Preface Plant fibres are being used by man for several thousand years. The fibre crops, like, cotton (Gossypium spp.), jute (Corchorus capsularis and C. olitorius), mesta/kenaf (Hibiscus cannabinus), roselle (H. sabdariffa), sunnhemp (Crotalaria juncea), sisal (Agave sisalana), ramie (Boehmeria nivea), flax (Linum usitatissimum ) and hemp (Canabis sativa), share the great economic importance in different countries. These crops, based on the type and origin of fibres, may be classified into three major groups, such as, (1) the plants producing fibres from stem bark or more precisely, from phloem tissues (e.g. jute, mesta, roselle, sunnhemp, ramie, flax and hemp); (2) the plants producing fibres from the whole vascular bundles of leaf (e.g. Sisal) and (3) the plants that produce fibres from a single elongated cell of fruit or seed (e.g. cotton). The fibres, which producing from phloem tissues, are known as bast fibres. The bast fibres are composed of lignocelluosic substances and mostly derived by retting only, except, for ramie which requires degumming after retting by chemical treatment. As regards the fibre production scenario in the world, the major fibre crop producing countries are Bangladesh, Bhutan, China, India, Myanmar, Nepal, Pakistan and Thailand for Jute; Argentina, China, Cuba, Egypt, Guatamala, Hewti, India, Indonesia, Iran, Italy, Malaysia, Mozambique, New Guina, Peru, Russia, South Africa, Spain, Thailand, U.S.A and Zimbabwe for Kenaf; Australia, Brazil, Caribbean countries, China, Egypt, Hawaii, India, Jamaica, Mali, Mexico, Philippines, Senegal, South Africa, Sudan, Tanzania, Thailand, U.S.A. for Roselle; Bangladesh, Brazil, Chilie, China, Hungary, India, Poland, Romania, Russia and Turkey for Sunnhemp; Brazil, China, Philippines, South Korea and Taiwan for Ramie; Argentina, Belgium, Canada, France, Germany, Holland, Italy, Russia, Switzerland, U.K. and Ukraine for Flax; Brazil, Chile, China, France, Holland and South Korea for Hemp; Angola, Brazil, China, Kenya, Madagascar, Morocco, Mozambique, South Africa, Tanzania and Venezuela for Sisal and African tropics, Australia, China, Egypt, India and United States for Cotton. Cotton is referred to as “King of Fibres” and “White Gold”. It is the most important fibre crops in the world and plays a pivotal role in socioeconomic development of India which is the second largest producer of cotton, producing 352 lakh bales as in 2015-16. Jute, also called as “Golden Fibre” for its natural lustre, is the second most important fibre crop. It is an important bast fibre produced mostly in Indo-Bangladesh region. India is the largest producer of jute, producing 114 lakh bales as in 2013-14. Kenaf fibre is produced mainly in India and China, followed by Bangladesh. The world kenaf production in 2008 was estimated at 272.000 tonnes. In the Indian subcontinent, especially in the Ganges Delta region, roselle is cultivated for plant fibres. However, this crop is grown for various other purposes in different countries. China and Thailand are the largest producers of different products of roselle and control much of the world supply. The sunnhemp cultivation is now dropped down with the present annual production of its fibre is around 18 thousand ton in India. The global production of flax fibre is 809258 tonnes as in 2016. France is the largest producer of flax fibre, produced 587,047 tonnes fibres in 2016, followed by Belgium with 87,162 tonnes. The world’s best flax fibre comes from Belgium and adjoining countries. In India, the manufacturer of linen fabrics import the flax fibres from European countries and does not utilize the flax produced in India. Sisal is the major source of vegetal hard fibres. Processed sisal fibres are used to make twine, cord, carpets, bags and hats. Global production of sisal fibre is amounted to 281 thousand tonnes as in 2013 of which Brazil produced 150,584 tonnes, Tanzania approximately 34,875 tons, Kenya 28,000 tonnes, Madagascar 18,950 tonnes and China 16,500 tonnes. Venezuela contributes 4,826 tonnes with a smaller amount coming from Morocco, South Africa, Mozambique, and Angola. As regards the ramie production, FAO estimated world production of ramie green plant as 280 000 tonnes in 2005, of which almost all was grown in China. The high fibre quality, such as, smooth, long and excellent tensile strength, is the reason why ramie is widely cultivated in China. In China, ramie is the second most important fibre crop, with its growth acreage and quantity of fibre production second only to cotton. Hemp is grown specifically for the industrial uses of its derived products. It is one of the fastest growing plants. Hemp fibre due to its qualities such as excellent strength, toughness and capability to hold oil is widely used for making canvases. The largest producer of hemp fibre is France, producing 48,264 tonnes fibres annually and that closely followed by