mid 1
A In which rust diseases leaf blades, sheath, glumes and awns are infected.
B Optimum and maximum temperature for yellow rust infection is..15-20.
C - Mosaic in sugarcane transmitted by........... Virus
Causal organism of downy mildew in mustard .................. Peronospora parasiti
Causal organism of grey mould........ Botrytis cineria
SECTION-B
2 A Write the symptom of loose smut and ergot of wheat.
A - Loose smut and ergot are two distinct diseases affecting wheat, each caused by different pathogens and exhibiting unique symptoms.
### Loose Smut of Wheat
**Pathogen:** *Ustilago tritici*
**Symptoms:**
1. **Early Appearance:** Symptoms are noticeable at the time of heading.
2. **Smutty Spikes:** Infected spikes (ears) emerge from the boot earlier than healthy ones. The entire spike, including the grains, is replaced by a black, powdery mass of smut spores.
3. **Powdery Mass:** The black spores are easily dispersed by wind, leaving only the bare rachis (central stem of the spike) after the spores are shed.
4. **Plant Growth:** Infected plants are often stunted and may show delayed development.
5. **Absence of Kernels:** There are no kernels in the affected heads as they are entirely replaced by the smut spores.
### Ergot of Wheat
**Pathogen:** *Claviceps purpurea*
**Symptoms:**
1. **Sclerotia Formation:** The most distinctive symptom is the presence of hard, dark purple to black sclerotia (ergot bodies) that replace the wheat kernels. These sclerotia are typically larger than the kernels they replace.
2. **Honeydew Stage:** Before the sclerotia mature, infected florets exude a sticky, yellowish to brown liquid known as honeydew. This stage is characterized by the presence of fungal spores that can spread the disease.
3. **Discolored Florets:** Florets may appear discolored or swollen.
4. **Reduced Grain Yield:** The presence of ergot bodies reduces the yield and quality of the grain.
5. **Toxicity:** Ergot sclerotia contain toxic alkaloids that can cause ergotism in humans and animals if ingested.
Q - Write causal organism of red rot, smut of sugarcane grassy shoot and pineapple diseases.
Sure, here are the causal organisms for the mentioned diseases of sugarcane:
1. **Red Rot of Sugarcane**
- **Causal Organism:** *Colletotrichum falcatum
2. **Smut of Sugarcane**
- **Causal Organism:** *Sporisorium scitamineum* (formerly known as *Ustilago scitaminea*)
3. **Grassy Shoot Disease of Sugarcane**
- **Causal Organism:** Phytoplasma
4. **Pineapple Disease of Sugarcane**
- **Causal Organism:** *Ceratocystis paradoxa* (formerly known as *Thielaviopsis paradoxa*)
Q - Discuss about wilting in gram.
- Wilting in gram (chickpea) is a serious disease caused by the soil-borne fungus *Fusarium oxysporum f. sp. ciceris*. This disease can lead to significant yield losses and affects the plant at various growth stages. Here's a detailed discussion on the wilting in gram:
### Causes
**Pathogen:** *Fusarium oxysporum f. sp. ciceris*
### Symptoms
1. **Seedling Stage:**
- Seedlings may wilt and collapse.
- Infected seedlings exhibit yellowing of leaves followed by drooping and withering.
2. **Adult Plant Stage:**
- **Yellowing of Leaves:** The disease typically starts with the lower leaves turning yellow.
- **Drooping of Leaves and Petioles:** Leaves and petioles droop and the plant begins to wilt.
- **Vascular Discoloration:** A characteristic symptom is the brown discoloration of the vascular tissues (xylem) when the stem is cut.
- **Stunted Growth:** Infected plants often exhibit stunted growth and may die prematurely.
- **Chlorosis and Necrosis:** Progressive yellowing (chlorosis) and browning (necrosis) of leaves occur, leading to the plant's death.
### Disease Cycle
1. **Soil-Borne Pathogen:** The fungus survives in the soil and plant debris for several years in the form of chlamydospores.
2. **Infection:** The pathogen infects the roots and blocks the xylem vessels, hindering the transport of water and nutrients.
