STUDY ON LEAF BLIGHT OF GLADIOLUS (BOTRYTIS GLADIOLORUM) IN BANGLADESH AND ITS MANAGEMENT

Abstract

A set of investigations comprising six experiments were conducted in the Department of Plant Pathology, Sher-e-Bangla Agricultural University, during the consecutive years 2016 to 2020 in Bangladesh. The investigation was aimed to find out the disease incidence and severity of gladiolus leaf blight disease in major gladiolus growing districts in Bangladesh and its management in vitro and in vivo. A survey was conducted in selected gladiolus growing districts in Bangladesh and the data on the disease incidence and disease severity were collected. Leaf blight infected leaves, stems and flowers samples were collected and studied. Survey data revealed that leaf blight incidence in all the districts showed statistically similar result except Bogura and Dhaka. Disease incidence was varied from 18.89% to 32.22%. On the other hand, the highest severity (17.22%) was found in Manikganj district which was statistically similar with Cox’s Bazar (15.56%), Faridpur (13%) and Jashore district (12.33%). The lowest disease severity (5.56%) was found in Gaibandha district. Forty-four (44) isolates of Botrytis gladiolorum were isolated and identified from the sample collected from survey areas. The highest mycelial radial growth of Botrytis gladiolorum (72.00 mm) was recorded from BGCCO3 whereas the lowest (33.00 mm) growth was recorded from BGCCO5 in PDA media at 16 DAI. The radial mycelia average growth rate /day ranged from 2.06 mm to 4.5 mm. Fourteen (14) cultural groups of B. gladiolorum were determined based on cultural characteristics. Among ten fungicides, Contaf 5 EC gave the best results in arresting radial mycelia growth and it was nil (00.00 mm) after 5 DAI in 100 ppm which was statistically similar with indofil 80 WP treated (00.00 mm) plate and the inhibition of growth was 100%. At 15 DAI the growth inhibition (87.34%) was highest in contaf 5 EC treated plate followed by Score 250 EC (78.02%) and Autostin 50 WDG (72.34%) respectively. In 200 ppm Contaf 5 EC showed the best performance against mycelial growth at 15 DAI and gave 100% growth inhibition which was statistically similar to Score 250 EC (100% inhibition) followed by Autostin 50 WDG (83.04) and Folicure 250 EC (82.90%). In 300 ppm Contaf 5 EC showed the best performance at 15 DAI against mycelia growth and showed 100% inhibition which was statistically similar to Score 250 EC (100% inhibition), Autostin 50 WDG, Tilt 250 EC and Folicure 250 EC. Among ten botanicals studied 20% garlic extract showed the best result at 5 DAI and the radial mycelia growth was nil (00.00 mm) which was statistically similar with onion extract and turmeric extract treated plate. At 15 DAI the inhibition of fungal growth was found (73.74%), (71.23%) and (66.90%), respectively with treated by turmeric extract (18.80 mm), garlic extract (20.60 mm) and onion extract (23.70 mm). Among nine organic acids tested at the rate of 1000 ppm Acetic acid gave the best performance and showed (57.02%) inhibition of mycelia growth at 15 DAI followed by Benzoic acid (48.04%) and oxalic acid (41.97%). Three fungicides (Score 250 EC, Contaf 5 EC and Autostin 50 WDG) at the rate of 300 ppm, three botanicals (Turmeric, Garlic and Onion) at the rate of 20% and three organic acids (Acetic acid, Benzoic acid and Oxalic acid) at the rate of 3000 ppm were evaluated in the field against gladiolus leaf blight. At the flowering stage lowest incidence (14.81%) was found in Score 250 EC treated plot which was statistically similar with Contaf 5 EC (14.81%), Autostin 50 WDG (18.51%) and Turmeric extract (20.37%). Disease severity was lowest in Score 250 EC treated plot (8.33%) which was statistically similar with Contaf 5 EC (9.00%), Autostin 50 WDG (10.00%) and Turmeric extract (10.67%). The growth parameters and yield were also found highest in score 250 EC treated plot, which was statistically similar with Contaf 5 EC, Autostin 50 WDG and Turmeric extract treated plot.