Mice, rats, and other rodents threaten food production and act as reservoirs for disease throughout the world. In Asia alone, the rice loss every year caused by rodents could feed about 200 million people. Damage to crops in Africa and South America is equally dramatic. Rodent control often comes too late, is inefficient, or is considered too expensive. Using the multimammate mouse (Mastomys natalensis) in Tanzania and the house mouse (Mus domesticus) in southeastern Australia as primary case studies, we demonstrate how ecology and economics can be combined to identify management strategies to make rodent control work more efficiently than it does today. Three more rodent–pest systems – including two from Asia, the rice‐field rat (Rattus argentiventer) and Brandt's vole (Microtus brandti), and one from South America, the leaf‐eared mouse (Phyllotis darwini) – are presented within the same bio‐economic perspective. For all these species, the ability to relate outbreaks to interannual climatic variability creates the potential to assess the economic benefits of forecasting rodent outbreaks.

R odents are among the most important global pests (Prakash 1988; Singleton et al. 1999a), and are often featured in fiction, as in Albert Camus' The Plague. The black rat (Rattus rattus) played a key role in the plague during the Middle Ages (Scott and Duncan 2001). Farmers in many parts of the world, particularly those in developing countries, tend to view economic losses due to rats and mice as unavoidable (Posamentier 1997; Singleton et al. 1999a). In fact, the impact of rodents has been greatly underestimated and largely ignored in the general scientific literature, with a small number of exceptions (Elton 1942; Singleton et al. 1999a). Competing with rodents for food Worldwide, there are about 1700 species of rodents, but only 5-10% are major pest species in agricultural and urban environments, and even fewer cause problems over larger geographic areas. Some of these consume substantial amounts of agricultural produce (Table 1), and in many developing countries, farmers consider rodents the main impediment to higher yields (Makundi et al. 1999). Every year, rats in Asia consume food crops that could feed 200 million people for an entire year (Singleton 2003). In Indonesia, rodents are the most important pre-harvest pests in economic terms, causing on average at least 15% annual losses of rice (Geddes 1992). In Africa, the numbers are similar. Damage due to rodents in Tanzania causes an estimated annual yield loss of 5-15% of maize (corn), corresponding to about $45 million, and food which could feed about 2 million people (Leirs 2003; Table 1). In parts of South America, native rodents cause crop damage varying between 5-90% of total production (Rodriquez 1993). Obviously, we need better pest control strategies than we have today. The design of rodent control strategies has both an ecological dimension, relating to the interaction of the pest population and its resources and enemies (Singleton et al. 1999a), and an economic dimension, relating to crop damage, which affects yield, and the use of pesticides, which in turn affects production costs (Carlson and 367

The temporal occurrence of the invasive and economically important pest fruit fly, Bactrocera invadens was studied in three agro-ecological areas of Morogoro Region, central Tanzania, during 2004Tanzania, during -2005. Weekly and monthly trappings were carried out with methyl eugenol, protein bait and synthetic food attractant. Bactrocera invadens was permanently present at low and mid-altitudes (380-520 m a.s.l.) with peak periods coinciding with the fruiting season of mango (Mangifera indica) and guava (Psidium guajava). At high altitude (1650 m a.s.l.) its incidence was only temporal and apparently the result of dispersal from lower altitudes after the mango fruiting season. Rearing results showed mango, loquat (Eriobotrya japonica), guava and grapefruit (Citrus · paradisi) to be the favoured commercial host fruits. Other Citrus species, cucurbits, papaya (Carica papaya) and avocado (Persea americana) were less favoured.

The host range of major fruit fly pests in Central Tanzania was evaluated from October 2004 to October 2006. Samples of 48 potential hosts were collected and incubated for fruit fly emergence. Bactrocera invadens was the dominant species in incidence expressed as the ratio of infested to total number samples collected, as well as infestation rate, expressed as number of flies emerging per unit weight. Eight new host fruits are reported. Infestation by native pests, such as Ceratitis capitata and C. cosyra, was minor compared to B. invadens. Ceratitis rosa was the dominant species in temperate fruits, and Cucurbitaceae were mainly infested by Bactrocera cucurbitae, a specialized cucurbit feeder. Among commercial fruits, high infestation incidences were observed in mango and guava, but they decreased throughout the fruiting season. Low infestation rates were observed in all Citrus species and in avocado, indicating these fruits as poor hosts for the studied fruit fly pests in this region. Widespread availability and abundance of fruit species studied here ensures year-round breeding of B. invadens. Seasonal infestation differs, with mango being the most important host in October to January, while guava being important from February to August. Tropical almond showed very high incidence and infestation rate for B. invadens and might act as an important reservoir host, bridging the fruiting seasons of mango and guava. Soursop acts as an important host for C. cosyra after the mango season. Ceratitis capitata is a pest of minor importance of the commercial fruits studied in this region.

