Each chapter has further been divided into sub-heads such as introduction and economic importance, symptoms on different parts, causal organism, disease cycle and favorable conditions. o Symptoms of important diseases have been illustrated with colored photographs which will help in their correct and easy diagnosis. o Management practices including, cultural, physical, biological, host resistance leading to integrated disease management. o This book will serve immensely for teachers and students in the field of plant pathology.
Preface This would be a long preface if I were to set down in detail the reasons why I attempted to write this book in present form. Suffice it to say that the text is based on course which I have been teaching to undergraduate students. The purpose is to provide the basic and emerging facts whereby the students may be introduced to the scientific foundation of this noble course called Diseases of Field Crops and Their Integrated Management. To a certain extent any course is a reflection of the teacher’s own training and of his special interest. The author as a regular teacher for undergraduate courses, has experienced that student do not take to books. They rely solely on class notes. One of the reason being the non availability of text books covering entire course content, the way they are delivered. In the present book, I have tried to arrange the topics and the contents in such a manner that students get an easy reading with due continuity and thus understanding. It is hoped that the book will prove useful for teachers, professionals, and students in the discipline of plant pathology and agronomy. I do not claim originality in the preparation of this book and has taken help from a large number of books, journals, periodicals, bulletins, internet, etc. I humbly thank authors, editors, and publishers of the books, journals, etc. I am also indebted to my wife Dr. (Mrs) Archana Rani for inspiration and help and children Saumya and Adyan for bearing with me during the preparation of this book. Besides my best effort some mistakes, factual or printing, might have inadvertently crept on for which, I solicit sorry in anticipation and if pointed to me, shall certainly correct them in subsequent edition. I shall also welcome suggestions and healthy criticism for the improvement of this publication.
Fungal Diseases Blast Pyricularia oryzae (Sexual stage: Magnaporthe grisea) Economic Importance Rice blast is the most important disease concerning the rice crop in the world. It has been found in over 85 countries across the world. The disease was first recorded in China in 1637. In India, occurrence of this disease was first reported from the Tanjore district of Tamil Nadu in 1918. The disease now occurs in almost all principal rice growing areas of India. Every year the amount of crops lost to rice blast could feed 60 million people. In severe cases losses amounting to 70-80% of grain yield was recorded.
Loose Smut Ustilago nuda tritici (Ustilago tritici) Economic Importance Loose smut has been observed and recorded on cultivated wheat from all over the wheat growing regions of the world. In India, it is prevalent in areas having cool, humid and semi humid climate during flowering period. Loose smut has recently became a more serious problem in the Ladakh region in the Himalayan mountains of India. If uncontrolled, loose smut can wipe out entire crops, since it replaces the grain. In areas where people depend on their grain crops for survival and don’t have the money or technology resources to control it, the disease can be devastating. Not only does it wipe out the crop, growers cannot even try again next year since any seeds they were able to harvest will be infected and will not produce seed the following season.
Rusts The following three rusts are known to occur on barley Stem black rust: Puccinia graminis tritici f. sp. tritici Leaf rust: Puccinia striiformis Leaf rust: Puccinia hordei Of these, the first two are described under wheat and the disease symptoms are identical. These two rusts occur commonly on barley and cause severe damage in certain years.
Southern Leaf Blight Helminthosporium maydis (Syn: H. turcicum) Economic Importance The first epidemics of the Southern corn leaf blight also known as Maydis leaf blight took place in the USA in 1970. A highly virulent strain called Race T appeared on maize hybrids with Texas male sterile cytoplasm. The disease development was related to the growing of maize with T-cytoplasm on large areas. Since 1990 the use of cultivars with T male sterile cytoplasm has been forbidden in selection. Presently, the cultivars with M and C types of sterility are used.
Loose Smut/Kernel Smut Sphacelotheca cruenta Economic Importance Loose smut is distributed in Africa, Europe, Asia and America. In India, it occurs in the states of Andhra Pradesh, Maharashtra, Karnataka, Madhya Pradesh and Tamil Nadu. It is less common than grain smut. The pathogen affects plant growth and development adversely. Grain yield losses correlate well with percentage of the disease distribution in fields.
Downy Mildew (Green Ear) Sclerospora graminicola Economic Importance Downy mildew is reported from temperate and tropical regions of the world. In India, the disease is a major stumbling block in the full exploitation of yield potential of hybrids. Several epidemics have been observed which resulted in substantial grain yield losses (upto 60 percent) in F1 hybrids under South Indian conditions. Usually the losses in grain yield are directly proportional to disease incidence in the field.
