Cercospora leaf spot is a common fungal disease that affects Chili plants, causing significant yield losses in many regions of the world. The disease is caused by the fungus Cercospora capsici. The presence of small, circular, brownish-black spots on the leaves can identify it. Over time, the spots can coalesce and cause the leaves to turn yellow and drop prematurely.
Cultural, chemical, and biological approaches manage the Cercospora leaf spot. Crop rotation, sanitation, and irrigation restrict disease spread. To prevent fungicide resistance, change fungicides with different ways of action. Microbial biocontrol agents and plant products can also manage the Cercospora leaf spot in Chili plants. Developing disease-resistant Chili cultivars can also aid.
Cercospora Leaf Spot Management in Chilli Pepper
Causes/Pathogen of Cercospora Leaf Spot in Chilli
Cercospora leaf spot is caused by a fungus known as Cercospora capsici, which thrives in tropical regions and can affect Chili plants in seedbeds and fields. Stromata are fully formed. Conidiophores measure between 30 and 60 x 4.5 and 5.5 microns. Conidia are acicular to obculate, and subhyaline to colored.
The fungus can survive from one growing season to the next in various ways, including on infected plant residues, in the soil, and even on or inside seeds. Once a plant is infected, the fungus causes characteristic brownish-black circular spots on the leaves, which can eventually cause the leaves to turn yellow and fall off prematurely.
The Disease Cycle of Cercospora Leaf Spot in Chilli
Cercospora leaf spots in Chili spread through various means, such as water, rain, wind, and contact between leaves or contaminated tools and workers. The disease cycle begins with the dormant mycelium of the Cercospora capsici fungus surviving in infected plant debris, seeds, and volunteer plants during the dormant season.
In the growing season, the disease spreads via air-borne conidia dispersed by wind. The primary source of infection is infected seeds, volunteer plants, and infected plant debris. Foliar infection occurs when the fungus penetrates the leaf directly, which is facilitated by prolonged leaf wetness.
Conditions Favorable for Cercospora Leaf Spot Spread in the Field
Cercospora leaf spot in Chili thrives under certain conditions that favour its spread in the field. The optimal conditions for infection include warm temperatures around 23°C and relative humidity of 77-85%. When these conditions are met, there is a high likelihood of significant yield losses, especially if the infection occurs early in the season. Foliar infection occurs when the fungus directly penetrates the leaf, facilitated by prolonged periods of leaf wetness.
Damage Symptoms of Cercospora Leaf Spot
- Circular spots with brown margins and grey centers appear on leaves.
- The spots enlarge and merge with others.
- The central portion of the spot becomes white, and the leaves turn yellow and defoliate.
- Sometimes, the central portion of the spot drops off.
- Spots on stems and twigs appear dark brown, irregular lesions with whitish centers.
- In severe cases, die-back of twigs can occur.
- Severely infected leaves drop off prematurely, resulting in reduced yield.
- The spots can gradually coalesce to form large leaf lesions with a ‘frog-eye’ appearance.
- The white center often dries and falls out, leaving a ‘shot-hole’ effect.
- At later stages of infection, leaves turn yellow and wilt or drop, exposing fruits to sunscald.
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Yield Loss due to Cercospora Leaf Spot on Chilli
Cercospora leaf spot on Chili can lead to a significant yield loss, with reports indicating a reduction of up to 50% or more.
Cercospora Leaf Spot Management in Chilli by Cultural Method
- Use healthy seeds that are certified.
- Provide enough spacing between plants to promote good air circulation and avoid prolonged leaf wetness.
- Stake plants to keep them upright.
- Use mulch to create a barrier between the plant and the fungus.
- Remove infected plants and destroy them away from the field.
- Monitor seedbeds, young plants, or transplants for any disease symptoms.
- Control susceptible weeds in and around the field.
Cercospora Leaf Spot Management in Chilli by Biological Method
Biological control methods for Cercospora Leaf Spot in Chilli involve using natural enemies, such as Trichoderma spp. and Bacillus spp. These beneficial microbes can be applied to the soil or as a foliar spray to enhance the plant’s natural defenses against the disease. Trichoderma spp. Colonize the roots and act as antagonists against the pathogen, while Bacillus spp. Produce antimicrobial compounds that inhibit the growth of Cercospora spp.
Cercospora Leaf Spot Management in Chilli by Chemical Method
To manage Cercospora Leaf Spot in Chilli using chemical methods, spray twice at 10-15 day intervals with Mancozeb 0.25% or Chlorothalonil (Kavach) 0.1%. Seed treatment with captan (3g/kg) can also be effective. Foliar spray of products containing copper hydroxide, chlorothalonil, or mancozeb can also be used. It is important to start the treatment when the spots first appear and continue at 10-14 day intervals until 3-4 weeks before the last harvest. Ensure that both sides of the leaves are sprayed.
Cercospora Leaf Spot Management in Chilli by Organic/Natural Method
Organic and natural methods can also manage Cercospora Leaf Spots in Chili. One effective method is seed treatment with hot water at 52°C for 30 minutes to reduce the presence of the fungus on seeds. However, care must be taken to avoid excessive time or temperature that may affect seed germination. Foliar sprays of copper hydroxide products can also be used when spots first appear, with intervals of 10-14 days until 3-4 weeks before the last harvest. It is important to spray both sides of the leaves for optimal effectiveness.
Preventive Measures for Control of Cercospora Leaf Spot
Preventive measures for Cercospora leaf spot on Chili include using healthy, certified seeds, proper plant spacing for good air circulation, mulching, staking, drip irrigation, monitoring for symptoms, removing infected plants, controlling weeds, avoiding field work when plants are wet, and implementing wide crop rotation over three years.
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Conclusion
Cercospora Leaf Spot in Chilli is a common fungal disease affecting plant growth and yield. Symptoms include circular spots with brown margins and a grey center, which can lead to defoliation and yield loss. Effective management can be achieved through cultural, biological, chemical, natural, and organic treatments. Proper identification and early detection are essential for successful treatment.
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