3. **Spread:** The disease spreads through contaminated soil, infected seeds, and irrigation water.
### Favorable Conditions
- **Warm Temperatures:** Temperatures between 25-30°C (77-86°F) are ideal for the development of the disease.
- **Moist Soil:** High soil moisture levels favor the growth and spread of the pathogen.
- **Susceptible Varieties:** Certain chickpea varieties are more susceptible to Fusarium wilt.
### Management and Control
1. **Cultural Practices:**
- **Crop Rotation:** Practice crop rotation with non-host crops (e.g., cereals) to reduce the pathogen load in the soil.
- **Field Sanitation:** Remove and destroy infected plant debris to minimize the source of inoculum.
- **Proper Irrigation:** Avoid over-irrigation and waterlogging, as these conditions favor the disease.
2. **Resistant Varieties:**
- Use chickpea varieties that are resistant or tolerant to Fusarium wilt. Breeding programs have developed several resistant cultivars.
3. **Seed Treatment:**
- Treat seeds with fungicides such as carbendazim or thiram before sowing to reduce the risk of seed-borne infection.
4. **Soil Treatment:**
- Soil solarization can reduce the pathogen load in the soil. This involves covering the soil with transparent plastic sheets for several weeks during hot weather.
5. **Biological Control:**
- Use of biocontrol agents such as *Trichoderma* spp. and *Pseudomonas fluorescens* can help suppress the Fusarium pathogen.
D - Discuss about alternaria leaf spot in musterd.
A - ### Alternaria Leaf Spot / Alternaria Blight in Mustard
Alternaria leaf spot, caused by the fungi *Alternaria brassicae* and *Alternaria brassicicola*, is a prevalent and damaging disease in mustard crops. This disease can lead to significant yield losses and affects various parts of the plant, including leaves, stems, and pods.
#### Causes
**Pathogens:**
- *Alternaria brassicae*
- *Alternaria brassicicola*
#### Symptoms
1. **Leaf Spots:**
- **Initial Spots:** Small, dark brown to black circular spots appear on the leaves.
- **Expansion:** These spots enlarge and often develop concentric rings, giving a target-like appearance.
- **Necrotic Areas:** In severe cases, the spots may merge, forming large necrotic areas, leading to leaf blight.
2. **Lesions on Stems and Pods:**
- **Stems:** Dark brown to black elongated lesions can appear on stems and branches.
- **Pods:** Similar lesions may form on pods, leading to premature pod shattering and seed contamination.
3. **Chlorosis and Defoliation:**
- Yellow halos or chlorotic areas may surround the spots.
- Severe infection can lead to premature leaf drop, reducing the plant's photosynthetic capacity and vigor.
4. **Seed Contamination:**
- Infected seeds may show discoloration and reduced germination rates.
#### Disease Cycle
1. **Survival:** The pathogen survives in plant debris and soil as conidia (spores) and mycelium.
2. **Spread:** Disease spreads via wind, rain splash, and infected seeds.
3. **Infection:** Typically occurs during periods of high humidity and moderate temperatures.
#### Favorable Conditions
- **Humidity:** High relative humidity (above 90%) and leaf wetness are crucial for spore germination and infection.
- **Temperature:** Optimal temperatures for disease development range from 20-25°C (68-77°F).
- **Dense Planting:** High plant density can create a microclimate that favors the disease due to reduced air circulation and prolonged leaf wetness.
#### Management and Control
1. **Cultural Practices:**
- **Crop Rotation:** Rotate with non-host crops (e.g., cereals, legumes) to break the disease cycle.
- **Field Sanitation:** Remove and destroy infected plant debris to reduce inoculum sources.
- **Proper Spacing:** Ensure adequate plant spacing to improve air circulation and reduce leaf wetness.
2. **Resistant Varieties:**
- Use mustard varieties that are resistant or tolerant to Alternaria leaf spot. Breeding programs focus on developing such varieties.
3. **Seed Treatment:**
- Treat seeds with fungicides such as thiram or carbendazim to prevent seed-borne infections.
