These are gram positive, non-motile strains of bacteria, which prefer a temperature of 24–27 oC. Meloidogyne incognita is abundant in cooler and warmer areas whereas M. javanica is common in warmer areas. If you keep a close eye on your plants' leaf health, watering status, and growth patterns, there's a good chance you'll be able to catch the disease early to treat or eradicate it. Damping off is a fungal disease found in nurseries where the seedlings are found to be overcrowded. The root lesions become brown and are dotted with fruiting bodies. To treat the problem, remove the infected areas as soon as you see them. • Spray milk on green house tomatoes to reduce TMV Photos: ipmimages.org and Purdue Univ. Spray asafoetida solution (@ 10 gm/litre of water). POTATO DISEASES VI. The quest to continually improve on solutions for comprehensive disease management in the bio-control field led to the establishment of Trichoderma and Pseudomonas Laboratories in this Department. Late Blight. BLOSSOM-END ROT. Dark olive greasy spots are found on the fruits and the tissues remain firm. stack of farm trash; solarisation by covering the nursery bed X. vesicatoria (ex Doidge) Vauterin et al. Surface of the seed becomes contaminated with the bacteria, remaining on the seed surface for some time. plant disease caused by a fungal pathogen called Alternaria Solani The entire leaf may be killed in 1–4 days, if the weather is moist. tomato. m. of nursery Maximum number of galls per plant and number of egg masses per gram of root occur when the plants are infected at two-week stage. The TNAU has a well articulated and structured research framework to develop ... Tomato 57 ii. In severe cases of infection, several spots coalesce to form large patches resulting in leaf blight. Wilts Fusarium wilt is distinctive among tomato plant diseases because it begins by attacking o… Diseases of Cucurbits 73-88 13. Seed treatment using leaf extract of Bougainvillea glabra (@. Diseases of Wheat 2. Early blight is first observed on the plants as small, black lesions mostly on the older foliage. Infected ripe tomato fruits show small, water soaked, sunken, circular spots. The leaves are 10–20 cm (4–8 in) long with 5–7 lobes The plant produces flowers with five white to yellow petals which are 4–8 cm (1.6–3.1 in) in diameter. Diseases of Potato 62-72 12. Powder neem cake or mustard oil cake, mix it with water and apply near the root region. Invalid Username or Email And Password! The pathogen is soil borne. Phytophthora infestans, P. palmivora and P. parasita are associated with fruit or stem rot of tomato plants in India. Downward rolling, crinkling, chlorosis of newly formed leaves and excessive branching are observed and the plants become completely sterile. PHYSIOLOGICAL DISORDERS OF TOMATO Important physiological disorders of tomatoes are blossom-end rot, catface, growth cracks, sunscald, yellow shoulder, chemical injury, and adventitious root. Disease cycle The pathogens are soil borne. A temperature of around 28 oC is optimum for development of the disease. The occurrence is more in heavy and compact soils that are not well drained and which do not have proper aeration. Search for: diseases of wheat tnau. Erwinia carotovora subsp. Severely diseased plants wilt in a few days causing severe loss in crop yield. IARI Toppers Provides Agriculture Notes,ICAR E Course Notes,JRF Notes,IBPS AFO,E krishi Shiksha,TNAU Notes,ANGRAU Notes,Agriculture Jobs Update,JRF Mock Test,JRF Old Exam Paper for agronomy horticulture,plant science,agriculture statistics,soil science,social science,icar ecourse pdf download,best agriculture books etc Blight: Two fungal diseases are known as blight: Alternaria solani or early blight, and Phytophthora infestans or late blight. Destruction of collateral host is desirable. Crop rotation with cruciferous vegetables, field bean, maize or soybean, Seedling root dip in asafoetida solution (@ 10g/litre of water). Seedling root dip in a solution containing ten grams each of turmeric and asafetida dissolved in a litre of water is preferred before transplanting. Tomato leaf curl virus (TcLCV), transmitted by the whitefly (Bemisia tabaci Gennadius) is one of the most devastating disease of cultivated tomato (Lycopersicon esculeutum Mill). Stem Diseases in Tomato Crop. The disease starts in patches and spreads to the entire lot in the nursery in the course of 2–4 days. Under humid conditions, pinkish fungal growth can be seen on the dead plants. The young seedlings are killed even before they emerge from the soil. Viruses: Tomato Spotted Wilt Tospovirus. The hybrids developed by Central Potato Research Institute viz., HPS 1/13, HPS 11/13 and HPS 24/111 are suitable for true potato seed production. with alkathene. The female lays eggs in the host root tissues in masses or egg sacs. Flea beetles are yet another insect pest of