China with 44,000 tonnes of annual production. Diseases and insect pests have a serious impact on the economic output of the fibre crops. The fibre plant pathogens and crop-feeding insects are integral part of agroecosystems in these crops, where they have coevolved with these crops over a period of thousands years. A cascade of mutual and complex interactions exists between the cultivated fibre crops and their pests and diseases. As such, the fibre crops are affected by various diseases and insect pests and these cause considerable yield losses. In addition to yield losses caused by diseases, these new elements of complexity also include post-harvest quality losses. Crop losses due to pests and pathogens are direct, as well as indirect; they have a number of facets, some with short-, and others with long-term consequences. An estimate was made on potential and actual losses despite the current crop protection practices with cotton and other crops for the period 2001-03 on a regional basis (19 regions) as well as for the global total. Insect pests that feed on plant structures directly produced yield, such as growing tips and fruiting structures, are generally the greatest problem in a cotton crop. The total global potential loss due to pests was 26-29% for cotton, while, overall losses due to animal pests and pathogens were 18 and 16%, respectively. Incidence of different diseases and insect pests is the major limiting factors in productivity improvement of fibre crops, except sisal, which is to some extent resistant to those. Crop losses due to harmful organisms can be substantial and may be prevented, or reduced, by crop protection measures. The fibre crop protection against plant diseases and insect pests, in particular, has an obvious role to play in meeting the growing demand for fibre quality and quantity. The crop protection is now primarily focused on protecting the crops from yield losses due to diseases and insect pests. Still, the problem remains as challenging today as in the 20th century. A comprehensive knowledge on the diseases and pests of fibre crops is essential to adopt any management method in combating their attacks. In this regard, vast research findings have already been achieved, but these are in very scattered way, either as short research articles or technical bulletin or somewhat in aggregated manner in a few chapters of a book on fibre crops or along with other crops. In certain cases, crop wise diseases and pests are described in books and in website documents, but these are mostly dealt with a few aspects of descriptions. Practically, there is no book at present which comprehensively and exclusively dealt with the diseases and insect pests of fibre crops. This book, entitled, ‘Diseases and Pests of Fiber Crops’, presents the major and alarming diseases and pests of different fibre crops, ignoring a few mere occurrences of pests. It covers major disease and pest damages with the methods to combat them in fibre crop cultivations. The diseases and pests are properly described giving emphasis on both morphological and molecular characteristics of pathogens and biology of different insect pests. The latest and most up-to-date knowledge on these aspects which acquired from diverse, complex, contemporary scientific discoveries in the field of fibre crop diseases and insect pests are compiled and presented in this book. This is a reference book; however the subject matters are described in textbook format which attempt to provide undergraduate, postgraduate and research personnel a means to acquire deeper knowledge on these subjects. Plant pathologists, entomologists and agricultural research scientists, and in academia, may find much of great use in this book. This book is written in 8 (eight) major chapters, each representing a type fibre crop, except for chapter 2 (two) which deals with both Mesta (kenaf) and Roselle for their similarities in disease and insect pest attacks. Each of the eight chapters is again subdivided into 2 or 3 (only for Chapter 2) subchapters to deal with different types of diseases and pests separately. In writing this book, the author has used various research findings of many scientists from different decades and computed in his own way of presentation. Practically, without their contributions, this book would never be possible to write. The author is very much thankful to them whose works are used in this book. The author is thankful to Dr. P.G. Karmakar, Ex Director of ICAR-Central Research Institute for Jute and Allied Fibres, Barrackpore for extending him research facilities. In addition, the author wishes to give thanks to the present Director and Scientists colleague of this institute for their heartfelt supports in all of his activities, which encouraged the author to write this book. The author is also thankful to his wife Mrs. Lila Biswas, for her support and encouragement.

