MID 2
SECTION-A (ATTEMPT ALL QUESTIONS)
1 A In which diseases leaf, fruit, stem are infected. .....
Q - Optimum and maximum temperature for powdery mildew in mango infection .... 0°C to 25°C (68°F to 77°F).
Mosaic in potato transmitted by............ Potato virus Y (PVY)
The causal organism of downy mildew in mustard is **_Hyaloperonospora parasitica_**.....
The causal organism of powdery mildew of mango is the fungus *Oidium mangiferae*.
SECTION-B
2 A Write the symptom of citrus canker.
Citrus canker, caused by the bacterium *Xanthomonas citri* subsp. *citri*, is a destructive disease affecting citrus trees. Here are the typical symptoms of citrus canker:
1. **Lesions on Leaves:**
- Small, round to oval lesions appear on the leaves.
- Lesions are initially water-soaked and surrounded by a yellow halo.
- As the lesions mature, they become raised, corky, and develop a whitish to tan center with a reddish-brown margin.
2. **Lesions on Fruits:**
- Lesions can also develop on fruits, typically near the stem end or calyx.
- Fruit lesions are similar to those on leaves, starting as water-soaked areas and becoming corky and raised with age.
- Lesions may cause fruit deformities or premature fruit drop.
3. **Lesions on Stems and Twigs:**
- Young stems and twigs may develop elongated, raised lesions that eventually girdle and cause dieback.
- Lesions on stems and twigs can lead to branch dieback and affect overall tree health.
4. **Leaf and Fruit Drop:**
- Severe infections can cause defoliation (leaf drop) and premature fruit drop, leading to yield losses.
- Infected leaves and fruits may drop prematurely, reducing the tree's photosynthetic capacity and fruit production.
5. **Shoot Dieback:**
- Infected shoots and branches may exhibit dieback, with wilting and browning of leaves and stems.
- Dieback can progress from the tips of branches towards the main trunk.
6. **Secondary Infections:**
- Citrus canker lesions can serve as entry points for secondary pathogens, leading to further damage and decay of affected tissues.
7. **Stunted Growth:**
- Young citrus trees or newly emerged shoots may show stunted growth and reduced vigor when infected with citrus canker.
8. **Spore Production:**
- Under humid conditions, the bacterium produces white to yellowish exudates (ooze) containing bacterial cells and spores on the surface of lesions.
Write causal organism of red rot, gummosis,apple scab downy mildew of grape.
A - Here are the causal organisms for each of the mentioned grape diseases:
1. **Red Rot of Grape:**
- **Causal Organism:** *Guignardia bidwellii* (previously known as *Phomopsis viticola*).
- **Description:** Red rot is a fungal disease affecting grapes, especially during humid and warm conditions. It primarily targets berries, causing them to develop red-brown lesions that eventually lead to fruit rot and shriveling.
2. **Gummosis of Grape:**
- **Causal Organism:** *Botryosphaeria* spp., including *Botryosphaeria dothidea* and *Botryosphaeria obtusa*.
- **Description:** Gummosis is a disease characterized by the formation of gummy exudates on grapevines, often near pruning wounds or injury sites. *Botryosphaeria* species are commonly associated with this condition, causing cankers and bark damage.
3. **Apple Scab of Grape:**
- **Causal Organism:** *Venturia inaequalis* (commonly known as apple scab), although apple scab primarily affects apple trees, it can occasionally infect grapevines as well under specific conditions.
- **Description:** Apple scab is a fungal disease that causes dark, scaly lesions on leaves, stems, and fruits. While it's not a primary grape disease, in rare cases, it can affect grapevines and lead to leaf damage and reduced vigor.
4. **Downy Mildew of Grape:**
- **Causal Organism:** *Plasmopara viticola*.
- **Description:** Downy mildew is one of the most significant fungal diseases affecting grapevines. It primarily targets leaves, causing yellow lesions on the upper surface and grayish-purple spore masses on the lower surface. Severe infections can lead to defoliation, reduced fruit quality, and yield losses.
Q - Discuss about wilting in gram cucurbits.