4. **Chemical Control:**
- Apply fungicides like mancozeb, chlorothalonil, or azoxystrobin at the first sign of disease. Repeat applications may be necessary, especially during favorable conditions for disease development.
5. **Biological Control:**
- Use biocontrol agents such as *Trichoderma harzianum* and *Bacillus subtilis* to suppress the pathogen.
6. **Integrated Pest Management (IPM):**
- Combine cultural, biological, and chemical control measures for effective and sustainable disease management.
Q- Discuss about brown rust in wheat.
A - ### Brown Rust in Wheat
Brown rust, also known as leaf rust, is one of the most common and economically significant diseases affecting wheat. It is caused by the fungus *Puccinia triticina*. The disease can lead to considerable yield losses, particularly under favorable environmental conditions.
#### Causal Organism
**Pathogen:** *Puccinia triticina*
#### Symptoms
1. **Initial Lesions:**
- Small, round to oval, orange-brown pustules appear on the leaf surface.
- These pustules primarily occur on the upper leaf surface but can also be found on the leaf sheaths and stems.
2. **Pustule Characteristics:**
- Pustules are scattered or may form in clusters.
- They rupture the epidermis, releasing rusty-colored spores.
3. **Advanced Infection:**
- Heavily infected leaves may turn yellow, wither, and die prematurely.
- Severe infections can result in significant leaf area reduction, impacting the plant's photosynthetic ability.
4. **Secondary Symptoms:**
- Infected plants may exhibit stunted growth.
- Yield losses occur due to reduced grain fill and smaller kernel size.
#### Disease Cycle
1. **Survival and Spread:**
- *Puccinia triticina* overwinters in volunteer wheat and other grass hosts.
- Urediniospores, which are the main infective spores, are dispersed by wind over long distances.
2. **Infection Process:**
- Spores germinate on the leaf surface under favorable conditions, penetrating through stomata.
- The fungus colonizes the leaf tissue, forming pustules that release new spores.
3. **Reproduction:**
- Urediniospores are produced throughout the growing season, perpetuating the disease cycle.
- Teliospores may form later in the season, contributing to the overwintering of the pathogen.
#### Favorable Conditions
- **Temperature:** Optimal temperature range for infection is between 15-22°C (59-72°F).
- **Humidity:** High humidity and leaf wetness are essential for spore germination and infection.
- **Wind:** Wind plays a crucial role in the dispersal of urediniospores.
#### Management and Control
1. **Cultural Practices:**
- **Crop Rotation:** Rotate with non-host crops to reduce pathogen carryover.
- **Field Sanitation:** Remove volunteer wheat and grass weeds that can harbor the pathogen.
- **Proper Planting Time:** Adjust planting times to escape peak infection periods.
2. **Resistant Varieties:**
- Use resistant wheat varieties. Breeding programs continually develop and release varieties with resistance to brown rust.
3. **Chemical Control:**
- Apply fungicides as a preventive measure or at the onset of the disease. Effective fungicides include those containing triazoles, strobilurins, and combination products.
- Fungicide application should be timed based on disease forecasting models and environmental conditions.
4. **Monitoring and Forecasting:**
- Regularly monitor fields for early signs of infection.
- Utilize disease forecasting models that predict rust outbreaks based on environmental conditions and spore presence.
5. **Integrated Pest Management (IPM):**
- Combine cultural practices, resistant varieties, and fungicide applications for effective and sustainable management.
- Encourage practices that promote plant health and reduce stress, as healthy plants are less susceptible to severe infections.
Q - Give the symptoms of Sclerotinia stem rot in mustard.
A - ### Symptoms of Sclerotinia Stem Rot in Mustard
1. **Water-Soaked Lesions:**
- Small, pale brown, water-soaked lesions on stems, especially near the soil line or leaf axils.
2. **Wilting:**
- Temporary wilting during the day, with potential recovery at night.
- Permanent wilting as the disease progresses.
3. **Stem Rot:**
- Enlarged lesions turning into soft, mushy, light brown to gray rotted areas.
- Stem tissue becomes bleached and dry, with a shredded appearance.
4. **Sclerotia Formation:**
- Hard, black, irregularly shaped sclerotia developing inside the stem cavity and on infected tissues.
