Toxicity of some Biocides in the Tomato leaf Miner Tuta Absoluta Meyrick (Lepidoptera: Gelechiidae) in Laboratory

Abstract

The experiment was conducted in the Entomology Laboratory/Plant Protection Department/College of Agriculture and Forestry/Mosul University/Iraq in the year 2021, to evaluated the toxicity of biocides, Beauveria bassiana (Bals.) Vuill, (conc. 1, 3, 5 g/L) Bacillus thuringiensis var. kurstaki (conc. 1, 3, 5 g/L), Spinosad (conc. 0.15, 0.30, 0.60 ml/L) and Neem plant extract (Azadirachta indica) (conc. 0.25, 0.50, 1.00 ml/L) on the third larval instar and pupal stage of tomato leafminer (TLM) under laboratory conditions, 25 - 27 °C, and the average relative humidity was 60 - 65%. The results of the study showed that the treatment with Spinosad at a concentration of 0.60 mm/L was significantly superior compared to the rest of the biocides, with an average mortality of 86.67% and 90.67% for larvae and pupae, respectively. All biocides differed significantly compared to the control, which amounted to 0.00%, and the highest mean of larval mortality was 71.67% for the reading after ten days of treatment, which differed significantly compared to the reading after one and three days of treatment, which amounted to 23.89 and 50.56%, respectively. While the reading after nine days of treatment outperformed significantly, and recorded the highest average of pupal mortality, which amounted to 68.00%, compared to the lowest average reading after seven days of treatment, which amounted to 44.00%. The treatment with the biocides B. thuringensis at a concentration of 1, 3 and 5 g/L was superior, with the lowest average percentage of transformation of larva to pupal stage reaching 15.56, 2.22 and 0.00%, respectively, compared to the rest of the concentrations of other biocides and the control, which was 73.33%. The biocides B. thuringensis was significantly superior to the rest of the biocides, and the lowest average percentage of emergence was recorded, as it reached 6.67% in the third concentration 5 g/L, which did not differ significantly compared to the third concentration of the rest of the biocides, however, it differed significantly compared to the rest of the concentrations of other biocides, and the control, as the highest mean of the percentage of emergence rate was 76.67%. It is noted from the study that all biocides had a significant effect on their toxicity to TLM compared to the control, and that the toxicity of biocides for the third larval instar and pupa of TLM increased with increasing concentration and number of days after treatment, and led to a decrease in the average percentage of adult emergence with an increase in concentration used compared to the control. From the results of this study, it is possible to introduce these pesticides in the integrated pest management programs for TLM in open fields and protected cultivation.