• M.K. Hasna Plant Pathology Division, Bangladesh Institute of Nuclear Agriculture, BAU Campus, Mymensingh-2202, Bangladesh


The efficacy of the antagonistic microorganism, Trichoderma harzianum in controlling purple blotch of onion (Alternaria porri) was investigated in the laboratory and field of Plant Pathology Division of the Bangladesh Institute of Nuclear Agriculture, Mymensingh. The antagonistic activity of three isolates of T. harzianum was observed against A. porri through dual culture technique and the superior one was used in the field experiment. Five treatments were given viz. T1: Seed treatment with T. harzianum, T2: Seedling treatment with T. harzianum, T3: Foliar application with T. harzianum, T4: Seed treatment and seedling treatment with T. harzianum and T5: Control (A. porri in absence of T. harzianum). The variety BARIpiaj-1 was used as tested crop. All treatments significantly reduced purple blotch disease intensity compared to the control. The least disease intensity on leaf and flower stalk was found in the treatment T4 (Seed and seedling treatment with T. harzianum) followed by the treatment T1 (Seed treatment with T. harzianum). The highest disease reduction over control (63.1% on leaf and 47.18% on flower stalk) was observed in the treatment T4 (seed and seedling treatment with T. harzianum) followed by the seed treatment only (T1) which gave disease reduction 58.7% on leaf and 37.03% on flower stalk over control. Therefore, application of T. harzianum both in seed and seedling was more effective in reducing disease intensity than individual application of T harzianum in seed or seedling.


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