Crop Diseases of Rice
1. Blast (or rotten neck): Pyricularia oryzaelea
(A) Most severe disease of rice also called as rich men's disease.(B) Air borne disease, conidia spread by wind cause secondary infection.
Symptoms:
(A) Brown spindle eye or boat shaped lesion on leaf, and leaf sheath.(B) At the end of season rotten neck or collar rot symptoms appear.
(C) The infected pedicels result in non production of seeds is called blanking.
Management:
(A) Seed treatment with Thiram @ 2.5 g/kg of seeds(B) Spray Mancozeb @ 0.3% on standing crops.
2. Bacterial leaf blight of rice (BLB): Xanthomonas oryzae pv. oryzae
Symptoms:
(A) Initially Kresek (seedling wilt) occurs in nursery, plant withers and dries up.(B) Later at 4-6 week old plants in field 'blighting' starts from tip of leaves to the base.
(C) Yellowing bacterial ooze appears on the surface of legions.
Management:
(A) Seed treatment with Streptocycline 0.015%(B) 3-4 spray of Agrimycin 100g + 500g of copper oxychloride in 500 liter water/ha.
(C) Spray of Bacteromycin@ 25 g/ha.
3. Brown leaf spot: Helminthosporium oryzae(= Drechslera oryzae)
(A) This disease is responsible for the great Bengal famine in 1943.(B) Perfcet stage-Cochliobolus miyabeanus, it is known as perfect stage or teleomorph
Symptoms:
(A) Pathogen infects the coleoptile of seedlings and cause blighting(B) Many dark brown circular to oval spots on upper surface of leaves
(C) This disease is severe in potash deficient soils.
4. Khairadisease: (IARI, Ph. D-1997)
(A) Due to zinc deficiency
(B) Usually in nursery chloratic or yellow patches at leaf base on both sides
of midrib
Management:
(A) Spray ZnSO4@ 5 kg/ha. Or application of zinc sulphate @ 25kg/ha at the time
of sowing in zinc deficient soils.
5. Bakanae disease:
(A) Foot rot or Bakanae "disease Gibberella fujikorai isolated by a
Japanese scientist, Kurasova.
(B) This disease is also known as 'foolish seedling disease'.
6. Pan Sukh: Physiological disease.
Management:
(A) drain excess water, apply ammonium sulphate @ 15-20 kg/ha.
7. Tungro disease: Rice Tungro virus
(A) Vector is: Green Leaf Hopper (Nephottetix virscence)
(B) The rice tungro is unique disease which is caused by two viruses, as RNA
virus (RTSV), and a DNA virus (RTBV).
(C) Stunting of plants and yellowing of leaves from tip and margins are two
main symptoms of tungro.
Other minor diseases of rice:
1. Sheath blight: Due to fungus: Rhizoctonia solani2. Grassy stunt: Viral disease transmitted by Brown plant Hopper (BPH): Nilaparvata lugens
3. Yellow dwarf: Due to Phytoplasma
4. Udbatta disease: Due to fungus Ephelis oryzae'
5. False smut: Claviceps oryzae-sativae (ICS Exam-1995)
Symptoms appears after flowering when infected spikelet is transformed in to a large velvety, yellow to orange mass which later changed to greenish in color.
