Biology, Population Dynamics and Management Options of Tomato Leaf Miner, Tuta Absoluta (Meyrick) (Lepidoptera: Gelechiidae) In West Shewa, Central Ethiopia
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Date
2018-06-02
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Addis Ababa University
Abstract
Tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an important pest infesting Solanaceous plants all over the world. It became a problem on tomato in Ethiopia since 2012. As the pest is new to the country basic studies are paramount importances for designing sound control measure. Such studies includes seasonal abundance and distribution, biology and yield losses, which lay fertile ground for developing sound integrated pest management against the pest. Hence, these studies were intended to monitor the population dynamics, biology, Economic threshold level and management of T. absoluta on tomato under laboratory, glasshouse and open field conditions in West Shewa, Central Ethiopia. Different stages of T. absoluta were investigated in the glasshouse and open fields during 2015 to 2017 for six and four plantation periods, respectively. The highest populations of T. absoluta per plant were recorded in August 2016 under glasshouse conditions whereas under open field conditions, the highest populations of T. absoluta per plant were recorded in March and April in 2015-2016. The field studies showed that T. absoluta population increased proportionality with growth periods. Accordingly, the period of peak activities of T. absoluta was at vegetative, flowering and early fruit setting growth stages of tomato. There were different records on the biology of T. absoluta in the world mainly due to variations in temperature and relative humidity. In Ethiopia, the night temperature is very low and the day temperature is very high. Due to this reason, it is expected that the biology of T. absoluta is different from what was so far recorded elsewhere. Accordingly, the biology of T. absoluta was studied at different temperatures and relative humidities under laboratory and glasshouse conditions for two consecutive seasons. In these studies, developmental stage, adult longevity, fecundity and ovipositon periods were recorded. T. absoluta female laid about 60.56% of her eggs on the upper side surface of tomato leaves, while the lowest (0.85%) were on tomato stem. The highest number of eggs, 233.75±14.42 was laid at the temperature of 20.5±2oC and 55±5% of R.H., whereas the lowest number of eggs, 177.5±9.26 was laid at the temperature of 32.0±2oC and 40±5% R.H. The life expectancy of adult T. absoluta was high at low temperature and low at high temperature. As temperature goes above 20.5°C developmental time of the moth decreased from 9.0±0.3 to 6.8±0.27 days for male and from 18.4±1.45 to 15.2±1.4 days for female T. absoluta. Based on the leaf and fruit-infestation data, tomato varieties such as Koshoro, Roman-VF, Galila and Local were found to be susceptible to T. absoluta, while potato varieties such as Jalane, Menagesha, Tolcha and Local found to be tolerant to T. absoluta. Pepper varieties such as M. Awaze, M. Fana, M. Zala and Local showed high level of resistance to T. absoluta. The economic threshold level of T. absoluta larvae on tomato plants were conducted from 2015 to 2017 under glasshouse and open field conditions. The economic threshold level of T. absoluta was determined under glasshouse and open field conditions. The glasshouse findings showed that control measures should be started at 2.25 larvae per plant while under open field conditions at 2.87 larvae per plant. The yield loss due to T. absoluta was found to be 87.50% - 100% and 60.08% - 82.31% under glasshouse and open field conditions, respectively. The studies were conducted to evaluate bio-pesticides against T. absoluta under laboratory and glasshouse conditions during 2015-2016. After screening of effective bio-pesticides, further studies were conducted under field conditions during 2016-2017 in three different locations of West Shewa. The extract of Azadirachta indica, Allium sativum, and Cymbopogon citrates were revealed that significant larval mortalities. Similarly, Beauveria bassiana and Metarrhizium anisopliae at 2.5 x 109 concentration were gave good results against T. absoluta larvae. The population number of T. absoluta was caught on sticky trap colors under glasshouse coditions. The white and blue sticky traps were caught more moths than yellow, green and red traps. Therefore, all these information can be utilized to know when to start monitoring and enhance the use of bio-pesticides and cultural practices as integrated pest management (IPM) strategies to control T. absoluta in Ethiopia.
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Keywords
Biopesticide, Economic threshold, Entomopathogenic fungi, Mortality, Oviposition, Sticky trap, Tomato, Tuta absoluta