Many emerging infections are RNA virus spillovers from animal reservoirs. Reservoir identification is necessary for predicting the geographic extent of infection risk, but rarely are taxonomic levels below the animal species considered as reservoir, and only key circumstances in nature and methodology allow intrinsic virus-host associations to be distinguished from simple geographic (co-)isolation. We sampled and genetically characterized in detail a contact zone of two subtaxa of the rodent Mastomys natalensis in Tanzania. We find two distinct arenaviruses, Gairo and Morogoro virus, each spatially confined to a single M. natalensis subtaxon, only co-occurring at the contact zone’s centre. Inter-subtaxon hybridization at this centre and a continuum of quality habitat for M. natalensis show that both viruses have the ecological opportunity to spread into the other substaxon’s range, but do not, strongly suggesting host-intrinsic barriers. Such barriers could explain why human cases of another M. natalensis-borne arenavirus, Lassa virus, are limited to West Africa.

Pulex irritans fleas were more common in villages with high plague incidence.

Biodiversity of fruit flies (Diptera, Tephritidae) in orchards in different agroecological zones of the Morogoro region, Tanzania.Abstract --Introduction. Fruit flies (Diptera, Tephritidae) are among the major constraints in commercial horticulture in many African developing countries. Knowledge of the tephritid spectrum in any given area is a prerequisite for the development of an IPM program to alleviate the pest problem. We studied the fruit fly diversity in four main agro-ecological zones which are significant fruit-producing areas in the Morogoro Region, Tanzania. Materials and methods. Fruit fly diversity was investigated for one year (October 2004 -October 2005. Parapheromones, synthetic food attractant and protein-bait traps were used to trap the flies at the different locations in Morogoro region, Tanzania. One mixed orchard was selected at each of four locations representing the different agro-ecological zones of the region. Results. The recently introduced alien species, Bactrocera invadens, and three indigenous pest species, Ceratitis rosa, Dacus bivittatus and D. punctatifrons, were found at all the four sites, while Bactrocera cucurbitae, Ceratitis cosyra, Dacus chiwira and D. humeralis were found in three out of the four sites. The Sokoine University of Agriculture (SUA) Horticulture Unit and Mikese sites had the highest species diversity while the Mkindo and Nyandira sites had the lowest diversity. The between-habitats diversity (Beta diversity) was similar among the SUA, Mkindo and Mikese sites. Only the Nyandira site had a higher dissimilarity in comparison with the other three sites. Discussion. The most abundant species at low-and mid-elevation sites was Bactrocera invadens while, at high elevation, Ceratitis rosa was the dominant species. Protein-baited traps attracted the highest diversity of fruit flies in comparison with the more specific parapheromones. The synthetic food attractant (three-component lure) was less efficient compared with the protein bait. The large dissimilarity at the Nyandira site is probably due to the different types of host fruits found and grown in high altitude areas (mainly temperate fruits). Fruit fly species associated with these types of fruits, e.g., Ceratitis rubivora and Trirhithrum coffeae, were found only at this site.Tanzania / fruit trees / Tephritidae / fruit flies / biodiversity / Ceratitis / Bactrocera / Dacus / surveys / traps / identification Biodiversité des mouches des fruits (Diptera, Tephritidae) en vergers, dans différentes zones agro-écologiques de la région de Morogoro, Tanzanie.Résumé --Introduction. Les mouches des fruits (Diptera, Tephritidae) font partie des principales contraintes de l'horticulture commerciale dans de nombreux pays africains en voie de développement. La connaissance du spectre des tephritides dans un secteur donné est un préalable au développement d'un programme d'IPM permettant d'atténuer le problème parasitaire. Nous avons étudié la diversité des mouches des fruits dans quatre principales zones agro-écologiques qui s...

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 7 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 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.