Test: Plant Diseases - UPSC MCQ

Downy mildew is a fungal-like disease that affects mustard plants. It manifests as yellow lesions on leaves, which enlarge and turn brown, accompanied by a white to grayish downy growth on the undersides. It thrives in cool, wet conditions and can lead to defoliation and reduced photosynthesis, impacting crop yield. Downy mildew spreads through spores carried by wind, water, and contaminated equipment. Control measures involve using resistant cultivars, crop rotation, and sanitation practices. In severe cases, fungicides may be necessary. Regular monitoring and appropriate management strategies are essential to prevent and manage downy mildew in mustard plants.

Leaf rust is a common fungal disease that affects wheat plants. It is caused by the fungus Puccinia triticina. Leaf rust is characterized by the appearance of orange to reddish-brown pustules on the leaves of infected plants. These pustules contain spores that can spread the disease to nearby plants. Leaf rust can significantly reduce crop yields by affecting photosynthesis and weakening the plants. The disease thrives in moderate temperatures and humid conditions. Control measures for leaf rust in wheat include using resistant cultivars, practicing crop rotation, and applying fungicides when necessary. Regular monitoring and early detection are crucial for effective management of leaf rust in wheat crops.

Fruit cracking disease in tomatoes, also known as fruit splitting, is commonly associated with a deficiency of boron in the plant. Boron plays a crucial role in various physiological processes, including cell wall formation and stability. When tomatoes experience a boron deficiency, it can lead to poor cell development and weak cell walls in the fruit, making them more susceptible to cracking. Cracks in the tomato fruit can occur due to fluctuations in moisture levels, such as rapid growth after a dry period or excessive watering. Ensuring an adequate supply of boron through proper soil management and fertilization can help prevent fruit cracking and promote healthy tomato development.

Alternaria blight, caused by the fungus Alternaria spp., is a disease that affects cumin seeds. It is characterized by the development of dark brown to black lesions on the leaves, stems, and seed heads of cumin plants. These lesions may have concentric rings and can cause significant damage to the crop. Alternaria blight is favored by warm and humid conditions. The disease spreads through spores produced by the fungus and can be carried by wind, water, or infected plant debris. Proper crop rotation, maintaining adequate plant spacing, and timely fungicide applications can help manage and control Alternaria blight in cumin plants, ensuring healthy seed production.

The option (a) Chickenpox is not a plant disease. Chickenpox is a viral infection that affects humans, primarily children, and is caused by the varicella-zoster virus. The other options, (b) Tuber diseases, (c) Root rots, and (d) Ring spot, are all plant diseases that can affect various crops and plants.

Fire blight disease is a bacterial infection that primarily affects apple trees and other members of the Rosaceae family, such as pears and other stone fruits. It is caused by the bacterium Erwinia amylovora. The disease is characterized by wilting, blackening, and "burning" appearance of blossoms, branches, and fruit, which gives it the name "fire blight." It can spread rapidly during warm, humid weather conditions, rain, or insect activity. Infected branches can develop characteristic shepherd's crook bends. Control measures include pruning infected branches, applying bactericides, and promoting good orchard sanitation practices. Preventive measures such as planting resistant varieties and maintaining proper tree health can also help manage fire blight in apple orchards.

Late blight, caused by the oomycete pathogen Phytophthora infestans, is a devastating disease that affects potatoes. It is characterized by the appearance of dark, water-soaked lesions on the leaves, stems, and tubers of potato plants. The disease can spread rapidly under cool and moist conditions, leading to complete crop loss if left unchecked. Late blight is notorious for causing the Irish potato famine in the 19th century. Control measures for late blight in potatoes include the use of resistant potato cultivars, proper crop rotation, timely fungicide applications, and good field sanitation practices. Early detection and management are crucial to prevent the spread of late blight and minimize its impact on potato crops.

Red rot is a fungal disease that affects sugarcane plants. It is caused by the pathogen Colletotrichum falcatum. The disease is characterized by the appearance of reddish-brown lesions on the stalks of infected sugarcane plants. These lesions can extend internally, causing rotting and decay of the affected tissues. Red rot can lead to significant yield losses and deterioration of cane quality. Control measures include planting disease-free seedlings, crop rotation, and timely application of fungicides. Proper sanitation practices and removal of infected plant debris also help in managing the spread of red rot in sugarcane crops.

Root-knot disease is caused by nematodes in plants. It is mainly found in tomatoes and peanuts.

Powdery Mildew is an example of a Fungal disease, the rest are viral diseases.

The green year disease is a fungal infection that affects plants, particularly cereals such as wheat, barley, and oats. It is caused by the fungus Pyrenophora tritici-repentis. The disease gets its name from the characteristic green coloration observed on infected plant tissues. It typically manifests as green streaks or patches on the leaves, stems, and glumes of the affected plants. The green year disease can cause significant yield losses and affect grain quality. Proper crop rotation, use of resistant cultivars, and fungicide applications are common control measures to manage and prevent the spread of this fungal disease.

