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Chemical Control of Pseudocercospora Leaf Spot (p. Abelmoschi) of Okra Seed Crop

M. G. Kibria
Senior Scientific Officer, Plant Pathology Section, HRC, BARI, Gazipur, Bangladesh.

Abstract/ Executive Summary:

Results of a field experiment conducted to evaluate the efficacy of five fungicides against Pseudocercospora (P. abelmoschi) leaf spot (PLS) or black mould of okra seed crops showed that foliar spray with Aimcozim 200 EW (Carbendazim) @ 0.10%, Emivit 50 WP (Copper Oxychloride) @ 0.35%, Indofil M-45 (Mancozeb) @ 0.20%, Tilt 250 EC (Propiconazole) @ 0.05% and Folicur 250 EC (Tebuconazole) @ 0.10% decreased percent disease index (PDI) by 485.74-2465.77, 240.74-970.68, 124.39-537.50, 92.81-366.50 and 72.80-209.40% reduction in PDI, respectively over control recorded at 65, 72, 79, 86 days after sowing. On the other hand, the fungicides increased plant height, fruit yield, seed yield, seed germination and seed vigor index by 7.50-30.78% in 18.88-46.70% in 29.02-94.02% in 15.03-19.79% in 21.71-58.07%, respectively over control. The maximum reduction in disease severity and increase in plant growth, yield and yield attributes were achieved with Emivit followed by Aimcozim, Folicur and Tilt. Based on findings of the study Emivit 50 WP and Folicur 250 EC may be recommended to control PLS of okra seed crop.

Keywords: Okra, Pseudocercospora leaf spot, Chemical control

Location: BSMRAU, Sulna, Gazipur,

Start Date: 00-03-2009

End Date: 00-06-2009

Program Area: Pest Management

Commodity: Okra

Objectives:

To evaluate the efficacy of five fungicides to control PLS of okra seed crop

Methodology:

Five fungicides namely Aimcozim 200 EW (Carbendazim), Emivit 50 WP (Copper Oxychloride), Indofil M-45 (Mancozeb), Tilt 250 EC (Propiconazole) and Folicur 250 EC (Tebuconazole) were tested against PLS of okra seed crop under natural field conditions. The fungicides were selected based on their effectiveness against foliar diseases of okra as reported by many other investigators (Pant and Mukhopadhayay 2001, Singh et al. 2003The experiment was conducted in the experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur, Bangladesh during March to June 2009. The experiment was laid out following a randomized complete block design with three replications. The unit plot size was 4.5 m × 1.2 m. Drains of 50 cm width and 30 cm depth were dug around each unit plot for facilitating irrigation and drainage of excess water. The experimental field was prepared properly for good tilth following standard practices (Razzaque et al. 2000). Fertilizers were applied @ 50-24-30-10-1-0.5 kg of N-P-K-S-Zn-B per hectare, respectively. Manure was applied as cowdung at the rate of 4 t/ha (Anon. 2005). The entire quantity of cowdung, P, K, S, Zn and B and half of N were applied at the time of final land preparation. Remaining N was applied around the base of the plant as top dress and incorporated with soil at 3rd and 5th week after sowing. Genotype BD 1911 was used in this experiment. It is susceptible to Pseudocercospora leaf spot. Seeds of the genotype were soaked in tap water for 12 hours. Water soaked seeds were dibbled in the field at 3-4 seeds/hill on 15 March 2008. Seeds of okra were sown at the rate of 3-4 seeds per pit maintaining row to row and plant to plant spacing of 60 and 50 cm, respectively. After 6 to 7 days of germination, the seedlings were thinned and only one apparently healthy seedling was allowed to grow per pot or per pit. If any seedling died within three weeks of germination it was replaced by seedling of same age raised in polyethylene bags (9 x 15 cm). The growth medium used in polyethylene bags was prepared by mixing with decomposed cowdung and soil in equal proportion. Irrigation and other necessary intercultural operations were done throughout the cropping season for proper growth and fruit production. Irrigation was applied after each top dressing of urea and whenever necessary. Every time, irrigation was followed by mulching and weeding. Suspensions of Aimcozim, Emivit 50 WP, Indofil M-45, Tilt 250 EC and Folicur 250 EC were prepared in water at 0.1, 0.35, 0.20, 0.05 and 0.10% concentration, respectively and were applied as foliar spray using a knapsack sprayer starting from the onset of PLS (78 days after sowing) and continued for four weeks with 7 days interval. Data on severity of PLS was recorded at 65, 72, 79 and 86 days after sowing (DAS) based on a 0-8 scale (Rahman and Nahar 1990). Disease severity was expressed in Percent Disease Index (PDI) for the leaf spot, which was computed according to the following a standard formula as described by Wheeler, (1969) and Mian (1995):

Source of Information: Bangladesh J. Plant Pathol. Vol. 28 (1&2): 53-60.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Findings of the present study are in agreement with the findings of many other investigators worked in Bangladesh and abroad. They also achieved satisfactory control PLS using foliar spray with fungicides. Srivastava et al. (1992) found the best control of Pseudocercospora on okra in field trials with Copper oxychloride followed by Carbendazim. Anon. (2011) mentioned the recommendation of spraying Mancozeb or Zineb 2 g or Carbendazim 1 g per liter of water to control the disease. In Philippines, Benlate 50 WP (Benomyl), Daconil 75 WP (Chlorothanil) and Funguran-OH (Copper hydroxide) are recommended to control PLS (Anon 2011). In Bangladesh, Rahman et al. (2000) evaluated the efficacy of Thiovit (0.45%) and Bavistin (0.1%) to control of Pseudocercospora leaf spot of okra. They found that Bavistin applied alone at 15 days interval showed the lowest incidence of the disease followed by Thiovin+Bavistin applied at 30 days interval. The yield and yield attributes of okra increased due to those treatment compared to control. They recommended Bavistin and Thiovit against PLS. Pabitra (2009) reported that Bavistin and Proud are effective to control PLS of okra and to improve plant growth, yield and seed quality and seed health. Based on findings of the present investigation Emivit 50 WP and Folicur 250 EC may be recommended to control PLS of okra seed crop.

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