tomato plants. Cultivation of the crop has been abandoned in some parts of the country due to the disease. The organism survives in alternate hosts, on volunteer tomato plants and on infected plant debris. The main root and the laterals have spherical or elongated galls of various sizes. Tomato Disease Identification Key By Affected Plant Part: Stem and Whole Plant Symptoms Generalized tomato plant adapted from Plant Pathology 4th edition by G. N. Agrios copyright 1997 as Figure 1-1 published by Academic Press, San Diego, CA, with permission from Elsevier. Bacterial stem rot Bacterial stem rot and fruit rot. Their movement in the soil is slow and, on contact with host roots, the larvae enter just above the root cap. Blights Early blight begins as small black lesions on the leaves and soon forms concentric rings like a target. Diseases of Bhendi 58-61 11. The fungus has a characteristic mycellium and reproduces both sexually and asexually. The lower leaves are more susceptible than the upper ones. Diseases of Apple 36-43 8. cepae Symptoms The leaves turn yellow and then dry up slowly. Under dry weather conditions, the spots remain restricted in size and the dead areas appear hard and break away easily from the rest of the lamina. 2016. Small, water-soaked spots first appear which later become raised and enlarge until they are one-eighth to one-fourth inch in diameter. tomato; and bacterial canker, caused by Clavibacter michiganensis subsp. Formation of raised beds with better drainage facilities. The pathogen is soil borne and can persist for long periods. Drooping and sudden wilting of leaves is observed. Dari . Diseases of Guava 33-35 7. It is commonly seen in many vegetables immediately after monsoon showers. When you see little sunken areas starting to appear in your tomato’s leaves, you’ll know they have a case of anthracnose. Infected unripe fruits do not show symptoms until ripening. The young leaves die in succession and later the entire plant will wilt and perish in a few days. These turn dark brown, corky and cankerous later. Clavibacter michiganensis subsp. Two white flies per leaf or three infected leaves per plant. Association of leaf curl with root knot causes more damage. Tomato bud blight disease is a serious constraint in tomato cultivation and causes greater yield loss which is caused by Groundnut bud necrosis (GBNV). The virus causes dwarfing, puckering, severe curling and mottling of the leaves. Infected leaves develop necrotic spots, often with concentric rings of brown tissue. This is a minor fungal disease in which a white powdery growth of the fungus is seen on the leaves. Tomato mosaic disease is caused by different strains of virus such as tobacco mosaic virus (TMV), cucumber mosaic virus (CMV), potato virus Y and X. Under suitable environmental conditions the fungus can cause damping off and collar rot. 4. Diseases of Tomato 110-120 15. Apparently fruit exposed to high temperatures during fruit maturation and ripening express this disorder. In advanced stages, the disease causes defoliation of plants, exposing the fruits to sun, causing sunscald. Diseases of Chilli 44-51 9. The plants remain pale and stunted and pod set is extremely low. Types 4. It is almost impossible to control the disease and prevent major fruit loss when environmental conditions remain favourable. The vascular system becomes brown. Trichoderma viride/Pseudomonas fluorescens. 10 April 2014 2. vesicatoria. Ripe fruits are not susceptible to the disease. Five kilos of wood ash should be mixed with 50 litres of water and kept aside for two hours. The fungus produces both macro conidia and micro conidia. Response of peanut, pepper, tobacco, and tomato cultivars to two biologically distinct isolates of Tomato spotted wilt virus. and the bacterium Bacillus penetrans can be used as bio- control agents. Chilli 73 v. Capsicum 78 vi. Fusarium wilt causes clearing of vein lets, chlorosis of leaves and drooping of petioles. In advanced stages, necrosis of the stem, petioles, leaves and fruit is observed. In fact, tasty and easy-to-grow tomatoes are the most popular garden vegetable. The pathogen can survive on alternate hosts like Solanum nigrum. Bacterial spot. The extract should then be strained and used as a spray to control late blight. POTATO DISEASES VI. Pseudomonas syringae pv. An average of about 400–500 eggs are found in a single egg mass. Pseudomonas syringae van Hall pv. Pull out the affected plants and destroy them. Common Names of Plant Diseases: Diseases of Tomato...J. P. Jones, T. A. Zitter, T. M. Momol, and S. A. Miller, collators (last update: 5/12/15) BACTERIAL DISEASESBacterial cankerClavibacter michiganensis subsp. Spray fifteen days' old panchagavya, diluted with ten parts of water. 