A - Wilting in Gram Cucurbits
Wilting in gram cucurbits, such as cucumbers, pumpkins, and squash, is a common issue that can affect the health and productivity of the plants. Wilting can be caused by various factors, including both biotic (living organisms) and abiotic (environmental) factors. Here are some common causes of wilting in gram cucurbits:
Biotic Causes of Wilting:
Fungal Diseases: Diseases like Fusarium wilt and Verticillium wilt can infect the plants, causing wilting of leaves and stems.
Bacterial Pathogens: Bacterial infections such as bacterial wilt can lead to wilting and decline in plant health.
Pests: Insects like cucumber beetles and squash bugs can damage the plant tissue, leading to wilting.
Abiotic Causes of Wilting:
Water Stress: Both overwatering and underwatering can cause wilting in gram cucurbits. Inadequate water supply can lead to wilting due to dehydration, while waterlogged soil can cause root rot and subsequent wilting.
Nutrient Deficiency: Lack of essential nutrients, particularly potassium and magnesium, can result in wilting symptoms.
Temperature Stress: Extreme temperatures, especially high heat, can stress the plants and cause wilting.
Soil Compaction: Compacted soil can restrict root growth and water uptake, leading to wilting.
Prevention and Management of Wilting:
Proper Watering: Maintain a consistent watering schedule, ensuring the soil is moist but well-drained.
Soil Health: Ensure good soil drainage and fertility to prevent waterlogging and nutrient deficiencies.
Disease Management: Practice crop rotation, use disease-resistant varieties, and apply appropriate fungicides to prevent fungal infections.
Pest Control: Monitor for pests regularly and take measures to control their populations.
Temperature Control: Provide shade during hot periods and protect plants from temperature extremes.
Maintain Plant Health: Keep plants healthy through proper nutrition and care to improve their resistance to stress factors.
By understanding the causes of wilting in gram cucurbits and implementing appropriate preventive measures, growers can help ensure the health and productivity of their plants.
D Discuss about early blight in potato.
A - Early blight in potato is a significant disease caused by the fungus Alternaria solani. Here is some information about early blight in potatoes:
Symptoms of Early Blight:
Circular lesions with dark borders on leaves.
Yellowing and browning of leaves.
Premature defoliation.
Reduced yield and quality of potatoes.
Causes:
Fungal infection by Alternaria solani.
Warm and humid conditions favor disease development.
Overhead irrigation can spread the spores.
Prevention:
Use disease-free seed potatoes.
Keep cull/compost piles away from potato growing areas.
Destroy any volunteer potato plants.
Keep tubers covered to prevent infection.
Management:
Apply fungicides if necessary.
Practice crop rotation to reduce disease pressure.
Monitor plants regularly for symptoms.
Remove and destroy infected plant material.
Discuss about downy mildew in grape.
A - Downy mildew in grape is a significant disease caused by the fungus Plasmopara viticola. Here is some information about downy mildew in grape:
Symptoms of Downy Mildew:
Yellow or pale green spots on the upper surface of leaves.
White to gray fuzzy growth on the underside of leaves.
Leaf distortion and eventual leaf drop.
Reduced fruit quality and yield.
Causes:
Fungal infection by Plasmopara viticola.
Thrives in warm and humid conditions.
Spreads through spores in wet weather.
Prevention:
Use disease-resistant grape varieties.
Ensure good air circulation around plants.
Avoid overhead irrigation to reduce moisture on leaves.
Remove and destroy infected plant material promptly.
Management:
Apply fungicides preventatively or at the first signs of infection.
Prune vines to improve air circulation.
Monitor vineyards regularly for symptoms.
Follow integrated pest management practices.
Give the symptom about gummosis.
SECTION-C
Explain in detail about the symptoms of anthracnose, causal organism and their management in mango.
A - Anthracnose is a common fungal disease that affects mango trees, causing various symptoms. Here is a detailed explanation of the symptoms, causal organism, and management of anthracnose in mango:
Symptoms of Anthracnose in Mango:
Leaf Symptoms:
Produces leaf spots, blossom blight, wither tip, twigs blight.
Small blister-like spots develop on the leaves and twigs.
Young leaves may wither and die.
Fruit Symptoms:
Small, angular, brown to black lesions on the fruit skin.
Slightly depressed grey-black areas on ripening fruit.
Panicle Symptoms:
Small black or dark-brown spots on panicles, which can enlarge and kill flowers.
