Pests and Diseases of sugercane

Matching with long diversity of conditions under which sugarcane is grown in the world, there is wide spectrum of pests and diseases which have come to acquire a place of priority for control on regional or inter-regional basis due to the agro-climatic management conditions associated with the area. In addition the susceptibility of the variety to the diseases and pests aggravates the situation and creates additive problems. Below herein is given a brief account of symptoms of important pests and diseases occurring in several parts of the world. For more information and pest and disease control measures consult the local Netafim Agronomist or Plant protection expert. Early Shoot Borer (Chilo infescatellus)- Symptoms Attacks the crop during the early part of cane growth, before internode formation. It also attacks the cane stalks in the years of scanty rainfall Larvae enter the cane laterally through one or more holes in the stalks (shoot) and bores downwards as well as upwards killing the growing point. Thus it cuts of the central leaf spindle, which eventually dries forming a ‘dead heart'. The dead heart can be easily pulled out. It emits an offensive odour. Borer infestation during the germination phase kills the mother shoots resulting in the drying up of the entire clump. This leads to gaps in the field. Causes heavy yield losses as it affects the plant stand/unit area. It also leads to canes of different age, which will be poor in juice quality, with less cane weight. When borer infects cane stalks, both yield and quality are reduced. Internode Borer (Chilo Saccharifagus Indicus) - Symptoms Damages the crop soon after internode formation and its activity continues till hatvest Lodging, high dosage of nitrogen, waterlogged condition and presence of water shoots favour buildup of pest Fresh borer attack is mostly found in the top five immature internodes Caterpillars bore at the nodal region and enter the stem and tunnel up-wards in a characteristic spiral fashion. Entrance hole is usually plugged with excreta. Larvae feed and multiply in water shoots. One larvae found in a single cane damages 1-3 internodes. The length and girth of the infected internodes get reduced. Yield loss and juice quality deterioration occurs when the infestation is severe (In the picture above: Internode borer damage) Top Borer (Scirpophaga Excerptalis) Waterlogging favours moth attack Larva first tunnels into the midrib of the leaves and causes a white streak which later turns reddish brown usually in the second to fifth leaf from the top. As a result of biting across the spindle, a number of shot holes are formed in the leaf. As larva nibbles into the central core of the cane a portion of the internal tissue is eaten resulting in dead heart formation. Dead heart when formed is reddish brown, appears charred, and cannot be easily pulled out. In tillering phase of the crop, the attacked shoots die, side shoots (tillers) develop producing a bunchy top appearance. In the grand growth period, the crop growth is arrested, and the crown with dead heart dries and may be blown off leaving the stump. Severe yield loss and quality deterioration occurs due to top borer. Depending upon the incidence level yield loss may be up to 20-30%. Scale Insect (Melanaspis Glomerata) Waterlogging, high temperature and humidity favour buildup of scale insect population. Rainwater and high wind velocity facilitate dispersal of the pest. It spreads to new areas through seed material. Men and animals passing through the infested fields also lead to spread of the pest to the adjoining areas. Scales usually establish on internodes covered with leaf sheath. The leaves of infested canes show signs of tip drying and unhealthy pale green colour and with continued infestation turn yellow. Desapping leads to non-opening of leaves also, which also turn yellow and finally dry out. Nodal region is more infested than internodal region. Infested crop losses its vigour, canes shrivel, growth is stunted and the internodal length is reduced drastically. Ultimately cane dries up. Such canes when slit open appear brownish red. Thus yield and quality suffer. The yield loss could range from negligible to total crop failure. Pyrilla (Pyrilla purpusilla Walker) Pyrilla is the most destructive foliage-sucking pest of sugarcane Heavy rainfall followed by 75-80% humidity, intermittent drought periods, high temperature (26-30°c) and wind movement favour rapid buildup of pyrilla. Other factors favouring pyrilla buildup are dense and luxuriant crop, excess nitrogen application, water logging, lodging of cane and varieties with broad and succulent leaves. Adults and the nymps suck leaf sap from the under surface of the lower leaves. When the infestation is heavy, leaves turn yellowish white and wither away. Due to continuous desapping by large number of hoppers top leaves in the