Wilt Fusarium udum Economic Importance Wilt is widely prevalent throughout the world but more important in India and in eastern Africa. Wilt is the worst disease of red gram in India, causing severe damage wherever the crop is grown, especially in Maharashtra, Madhya Pradesh, Uttar Pradesh, Bihar and Tamil Nadu. The disease is reported to cause 30-100% loss in grain yield and may cause 100% yield losses in susceptible genotypes. The annual losses due to wilt have been estimated at $71 million in India.
Wilt Fusarium oxysporum f. sp. ciceris Economic Importance Wilt is a serious disease of chickpea in India, Iran, Pakistan, Nepal, Myanmar, Spain, Tunisia, Morocco, Algeria, and Syria. Wilt is prevalent in most chickpea growing countries and is a major disease of economic importance in Asian countries. It was first reported in India. The yield losses encountered was reported to the tune of 60 per cent. However, it causes complete loss in grain yield if the disease occurs in the vegetative and reproductive stage of the crop. Seeds harvested from infected plants are lighter and duller than those from healthy plants.
Powdery Mildew Erysiphe polygoni Economic Importance Powdery mildew can be a serious disease of peas grown in India. It appears in epidemic form in the plains almost every year when the pods are formed in January-February. Since the disease occurs more frequently and covers a large host surface, it proves much more destructive than the downy mildew disease of the same crop. It is worst in dry weather as against the downy mildew, which flourishes in moist weather. Severe infections can reduce yield by 10–20%. Severe pod infection can lead to poor seed quality.
Anthracnose Colletotrichum lindemuthianum (Sexual stage: Glomerella lindemuthianum) Diagnostic Symptoms The pathogen attacks all aerial parts of plants and at any stage of their growth. Initial symptoms are circular, black, sunken spots with dark center and bright red orange margins on leaves and pods. In severe infections, the affected parts wither off. Seedlings get blighted due to infection soon after seed germination. The infected pods have discolored seeds.
Anthracnose Colletotrichum lindemuthianum (Sexual stage: Glomerella lindemuthianum) Diagnostic Symptoms The pathogen can attack all aerial parts at any stage of plan growth. Main symptoms are circular, black, sunken spots with dark center and bright red orange margins on leaves and pods. In severe infections the affected parts wither off. Seedling get destroyed due to infection soon after seed germination.
Wilt Fusarium oxysporum f. sp. lentis Economic Importance The disease is present in countries such as India, Jordan, Nepal, Pakistan, Syria, Turkey, Russia, France, Hungary, Ukraine, Egypt, Ethiopia, Morocco, Sudan, Tunisia, Canada, Argentina, Chile and Uruguay etc. It may cause 5-10% yield losses but sometimes severe damage may result complete crop failure under favorable conditions.
Anthracnose Colletotrichum lindemuthianum (Sacc. & Magnus) Glomerella lindemuthianum Shear Economic Importance Anthracnose warrants a serious attention as it inflicts heavy economic losses to the crop, which may reach up to 100%, under conducive conditions. In India disease incidence has been reported to vary between 24.59 to 51.72 per cent. In Jammu region of Jammu and Kashmir state disease incidence of 63.46% was recorded.
Anthracnose Colletotrichum lindemuthianum, Glomerella lindemuthiana Shear [teleomorph] Economic Importance Anthracnose is an important disease in Kenya, Uganda, Brazil, Argentina, Mexico, Guatemala, Costa Rica, Nicaragua, India, Peru, Ecuador, and Colombia . The disease causes huge losses in temperate and subtropical zones. Yield losses of 95% have been recorded in Colombia and over 92% in Malawi. Anthracnose also affects seed quality and marketability of the crop.
Dry Root Rot / Charcoal Rot Macrophomina phaseolina Economic Importance Dry root rot has been found in most of the soybean-growing areas of the India. The disease has been increasing in importance and can result in substantial yield losses. In most fields, stand losses range from less than 5% to over 50% in severe cases. It is most prevalent on seedling and young plants, causing a root and stem rot.
Tikka or Leaf Spot Cercospora arachidicola/ Phaeoisariopsis personatum Economic Importance Tikka disease of ground nut is regarded as the most important fungal disease of this crop. The infection appears when the plants are one to two month old; one can see this disease in the month of September in the plains of our country. Losses due to this disease may go up to 15-50%.
