Browsing by Author "Rwegasira, Gration M"

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Optimizing methods for rearing mated queens and establishing new colony of Oecophylla longinoda (Hymenoptera: Formicidae)
(International Journal of Tropical Insect Science, 2017) Rwegasira, Rozalia G; Mwatawala, Maulid W; Rwegasira, Gration M; Axelsen, Jörgen
Oecophylla spp. are used as biocontrol agents for many types of insect pests. A large and stable population is essential for effective control of pests. Colonies of Oecophylla spp. can be transplanted from wild habitats into orchards. Transplanted colonies can only survive in the presence of egg laying queens. It is difficult to locate nests with egg laying queens in large colonies that may sometimes contain more than 100 nests. Therefore, the need to explore and develop methods for rearing newly mated queens in nurseries may not be over emphasized, hence the current study. In the first experiment, we tested three rearing methods on queen survival and colony establishment. In the second experiment, we compared feeding techniques of different weaver ants on young colony growth. We observed that queens were best reared under continuous, indirect access to water. The first workers emerged earlier (32 days on average) in indirect and direct continuous access to water methods than on limited access to water (sprinkled) (38 days on average). Moreover, rearing mated queens under continuous indirect access and continuous direct access to water methods saved labour and time, because of limited attendance to the colonies. Availability of water, sugar solution and different sources of protein throughout improved the growth of young colonies. Likewise, the number of workers increased rapidly. Therefore rearing mated queens in nurseries is possible and would minimize hustles in hunting for the colonies and their queens in the wilderness
Temporal abundance and distribution of rice yellow mottle virus vectors in farmers’ fields in Morogoro, Tanzania
(2017-08) January, Bonaventure; Rwegasira, Gration M
ice yellow mottle virus (RYMV), endemic to Africa, is spread within and between rice fields by several species of Chrysomelid beetles and grasshoppers. In Tanzania and particularly in Morogoro, the virus is increasingly becoming a serious problem to rice production. The part of the field and developmental stage of rice at which RYMV vectors are predominantly abundant were not known since the need for the study. The assessment of population abundance of RYMV insect vectors were conducted in the three divisions of Mngeta, Ifakara and Mang’ula of Kilombero district, in Morogoro Tanzania using sweep net in 4 m 2 quadrats. Results revealed the highest abundance of two RYMV vectors, Oxya hyla Serville, 1831 and Chaetocnema sp, on the border parts of the rice fields rather than in the middle parts. The study established that the density of RYMV vectors was dependent on crop growth stages where the number of vectors increased with increase in crop age and it is concluded that the two insects are the main vectors of RYMV in the study area.