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Nyamu_Thesis-Final 8162020.pdf (1.32 MB)

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Management of Tuta absoluta in Kenya

Nyamu, Denis Gachau
http://rave.ohiolink.edu/etdc/view?acc_num=osu1597392477572665

Abstract Details

2020, Master of Science, Ohio State University, Entomology.
The tomato crop (Solanum lycopersicum) is an economically important vegetable in Kenya, where it is grown in many counties. Pest and diseases are some of the major challenges that face tomato production in Kenya. Among these pests, the South American tomato moth (Tuta absoluta) is a serious, new and exotic pest affecting tomato production in Kenya. Insecticides are traditionally used to control T. absoluta. Excessive use of insecticides could lead to the development of insecticide resistance, resulting in reduced pest control. T. absoluta has developed resistance to several classes of insecticides, including diamides, one of the most recent insecticide molecules, in several countries. Use of integrated pest management (IPM) is a potent tool to slow down the development of insecticide resistance. Monitoring and detection of resistance development is key to the development of IPM for T. absoluta. Since T. absoluta was introduced into Kenya in 2014, it has spread to all the tomato producing regions in the country. Management of this pests can best be achieved through IPM. We developed a survey to document and understand how farmers currently manage T. absoluta (Chapter 2). To understand the status of insecticide use in Kenya conducted the survey using electronic tablets formatted with questionnaires using Kobo toolbox software in three major tomato producing counties. The results from 448 farmers indicated that T. absoluta is perceived as one of the two most important pests of tomato. Furthermore, insecticides are the major control tactic used, with diamides being the most widely used insecticide group. Most Kenyan farmers use insecticides registered for the control of this pest. Despite its huge potential, IPM is still a foreign concept among farmers. Diamides and emamectin benzoate were among the first insecticides registered for the control of T. absoluta in Kenya. Therefore, overuse and over reliance is not uncommon. Screening for the susceptibility and efficacy of these insecticides is therefore key to resistance management. Understanding the dynamics of insecticide control in reference to their efficacy and potential development of increasing intensity of resistance is imperative for the creation of insecticide rotation programs and of resistance management. We present data from insecticide trials conducted both under field and laboratory conditions. In both field and laboratory conditions, Escort (active ingredient: emamectin benzoate) was the most effective for control of T. absoluta. The diamides Belt (flubendiamide) and Coragen (chlorantraniliprole) had intermediate performance, while Halothrin (lambda-cyhalothrin) was the least effective. I found that diamide products (flubendiamide and chlorantraniliprole) was not the most efficacious for control of a lepidopteran pest such as T. absoluta. This suggested that insecticide resistance to diamides might be developing. Insecticide control remains the most widely used method of vegetable pest management globally. Due to the overreliance of one active ingredient to manage a particular pest, resistance development is common in some pest species. Diamide insecticides, including flubendiamide and chlorantraniliprole, have been widely used to manage lepidopteran pests. In Kenya, as documented by the survey, diamides have been widely used for management of T. absoluta. For this reason, we investigated potential diamide insecticide resistance. In this study, I investigated point mutations in the ryanodine receptor previously described to confer diamide insecticide resistance, notably two sites which include G4903 and I4747. We compared field populations exposed to insecticides versus susceptible populations reared in the laboratory without exposure to insecticides by sequencing of ryanodine receptor. Results revealed no presence of mutations in the ryanodine receptor. Future studies should focus on evaluating the efficacy of these insecticides as well as possible development of insecticide resistance.
Luis Canas (Advisor)
87 p.
Entomology

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Citations

  • Nyamu, D. G. (2020). Management of Tuta absoluta in Kenya [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1597392477572665

    APA Style (7th edition)

  • Nyamu, Denis . Management of Tuta absoluta in Kenya. 2020. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1597392477572665.

    MLA Style (8th edition)

  • Nyamu, Denis . "Management of Tuta absoluta in Kenya." Master's thesis, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1597392477572665

    Chicago Manual of Style (17th edition)

osu1597392477572665
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