1-Group are caused by microorganism or (infectious organisms). Generally, good cultural practices that ensure consistent plant … Sporangia aid in asexual reproduction. Diseases of Cucurbits 73-88 13. Short day length, low light intensity, low nitrogen and phosphorus and high potassium predispose the plants to the disease. The large, brown leaf spots on the bittersweet nightshade in the images below are symptoms of late blight. Upon entering the roots, the larvae move between the undifferentiated cells and reach the endodermis where they become sedentary. Spray a mixture of milk and water in equal quantities every three to four days at the first sign of mildew symptoms. The fungus attacks any aerial part of the plant. Lecture 16 - Diseases of Onion & Garlic Basal Rot: Fusarium oxysporum f.sp. Outline Tomato Diseases Fungal disease Bacterial disease Viral disease Nematode disease Conclusion 3. 51: 37-42. Numerous small, circular spots with dark borders surrounding a beige-colored center appear on the older leaves. Infected leaves develop necrotic spots, often with concentric rings of brown tissue. • Application of 400 gm of neem cake per sq. Managing tospoviruses through … Pathogen/Disease description: This virus is spread from plant to plant by thrips insects. IARI Toppers Prov This is on MLO (mycoplasma-like organism) disease transmitted by leafhoppers. Late blight is a very serious disease of the potato which also attacks the tomato. Sexual reproduction is characterized by the formation of oogonium, antheridiums and zoospores. The fungus produces mycellium which has both inter and intra cellular cells in the host tissues. In certain cases, downward curling of the leaves is also seen. Crop rotation – avoid growing solanaceous crops in sequence. This is a common disease of tomato occurring on the foliage at any stage of the growth. Disease cycle The disease is soil borne and the pathogen is present as a saprophytic ally in the soil for several years. michiganensis. They spread through diseased seedlings and fruits. reduction in the population. Bacterial diseases : In nature, bacterial canker is found only in tomato. Institution: Tamil ... the management of nematode fungal disease complex involving Meloidgyne incognita and Fusarium oxysporum f.sp. Disease-free seed and seedlings should always be used and the crop should be rotated with non-host crops so as to avoid last years crop residue. The cost of seed tubers and spread of virus disease can be greatly minimized by using ‘true potato seeds’. Res. They remain in the soil as zoospores during adverse conditions and germinate when there is sufficient moisture. Diseases of Groundnut 4. High moisture content, close planting and poor aeration predisposes the seedlings to damping off. Since this happens in the subsoil it cannot easily be spotted by the farmers who may have been misled on the quality of the seeds. Crop rotation with a non-solanaceous crop. m. in the nursery. Cultivars like Long Green Smooth, IC- 9273 and IC-18960 are reported to be resistant to root knot nematodes. tomato (Okabe) Young, Dye, & Wilkie Bacterial spot Xanthomonas euvesicatoria Jones et al. The organism survives in alternate hosts, on volunteer tomato plants and on infected plant debris. Brinjal 63 iii. Symptoms. Infection may also occur on unripe fruits, stems, leaves, and roots. Plant Disease. Identification of four thrips species (Thysanoptera: Thripidae) by multiplex polymerase chain reaction. beds with 1 mm thick black polythene sheets for 48 hours to Late blight affects the leaves, stems, and fruit of tomatoes. A strain of late … A. Balamurugan's 7 research works with 3 citations and 1,797 reads, including: Characterization of Dickeya fangzhongdai causing bacterial soft rot disease on Dendrobium nobile in India Keep the fruits away from the soil by proper training and pruning. Later, the lesion girdles the stem and spreads both upwards and downwards. Crop Protection :: Post Harvest Diseases Fruits: Apple: Banana: Citrus: Grapes: Guava : Mango: Papaya: Sapota The most striking symptoms are on the green fruit. Occurs during the vegetative and fruiting stage. The affected seedlings are pale green with a brown water soaked lesion at the base of the stem. The other species of fungi causing fruit rot both in the field and in storage are Fusarium sp., Alternaria solani, Rhizopus sp. Pumpkin 82 Meaning of Post-Harvest Diseases: The diseases which develop on harvested parts of the plants like seeds, fruits and also on vegetables are the post-harvested diseases. Paprika 81 vii. Dari . Pappu, H.R. Remove infected plant parts such as branches, leaves, buds, and burn them. Diseases of Brinjal 52-57 10. They are week saprophytes and poor parasites. Bacterial speck. Disease symptoms: In addition to the potato, the pathogen also damages plants such as chili, tomato, tobacco and egg plant, as well as several species of weeds. The affected plant shows drying of leaf tip downwards. kill nematodes and weed