5. **Leaf Symptoms:**
- Water-soaked spots on leaves expanding into large, irregular necrotic areas.
- Yellowing and premature death of leaves attached to infected stems.
6. **Pod Symptoms:**
- Water-soaked lesions on pods leading to rot.
- Presence of sclerotia inside the pods, causing seed contamination.
7. **Plant Death:**
- Girdling of the stem disrupting nutrient and water transport, leading to plant collapse and death.
8. **Yield Reduction:**
- Fewer, shriveled, and low-quality seeds.
- Significant yield losses in dense, humid crop stands.
SECTION-C
3A Explain in detail about the symptoms of white rust, causal organism and their management in mustard.
A - ### White Rust in Mustard
**Causal Organism:**
- **Pathogen:** *Albugo candida*
White rust, also known as white blister, is a significant disease affecting mustard and other cruciferous crops. It primarily impacts leaves, stems, and inflorescences, leading to yield reductions and poor crop quality.
### Symptoms 2 types
a. Localised infection - White raised pustules or sori are formed on surface of leaf , stem and infloresence .
Mature pustules ruptures to release mass of white powdery spores.
b. Systematic infection - young stem and flowering parts are infected .
this is called stag head .
flowers get malformed , fungus produces oospores in the later stage of season.
### Disease Cycle
1. **Survival:**
- The pathogen survives in the form of oospores in plant debris and soil.
2. **Infection:**
- During favorable conditions, oospores germinate to produce sporangia, which are spread by wind and water to new host plants.
- Sporangia infect the plant through stomata or wounds, leading to the development of pustules.
3. **Spread:**
- Secondary spread occurs through the release of zoospores from sporangia, which further infect nearby plant tissues.
### Favorable Conditions
- **High Humidity:** High relative humidity and leaf wetness are crucial for the development and spread of the disease.
- **Moderate Temperatures:** Optimal temperatures for disease development range from 15-25°C (59-77°F).
- **Dense Planting:** Dense crop stands with poor air circulation favor disease spread.
### Management and Control
1. **Cultural Practices:**
- **Crop Rotation:** Rotate with non-host crops to reduce the pathogen load in the soil.
- **Field Sanitation:** Remove and destroy infected plant debris to minimize sources of inoculum.
- **Proper Spacing:** Ensure adequate spacing between plants to improve air circulation and reduce humidity levels around the plants.
- **Avoid Overhead Irrigation:** Use drip irrigation to keep foliage dry and reduce leaf wetness.
2. **Resistant Varieties:**
- Plant resistant or tolerant varieties of mustard that are less susceptible to white rust. Breeding programs focus on developing such varieties.
3. **Chemical Control:**
- **Fungicides:** Apply fungicides such as metalaxyl, fosetyl-aluminum, or chlorothalonil at the first sign of disease. Regular applications may be necessary, especially under favorable conditions for disease development.
- **Seed Treatment:** Treat seeds with appropriate fungicides to prevent initial infections.
4. **Biological Control:**
- Use biological control agents such as *Trichoderma* spp. and *Bacillus subtilis* to suppress the pathogen.
5. **Integrated Pest Management (IPM):**
- Combine cultural, chemical, and biological control measures for effective and sustainable disease management.
- Monitor environmental conditions and crop health regularly to implement timely interventions.
B Give the Ascochyta blight symptom, favourable conditions and management in gram.
A - ### Ascochyta Blight in Gram (Chickpea)
**Causal Organism:** *Ascochyta rabiei*
### Symptoms
1. **Leaf Symptoms:**
- **Small Lesions:** Initially, small, water-soaked lesions appear on the leaves.
- **Darkening:** Lesions darken and expand, becoming angular or irregularly shaped with distinct margins.
- **Necrosis:** The affected areas become necrotic, turning brown to black in color.
2. **Stem and Pod Symptoms:**
- **Stem Lesions:** Similar lesions can develop on stems, causing stem blight.
- **Pod Lesions:** Pods may also show lesions, affecting seed quality and yield.
3. **Leaf Drop:**
- Severe infections can lead to extensive leaf drop, weakening the plant and reducing photosynthetic capacity.