affected canes dry up and lateral buds germinate. The hoppers exude a sweet sticky fluid known as honeydew, which promotes quick and luxuriant growth of the fungus, capanodium species and as a result the leaves are completely covered by the sooty mould. This affects photosynthesis. The loss in cane yield due to pyrilla have been estimated to be around 28% with about 1.6% unit loss in sugar. Termites (Coptotermes Heimi Wasmann; Odontotermes Assmuthi Holmgr; O. Obesus Rambur; O. Wallonensis Wasmann; Microtermes Obesi Holmgr; Trinervitermes Biformis Wasmann) Polyphagous and found throughout the world. More serious under prolonged drought conditions and in light textured soils viz., sandy and sandy loam soils The termites attack setts, shoots, canes and also stubbles The termites gain entry through the cut ends or through buds of the setts and feed on the soft tissue. The tunnel excavated is filled with the soil. This affects germination and thus the initial crop stand and ultimately the cane yield. The germination failure could be up to 60%. In the stalks the termites feed on the inner tissues leaving the rind intact. The cavity formed is filled up with moist soil, having galleries, in which, they move about. The affected canes die.   Whitefly (Aleurolobus Barodensis Mask) Waterlogging and nitrogen starvation cause severe out break of whiteflies. Summer droughts and dry spells during monsoon season also favour buildup of this pest Varieties with broad and long leaves are more susceptible to this pest The nymphs of white flies suck the sap from the under surface of leaves which turn yellow and pinkish in severe cases and gradually dry up. Heavy infested leaves are covered by the sooty mould caused by the fungus, which adversely affects photosynthesis. The whitefly infestation retards cane growth and reduces sugar content Considerable loss on yield and sugar recovery has been observed. At 80% leaf infestation 23.4% loss in cane yield and 2.9% units loss in sucrose has been reported. (In the picture above: White fly infestation)  Red Rot (Colletotrichum Falcatum) It is the most dreaded disease of sugarcane which has caused the elimination of several important sugarcane varieties from cultivation Yellowing and drying of leaves from margin to midrib, drying of the entire top including the crown, loss of natural colour and considerable shrinkage of the stalk, appearance of reddish lesions on the rind are some of the external symptoms of red rot disease. Most characteristic and diagnostic symptom of the disease is the presence of reddish discoloured patches or lesions interspersed with white horizontal patches on the internal tissue. As the diseases progresses the internal tissues become dark in colour and dry resulting in longitudinal pith cavities. Smut (Ustilago Scitaminea) Primary spread of the disease is through infected setts and the secondary spread is through wind borne teliospore Stunting of infected stools, profuse sprouting of lateral shoots i.e., tillers, reduction in internodal length, formation of thin stalks and narrow erect leaves are certain symptoms of smut. Characteristic symptom is the production of long whip like structure from the terminal bud of the stalk, which is black in colour covered by thin silvery membrane. This silvery membrane ruptures releasing millions of reproductive spores of smut fungus, which are present in the form of powdery mass. Losses due to smut in sugarcane depend on various factors viz., primary or secondary infection, plant or ratoon crop that is affected and early or late infection and have been reported to range from 30 - 40% in plant crops and even up to 70% in ratoons. Sucrose content of infected cane is reduced to 3 - 7%. Pineapple Disease (Ceratocystis Paradoxa) Essentially a disease of seed material i.e., setts. Typical disease symptoms are detected in setts after 2 - 3 weeks of planting. Pathogen enters the sett mainly through the cut ends and destroy the central soft portion i.e., parachymatous tissues of the internode and then damages the buds. Affected tissues first develop a reddish colour, which turns to brownish black in the later stages. Cavities are formed inside the severely affected internodes. The presence of the fungus inside the sett prevents their rooting. In most cases setts decay before bud sprouts or the shoots grown to an height of 6 - 12cm. Thus causing germination failure leading to reduced initial crop stand per unit area. Occasionally, the disease occurs in standing crop too due to the entry of the pathogen through stalk damaged by borers, rat damage or any such injuries. Drought accelerates the damage. Pathogen spreads rapidly throughout the canes, foliage turns yellow, and ultimately plant withers. The diseased stalk when cut open smells like mature pineapple. The pineapple odour is due to production of ethyl acetate by the fungus. Wilt (Cephalosporium Sacchari) Disease