seeds. Caused by Fusarium solani, Sclerotium rolfsii, Rhizoctonia solani and Macrophomina phaseolina. As it ages, the centre of an older spot becomes blackish and emits gelatinous pink spore masses. TOMATO CANKER (Clavibacter michiganesis pv.michiganesis) INTRODUCTION GRAM +Ve Non motile Non flagellate strictly aerobic bacteria. Click on images to view full-size . Spraying with a combination of copper and organic fungicides in a regular preventative spray program at 5 to 10 day intervals or Spraying with Agrimycin-100 (100 ppm) thrice at 10 days intervals effectively controls the disease. The cause of yellow shoulder is not fully understood. As the cankers grow, they encircle the stem, causing the plant to die. The dark-brown to black cankers form on tomato plant stems, this cause most damage to the plant. Stem lesions are black and canker-like and the fruit lesions are corky. The zoospores germinate to produce mycellium which multiplies rapidly and infects the host tissues. 1. Diseases of Wheat: In India, during summer season, high temperatures do not allow either the wheat crop or the rust to survive in the plain areas. Crop rotation – in the case of cereals, there is a definite The fungus attacks the germinating seeds and they rot even before the hypocotyls emerge. × Login. The pathogen produces leaf spots of varying size. So is scorching from the margins inward. Diseases of Crucifers 89-109 14. It begins with light tan, water-soaked lesion, which then enlarges, turn black and leathery (Figure 1). However, tomato pests and diseases such as tomato wilt can harm your crop. Crop rotation with non-solanaceous crops reduces inoculums in the soil. PATH272 - Disease of Field Crop and their Management: Plant Breeding and Genetics: PATH371 - Disease of Horticultural crops and their management: GPBR111 - Principles of Genetics : Agricultural Engineering: GPBR112 - Principles of Seed Technology: AENG151 - Fundamentals of soil water conservation and engineering : GPBR211 - Principles of Plant Breeding : AENG252 - Protected … This tomato diseases tell tale mark is found at the stem end of the fruit which will turn black. Yellow spots are seen on the fruits. manure. There will be a whitish mouldy growth on the scale. Tomato Disease and Insect Control Manual with Variety Selection Anthony Carver Extension Agent – Grainger County 3 Disease Identification Pictures taken from Cornell University, Rutgers University, A.F. The symptoms of bacterial wilt infection can be seen on all parts of infected plants. Bacterial Infection: Exposed to the plant through a cut or damage in the vine or plant, bacterial diseases can wreak havoc on your tomato plants. Occurs at the seedling stage and with older plants. Tomato Spotted Wilt. Fungal species such as Paecilomyces lilacinus, Verticillium Nematodes are introduced through infected seedlings and shifting soil from neighbouring infested fields. Diseases of Guava 33-35 7. Described in 1910 as the cause of bacterial canker of tomato in North America. Like any crop, the coffee plant is vulnerable to pests and diseases. Tomato diseases presentation 1. Fungal hyphae spread both inter and intra cellular in the host tissues. A 2012 report by Fabienne Ribeyre, a researcher at French agricultural research center CIRAD, states that “most coffee diseases are caused by pathogenic fungi and less frequently by bacteria and viruses.” Postharvest Diseases of Tomato • Heating dump-tank water 10°F (about 5°C) above the incoming tomato pulp temperature eliminates fruit cooling. Tomato varieties Most outbreaks of the disease can be traced back to heavy rainstorms that occur in the area. This disease, shown here on wheat leaves, covers your tomato leaves with small, circular spots that have gray-white centers and darker edges. The symptoms may appear only on a few branches. Diseases of Potato 62-72 12. These are soil borne pathogens also found in crop debris. Under favourable climatic conditions (humid and cloudy weather), the lesion spreads to the entire leaf and petiole causing brown dead spots. Root knot or root galls caused by nematodes are a common disease of many vegetables in tropical and subtropical climates. Tomato plants can develop disorders that distort plants and blemish fruits. The harvested products may get infected on the way to storage or to market or even before their final consumption. Organic Farming :: Organic Farming Practices. Spraying 5% NSKE or neem leaf extract to control the white You’ll see this issue most often when the weather has been warm and wet. (Figure 5). Flea beetles. Healthy leaves. Okra, Abelmoschus esculentus, is an herbaceous annual plant in the family Malvaceae which is grown for its edible seed pods.Okra plants have small erect stems that can be bristly or hairless with heart-shaped leaves. Pythium is the most common species of fungus responsible for damping off disease