Effect of Plant Extracts against Alternaria Leaf Spot of Chilli
Abstract
Chilli (Capsicum annuum L.)is one of the most important vegetables in the world, Alternaria leaf spot caused by Alternaria alternata is one of the major diseases of chilli worldwide. It is responsible for causing up to 10-15 % yield losses in chilli. An experiment was conducted using Nilgiri leaf extract, Lemongrass leaf extract, Neem leaf extract, Datura leaf extract and Lantana camara leaf extract and Mancozeb were tested against Alternaria leaf spot (Alternaria alternata) (Fr.) keissler under field condition during Rabi season 2023. Among all treatments, neem leaf extract@10%FSwas found highly effective in showing the minimum disease intensity (%) with (18.51%) followed by nilgiri leaf extract @10%FS (20.07%). The maximum plant height (cm) (37.14cm) were found in neem leaf extract @10%FSfollowed by nilgiri leaf extract @10%FS (35.55cm) , highest number of leaves were found in neem leaf extract @10%FSwith (41.66) followed by nilgiri leaf extract @10%FS (40.43) and highest yield (t/ha) of chilli were found in neem leaf extract@10%FS (3.78t/ha)followed by nilgiri leaf extract @10%FS (3.26t/ha) compared to untreated check and treated check (Mancozeb) @0.2%FSand C:B ratio is highest in neem leaf extract @10%FS(1:4.0) followed by nilgiri leaf extract @10%FS (1:3.4).
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Introduction
Chilli (Capsicum annuum L.)is well known for its aroma, pungency and medicinal value. It is a perennial herbaceous plant that belongs to the family Solanaceae having 2n = 24 chromosome number. Both vegetarian and non-vegetarian dishes considered chilli as the most important ingredient for its taste and flavour. According to a report published on Indiastat.com by Professor Jayashankar Telangana State Agricultural University (Agricultural Market Intelligence Centre) showing the area, production, and productivity of chilli in India (2020-30th June 2021), so as per the report, the chilli covered 7.43 lakh ha area with 19.14 lakh tonnes production and productivity of 2576 kg/ha and for this reason it makes India the world’slargest producer, consumer and exporter of chilli. According to Spice Board India report (2019-2020 Est.), chilli growing states in India with their production (lakh Tonnes) are: Andhra Pradesh (6.60 lakh tonnes), Telangana (3.28 lakh tonnes), Madhya Pradesh (2.18 lakh tonnes), Karnataka (1.80 lakh tonnes) and West Bengal (1.04 lakh tonnes) (Goswami and Mishra, 2022).
The important diseases are Anthracnose (Colletotrichum capsici), Cercospora leaf spot (Cercospora capsici), damping off and root rot (Rhizoctonia solani, Pythium sp., and Fusarim sp.), Fusarium wilt (Fusarium oxysporumf. sp. capsici), gray mould (Botrytis cinerea), powdery mildew (Leveillula taurica) etc (Vidhyasekaran and Thiagarajan 1981; Meon and Nick,1988; Pandey et al., 2012).
Fungi, bacteria, viruses, nematodes and abiotic stress are the causal entities for this. Among fungal diseases, leaf spot caused by Alternaria alternata (Fr.) Keissler and Cercospora capsici. Heald and Wolf causing damage from seed to seed stage in chilli. As foliar pathogen they are more severe compared to their seed-borne nature in many regions around the world. These pathogens will cause damage to crop from early stage itself. In later stages pathogens cause damage to fruits also, ultimately less yield and reduction in quality of the produce reported that 70-80 percent chilli fields are affected with Alternaria sp. in Shouguang district. Among the major constraints in the production of chilli biotic factors plays an important role. Leaf spot disease caused by Alternaria alternata and Cercospora capsici were the very common biotic factors in almost all chilli growing areas around India (Kumari and Zacharia, 2023).
A pathogenic fungus is Alternaria alternata. Throughout the world Alternaria is caused disease in many plants. Symptoms of this disease is caused by Alternaria and development in 1997. Alternaria is a genus of Ascomycota fungi. Alternaria species are the leading plant pathogens causing diseases. The Genus Alternaria Nees. Ex Fr. Associate to the subdivision Deuteromycotina class Hyphomycetes, family Dematiaceae (Woudenberg et al., 2013). The genus is spread allover the world and caused disease in crops (Bochalya et al., 2012).
Alternaria pathogen attacks on the aerial parts of host. Small circular, dark spots symptoms of Alternaria infections are produced. These spots size is ½ inch and are these spots are usually gray and black in color. Around the spots concentric rings are developed and pathogen growth rate is uniform due to environmental conditions. Lesion are developed on plants parts that appear in a specific pattern (Spalding and King, 1999). Spores are appeared on leaf surface of the infected plant. Effected area is covered by fungus spores. Pathogen directly penetrate into the host by stomata, wounds and other open cells. By spores and mycelia, pathogen is survived on host plant (Anwar and Arshad, 2010). Alternaria pathogen spreads by plant residues and infected seeds. If fungus is seed borne then should appear at seedling stage which is observed incase of Alternaria. Leaf spot is most destructive disease of chilli. Spores of this pathogen cause allergies and asthma symptoms inhuman (Khan et al., 2014). Antifungal activity of plant extracts may be more effective than some commercial synthetic fungicides due to presence of naturally occurring substances in plants with anti-microbial properties that have been recognized and tested against a wide range of pathogenic microbes (Tamuli, 2014). Therefore, it has become necessary to adopt ecofriendly management practices for better crop health management and yield. The systematic search of higher plants has shown that the plant extracts have antifungal activity against many species of fungi (Guerin et al., 1984; Natarajan et al., 1987; Singh et al., 1987). In recent years, plant extracts mainly, neem derivatives gaining importance for the control of plant diseases due to their antifungal and antibacterial properties (Yin et al., 1998).
Before management of leaf spot disease symptoms of the disease should be identified based on the reports of this pathogen. Usually, disease free seed is used for cultivation ad if there are chances of seed borne pathogens then it must be treated with suitable fungicide. Moisture on the plant surface favors the disease development while during wind there are less chances of disease due to lack of surface moisture. If we keep plant free of injuries and insect, there are very less chances of disease. Disease is reduced by the weed control and crop residue destruction. Incidence of some Alternaria species is reduced by the ultraviolet light exposure. Free pathogenic plant stock material should be used. There are number of fungicides which are used against Alternaria. Chlorothalonil, captan, fludioxonil, imazalil, iprodione, maneb, mancozeb, thiram, and selected copper. Leaf spot disease is also managed from bio-control, plants extract, and chemical management (Narain et al., 2000). Fungicides are the most common tools for controlling the disease losses. In recent years, the indiscriminate use of fungicides is being observed. They are potentially hazardous to public health, environment and increases pollution and it remains in soil for long time. Nowadays an alternative attempt was made in controlling the plant disease management. The use of organic manures, soil amendments, and Plant extracts which are eco-friendly, non-phytotoxic, easy decomposition and does not affect human health. Considering the above-mentioned facts, a study entitled, “Effect of plant extracts against alternaria leaf spot (Alternaria alternata) disease of chilli (Capsicum annuum L.)” was proposed with the following objectives:
Conclusion
Neem leaf extract @10% concentration as foliar spray was most effective against Alternaria leaf spot of chilli which causes Alternaria alternata in chilli resulted minimum disease intensity (%), Plant height (cm), number of leaves , yield (t/ha) of chilli and C:B ratio . Results of the present study are of one crop season (December 2023 to April 2024) under prayagraj agroclimatic conditions as such to validate the findings more such trials should carried out in future.