4. **Secondary Infections:**
- Secondary infections by other pathogens may occur in the necrotic areas, further damaging the plant.
### Favorable Conditions
- **Humidity:** High humidity and moisture favor the development and spread of Ascochyta blight.
- **Temperature:** Optimal temperatures for disease development range from 20-25°C (68-77°F).
- **Dense Planting:** Dense crop stands with poor air circulation promote disease spread.
- **Overhead Irrigation:** Overhead irrigation or frequent rainfall can contribute to leaf wetness and disease progression.
### Management
1. **Cultural Practices:**
- **Crop Rotation:** Rotate with non-host crops to break the disease cycle and reduce inoculum levels.
- **Resistant Varieties:** Plant resistant chickpea varieties whenever possible. Resistant cultivars are available and offer effective control.
- **Field Sanitation:** Remove and destroy infected plant debris after harvest to reduce the carryover of the pathogen.
2. **Seed Treatment:**
- Treat seeds with fungicides or biofungicides before planting to protect seedlings from early infections.
- Use seed treatments containing chemicals like thiram, carbendazim, or metalaxyl.
3. **Fungicide Applications:**
- Apply fungicides preventively or at the first sign of disease to protect healthy plants.
- Effective fungicides include azoxystrobin, chlorothalonil, tebuconazole, and others. Follow label instructions for application rates and timings.
4. **Avoiding Stress Factors:**
- Ensure proper plant spacing to promote good air circulation and reduce humidity around plants.
- Avoid excessive nitrogen fertilization, as lush growth can be more susceptible to diseases.
5. **Biological Control:**
- Use biocontrol agents like *Trichoderma* spp. and *Bacillus subtilis* to suppress the growth of Ascochyta rabiei.
6. **Integrated Pest Management (IPM):**
- Combine cultural practices, resistant varieties, seed treatments, fungicides, and biological controls for comprehensive disease management.
- Regularly monitor fields for early signs of disease and adjust management strategies accordingly.
A- Describe the symptoms, etiology and management of smut in sugarcane.
A- - ### Smut in Sugarcane
**Symptoms:**
1. **Inflorescence Changes:**
- Initially, the young inflorescence or flower spike of sugarcane appears normal.
- As the disease progresses, the affected inflorescence becomes swollen, black, and distorted in shape.
2. **Smut Balls:**
- Eventually, the swollen inflorescence bursts open to reveal masses of dark-colored, powdery spores known as "smut balls."
- These smut balls are composed of fungal spores and can easily disperse in the wind.
3. **Plant Growth and Yield:**
- Infected plants often exhibit stunted growth, reduced vigor, and a decline in overall health.
- Yield losses can be significant as the smut infection affects the reproductive structures of the plant, leading to poor seed set and smaller cane size.
**Etiology:**
- **Causal Agent:** The smut disease in sugarcane is caused by the fungus *Sporisorium scitamineum*, previously known as *Ustilago scitaminea*.
- **Infection Process:** The fungus enters the sugarcane plant through wounds or natural openings and establishes itself in the developing inflorescence tissue. It then replaces the normal reproductive structures with smut balls containing fungal spores.
**Favorable Conditions for Disease Development:**
- **Warm and Humid Climate:** The fungus thrives in warm temperatures ranging from 25-30°C (77-86°F) combined with high humidity.
- **Moisture:** Moist conditions, such as heavy rainfall or irrigation, promote the germination and spread of fungal spores.
**Management:**
1. **Cultural Practices:**
- **Field Sanitation:** Remove and destroy infected plant debris, especially inflorescences, to reduce the source of inoculum.
- **Healthy Seed Selection:** Planting disease-free and certified seed cane helps prevent initial infections.
- **Crop Rotation:** Rotate with non-host crops to break the disease cycle and reduce pathogen buildup in the soil.
2. **Chemical Control:**
- **Seed Treatment:** Treat sugarcane setts (seed pieces) with fungicides before planting to protect against smut infections.
- **Foliar Fungicides:** Application of fungicides during the early stages of inflorescence emergence can help manage smut. Common fungicides include triazoles and strobilurins.
