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North-West University (2020)

Damage to citrus and vegetables by Thaumatotibia leucotreta (Lepidoptera : Tortricidae) and prospects for control with entomopathogenic fungi

Mkiga, Abdullah Mohamed

Titre : Damage to citrus and vegetables by Thaumatotibia leucotreta (Lepidoptera : Tortricidae) and prospects for control with entomopathogenic fungi

Auteur : Mkiga, Abdullah Mohamed

Université de soutenance : North-West University

Grade : Doctor of Philosophy in Environmental Sciences 2020

Résumé partiel
Globally, orange is one of the major fruit crops contributing to nutrition and monetary income. False codling moth (FCM), Thaumatotibia leucotreta, is one of the major constraints of orange production. Before this study, little was known regarding the bio-ecology of FCM in orange and vegetables in Kenya and Tanzania and the potential use of dry conidia of entomopathogenic fungi for control of T. leucotreta moths has not been tested. There is also no IPM strategy available for FCM in East Africa. This PhD study therefore aimed at generating information on these aspects. Field surveys on damage inflicted by the pest on orange and vegetables were conducted in Kenya and Tanzania. The spatial-temporal population dynamics and genetic diversity of FCM were evaluated in citrus orchards in these two countries. The highest FCM larval incidence (46%) was recorded on orange produced at high altitudes in Kenya while the lowest (33%) was recorded at low altitudes in Tanzania. The highest FCM infestation amongst the vegetables was recorded on African eggplant (12%) while the lowest was on okra (3%). A similar spatio-temporal pattern of FCM was observed in both countries, with the highest catches being recorded in August, during the 2017 and 2018 orange fruiting seasons in these regions. Microbial control of the pest was tested by screening dry conidia of entomopathogenic fungi isolates of Metarhizium anisopliae and Beauveria bassiana species. Dry conidia of these EPF isolates were found to be pathogenic to the moths, the ICIPE 69 isolate caused the highest mortality of 94.2%. Fecundity was reduced by 33.6 and 25.9% for the donor (fungal contaminated moths) and recipient (fungus-free moths allowed to mate with fungal contaminated moths) FCM females, respectively after horizontal transmission. Compatibility of the potent entomopathogenic fungal isolate, ICIPE 69 and the FCM sex pheromone was tested in an auto-inoculation device. The fungus remained viable and was therefore compatible with the pheromone.

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