in seedling nurseries. Vector – Thrips tabaci, Frankliniella insularis, F. occidentalis. It is very difficult to control nematodes in an infested field since the eggs survive in the soil protected by host tissues. Hot water treatment of seeds is desirable. Sherf, R. Providenti, and Grainger County Producers Calcium Deficiency or Blossom-End Rot use Calcium Nitrate the 4th, 6th and 9th Three bacterial diseases are common in Ontario tomato fields: bacterial spot, caused by Xanthomonas campestris pv. One of the most common tomato diseases—septoria leaf spot—appears just as its name suggests. The fungus attacks the foliage causing characteristic leaf spots and blight. This disease occurs under humid weather conditions. The fungus produces zoospores under advanced conditions. Seed treatment should be carried out with 50 gm The leaves show light and dark green mosaic symptoms. FIELD SANITATION: The implementation of good agricultural practices (GAPs) in the field and at Cover the nursery This phase is characterized by toppling over of infected seedlings at any time between the period that they emerge from the soil and the stage the stem hardens to resist pathogen attack. Bronzing of the upper surface of young leaves which extends from leaf blade to petiole and stem, causing upward rolling of leaves. Bhendi 69 iv. If plants are infected early some whole stems may turn brown and die. Small, water soaked lesions are seen on the fruits. technology capsule for pests and diseases management, labour saving farm machineries and post-harvest management practices. Tomato Spotted Wilt. It also occurs in warmer areas. fly vector. The leaves show light and dark green mosaic symptoms. From containers to expansive garden plots, growing tomatoes is a popular and relatively easy way to harvest at least some of your own produce. Good phytosanitary measures can reduce attacks by these fungal pathogens. Use of light soil for nursery beds, thin planting, light and Some disorders are not caused by diseases, but are the result of cultural practices or environmental conditions. IARI Toppers Prov The pathogen is both seed borne and soil borne. The outer pericarp in the affected area is hard and white. Blossom end rot is a very common problem on green and ripe tomatoes. The fully formed fruit rots on the vine before it fully ripens. The bulb of the affected plant shows soft rotting and the roots get rotted. Bull. SYMPTOMS • First symptom is downward curling and wilting of lower leaves. Spray 5% eucalyptus or lantana leaf extract in the evening. The anthracnose lesions easily attract other rotting organisms which now completely rot the infected fruit. Seed treatment with mercuric chloride (1:1000) is also recommended for control of disease. Caused by Xanthomonas species such as (X. campestris pv. If a segment of a lower stem is cut, it yields bacterial ooze. Diseases of Brinjal 52-57 10. In advanced stages of infection, these tissues decay and are attacked by other pathogenic and saprophytic organisms. The disease appears on the foliage as water soaked light brown lesions. Tomato Diseases to Treat . Viral diseases : Tomato mosaic : Tomato mosaic disease is caused by different strains of virus such as tobacco mosaic virus (TMV), cucumber mosaic virus (CMV), potato virus Y and X. Diseases of Grapes 24-27 5. Partial sterilisation of the soil by surface burning of a thick This fungal pathogen is one of the most common tomato plant diseases, and is caused by Colletotrichum phomoides fungus. Florida tomato production is often challenged by an array of plant diseases promoted by a warm and humid climate. If The seeds are raised in nursery beds like other vegetables and seedlings are transplanted 30 days after sowing. One diseased leaf for every four healthy leaves or 25% damage. Growing healthy, pest- and disease-free toma… They eject secretions while they feed on the cells which cause enlargement of cells or formation of galls. Whitish growth of fungus can be seen on the lower surface on close examination of infected leaves. Diseases of Pulses 5. They spread both inter and intra cellular-wise in the host, producing free branching hyphae. bed 15 days before sowing, and watering at 3–5 days'. The outer layer of the infected roots is completely rotten. michiganensis (Smith) Davis et al. The eggs hatch under suitable environmental conditions. vesicatoria; bacterial speck, caused by Pseudomonas syringae pv. Surface of the seed becomes contaminated with the bacteria, remaining on the seed surface for some time. Wilting, stunting, yellowing of foliage and a severe case of infection leads to death of the plant. The lower leaves droop before wilting occurs. The fungus multiplies rapidly within the host tissue, clogs the vascular tissues and interferes with the transportation of water and nutrients upwards thereby resulting in the wilting of the