Preface Mildews on plants include downy mildews and powdery mildews  and are one of the important diseases of crop plants. Mildews occurs on cereal crops, pulse crops, oilseed crops, fiber crops, cash crops , vegetable crops, fruit crops, spices crop, ornamental and flowering plants, medicinal and aromatic plants, forage crops and forest trees and causes enormous losses in the  absence of suitable control measures. These losses includes the loss of crop foliage (in leafy vegetables), grains (in cereals), deformation of fruits (in fruit crops), death of plants (in cereals and vegetables) and quality of yield (in fruit crops). The losses reported due to mildews are as high as 60 percent in grapevine in term of fruit quality and crop monetary returns. Total crop loss can occur in case of susceptible variety of the crop to mildews. The mildew disease occurs in all the continents of the world on all kind of crop plants. Application of appropriate fungicides are important to control these diseases as many mildew pathogens have developed the fungicidal resistant. The book “The Plant Mildews: A Colour Handbook” includes 24 chapters. 11 chapters are on downy mildews of various crop plants with 55 downy mildew diseases while 13 chapters are on powdery mildew diseases of various crops with 92 powdery mildew diseases. The mildew diseases around the world included in the book are 147 with detailed information on each mildew disease including pathogen responsible, its host range, geographical distribution, disease symptoms, epidemic and losses, disease cycle, weather parameters and disease forecasting, and disease managements.

Downy mildew is refered to a condition of plant disease where the fungal growth and infection appears on the dorsal side of the leaf surface while the corresponding ventral side of the leaf shows faint yellowish color. It is also refered to the fungus which causes this disease.The word mildew in Latin language means mil + dew i.e honey like dews.The fungal growth on plant surface resembles to the milky dews in the beginging which turn to golden brownish honey like dews in later stage. Subsequently the affected areas turn grayish brown and dry. Besides the infection of leaves, the fungus also infects the fruits. The downy mildew infection on fruits causes the deformities on the affected fruits. The infection of the downy mildew pathogen on some of the cereals like pearlmillet causes the symptoms like green ear disease . Downy mildew pathogens can cause major damage in the nursery, in greenhouse, in field crops and in landscape in the form of leaf spots, blights, and distortions with mildew growth. Downy mildews are primarily foliage blights with mildew growth of the fungus on affected portion. The fungus attack and spread rapidly in young, tender green leaf, twig, and fruit tissues. The fungal development are severe when a film of water is present on the plant tissues and the relative humidity in the air is high during cool or warm, but not hot, periods. Downy mildews can cause severe losses in short periods of time. Downy mildews often cause rapid and severe losses of young crop plants still in the seedbed or in the field. They often destroy from 40 to 90% of the young plants or young shoots in the field, causing heavy or total losses of crop yields. The severity of loss depends on the prolonged presence of wet, cool weather during which the downy mildews fungus sporulate profusely, cause numerous new infections, and spread into and rapidly kill young succulent tissues.

2.1. Downy mildew of Sorghum Pathogen: Peronosclerospora sorghi (W. Weston & Uppal) C.G. Shaw, (1978) Host plants Major hosts: Sorghum bicolor (sorghum), Sorghum caffrorum, Sorghum Sudanese (sudan grass), Zea diploperennis, Zea mays.  Minor hosts: Andropogon sorghi, Panicum trypheron, Pennisetum glaucum (pearl millet), Sorghum halepense (Johnson grass), Zea mexicana (teosinte)  Geographic Distribution It is found worldwide in tropical and subtropical regions. Sorghum downy mildew is widely distributed in following countries. Asia: Bangladesh, China, India, Iran, Israel, Japan, Nepal, Pakistan, Philippines, Thailand and Yemen (CMI, 1988; Jeger et al., 1998).In India though the losses are reported from the states of U.P. and Madhya Pradesh, the disease is very common and destructive in Karnataka, Tamil Nadu, Andhra Pradesh, and Maharashtra

3.1. Downy mildew of peas It is an important disease of pea crop particularly in those areas where cool and wet climate is prevalent during its cultivation. The disease during favourable weather conditions causes considerable yield losses. Pathogen: Peronospora viciae (formerly P. pisi) Host range Vigna faba, Vigna sativa. Pisum arvensis, P.sativum, Lathyrus sativus, Vicia hirsuta, Vicia sativa, Vicia villosa (Dixon, 1981). Geographical distribution Reports of the pathogen are from different countries on different crop host. On Pea- Berkeley in England first discovered the disease in 1846 (Chupp and Sherf, 1960) and since then it has been found in all parts of the world where the crop is grown intensively. The occurrence of the disease has been reported from Argentina, Australia, Canada, Chile, Denmark, France, Germany, Kenya, Netherland, New Zealand, Rhodesia, Spain, Tasmania, USA, Ukrain, Italy, Poland and Australia (Dixon,1981). In India it is prevalent in Indogangetic plains including Uttar Pradesh and Punjab (Bains and Dhaliwal, 1986).