Root Rot or Charcoal Rot Rhizoctonia bataticola (Pycnidial stage: Macrophomina phaseolina) Economic Importance Charcoal rot is of great economic importance in the World and has been found to reduce head weight and diameter, stem height and weight and in particular, the stem girth and root weight of sunflower plants. The first report of the occurrence of charcoal rot on sunflower was from Sri Lanka by Small (1927). Under favourable condition, losses can reach 60-90%. Infected plants generally die before seed set is finished.
White Rust Albugo candida Economic Importance White rust is an important disease affecting mustard crop in world. Countries where the disease occurs include the Brazil, Canada, Fiji, Germany, India, Japan, New Zealand, Pakistan, Turkey and UK. Up to 60 per cent or more yield losses on B. rapa and B. juncea from this disease have been reported in India.
Seedling Blight Phytophthora parasitica Economic Importance Seedling blight is wide spread in Africa, India and other Asian countries. The average economic loss due to the disease has been 10%.
Wilt Fusarium oxysporun lini Economic Importance The wilt is very serious disease and occurs in almost all the countries where linseed is grown. Continuous cropping in the infected field makes the soil sick. Yield losses upto 80 percent has been reported due to this disease. However, in severe cases crop is destroyed completely.
Ozonium Wilt Ozonium texanum var. parasiticum Thirum / Guizotia abyssinica Economic Importance The disease was reported around Varanasi. Heavy losses are incurred as the diseased plants dry.
Wilt Fusarium oxysporum f.sp. carthami Economic Importance The disease was reported for the first time from America in 1950. Wilt is a devastating disease infecting the crop right from seedling to maturity resulting in crop losses to varied degrees depending on the severity of infection. The disease incidence has been reported in India to the tune of 80 percent under favorable condition.
Wilt Fusarium oxysporum f.sp. carthami Economic Importance The disease was reported for the first time from America in 1950. Wilt is a devastating disease infecting the crop right from seedling to maturity resulting in crop losses to varied degrees depending on the severity of infection. The disease incidence has been reported in India to the tune of 80 percent under favorable condition.
Root Rot or Stem Rot or Charcoal Rot Macrophomina phaseolina (Sclerotial stage: Rhizoctonia bataticola) Economic Importance Root rot is an important disease of sesame as infection occurs from seed germination and emergence to adult plant stage. The losses incurred are even up to 100 per cent, if conditions are favorable.
Red Rot Colletotrichum falcatum (Perfect stage: Physalospora tucumanensis) Economic Importance The disease is so devastating in nature that it has been referred to as cancer of sugarcane. Red rot occurs in all sugarcane growing tracts of India and several epiphytotics have been recorded in the past from states like U.P., Bihar, Haryana, Punjab, Andhra Pradesh and Kerala. In U.P and Bihar, the two popular varieties, namely, CO 213 and CO 312 were badly hit by the epidemics of 1938-40 and 1946-47. There have been reports of red rot epidemics in many other countries viz., USA, Mauritius, Australia, Hawaii and Myanmar. Red rot also causes appreciable damage to canes in Bangladesh, Taiwan and Pakistan. The loss in cane yield has been estimated 12 to 44.5% and 35 to 86 % in cane yield of ratoon over preceding plant crops have different levels of disease.
Wilt Fusarium oxysporum f.sp. vasinfectum Economic Importance Wilt is one of the major diseases of cotton, found wherever this crop is grown like Mexico, African countries, France, Italy, Yugoslavia, India and West Indies. In India, the disease was first reported from Nagpur by Evans in 1908. It appears in almost every cotton tract of the country. However, it is more or less absent in the loamy soils of Indo Gangetic plains and sandy loams of Maharashtra, Tamil Nadu, Karnataka and other States. In affected susceptible varieties yield losses exceed 45-50%.
Damping Off Pythium aphanidermatum Economic Importance The disease is reported from China, Indonesia, South Africa and the USA. It causes extensive damage in the tobacco tracts of Andhra Pradesh, Maharashtra and Gujarat in India. The damage in some areas can be hundred percent, in the absence of protective sprays.
Leaf Spot Colletotrichum capsici Economic Importance The disease is common in many parts of South India, and in recent years has become very severe, causing much damage to the crop. The yield losses occur due to leaf spot infection is through the loss of photosynthetic green surface. During the period of heavy infestation, yield loss could be as much as 50%.
Colour Photographs Chapter 1: Diseases of Rice and Their Management