plants. There is uneven growth of the light and dark green portions. However, when conditions are optimal for bacterial disease, losses in marketable yield ca… It is extremely common, and it will eventually rot the entire plant, including the fruit. The pathogen is air borne. Formation of knots or galls in the root system is a characteristic symptom. Control. Temperatures between 27–31 oC are conducive for spread. o Fungi o Bacteria o Virus o Nematodes 2- Group are caused by physical and chemical factors (non- infectious). There is uneven growth of the light and dark green portions. Infected roots, called black dot root rot, become evident only when the fruits begin to ripen. They can be controlled by uprooting the diseased plants along with the infested soil and burning them. On older plants the leaflet infection is mostly on older leaves and may cause serious defoliation. This is one of the most common diseases of the potato and is also found to attack the tomato. Nematology TNAU. Plant diseases don’t affect people and the tomato fruits that only present an initial stage of the disease will only present a tiny black spot at the stem that can easily be removed. Infected leaf . Xanthomonas campestris pv. The conditions that promote plant diseases also favor the development of fruit rots, both in the field and during handling and shipping. Light brown streaks appear on the stem and the petiole later turns black and cankerous. Seeds may be the primary source of infection, and soil the secondary source. These tiny metallic, … • Limiting tomato residence time in dump tanks and flumes to less than 2 minutes, and minimizing contact of tomatoes in gondolas with large streams of water will reduce the potential for infiltration. Some diseases … Treatment with Trichoderma viride or Pseudomonas fluorescens @ 5 gm/100 gm of seeds. Diluted cow dung can be applied to the root zone of the affected plants. 90(9):468-478 Nakahara S and K. Minoura. Classification of Post-Harvest Diseases 3. Tomato diseases can be fatal unless you take management steps in a timely manner. Moist weather and splattering rains are conducive to disease development. Blight is followed by soft rot due to invasion by secondary pathogens. Attempt soil solarisation before sowing. Photos: ipmimages.org and Purdue Univ. Infected plants show stunted growth with shorter internodes and petioles, and large number of branches and roots than normal giving the plant a bushy appearance. Disease symptoms: In addition to the potato, the pathogen also damages plants such as chili, tomato, tobacco and egg plant, as well as several species of weeds. December 13, 2020 Uncategorized Uncategorized The fruits undergo a semi-soft decay. Diseases of Pomegranate and Papaya 28-32 6. 2015. The affected tissues are soft and water-soaked and they usually rot, leading to the collapse of the seedlings. A few research reports also suggest that wilting is caused by the toxins produced by the fungus. X. perforans Jones et al. Use varieties like Mar globe, Kanora, Sioux and Roma which are resistant. The entire plant shows complete drying of the foliage. Diseases of Grapes 24-27 5. Dried powdered ash can also be applied to the crops. 2016. Late blight usually occurs when late season temperatures cool and dew is heavy, with dark water soaked spot on the leaves. Forgot password ? The organism survives in alternate hosts, on volunteer tomato plants and on infected plant debris. This is a deadly disease of tomato. Infection usually occurs on the lower leaves near the ground, after plants begin to set fruit. Surface of the seed becomes contaminated with the bacteria, remaining on the seed surface for some time. Diseases of Apple 36-43 8. gm/sq. Pathogen/Disease description: This virus is spread from plant to plant by thrips insects. carotovora. Infected leaves show small, brown, water soaked, circular spots surrounded with yellowish halo. and Erwinia sp. Alternaria stem canker: This disease affects not only the stems but also the leaves and fruits. The infection weakens the plants and pre-disposes them to invasion of many root rot and wilt causing fungi and bacteria, thus compounding the damage. The disease is more severe at a pH less than 6.4 and greater than 7. The disease may affect the entire shoulder or only a small irregular patch. The plants remain stunted due to the pathogen attacking the roots. Diseases of Crucifers 89-109 14. Diseases of Potatoes. Occurs during summer (February–June) from seedling to harvest stage. Sow seeds thinly, leaving one inch spacing between the rows. In Ontario, bacterial disease is present at some level every season, though not always at destructive levels. Ripe fruits are not susceptible to the disease. Pl. frequent irrigation and application of well decomposed TNAU is the first in India develop Talc based biocontrol agents commercially in early 90’s.