Exploring Enhanced Insecticidal Activity of Mycelial Extract of Trichoderma harzianum against Diuraphis noxia and Tribolium castaneum
Exploring Enhanced Insecticidal Activity of Mycelial Extract of Trichoderma harzianum against Diuraphis noxia and Tribolium castaneum
Sadaf Rahim and Mudassar Iqbal*
ABSTRACT
Fungi are important organisms that produce potent secondary metabolites with antimicrobial, herbicidal, insecticidal and other such beneficial activities. Production of such compounds can be increased or decreased depending on growth conditions. For these reasons a Trichoderma harzianum was selected for its growth optimization conditions and extraction of insecticidal compounds effective against two major insects pests including Diuraphis noxia and Tribolium castaneum. The pure fungal strain of Trichoderma was grown using two different nutrient media including Glucose Peptone Yeast Broth (GPYB) and Potato Dextrose Broth (PDB) and the effect of organic extract was investigated against selected insects’ pest. From this study it was found that the mycelial extract of T. harzianum fermented on PDB showed enhanced insecticidal mortality (73% and 76%) against Diuraphis noxia and Tribolium castaneum respectively while the extract obtained from GPYB media showed merely 46% and 56% mortality against Diuraphis noxia and Tribolium castaneum respectively at highest concentration after 2 hours exposure. Increased potency of extracts was observed with the increased exposure time. The LC50 value calculated for organic extract obtained from T. harzianum grown on PDB against Diuraphis noxia was 398.69 μg mL-1 after 3 hours with increased potency (237.46 μg mL-1) after 24 hours, whereas against Tribolium castaneum it was 213.85 μgmL-1 after 24 hours while its decreased potential was recorded (1153.5 μg mL-1) after 3 hours. Similar pattern of toxicity level was observed for organic extract exposure of T. harzianum grown on GPYB viz increasing exposure time increased the mortality rate, The LC50 value against Diuraphis noxia was reduced to 1083.49 μg mL-1 after 24 hours from 2269.08 μg mL-1 after 3 hours, whereas against Tribolium castaneum it reduced significantly from 1849.69 μg mL-1 after 3 hours to 677.21 μg mL-1 after 24 hours. From the results it is concluded that T. harzianum grown on PDB produced potent secondary metabolites that could be used for the development of target specific insecticides against Diuraphis noxia and Tribolium castaneum. Further studied towards the isolation and structural elucidation of lead compounds is recommended for the development of local agro-chemical product as environmental friendly biodegradable organic insecticides.
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