Agri Diseases

DISEASES OF SUGARCANE – Agricultural study materials

DISEASESCAUSAL ORGANISM
Red rotColletotrichum falcatum
Whip smutUstilago scitaminea
Sett rot or pine apple diseaseCeratocystis paradoxa
RustPuccinia erianthi
GummosisXanthomonas campestris pv. vasculorum
MosaicSugarcane mosaic virus
Grassy shootMycoplasma like organism [MLO]
Iron chlorosisIron deficiency
Ratoon stuntingClavibacter xyli
Witch weedStriga angustifolia [Partial root parasite]
1. RED ROT – Colletotrichum falcatumSymptomsThe first external symptom appears on 3rd or 4th leaf which withers away at the tips along the margins. Typical symptoms of red rot are observed in the internodes of a stalk by splitting longitudinally. The reddening of the internal tissues with cross-wise white patches is the characteristic symptom of red rot. Reddish lesions on the upper surface of leaves with dark brown dots in the centre [Acervuli] appear. The diseased canes emit a typical acidic sour smell.Mode of SpreadConidia spread through infected setts, irrigation water and implementsSurvivalSurvives in infected setts (Chlamydospores survive in soil for 60-150 days)EpidemiologyMonoculturing of sugarcane, water-logged conditions encourage the disease developmentManagement
  • Adopt crop rotation by including rice and green manure crops
  • Avoid ratooning of the diseased crop
  • Select setts from the diseased free field or area
  • Soak the setts in 0.1 % carbendazim or 0.25 % Emisan for 20 min. before planting.
  • Grow resistant varieties like COC 62198, CO 7704, COC 771,772 and CO 86249

2. WHIP SMUT – Ustilago scitaminea
SymptomsThe affected plants are stunted and the central shoot is converted in to long whip – like, dusty black structure. In early stages, this structure is covered by a thin, white papery membrane and on maturity, it ruptures and millions of tiny black spores (teliospores) are liberated and dessiminated by wind. Affected plants produce more tillers than the healthy onesMode of Spread and SurvivalThe pathogen spreads through air borne teliospores and survives as Teliospores in soil and infested settsEpidemiologyMonoculturing of sugarcane and dry weather during tillering stage helps the diseaseManagement
  • Plant healthy setts taken from disease free area
  • Remove and destroy the smutted clump
  • Discourage ratooning of the diseased crops
  • Setts can be treated with aerated steam therapy [AST] at 52o C for 5 min.
  • Grow resistant varieties like CO 449, 527, 6806, 7704, 8139 and COC 86062

3. SETT ROT OR PINE APPLE DISEASE – Ceratocystis paradoxaSymptomsThe affected tissues first develop a reddish colour which turns to brownish black in the later stages. A characteristic pine apple smell is associated with the rotting tissues and hence the name. In severe cases, the infected shoots are stunted and chlorotic.Mode of Spread and SurvivalThe pathogen spreads through wind borne conidia and irrigation water. Survives in the soilEpidemiologyProlonged rainfall after planting encourage the diseaseManagement
  • Use long setts with 3-4 buds for planting and provide adequate drainage facilities during rainy periods
  • Soak the setts in 0.05 % carbendazim or 0.25 % Emisan for 15 mins

4. RUST – Puccinia erianthiSymptomsInitially minute, elongated, yellow spots (uredia) which are visible on both the leaf surface appear and later turn brown in colour. In severe cases, the uredia also appear on the leaf sheath and the entire foliage looks brownish in colour.Mode of Spread and SurvivalSpreads through air borne uredospores and the pathogen survives in the infected plant debrisEpidemiologyHigh wind velocity and continuous rain favour the diseaseManagement
  • Remove the collateral hosts
  • Spray tridemorph @ 1 kg/ha or mancozeb @ 2 kg/ha
  • Grow resistant varieties like CO 475, CP 44-101 and Q 50

5. GUMMOSIS – Xanthomonas campestris pv. vasculorum
SymptomsAffected mature leaves produce longitudinal stripes which are pale yellow in colour which later turn to brown. The infected canes are stunted with short internodes, gives a bushy appearance. Infected canes split open longitudinally, a dull yellow bacterial ooze comes out from the cut endsMode of Spread and SurvivalSpreads through wind splashed rain and animals. Survives in the infected settsEpidemiologyA temperature of 280 C encourage the diseaseManagement
  • Remove and burn the affected clumps and the stubbles in the field
  • Select setts from the disease free areas
  • Grow resistant varieties like CO 281, 290
6. MOSAIC – Sugarcane mosaic virusSymptomsBasal portion of the younger foliage turns as chlorotic or yellowish stripes alternative with normal green portions of the leaf. In severe cases, yellow stripes appear on the leaf sheath and stalks and stem splitting occursVector    Aphid – Rhopalosiphum maidis transmit the diseaseManagement
  • Rogue out the diseased clumps periodically
  • The setts may be treated 3 days before planting [1st day – 520 C for 20 mins. 2nd day – 57.30 C for 20 mins. 3rd day — 57.30 C for 20 mins]
  • Treat the setts in Aerated steam therapy [AST] at 510 C for 2 hrs
DIFFERENCE BETWEEN GRASSY SHOOT AND IRON CHLOROSIS
    GRASSY SHOOT  IRON CHLOROSIS
Caused by MLO and transmitted by Aphid – Rhopalosiphum maidisCaused by iron deficiency
Leaf size is reduced. Spindle leaf turns papery whiteLeaf size is normal and leaves are chlorotic
Tillering is profuse and canes give grassy shoot appearance [lanky]. Canes are not millable.Tillering is normal and canes are nearly normal and millable
Secondary spread is through insectsIron chlorosis do not spread from one plant to another
Disease occurs not in patchesChlorotic plants are seen in patches
No chemicals available to control in MLO but disease spread is checked by spraying insecticidesSalt containing iron (FeSO4) applied as foliar spray or soil application rectifies the deficiency

7.RATOON STUNTING – Clavibacter xyli


SymptomsDiseased clumps usually display stunted growth, reduced tillering, thin stalks with shortened internodes and yellowish foliage. In young growing shoots, both the nodes and internodes show pink colour and in the mature canes, the nodes show discolouration of vascular bundlesMode of SpreadThe disease spreads through use of diseased setts.ManagementSelect the setts from disease free fields and remove and burn the clumps showing the disease incidence. In hot air treatment setts are exposed to 540 C for 8 hrs. In AST, setts are treated at 520 C for 4 hrs8. WITCH WEED – Striga angustifolia [Partial root parasite]Witch weed is a partial root parasite. This parasite is a small erect herb and covered with short, stiff hairs which make them rought to touch. White colour flowers are sessile and borne in terminal interrupted spikesSymptomInfected plants produce yellowing, wilting of leaves, stunted in growth and may die in severe casesDisease CyclePrimary infection occurs from the seeds in the soil and the seeds are dispersed by wind, irrigation water, cattle and human beingsManagement
  • The crop stubble should also be uprooted and burnt to prevent the continued growth and seedling of the parasite
  • Grow trap crops such as cotton, sunflower, groundnut and other legumes are reduces the seed reservoir of Striga
Application of 20 % urea as a direct spray on mature striga plant can kill the plants by scorching

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