4.1. Downy mildew of sunflower Pathogen: Plasmopara halstedii (Fort.) Berl.& de Tom. Hosts Over 100 host species from a wide range of genera in the family Asteraceae have been reported susceptible to this pathogen, including wild and cultivated species of Helianthus, e.g. sunflowers, which is the principal economic host. Wild Asteraceae hosts (e.g. species of the genera Helianthus, Artemisia, Xanthium, etc.) may also occur widely in the corresponding areas but their potential as reservoirs of the pest is not yet known (Virányi, 1984). For lists of hosts see Leppik (1966) and Novotel’nova (1966). Geographical distribution EPPO region: Present wherever sunflowers are grown, in Albania, Austria, Bulgaria, Czech Republic, Egypt, Estonia, France, Germany, Hungary, Italy, Moldova, Morocco, Poland (unconfirmed), Romania, Slovakia, Spain, Switzerland, Turkey, Russia (European, Siberia), Ukraine and Yugoslavia. Asia: Azerbaijan, China, Georgia, India, Iran, Iraq, Israel, Japan, Kazakhstan, Pakistan, Russia (Siberia), Turkey.  Africa: Egypt, Ethiopia, Kenya, Morocco, Zimbabwe, Uganda.

5.1 Downy Mildew of hemp Pathogen: Pseudoperonospora cannabina Geographical distribution   It’s spread has been limited to Asia and Europe. Symptoms Downy mildew begins as yellow leaf spots of irregular size and angular shape, limited by leaf veins. Opposite the spots, on the underside of leaves, the fungus emerges from stomata to sporulate. Mycelial growth on the underside of leaves is best seen in early morning when dew turns the mycelium a lustrous violet-grey colour (Fig 5.1). Lesions enlarge quickly and affected leaves become contorted. Leaves soon become necrotic and fall off. Whole plants and entire fields may follow this pattern.

6.1. Downy mildew of Sugarcane Pathogen: Sugarcane downy mildew can be caused by four species:     1)    Peronosclerospora sacchari     2)    P. miscanthi     3)    P. spontanea and     4)    P. philippinensis Major Host Hosts in the Saccharum genus include: S. officinarum, S. robustum, S. spontaneum and S. edule. Minor Host Other hosts include Zea mays (maize), teosinte (Euchlaena mexicana), Sorghum halapense (Johnson grass), S. sudanense (Sudan grass), Tripsacum dactyloides (Gama grass), Sorghum bicolor (broom corn). Other studies suggest there are 18 species that are systemically infected in the sub-family Panicoideae; these include species of Andropogon, Bothriochloa, Eulalia, Schizachyrium and Sorghum (Bonde & Peterson 1981) Geographic Distribution The disease is restricted to the Pacific, South Asia and South East Asian regions viz Fiji, India, Indonesia, Japan, Papua New Guinea, Philippines, Taiwan and Thailand (Suma & Magarey 2000).

7.1 Downy mildew of grape Pathogen: Plasmopara viticola History and Epidemics In France downy mildew is called as “le mildiou” while in Germany it is called as “falscher Meltau”. Downy mildew is undoubtedly of American origin and was probably indigenous on the wild grapes of the eastern United States, from which it spread to the cultivated vineyards when these were established by the colonists. It was not known to occur outside America until 1870, although it was first described from this country as early as 1834. In the early part of the last century various horticultural writers referred to the destructive action of the mildew on cultivated grapes. Its history in Europe dates back to the time when French vine-yards were suffering from the grape Phylloxera, an aphid insect pest that was also introduced into Europe from America. It was found that rootstocks of the American species were more resistant to this aphid than was the European vinifera grape, and therefore consequently around 1870 importations of the American Vines were made into Europe, and somewhere around 1875 the downy mildew fungus evidently was also introduced with these importation and became established, and by 1878 it was prevalent enough to cause alarm. Since the European vinifera grapes were far more susceptible to this disease than were the American species, it soon became a real menace to grape culture throughout the humid sections of Europe.