Causal Organism of Anthracnose in Mango:
The causal organism of mango anthracnose is the fungus Colletotrichum gloeosporioides var minor (also known as Glomerella cingulata var minor).
Management of Anthracnose in Mango:
Cultural Practices:
Prune trees yearly and remove fallen debris to reduce disease spread.
Maintain good orchard hygiene.
Chemical Control:
Periodic fungicide sprays on very susceptible mango cultivars.
Use of fungicides like Prochloraz for post-harvest treatments.
Biological Control:
Spray Pseudomonas fluorescens at regular intervals to manage the disease.
Post-Harvest Treatments:
Cold non-recirculating spray with Prochloraz.
Hot water dips for controlling post-harvest anthracnose.
Give the late blight symptom, favourable conditions and management in potato.
A - Late Blight in Potato:
Symptoms:
Leaf Symptoms:
Watery blisters of green or yellow color appear on the leaf foliage.
Brown or black lesions develop on the lower leaf.
Leaf rotting can occur within 1-4 days.
Stem and Tuber Symptoms:
Water-soaked spots on stems and tubers.
Spots increase in size, turn purple-brown, and finally black.
Favorable Conditions:
Temperature: Night temperatures of 50 to 60°F and day temperatures of 60 to 70°F are ideal for disease development.
Humidity: High humidity above 90% is conducive to late blight spread.
Weather: Cloudiness before rainfall and rainfall of at least 0.1mm followed by subsequent days of rain.
Management:
Cultural Practices:
Eliminate cull piles and volunteer potatoes to control late blight.
Proper harvesting and storage practices are essential.
Chemical Control:
Protective spraying with fungicides like mancozeb or zineb at recommended concentrations.
Use foliar fungicides on a regular schedule to manage late blight.
Tuber Protection:
Proper hilling and earthing up practices to reduce tuber infection.
Minimize injuries to tubers to prevent contamination.
Describe the symptoms, causal organism and management of leaf spot in strawberry.
A - Symptoms of Leaf Spot in Strawberry:
Appearance:
Light-to-dark-brown spots of varying sizes on infected leaves.
Circular, deep purple spots that enlarge and turn grayish.
Small, round, necrotic spots on leaves.
Causal Organism of Leaf Spot in Strawberry:
The causal organisms of leaf spot in strawberry include:
Pestalotia leaf spot and fruit rot caused by species of Neopestalotiopsis.
Mycosphaerella fragariae causing common leaf spot.
Management of Leaf Spot in Strawberry:
Chemical Control:
Applications of captan and other fungicides are effective in reducing disease incidence.
Use fungicides like mancozeb or zineb at recommended concentrations.
Cultural Practices:
Proper orchard hygiene to reduce disease spread.
Eliminate infected plant debris and maintain good garden sanitation.
Preventive Measures:
Early detection and removal of infected plants.
Implement crop rotation to reduce disease pressure.
By combining chemical control, cultural practices, and preventive measures, you can effectively manage leaf spot in strawberry plants. If you need more information or assistance, feel free to ask!
B= Explain disease cycle in late blight of potato with diagram.
A -
A Explain about symptom, causal organism, management of fire blight in apple
A - Symptoms of Fire Blight in Apple:
Rotted areas turn brown to black and become covered with droplets of whitish tan colored bacterial ooze.
Blossom symptoms become apparent one to two weeks after infection, with the floral receptacle, ovary, and peduncles becoming water-soaked and dull.
Most infected leaves and branch tips wilt rapidly, turn brown or black, and the leaves die but do not drop off.
The bark at the base of blighted twigs becomes water-soaked, then dark, sunken, and dry.
Causal Organism of Fire Blight in Apple:
The disease is caused by the bacterium Erwinia amylovora, a gram-negative, rod-shaped bacterium.
Erwinia amylovora can infect and cause severe damage to many plants in the rose (Rosaceae) family.
Management of Fire Blight in Apple:
Spray streptomycin at bloom to kill fire blight bacteria before they enter the apple tree.
Prune off infected branches 1 foot below the diseased sections as soon as fire blight is discovered and burn them to prevent further infection.
Apply blossom sprays if fire blight has been a problem in the past to prevent new infections.
Effective management is multi-faceted and largely preventative, utilizing a combination of sanitation, cultural practices, and other control methods.
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