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Botswana International University of Science & Technology (BIUST) 2017

Biology of Bactrocera dorsalis (DIPTERA : TEPHRITIDAE) : implications on population dynamics and pest management

Motswagole, Rebaone

Titre : Biology of Bactrocera dorsalis (DIPTERA : TEPHRITIDAE) : implications on population dynamics and pest management

Auteur : Motswagole, Rebaone

Université de soutenance : Botswana International University of Science & Technology (BIUST)

Grade  : MSc-Biological Sciences, Applied Entomology 2017

Résumé partiel
Fruit production is one of the fastest growing sectors in Botswana. As one of the agricultural sectors, fruit production is very crucial as it contributes immensely towards income generation and employment opportunities, especially for vulnerable rural livelihoods. Despite all the benefits, one of the biggest hurdles in the fruit production industry is disease and insect pests. Chief among these insect pests is the Bactrocera dorsalis (Hendel) (Diptera : Tephritidae). Bactrocera dorsalis is a worldwide economic insect pest of fruit and vegetables that has spread its geographical range to many African countries including Botswana. It was first detected in Botswana in 2010 in the Chobe district. However its spread and establishment around the country following its first detection is largely unknown. Furthermore despite this pest being of economic importance and a biosecurity threat, its response to prevailing Botswana microclimates and global change remained unknown. My study therefore investigated (i) presence and (ii) seasonal population dynamics of B. dorsalis in Botswana. Furthermore I investigated the thermal tolerance of B. dorsalis by measuring its different thermal low and high temperature activity traits vis a vis Critical thermal limits (CTLs), Lethal temperature assays (LTAs), and Supercooling points (SCPs), in order to understand how temperature largely impact this specie’s activity and thus population dynamics, abundance and consequently invasive potential. My seasonal monitoring results indicate that B. dorsalis is now established in the Chobe district, (its first area of detection) as shown by its continued presence all year round and high average monthly trap catches (<0.1) as compared to other districts. . Furthermore the insect pest has been detected in other districts south of Botswana, including Kgatleng, Kweneng, South-east, and Southern. This indicated that since 2010, the insect pest has spread down south of the country, with potential negative effects on fruit industries in those areas. Nevertheless, records of this insect pest in some of the areas (South-East and Kgatleng) were erratic, symbolizing that the areas did not have ‘resident breeding populations’ for B. dorsalis but rather repeated introductions from ‘endemic’ or highly infested areas. Laboratory thermal activity experiments showed there was an improvement in critical thermal maxima (CTmax) at higher ramping rate across all the two developmental stages, indicating the lack of potential to shift high temperature tolerance for the two developmental stages at short timescales. The average high temperature of activity (CTmax) for adults and larvae were 46.16°C and 45.23°C respectively

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