First report of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) in the Republic of Benin

Tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious pest of tomato Solanum lycopersicum L. (Solanaceae) originating from South America. Due to previous outbreaks in neighbouring West African countries, surveillance was ongoing since 2014 in Benin. Tomato plants were regularly inspected and pheromone traps placed in tomato-producing localities in northern, southern and central Benin, including fields close to the border with Niger and Nigeria. In late 2017 and beginning of 2018 Gelechiidae moths were obtained from both the traps and the reared plant material. Morphological examination and molecular analysis of the gained specimens allowed to confirm the presence of the pest in the northern and central regions of Benin. We hence confirm the presence of T. absoluta in yet another West African country

Management of Tuta absoluta with introduced and native biocontrol agents

PhD (Science with Environmental Sciences), North-West University, Potchefstroom CampusTomato, Solanum lycopersicum L. (Solanaceae) is severely damaged by the South American tomato moth, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). Surveys among producers confirmed that the use of synthetic insecticides increased since the invasion of T. absoluta. The risks associated with the residual effect of insecticides in edible food and the negative effects it may have on ecosystem services, also increased. The aim of this project was to investigate the management of T. absoluta with introduced and native biocontrol agents in Kenya. These included a parasitoid introduced from South America, Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae), native parasitoids, and the entomopathogenic fungus, Metarhizium anisopliae ICIPE 20. Release of D. gelechiidivoris was preceded by studies of its functional responses and the tritrophic interactions between the parasitoid and native parasitoids. For the functional responses, densities of T. absoluta larvae (20, 50, 100, 150, and 200)were tested with two densities of parasitoid (1 and 3 females). For the interaction with the nativeparasitoids, short term interspecific competition assays between D. gelechiidivoris and Stenomesius sp.near japonicus (Ashmead) (Hymenoptera: Eulophidae) have been conducted. Bioassays were alsoperformed to investigate long term interaction between D. gelechiidivoris and a native parasitoid,Bracon nigricans Szépligeti (Hymenoptera: Braconidae). The susceptibility of D. gelechiidivoris to M.anisopliae ICIPE 20 was also assessed, followed by testing of the parasitism performance of D.gelechiidivoris and M. anisopliae individually as well as in combination under greenhouse conditions.The exotic parasitoid was also released in open-field and its dispersal was evaluated. Parasitism by D. gelechiidivoris was positively correlated with density of the larval host, regardless of whether the wasp occurred individually or in groups. The highest emergence of these wasps from parasitized host larvae was at a high larval pest density of 100 larvae. Two native endogenous parasitoids species viz. Bracon nigricans, and Stenomesius sp. near japonicus, were identified and successfully maintained on T. absoluta larvae. Using an ecological niche prediction, high to very high suitability was shown for occurrence of B. nigricans in major parts of Africa. In a short-term interaction between D. gelechiidivoris and Stenomesius sp. near japonicus, the exotic parasitoid performed much better than the native species. However, in a long-term interaction study between D. gelechiidivoris and B.nigricans, the native parasitoid negatively affected population growth of the exotic D. gelechiidivoris.The same level of pest control was achieved where both species co-occurred as well as where eachspecies of parasitoid was individually present. The investigation of the potential use of M. anisopliaeICIPE 20 with D. gelechiidivoris showed the fungus to negatively affect the longevity of the adultparasitoids as well as the survival of parasitised larvae. However, the percentage parasitism by fungus-infected female wasps, remained high (> 70%). Fungus infection of parasitized larvae at different ages,reduced parasitoid emergence by 35% and 23% for infection at one and five days post-parasitisation.Exposure of healthy-D. gelechiidivoris adults to a plant-sprayed with fungus did not affect theirlongevity, and no discriminatory host selection was found. The parasitoid did also not differentiatebetween sprayed and non-sprayed host plants. Significantly fewer T. absoluta moths eclosed from hostplants sprayed with M. anisopliae ICIPE 20, prior to being exposed to D. gelechiidivoris compared toinfested plants sprayed with the fungus only or exposed to the parasitoid only. These results wereconfirmed in a greenhouse trial with fewer fruits infested with T. absoluta when both agents werecombined for control of the pest. Establishment of D. gelechiidivoris after its release was confirmed withrecovery from the area of release, one year after its introduction. The findings of this thesis offerpromising tactics including the use of the exotic parasitoid D. gelechiidivoris, native parasitoids, and anentomopathogenic fungus to develop sustainable IPM methods to control T. absoluta.Doctora

Habitat factors associated with Fopius caudatus parasitism and population level of its host, Ceratitis cosyra

Biotic and abiotic factors affect herbivores and their natural enemies and understanding of their requirements may permit habitat modification enabling conservation biological control. Ceratitis cosyra Walker (Diptera: Tephritidae), an African-native fruit fly pest is mostly parasitized by the parasitoid wasp Fopius caudatus Szepligeti (Hymenoptera: Braconidae). To assess F. caudatus habitat, the wasp parasitism levels and infestation of its fruit fly host were examined in Sarcocephalus latifolius (Smith) Bruce (Rubiaceae), a shrub of which the fruits are among the preferred hosts of C. cosyra and F. caudatus. Fruit-collection site descriptions, including plant species presence, were analysed in relation to the target insect abundances (emergence from target fruit). Ceratitis cosyra and F. caudatus emerged from all sites; nonetheless, their population levels were associated with both abiotic and biotic factors, of which some can be manipulated. Several factors, such as cultivation level, topography, and vegetation coverage, were correlated with F. caudatus parasitism. Ceratitis cosyra infestation level was correlated with factors such as density of S. latifolius, vegetation cover, cultivation practices, temperature, altitude, rainfall pattern, and stoniness. Proximity to other fruit fly host plants correlated with both pest abundance and F. caudatus parasitism level of the fruit fly. The findings that insects' interactions and abundance are influenced by habitat structure and that parasitism is positively related to natural habitat indicates the importance of maintaining natural habitats in closeness to cultivated areas with the aim of enhancing pest suppression by parasitoids. Further studies should attempt to identify how plant species composition in and around orchards could affect the management of tephritid fruit fly pests

Interactions between the Entomopathogenic Fungus Metarhizium anisopliae ICIPE 20 and the Endoparasitoid Dolichogenidea gelechiidivoris, and Implications for Combined Biocontrol of Tuta absoluta

The Integrated Pest Management (IPM) approach have been widely promoted and used for the management of native and invasive pests, while the use of various components of the IPM can have a synergetic, additive, or antagonistic effect on each other; this study evaluated the susceptibility of Dolichogenidea gelechiidivoris (Marsh) (Hymenoptera: Braconidae), to the Metarhizium anisopliae (Metschnikoff) ICIPE 20 through direct and indirect infection approaches. The effect of fungus on parasitoid longevity, survival of parasitized-larvae, preference of the parasitoid to fungal treated and untreated larvae, and percent parasitism of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under different infection scenarios were assessed. The direct application of dry conidia to the parasitoid prior to exposure to the host, reduced D. gelechiidivoris longevity, though the infected female wasps still yielded high parasitism (over 70%). Infecting the parasitized larvae at different ages led to a respective reduction of parasitoid emergence by 35% and 23% for infection at 1 and 5 days post-parasitisation. Exposure of healthy-D. gelechiidivoris adults to a plant-sprayed with fungus did not affect their longevity, and no discriminatory host selection was observed. The highest mortality (~80%) of T. absoluta was achieved when D. gelechiidivoris and M. anisopliae ICIPE 20 were used in combination, indicating an additive impact on the target pest; however, field validation can shed more light on this outcome