Molecular Identification and Biological Control of Tomato Leafminer, Tuta absoluta Using Plant Extracts and Microbial Bio-agents

Abstract

Khidr, S.K. and S.S. Abdulla. 2023. Molecular Identification and Biological Control of Tomato Leafminer, Tuta absoluta Using Plant Extracts and Microbial Bio-Agents. Arab Journal of Plant Protection, 41(4): 427-436. https://doi.org/10.22268/AJPP-41.4.427436 This study was conducted to evaluate the efficacy of some biopesticides (i.e. aqueous plant extracts and entomopathogenic microorganisms) against the tomato leafminer, Tuta absoluta Meyrick, as either an alternative or as integrated with chemical pesticides. The results obtained revealed that the aqueous plant extracts from Eucalyptus camaldulensis showed highest mortality (57.78%) against the larval stage, followed by Cupressus sempervirens (46.67%) seven days after treatment. Highest mortality was obtained by using 50,000 or 25,000 ppm extracts with no significant difference between the two concentrations. However, the 12.500 ppm concentration produced the lowest mortality rate. On the other hand, the larvae were more susceptible to the tested entomopathogenic microorganism. Nevertheless, the susceptibility and resistance varied in response to the pathogen species utilized in the test. The results obtained indicated that both Beauveria bassiana and Bacillus thuringiensis achieved maximum mortality rate (92.5 and 85.83 %, respectively) seven days after treatment, and the mortality rate for all bio-agents gradually increased with increasing concentration. The LC50 value of the above mentioned bioagents was 682340.58 and 995679.42 conidia/ml, respectively. Both positive and negative controls (Indoxacarb 15% and sterilized distilled water) displayed the highest and lowest mortality rate throughout the study. The identification of the bio-agents species was carried out via a DNAbased test. Various specific primers were designed for species identification with a product size ranging between 164 and 560 bp for further use in future agricultural research. Keywords: LC50, exposure time, DNA extraction, mortality