Evaluate The Pathogenicity Of Indigenous Entomopathogenic Nematodes Against Tomato Leaf Miner Tuta Absoluta In Wasit Province, Iraq
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Abstract
The study was conducted after collecting the pathogenic nematodes (EPNs) soil samples from Wasit Province, Iraq, using the white trap method using Galleria mellonella larvae, then identification as local nematodes (Heterorhabditis indica, H. megidis) comparing with commercial nematode H. bacteriophora. The commercial and native EPNs were used as biological control agents targeting Tuta absoluta larvae and pupae during the tomato growing season in the Suwayra area in Wasit province. A laboratory experiment used one microliter of nematode suspension containing Heterorhabditis indica or H. migidis and H. bacteriophora per larva. All three species of EPNs, both native and commercial, impacted Tuta absoluta larvae and resulted in varying mortality rates. The longer exposure time and higher concentration both amplified the effect. After seven days of treatment, the larvae in the current study experienced high mortalities. Among the species utilized in the study, H. bacteriophora was the most effective, with the most significant average mortality rate of 94.4% at a 200 Ijs/ml dosage. At the same concentration, H. megidis came in second with 90.7%. Additionally, after seven days of mortality, the species H. bacteriophorarecorded the most significant average mortality rate, at 80.6%, followed by the species H. indica, at 77.8%, while the average EPNS species with time in the seven days that showed in H.bacteriophoria at 80.6% most effective than the H.indica at 77.8% and H.megidis at 73.6%, This is mainly significant against the larvae of T. absoluta. The examined pupae exhibited sensitivity to infection by all evaluated EPNs, with the highest mortality rate seen at the maximum dose (200 IJs/ml) after 7 days of exposure. which was 100%. The mortality of tested pupae was increased with the increase of EPN concentration and period of exposure in all treatments. The highest average of pupal mortality was recorded at the concentration of (200 Ijs /ml) in the instance of H. megidis, which was 94.44%, and the lowest average of pupal mortality was recorded at the concentration of (50 Ijs/ml) in the particular situation of H. indica, which was 24.11%. The result also revealed that H. megidis was more effective than the other species, recording the highest average of pupal mortality (66.86% ), followed by H. bacteriophora (58.89% ) and the lowest by H. indica (54.01% ).In the field condition that all entomopathogenic nematodes affect the larvae of T. absoluta and the highest percentage of larval fatality was 83.33% in the case of H. bacteriophora at the concentration (200 ijs/ml) and the lowest one in the case of H. migidis at the concentration (150 ijs/ml). The mortality of larvae was proportional with the concentration, while the p-value in concentration (150 ijs/ml) was 0.720 and in concentration (200 ijs/ml) was 0.609 >0.05. These results were significant, and the L.S.D resulted in 1.762 in concentration (150 ijs/ml) and 1.489 in concentration (200 ijs/ml>0.005); also the findings indicated that the pupae of the leaf miner Tuta absoluta exhibited vulnerability to all three examined nematode species. The highest percentage of pupal mortality was 66.67% in the case of H. bacteriophoraand H. Indica at a concentration of (200 ijs/ml) and the lowest one in the case of H. migidisat the concentration of (150 ijs/ml), which was 33.33%. The mortality of pupae was proportional with the nematode concentration, and the P value in (150 ijs/ml) was 0.903 and in (200 ijs/ml) was 1.186.L.S.D in (150 ijs/ml) was 2.209 and in (200 ijs/ml) was 2.903 this resulted was accepted that showed the affected of entomopathogenic species in the field condition. Our research showed that the pathogenic nematodes of three species (Heterorhabditis. ssp.) are effective against the T. absoluta stages of life. This biological control is the best and safest way for humans, animals, and plants to eliminate insect pests without collateral damage.