Study on Fungitoxicity and Fungistatic Properties of Seed Treating Insecticides toward Trichoderma harzianum and Efficacy of Biological Control of Cotton Damping-off Disease
2010
M Houshiar-fard | T Darvish-mojeni
Fungistatic and toxicity of 3 insecticides including of Thiodicarb (Larvin® 80DF), Thiametoxam (Cruiser® 350DF) and Imidacloprid (Guacho® 70WS) were evaluated on mycelial growth of Trichoderma harzianum Rifai. The experiments were factorial based on a randomized complete design with 18 treatments and 5 replications that were made on M.A 2 % medium containing each of the insecticides at 4, 5, 6, 7, 8 (×103) ppm (Controls were also prepared without any insecticides). Dose-response curves were drawn by plotting mycelial growth inhibition % against the insecticide concentration on log-probit scale and the concentration causing 50 % inhibition (ED50 value) was reported in log µg/ml. All three insecticides inhibited to some extent the growth of T. harzianum, this inhibition was a result of a particular insecticide-fungus combination. Sensitivity of T. harzianum against tested insecticides showed 30.6-77.6 % and 1-9.8 % inhibition of the growth of fungal antagonist with Thiodicarb and Imidacloprid, respectively. In addition, Thiodicarb had more toxicity effect (ED50= 3.74) on fungus than Thiametoxam (ED50=3.89). In greenhouse, treated seeds with 1.5 % Trichodermin B (w/w), 3 recommended dosages of tested insecticides were sown in artificially infected soils with 5, 1 and 6 % (W/V) inoculum of Fusarium moniliforme, Pythium ultimum and Rhizoctonia solani. Experiments confirmed in vitro results so that, Trichodermin B + Imidacloprid (5 and 6 gr of commercial product. Kg-1 cotton seed) provided excellent integrated control against pre- and post-emergence damping-off by 88.9 and 75 %, respectively. It is concluded that Imidacloprid had the least deleterious effects on T. harzianum and could have been used in IPM and sustainable production of cotton.
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