spreads through infected setts. The fungi gain entry mainly through injuries. Biotic stresses like nematode, root borer, termite, scales, mealy bugs etc and abiotic stresses like drought, water logging etc predispose the plants for wilt infection Moisture stress coupled with high temperature and low humidity reduces plant resistance to wilt. Typical wilt symptoms appear during monsoon and post monsoon periods. Affected plant appears wilted and conspicuously stunted. The crown leaves turn yellow, loose turgor and eventually withers. Wilt-affected canes loose their normal colour and are light in weight. The most characteristic symptom during the early stage of infection is the presence of diffused reddish brown patches on the internal tissue. Later canes become light and hallow and shrink. Disease reduces germination and in severe cases total cane yield losses occur due to drying up of shoots and wilting of the stalks. Ratoon Stunting Disease Ratoon stunting disease has been considered as the most important cause for sugarcane varietal degeneration Primary spread of the disease is through infected setts. Also spreads through harvesting implements contaminated with the juice of diseased canes. Expression of disease is more under adverse conditions. Progressive yield decline takes place due to the disease. Ratoon crop suffers more damage due to RSD than the plant crop. Disease is known to reduce germination and yield Most characteristic symptom of the infected stalks is the presence of pin head like orange coloured dots of bacteria on the internal soft tissue in the nodal region. Other symptoms include stunted growth, thin stalks with short internodes, pale yellowish foliage and rapid tapering of the stem towards the top (In the picture above: Ratoon stunting disease symptom)  Grassy Shoot Disease (Phytoplasma) It is a mycoplasamal disease. Primary transmission of disease is through disease infected setts Profuse tillering with narrow chlorotic leaves giving a grass like appearance is characteristic symptom of GSD incidence Very few tillers of GSD infected plants develop into canes, which are thin and produce white shoots from the side buds. Leaf Scald (Xanthomonas Albileneans) It is a bacterial disease, widely spread in many countries. Disease is favoured by wet seasons, water stress due to drought, water logging and low temperatures. Disease symptoms appear in two phases, the chronic and acute phases. In the chronic phase, "white pencil line" extending entire length of lamina reaching the margin of young leaves and stripes diffuse later resulting in leaf etiolation. Drying from tip onwards presents a scalded appearance and hence the name. Different degrees of chlorosis from total albinism to interveinal chlorosis in young leaves during summer, germination of buds in acropetal manner with bushy appearance in standing cane, cut open stalks showing dark red vascular strands, prominent streaks at node invariably in the side shoots, are other prominent symptoms of chronic phase. In the acute phase the symptoms appear suddenly and die without any major leaf symptoms. The masking of symptoms is more common during monsoon and symptoms may appear suddenly any time during crop growth. Yellow Leaf Spoot (Cercospora Koepkei) Prolonged rain with intermittent sunshine, waterlogged conditions and higher nitrogen doses are congenial for disease development. Warm humid weather favours rapid and abundant production of conidia by the pathogen and sopread of the disease. Characteristic symptoms are presence of small, yellow coloured, irregularly shaped spots over the leaf surface. Density of spots is minimum in the lower surface, moderate in the middle and maximum towards the tip of the leaf. Spots coalesce at late stages and cause drying of leaves. Badly affected foliage looks reddish-brown when viewed from a distance. In the picture: Yellow leaf spot showing small yellow coloured spots  Eye spot (Helminthosporium sacchari) Usually a crop of 6 - 7 months is more susceptible to the disease. Fungus penetrates the host tissue either through stomota, bulliform cells or directly through the cuticle. Cloudy weather, high humidity with drizzle coupled with low night temperatures, wetting of leaves either through precipitation or dew greatly enhance disease development. Likewise water logging, high fertility status and excess nitrogen fertilization also favour the spread of the disease. Lesions first appear as small water soaked spots, darker than the surrounding tissues. The spot becomes more elongated, resembling the shape of an ‘eye' and turns straw coloured within a few days. Finally the central portion becomes reddish brown surrounded by straw coloured tissues. Then reddish brown streaks of ‘runners' develop extending from the lesions towards the leaf tip along the veins. Later the spots and streaks coalesce to form large patches and causes drying of leaves.