3. **Biological Control:**
- Utilize biocontrol agents such as *Trichoderma* spp. and *Pseudomonas fluorescens* to suppress the growth of *Sporisorium scitamineum*.
- Biocontrol agents can be applied to the soil or as seed treatments.
4. **Resistant Varieties:**
- Develop and plant sugarcane varieties with genetic resistance or tolerance to smut disease.
- Breeding programs focus on selecting and breeding resistant cultivars.
5. **Integrated Pest Management (IPM):**
- Implementing an integrated approach combining cultural practices, chemical control, biological control, and resistant varieties provides effective and sustainable management of smut in sugarcane.
- Regular monitoring of fields for early signs of smut and prompt action are essential for successful disease management.
Q - Explain in detail downy mildew diseases of sugarcane
A - **Downy Mildew in Sugarcane**
**Causal Organism:**
- **Pathogen:** *Peronosclerospora sacchari* (previously known as *Sclerospora sacchari* or *Peronospora sacchari*).
**Symptoms:**
1. **Leaf Symptoms:**
- **Initial Signs:** Yellow or pale green patches appear on the upper surface of leaves.
- **Under Leaf:** Upon closer inspection, a whitish to grayish downy growth can be observed on the lower surface of infected leaves.
- **Lesions:** Lesions on leaves may develop irregular shapes and may coalesce, leading to large areas of infection.
- **Leaf Curling:** Infected leaves may curl or twist, affecting the overall appearance of the plant.
2. **Stem and Bud Symptoms:**
- **Stem Lesions:** Dark brown to black lesions can occur on stems, especially near the nodes.
- **Bud Rot:** In severe cases, the fungus can infect and rot the growing points or buds, causing death of the terminal bud and shoot.
3. **Inflorescence and Flower Symptoms:**
- **Inflorescence Rot:** Infected flower spikes or inflorescences may exhibit rotting, affecting seed set and quality.
- **Seed Coat Lesions:** Fungal lesions may also develop on the outer coat of seeds, reducing their viability and germination rates.
4. **Plant Growth Symptoms:**
- **Stunted Growth:** Infected plants often show stunted growth and reduced vigor.
- **Yield Reduction:** Severe infections can lead to significant yield losses due to reduced sugar content and overall plant health.
**Disease Cycle:**
1. **Survival:** The pathogen survives in infected plant debris, soil, and on seeds.
2. **Infection:**
- Sporangia (asexual spores) are released from infected plant parts during wet and humid conditions.
- These spores are dispersed by wind or splashing water to nearby plants, initiating new infections.
3. **Colonization:** The fungus colonizes host tissues, forming a downy growth on the lower leaf surface and causing damage to plant cells.
4. **Spread:** Disease spread occurs through rain splash, wind, and movement of infected plant material.
**Favorable Conditions:**
- **High Humidity:** Downy mildew thrives in high humidity and moist conditions.
- **Moderate Temperatures:** Optimal temperature range for disease development is around 20-25°C (68-77°F).
- **Heavy Rainfall:** Extended periods of rain or frequent rainfall facilitate disease spread and severity.
**Management:**
1. **Cultural Practices:**
- **Field Sanitation:** Remove and destroy infected plant debris to reduce the source of inoculum.
- **Crop Rotation:** Rotate with non-host crops to break the disease cycle and reduce pathogen buildup.
- **Healthy Seed Selection:** Use disease-free and certified seeds for planting to minimize initial infections.
2. **Chemical Control:**
- **Fungicides:** Apply fungicides containing active ingredients such as metalaxyl, mefenoxam, or dimethomorph to protect plants from downy mildew.
- Follow recommended application rates and timings based on disease severity and local recommendations.
3. **Biological Control:**
- Utilize biocontrol agents like *Trichoderma* spp. or *Pseudomonas fluorescens* to suppress the growth and spread of *Peronosclerospora sacchari*.
- Biofungicides can be applied as soil drenches or foliar sprays.
4. **Resistant Varieties:**
- Plant sugarcane varieties with genetic resistance or tolerance to downy mildew.