A. Diseases 1. Bacterial leaf blight Occurrence & severity status The disease Bacterial leaf blight, also known as ‘Bacterial leaf spot’, occurs on white jute (Corchorus capsularis) and tossa jute (C. olitorius) in seed crops of jute at the ICARCRIJAF research farm, Barrackpore, West Bengal, India (Biswas et al., 2013, 2014), in Formosa (Elliott, 1951) and Sudan (Sabet, 1957). The incidence of the disease varies from 25% (Borker and Yamlembam, 2017). Symptoms The disease initially appears on leaves as small brown circular spots of 25mm diameter (in tossa jute) or angular brown spots (in white jute), In most cases, the spots are surrounded by a yellow halo and the angular spots coalesce at later stage show larger blighted areas on lamina (Borker and Yamlembam, 2017). The lesions on the stems are elongated; sometimes the spots girdle the stem. The disease on the capsules produces small sunken brown spots. Defoliation and death of the plants may result in severe infections. In the later stages of disease, brown sunken spots were found on the green capsules (Sabet, 1957; Biswas et al., 2013, 2014).

A. Mesta diseases 1. Anthracnose Occurrence & severity status Mesta (Hibiscus cannabinus) is very much prone to be attacked by anthracnose disease (Singh, 2014). It is very destructive disease in India (Ghosh, 1983). The disease also occurs in South Korea with overall disease incidence of 20%. (Kwon et al., 2015). Symptoms Symptoms on kenaf plants include dark brown spots on the leaves, petioles and stems. New leaves and shoots are most susceptible to infection (Kwon et al., 2015). Initially the terminal bud is attacked, where stipules and young leaves are affected and develop necrotic spots and withers (Singh, 2014). Mature lesions on fully expended leaves are dark brown and often irregular in shape, and not vein delimited. Later, the infected leaves fall off; Flowers and seed capsules are also affected by the disease (Singh, 2010). The stems are affected in patches. On stem the lesions are elongated and black, which later form cavities and in severe cases, stem-dieback or wilt occurs (Singh, 2010; Kwon et al., 2015).

A. Diseases 1. Anthracnose Occurrence & severity status The Anthracnose [Fig. 14 (A-B)], also called as ‘Stem-break’, is one of the most serious diseases of sunnhemp (Crotalaria juncea ) in India. It occurs in all sunnhemp growing areas of India (Mitra 1934; Kempanna et al., 1960; Kundu, 1964; Kumar et al., 2016). Apart from India, its occurrence in several countries of South Tropical Africa, like, Rhodesia (Whiteside,1955), Zimbabwe, and other tropical countries including Trinidad and Tobago (Damm et al., 2009), was also noticed as a major disease (Purseglove, 1974). In many places, the disease is considered as the second most serious disease of sunnhemp, causing wilt and weakening of the stem.

A. Diseases 1. Alternaria leaf spot Occurrence & severity status In the years 2012 and 2013, black leaf spot disease was observed on ramie plants in Hunan and Hubei Provinces, China (Yu et al., 2016). Yu et al. (2016) claimed that their report was the first report of Alternaria leaf spot of ramie in China. Symptoms In the field, the symptoms of this disease included dark green to black big spots on leaves (Fig. 20A), often resulting in upwardly curled leaf margins (Yu et al., 2016).

A. Diseases 1. Anthracnose Hemp anthracnose is caused by two different fungi, viz., Colletotrichum coccodes (=C. atramentarium) and Colletotrichum dematium (Saccardo, 1882; Cavara, 1889). i) Anthracnose (Colletotrichum coccodes) Occurrence & severity status The anthracnose disease occurs on many plants, including hemp (Cannabis sativa). The disease causing fungus is well-studied and it is an important pathogen responsible for black dot disease on potato. The fungus is an unspecialized pathogen, infecting a wide range of host families. It is most common in Canada and commonly regarded as a minor pathogen or secondary invader, but the fungus may seriously affect yield where intensive cropping without rotation occurs. It primarily affects the growth rate of plants and diminishes harvest. Moreover, it becomes fatal occasionally. Hoffman (1958, 1959) reported heavy hemp losses in central Europe. Conversely, Gitman (1968b) considered the pathogen was of little importance in the USSR.

