ABSTRACT
College of Horticulture and Forestry, Central Agricultural University, Pasighat – 791102, Arunachal Pradesh, India, E-mail: rcshakywar@gmail.com
13.1 Introduction ................................................................................ 244 13.2 Bacterial Diseases ...................................................................... 245 13.2.1 Soft Rot ........................................................................ 245 13.2.1.1 Symptoms .................................................... 245 13.2.1.2 Causal organism .......................................... 245 13.2.1.3 Etiology ....................................................... 245 13.2.1.4 Mode of spread ............................................ 246 13.2.1.5 Favorable Conditions for Disease
Development ................................................ 246 13.2.1.6 Disease cycle ............................................... 246 13.2.1.7 Management ................................................ 246 13.3 Fungal Diseases ......................................................................... 247 13.3.1 Introduction .................................................................. 247 13.3.2 Leaf Blight ................................................................... 247 13.3.2.1 Symptoms .................................................... 247 13.3.2.2 Causal Organism .......................................... 248
13.3.2.3 Etiology ....................................................... 248 13.3.2.3 Mode of Spread ........................................... 249 13.3.2.4 Favorable Conditions for Disease
Development ................................................ 249 13.3.2.5 Disease Cycle .............................................. 249 13.3.2.6 Integrated Disease Management .................. 250 13.3.3 Corm Soft Rot .............................................................. 251 13.3.3.1 Symptoms .................................................... 251 13.3.3.2 Causal Organism .......................................... 251 13.3.3.3 Etiology ....................................................... 251 13.3.3.4 Mode of Spread ........................................... 252 13.3.3.5 Favorable Conditions ................................... 252 13.3.3.6 Disease Cycle .............................................. 252 13.3.3.7 Integrated Disease Management .................. 252 13.3.4 Phyllosticta Leaf Spot .................................................. 253 13.3.4.1 Symptoms .................................................... 253 13.3.4.2 Causal Organism .......................................... 253 13.3.4.3 Etiology ....................................................... 253 13.3.4.4 Mode of Spread ........................................... 254 13.3.4.5 Favorable Conditions ................................... 254 13.3.4.6 Disease Cycle .............................................. 254 13.3.4.7 Integrated Disease Management .................. 254 13.3.5 Sclerotium or Southern Blight ..................................... 255 13.3.5.1 Symptoms .................................................... 255 13.3.5.2 Causal Organism .......................................... 255 13.3.5.3 Etiology ....................................................... 255 13.3.5.4 Mode of Spread ........................................... 256 13.3.5.5 Favorable Conditions ................................... 256 13.3.5.6 Disease Cycle .............................................. 256 13.3.5.7 Integrated Disease Management .................. 256
13.4 Minor Fungal Diseases .............................................................. 257 13.4.1 Cladosporium Leaf Spot (Cladosporium
colocasiae Sawada) ...................................................... 257 13.4.1.1 Symptoms .................................................... 257 13.4.2 Spongy black rot (Botryodiplodia theobromae Pat.) ... 257 13.4.3 Black rot (Ceratocystis fimbriata Ell. and HaIst.) ....... 257 13.4.4 Rhizopus rot (Rhizopus stolonifer Sacc.) ..................... 258 13.4.4.1 Symptoms .................................................... 258 13.4.4.2 Management ................................................ 258 13.4.5 Fusarium dry rot [Fusarium solani (Mars.)
Syn. and Hans.] ............................................................ 258 13.5 Viral Diseases ............................................................................. 258 13.5.1 Colocasia Bobone Disease Virus (CBDV) ................... 258 13.5.1.1 Symptoms ........................................................ 259 13.5.1.2 Etiology ........................................................... 259 13.5.1.3 Mode of Transmission ..................................... 260 13.5.1.4 Management .................................................... 260 13.5.2 Dasheen Mosaic ........................................................... 260 13.5.2.1 Symptoms ........................................................ 260 13.5.2.2 Causal agents ................................................... 260 13.5.2.3 Mode of Spread ............................................... 261 13.5.2.4 Detection and Identification of Virus .............. 261 13.5.2.5 Management .................................................... 261 13.6 Nematode Diseases .................................................................... 261 13.6.1 Root-knot nematodes (Meloidogyne spp.) ................... 262 13.6.2 Management ................................................................. 262 13.7 Non-Parasitic Diseases/Physiological Disorders ....................... 262 13.7.1 Management ................................................................. 263 Keywords .............................................................................................. 263 References ............................................................................................. 263
13.1 INTRODUCTION
Colocasia (Colocasia esculenta) is tuber/rhizome crop and belongs to the family Araceae. It is also locally known as Arvi or Ghuiyan in north India and Kachchu in northeastern parts of India. This crop grows wild in sub-Himalayan tract, peninsular region and northeastern region, mostly in waterlogged humid tropical areas. It shows extensive genetic variability in eastern region. Like other tuber crops, polyploidy as well as diploidization have occurred in this crop also during the course of evolution. The variable diploid (2n) chromosome numbers 24, 28, 42 and 48 and triploid (3n) 42 have been recorded in various cultivars. Most of the important characters such as, plant height, size of leaves, tuber weight and number and yield show polygenic inheritance. This crop is mainly cultivated in Bangladesh, Brazil, Egypt, India, Indonesia, Malaysia, Nigeria, Pacific region, Philippines, West Indies and few other countries. In India, it is grown in Andhra Pradesh, Bengal, Bihar, Gujarat, Karnataka, Kerala, Madhya Pradesh, Maharashtra (Konkan region), Tamil Nadu, Uttar Pradesh and West Bengal. It grows well in lowland and upland areas (Swarup, 2006). All the above ground (leaves) and underground (cormel) parts of this crop are edible. However, it is mainly grown for corms. The cormels and leaves are eaten fried and cooked vegetable. Delicious dish is prepared frying the rolled leaves dipped in gram paste (besan). The corms are used for culinary purposes and in preparation of chips. Cormels are rich source of starch, protein, vitamin C, calcium and phosphorus (Fageria et al., 2006). Besides, this crop is of great medicinal value and is included in many Ayurvedic preparations. The juice from petioles or whole leaves is used for styptics, poultices and pulmonary congestion. Taro lactic is now a commonly prescribed infant food in Hawaii and is fed to a newborn baby. Patients suffering from ulcers and other alimentary disorders or convalescents derive great relief from this easily digestible, nutritive food. It is also strongly recommended in prenatal diets as well as to nursing mothers (Chadha, 2003). Planting of Colocasia esculenta var. antiquorum is normally done during the rainy season (June-July) and summer season (February-March) in northern states. September-October is the best time of planting in southern parts of Gujarat. However, it can be
planted at any time where irrigation facilities are available. The results obtained at Central Tuber Crops Research Institute indicated that AprilJune was the ideal time of planting under rainfed conditions. The crop is harvested after 6-8 months of planting. It grows in all kinds of soils but thrives best in deep, well-drained, well-manured, friable loam. Where rainfall is sufficient, the fields are frequently irrigated. It is often grown in Kitchen gardens under intensive cultivation and irrigation (Shakywar et al., 2012).