- Select and use resistant cultivars developed through breeding programs for improved disease management.
5. **Integrated Pest Management (IPM):**
- Adopt an integrated approach combining cultural practices, chemical control, biological control, and resistant varieties for effective and sustainable downy mildew management.
- Regular scouting and monitoring for disease symptoms, coupled with timely interventions, are essential for successful disease control.
Q - Explain about symptom red rot in sugarcane.
A - **Red Rot in Sugarcane**
**Causal Organism:**
- **Pathogen:** *Colletotrichum falcatum* (previously known as *Glomerella tucumanensis*).
**Symptoms:**
1. **Internal Discoloration:**
- **Early Stages:** Initial symptoms of red rot may not be visible externally.
- **Internal Rot:** The fungus infects the inner tissues of sugarcane, causing internal discoloration.
- **Reddish Coloration:** The infected tissues turn reddish-brown to dark red in color, giving the disease its name.
2. **Stalk and Root Symptoms:**
- **Lesions on Stalks:** As the disease progresses, external symptoms become evident on the stalks.
- **Lesion Appearance:** Lesions initially appear water-soaked and soft, later turning dark red or brown.
- **Cracking:** Infected stalks may exhibit longitudinal cracking and splitting, leading to structural weakness.
3. **Exudation of Red Gel:**
- **Red Gel Formation:** Infected stalks may exude a characteristic red gel or ooze from the lesions.
- **Presence of Spores:** The red gel contains fungal spores, contributing to disease spread.
4. **Leaf Symptoms:**
- **Yellowing and Wilting:** Infected plants may show yellowing and wilting of leaves as the disease progresses.
- **Premature Leaf Shedding:** Severe infections can cause premature shedding of leaves, reducing photosynthetic capacity.
5. **Stunted Growth and Yield Loss:**
- **Reduced Vigor:** Infected plants often exhibit stunted growth and reduced vigor.
- **Yield Reduction:** Red rot can lead to significant yield losses due to reduced sucrose content in affected stalks and overall plant health.
**Disease Cycle:**
1. **Survival:** The pathogen survives in infected plant debris, soil, and on sugarcane stalks.
2. **Infection:**
- The fungus enters sugarcane plants through wounds, natural openings, or insect feeding sites.
- Rain splash and irrigation water facilitate spore dispersal and infection during humid conditions.
3. **Colonization:** The fungus colonizes the vascular tissues of sugarcane, causing internal discoloration and rot.
4. **Spread:** Disease spread occurs through infected planting material, contaminated soil, and movement of infected plant parts.
**Favorable Conditions:**
- **Warm Temperatures:** Optimal temperature range for disease development is around 25-30°C (77-86°F).
- **Moisture:** High humidity and wet conditions, such as heavy rainfall or irrigation, promote disease spread and severity.
**Management:**
1. **Cultural Practices:**
- **Field Sanitation:** Remove and destroy infected plant debris and diseased stalks to reduce inoculum levels.
- **Crop Rotation:** Rotate with non-host crops to break the disease cycle and minimize pathogen buildup.
- **Healthy Seed Selection:** Use disease-free and certified planting material to prevent initial infections.
2. **Chemical Control:**
- **Fungicides:** Apply fungicides containing active ingredients such as triazoles, strobilurins, or copper-based compounds to protect against red rot.
- Follow recommended application rates and timings based on disease severity and local recommendations.
3. **Biological Control:**
- Utilize biocontrol agents like *Trichoderma* spp. or *Bacillus subtilis* to suppress the growth and spread of *Colletotrichum falcatum*.
- Biofungicides can be applied as soil drenches or foliar sprays.
4. **Resistant Varieties:**
- Plant sugarcane varieties with genetic resistance or tolerance to red rot.
- Utilize resistant cultivars developed through breeding programs for improved disease management.
5. **Integrated Pest Management (IPM):**
- Adopt an integrated approach combining cultural practices, chemical control, biological control, and resistant varieties for effective and sustainable red rot management.
- Regular scouting and monitoring for disease symptoms, coupled with timely interventions, are essential for successful disease control and minimizing yield losses.
Comments