All of the above factors, (a) air, (b) rainfall, and (c) birds, can contribute to the spreading of plant diseases. Plant diseases can be transmitted through the air, where fungal spores or bacteria can be carried by wind currents to infect nearby plants. Rainfall can facilitate the dispersal of pathogens, especially those that thrive in moist conditions, by splashing water droplets containing spores onto plant surfaces. Birds can also play a role in spreading plant diseases as they can carry pathogens on their bodies or in their droppings, potentially contaminating plants they come into contact with.

Dieback disease is a condition in plants that occurs due to the deficiency of copper. Copper is an essential micronutrient for plants, and its deficiency can lead to dieback symptoms. The disease is characterized by the progressive death of branches and twigs, starting from the tips and extending towards the main stem. Leaves may also exhibit discoloration and premature shedding. Copper is crucial for various physiological processes in plants, including enzyme activation and lignin formation. Treating copper deficiency with appropriate fertilization can help prevent and manage dieback disease, promoting healthy growth and development in affected plants.

Soft rots are diseases in plants caused by bacterial pathogens. These bacteria, often from the genera Pectobacterium and Dickeya, infect various plant tissues, such as roots, stems, and fruits. Soft rot bacteria produce enzymes that break down plant cell walls, leading to tissue decay and a soft, mushy texture. Infected plant parts may develop a foul odor and become discolored. Soft rot diseases can cause significant damage to crops and result in post-harvest losses. Proper sanitation practices, crop rotation, and disease-resistant cultivars can help manage and control soft rot bacterial infections in plants.

Anthracnose blight is a fungal disease that affects corn plants. It is caused by the pathogen Colletotrichum graminicola. The disease primarily affects the leaves, stalks, and ears of corn, causing brown to tan lesions with distinct dark borders. In severe cases, it can result in premature death of the plants and reduced yield. Anthracnose blight spreads through infected seeds, plant debris, and splashing rainwater. Proper crop rotation, use of resistant varieties, and timely fungicide applications can help manage and control anthracnose blight in corn crops, minimizing its impact on yield and plant health.

"Black spot," "Black stripe," and "Brown spot" are common diseases that affect sugarcane plants.

Black spot, caused by the fungus Colletotrichum falcatum, leads to the development of black lesions on the leaves and stems of sugarcane.

Black stripe, caused by the bacterium Xanthomonas albilineans, causes black streaks along the leaf midribs and stems.

Brown spot, caused by the fungus Pseudomonas syringae pv. sacchari, results in small brown lesions on the leaves.

These diseases can weaken the plants, reduce yield, and impact the quality of sugarcane. Proper sanitation, use of disease-resistant varieties, and application of appropriate control measures can help manage these diseases.

The odd one from the given options is (a) Leaf scaled. Downy mildew, mottled stripe, and ratoon stunting are all plant diseases that can affect various crops. However, "leaf scaled" is not a commonly recognized plant disease. It is possible that the term "leaf scaled" is either not a well-known disease or it may be a term that is not commonly associated with plant diseases. The other options, downy mildew, mottled stripe, and ratoon stunting, are known diseases that can have significant impacts on crop health and yield.

Tikka is a disease that affects groundnut plants. It is caused by the fungus Cercospora arachidicola. The disease is characterized by the appearance of small, dark brown to black spots with concentric rings on the leaves, stems, and pods of the groundnut plants. These spots can coalesce, leading to defoliation and reduced plant vigor. Tikka can cause significant yield losses if not managed properly. Control measures for Tikka in groundnut include the use of disease-resistant varieties, crop rotation, proper sanitation practices, and timely fungicide applications when necessary. Regular monitoring and early detection are crucial for effective management of Tikka disease.

Spotted wilt is a plant disease caused by the Tomato spotted wilt virus (TSWV) and other related viruses. It affects a wide range of crops, including tomatoes, peppers, and various ornamental plants. The disease is characterized by the appearance of dark, necrotic spots or rings on the leaves, along with stunted growth and distorted or discolored fruits. TSWV is primarily transmitted by thrips, tiny insects that feed on plant sap. Effective management of spotted wilt involves using virus-free planting materials, controlling thrips populations, and practicing good sanitation to reduce the spread of the virus within and between crop seasons.

Ergot is a disease that affects Bajra, also known as pearl millet. It is caused by the fungus Claviceps fusiformis. Ergot infects the developing flowers of Bajra, replacing the grains with dark, elongated fungal structures called sclerotia. These sclerotia contain toxic compounds that can pose health risks to humans and livestock if consumed. The disease can lead to reduced grain yield and quality. Managing ergot in Bajra involves planting resistant varieties, practicing crop rotation, and removing and destroying infected plant material. Harvesting Bajra at the appropriate maturity stage can also help minimize the impact of ergot on grain quality.