due to rodent attacks (Meheretu et al. 2010), while Central Ethiopia showed 26.4% loss of yield in maize (Bekele et al. 2003). In Tanzania, rodents are estimated to cause on average 15% yield loss (Makundi et al. 1991), which would mean the loss of around 382 673 tonnes per year of the actual yield (FAO statistics 2014). This amount of maize, with an estimated value of US$42.5 million (at US$11.1 per 100 kg bag of maize), would be enough to feed 2.1 million people for a whole year (at about 0.5 kg/day/person). However, in many parts of Africa, this figure has risen dramatically over the last few years, most noticeably in places where rodent outbreaks occur (Mwanjabe et al. 2002; Taylor and Green 1968, 1976). Toda

Effect of Mango weevil (Coleoptera: Curculionidae) damage on Mango seed viability in Tanzania

Research articleStudies were conducted at the horticulture unit of Sokoine University of Agriculture, Morogoro, Tanzania, to assess the incidence and effect of mango weevil, Cryptorhynchus mangiferae (F.) (Coleoptera: Curculionidae), infestation on mango, Mangifera indica L., seed viability. Three polyembryo mango cultivars (ÔSindano nyeusiÕ, ÔSindano nyeupeÕ, and ÔDodoÕ) as well as three monoembryo mango cultivars (ÔEx-horticultureÕ, ÔTangoÕ, and ÔBongwaÕ) were collected and examined for the presence ofC. mangiferae. The effect of seed damage on viability was assessed for both naturally and artiÞcially damaged seeds. However, for artiÞcially damaged seeds, the viability was assessed by cutting away 0, 25, 50, or 75% of the cotyledon before planting. In this experiment, only monoembryo mango cultivars were used. All the examined cultivars were infested by C. mangiferae, although at varying levels. Polyembryo mango cultivars were relatively more infested than monoembryo cultivars. Bongwa and Tango were least infested, whereas Sindano nyeusi recorded the highest C. mangiferae incidence. Germination rates of damaged seeds of polyembryonic cultivars differed signiÞcantly from the uninfested control, except for Sindano nyeusi. There were no signiÞcant differencesin germination percentage among the three monoembryo cultivars, and all the cultivars differed signiÞcantly from the uninfested control. The germination rates of seeds with 25% of their cotyledons removed did not differ signiÞcantly from the undamaged seeds, indicating that monoembryo cultivar seeds can withstand up to 25% damage and germinate successfully.Government of Tanzania through Ministry of Higher Education, Science and Technolog

Breeding seasonality and population dynamics of three rodent species in the Magamba Forest Reserve, Western Usambara Mountains, north-east Tanzania

We investigated breeding seasonality and population dynamics of three rodent species, Lophuromys flavopuncatus, Grammomys dolichurus and Praomys delectorum, in the Magamba Forest, Western Usambara Mountains, northeast Tanzania. Capture–mark–recapture studies were conducted in 2002–2004. Reproductive conditions of males and females showed temporal variations, an indication of breeding seasonality. Animals were reproductively active between February and May. Rainfall in November–January was instrumental for the onset of breeding and continued throughout the wet season. The recruitment of new individuals born during the season led to highest population densities between end of May and August. Populations declined progressively towards the end of the dry season (September–October). Only P. delectorum showed a marked density increase during January–February, indicating greater survival and/or recruitment during the November– January rains. The study shows that despite a relatively stable environment of the forest reserve, rainfall has strong influence on reproduction and population dynamics, probably because of its effect on primary food resources. Key words: breeding, dynamics, Grammomys, Lophuromys, Praomys, Tanzania Re´sume´ Nous avons e´tudie´ la chronologie saisonnie`re de la reproduction et la dynamique de la population de trois espe`ces de rongeurs, Lophuromys flavopunctatus, Grammomys dolichurus et Praomys delectorum, dans la foreˆt de Magamba, dans la partie ouest des monts Usambara, au nord-est de la Tanzanie. Des e´tudes par capture – marquage – re-capture ont e´te´ re´alise´es en 2002 – 2004. La condition reproductrice des maˆles et des femelles pre´sentait des variations saisonnie`res, un indice de saisonnalite´ de la reproduction. Les animaux e´taient en e´tat de reproduction active entre fe´vrier et mai. Les chutes de pluie de novembre a` janvier e´taient tre`s importantes pour le de´clenchement de la reproduction et continuaient pendant toute la saison des pluies. Le recrutement de nouveaux individus ne´s durant cette saison conduisait a` une densite´ de population qui culminait entre fin mai et aouˆ t. Les populations de´clinaient progressivement jusque vers la fin de la saison se`che (septembre – octobre). Seul P. delectorum montrait un taux de recrutement et/ou de survie plus e´leve´ pendant les pluies de novembre a` janvier. Cette e´tude montre que malgre´ l’environnement relativement stable de la re´serve forestie`re, les chutes de pluie ont une forte influence sur la reproduction et la dynamique des populations, probablement a` cause de leur effet sur les ressources primaires en nourriture