Epidemiology and management of leaf spot of chilli caused by alternaria alternata ( Fr.) keissler
Loading...
Date
2021
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
JNKVV, Jabalpur
Abstract
The investigation entitled “Epidemiology and Management of Leaf spot of Chilli caused by Alternariaalternate (Fr.) Keissler” was conducted at Department of Plant Pathology, J.N.K.V.V, Jabalpur (M.P) during 2020-2021. The present investigation was conducted with the following objectives.
1. To determine the status of Alternaria leaf spot of chilli in and around Jabalpur.
2. To study the effect of weather parameters on the development of the disease and cultural characterization of Alternariaalternata.
3. To determine the impact of fungicides application on the development of disease.
Chilli (Capsicum annuum L.) is well known for its aroma, pungency and medicinal value.Its multipurpose functions and good nutritive value is well known to the World.The losses caused by the Alternaria leaf spot, 5–85 per cent as reported by Mathur and Agnihotri (1961), thus attention has been given to this disease of chilli.The Alternaria sp. survives as a saprophyte on the plant debris in soil, dissemination takes place by wind and on favourable environmental conditions they germinate andinvade into the host.
The highest per cent disease incidence was observed during the survey inOnriya village (40 per cent) while lowest was observed in PadwarKalan (20 per cent). The pathogen was identified as Alternariaalternata based on the cultural and morphological characters.The pathogenicity test was demonstrated on healthy chilli plants in their natural environment as well as under in vitro conditions on detached chilli leaves using the spore suspension method.The most noticeable character of the fungus is the development of the concentric rings in the centre of the spots on leaves.The maximum radial growth of the fungus was observed at 30°C (71mm) temperature followed by 25°C (69.5mm) and the minimum growth was observed at 15°C (26.5mm) temperature. For the maximum growth of the fungus, the best pH observed was 6.5 (68.5mm) followed by 6.0 (61mm) and the minimum growth was observed at pH 4.0 (47mm). The best relative humidity on which the pathogen exhibits maximum radial growth was 80 per cent (78.16mm) followed by 90 per cent (74.66mm) and the minimum growth was observed at 60 per cent (68.33mm). The best synthetic media on which the maximum radial growth was observed is Richard’s agar (86.83mm) and the best non-synthetic media on which the maximum radial growth was observed is Oatmeal agar media (75.5mm). Among all eight tested fungicides, the best combination found in reducing the per cent disease incidence against A.alternata was Tebuconazole 50% + Trifloxystrobin 25% WG (4.44 per cent) followed by Tebuconazole 10% + Sulphur 65% WG (11.11 per cent) and least effect was observed in case of Carboxin 37.5% + Thiram 37.5% WS (57.8 per cent) as compared with the control. On analyzing the disease development with the weather parameters, the maximum per cent disease incidence (12.67 per cent) was observed in January month when the maximum temperature goes 26.5°C and relative humidity 87 per cent with 0.5mm rainfall and the minimum per cent disease incidence (2.50 per cent) was observed in March when the maximum temperature goes 33.9°C and relative humidity 67 per cent with 0.0mm rainfall.