A. Diseases 1. Anthracnose Occurrence & severity status Anthracnose has a serious impact on yield and fibre quality of flax (Linum usitatissimum) and is well-known in Europe, Asia and America. Flax anthracnose increased in Germany when flax production was expanding in the 1930s (Rost 1938). The anthracnose pathogen is seed- and soilborne, causes damping off of flax seedlings (Rost 1938), and is one of the causal organisms of so-called flax-sick soils (Bolley & Manns 1932). It has been recorded in nearly every country where the crop is grown either for fibre or oil. It is known to occur in Belgium, the British Isles, Canada, Formosa, France, Germany, Holland, Japan, Latvia, Lithuania, New Zealand, Poland, U.S.A. and the U.S.S.R. (including Siberia), in most of which countries its incidence has resulted in appreciable crop losses (Muskett and Colhoun, 1947). The disease is most common in cool and humid flax-growing areas (Nyvall, 1989). The disease is destructive to the crop, especially when the seed source is contaminated by the fungus. It can spread rapidly under favourable conditions causing severe local epidemics and heavy losses in yield and quality of both fiber and seed (Mercer, 1992c; Rashid, 2003b). The losses of 50% in fibre yield in an epidemic year were reported by Muskett and Colhoun (1947). Ondrej (1985) indicated a considerable loss in fibre strength on attack by anthracnose.

A. Diseases 1. Anthracnose Occurrence & severity status Anthracnose of sisal is also called as leaf spot or ring spot disease. The disease is frequently accompanied with sun scorch in Kenya and Tanganyika (Morstatt, 1930). This is considered as a leaf disease of minor importance, occurring on numerous species of Agave as well as the closely related genus Furcraea, including F. macrophylla Baker (wild sisal). The disease is distributed in warm temperate and tropical regions including southern Europe, British Guiana (Bancroft, 1914), the Neotropics, Cyprus (Georghiou and Papadopoulos, 1957), Kenya (Nattrass, 1961) and USA (Parris, 1959). It is also been reported to occur in various countries of Asia, including China (Tai, 1979), Korea (Cho and Shin, 2004), the Philippines (Teodoro, 1937) and Taiwan (Anonymous, 1979). In India, the disease was first reported as leaf spot caused by Colletotrichum agaves Cav. (Butler, 1905). Its occurrence was also reported from Antigua (Bancroft, 1910) and Puerto Rico (Macedo, 1943). Apart from sisal, the disease also occurs on tomato (Lycopersicon esculentum), potato (Solanum tuberosum) and over 35 other hosts, representing 13 families, chiefly in the Cucurbitaceae, Leguminosae and Solanaceae (Chesters and Hornby, 1965). The disease also occurs on onion and strawberry (Mordue, 1967).

A. Diseases 1. Bacterial Disease: Angular leaf Spot Occurrence & severity status Angular leaf spot disease, also known as ‘Black arm disease’ or ‘Bacterial blight’ is a disease of cotton potentially destructive in all cotton-growing areas of the world. The disease became prevalent in the USA during the 1950s (Schnathorst et al., 1960) and in India in the 1970s (Verma, 1986). In the USA, losses of between 34 and 59% were reported (Leyendecker, 1950; Bird, 1959). In India, losses of 5-20% were common in crops (Verma and Singh, 1971). Late and very late sowing of crops resulted in more yield reductions (Meshram and Raj, 1992). In general, losses due to bacterial blight in India are ranged between 1% and 27% depending on the cultivar and crop age (Mishra and Krishna, 2001). In Africa, data on crop losses is available for only a few countries. In Sudan, losses of 20% were common from severe infection (Last, 1960). However, nowadays, due to the wide availability of resistant varieties, its importance has been declined, with certain deviations where proliferation of new races has occurred as in Australia (Anonymous, 1980).

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