8.1. Downy mildew of cruciferous vegetables Cruciferous vegetables are important Kharif vegetable crops, which are grown both for table and seed purpose. This vegetable group constitutes crops like cauliflower, cabbage, radish, turnip, broccoli, brussel’s sprouts; knol-khol and rutabaga .The vegetable crops affected by downy mildews pathogen Peronospora parasitica are members of the genus Brassica and the downy mildew diseases on these crops are widespread in those regions of the world, which have cool and wet climate. Geographical distribution The downy mildew disease on cruciferous crops has worldwide distribution. The disease was first recorded in 1883 in USA on Brassica spp. (Farlow, 1883). In India, this disease was first reported by Butler in 1918. Subsequently various authors reported this disease from many countries of the world (Channon, 1981) particularly Angola (Serafim and Serafim, 1968), Argentine (Lindquist, 1939), Australia (Samuel, 1925; Anon., 1955), Austria (Glaeser, 1970), Bermuda (Waters-ton, 1940), Brazil (Grillo, 1937), Britain (Moore, 1959), Brunei (Herb. IMI), Canada (Jones, 1944; Downey and Bolton, 1961), Chile (Mujica and Vergara, 1960), China (Porter, 1926; Pai, 1957), Columbia (Orjuela, 1965), Costa Rica (McGuire and Crandall, 1967), Cuba (Fernandez Rosenada, 1973), Cyprus (Herb.IMI), Czechoslovakia (Rydl, 1968), Denmark (Gram and Rostrup, 1924), Dominica (Anon., 1972a), Egypt (Elarosi and Assawah, 1959), Ethiopia (Herb. IMI), Fiji (Anon, 1969), Finland (Herb. IMI), France (Darpoux, 1945), Germany (Neumann, 1955), Greece (Herb.IMI), Guatemala (Muller, 1950), Haiti (Anon., 1972a), Hong-Kong (Johnston, 1963), India (Thind, 1942), Iran (Ershad, 1977), Iraq (Herb.IMI), Israel (Peleg, 1953), Italy (Ciferri, 1961), Jamaica (Leather, 1967), Japan (Hiura and Kanegae, 1934), Kampuchea (Soonthronpoct, 1969), Kenya (Anon., 1957), Korea (Anon., 1972b), Libya (Herb.IMI), Malawi (Peregrine and Siddiqi, 1972), Malaysia (Mcintosh, 1951), Malta (Herb.IMI), Mauritius (Orian, 1951), Mexico (Rodriguez, 1972), Morocco (Herb. IMI) , Mozambique (Decarvalho, 1948), Nepal (Bhatt, 1966), Netherlands (Thung, 1926b), New Zealand

9.1. Downy mildew of Opium poppy Pathogen: Peronospora arborescens (Berk) de Bary Geographical distribution and losses This is one of the serious and widespread diseases of opium poppy. The disease was observed epiphytotic in Argentina, Germany, Iran, Hungary, Austria and India. The disease was first recorded in India in 1918 and with the introduction of susceptible varieties, the disease rapidly became serious due to favourable environment in its cultivation area in India. Downy mildew now occurs in most regions in India (Rajasthan, Madhya Padesh and Uttar Pradesh). Downy mildew caused 20-30% loss of yield of opium latex. The secondary infection of downy mildew was found to reduce 11-22% latex. Symptoms The infection spread upwards from lower leaves. The entire leaf surface is covered by downy mildew coating, which is composed of sporangiophores and sporangia of the pathogen (Fig 9.1). The stem, branches and even capsules are attacked resulting in the premature death of the plants. The infection start from the moment the seed germinate and persist during the whole period of growth (Yossi fovitch 1929). Khristov (1943) reported that the pathogen often cause abnormal development in opium poppy. The pathogen also causes hypertrophy and curvature of stem and flower stalks.

10.1. Downy mildew of Plantago psyllium Downy mildew is the major and serious disease of Plantago particularly P. ovata. It causes enormous quantitative and qualitative loss and often becomes a limiting factor in the successful cultivation of the crop (Desai and Desai, 1969). Usually the disease appears at the time of spike initiation. Pathogen: Peronospora alta and P. plantaginis Geographical distribution Plantago ovata under commercial cultivation has been reported to suffer from downy mildew disease. Downy mildew occurs on ripe seeds of Spanish, French and European plantago. The downy mildew is a native of Mediterranean region especially Southern Europe, North Africa and West Pakistan. The plantago commercially cultivated in Gujarat and to a limited extent in Haryana and Rajasthan provinces in India is observed to be infected with downy mildew.

Downy mildew has been reported on a wide range of ornamentals, especially those in home gardens, but only in a few instances the diseases have been sufficiently severe and widespread .Generally the diseases have been of most concern in a few ornamentals grown as crops either out doors or under glass or in nurseries, where many seedlings are raised in close proximity, often under humid conditions which favour this disease. Downy mildew having importance on ornamentals and flowering plants are: 11.1. Downy Mildews of Anemone (Windflower) Two downy mildews are reported on cultivated anemones. The one is caused by Plasmopara pygmaea while the other is caused by Peronospora sp. Pathogen .1. : Plasmopara pygmaea It was first recorded in Britain on decaen anemones near Liskeard, Cornwall, in september 1917 Symptoms It causes blackening of the foliage of the planting. The sporangiophores emerged from stomata at the periphery of the blackened zone. The fine white mildew covers the under surface of the leaves. Plants become discolored with aborted stamens. Oospores are found in the discolored tissues.