Question

Paddy diseases and their pesticides

Answer 1

Tungro disease

Plants affected by tungro exhibit stunting and reduced tillering. Their leaves become yellow or orange-yellow, may also have rust-colored spots. The leaf discoloration starts from the tip and may or may not extend to the lower part of the leaf blade; often only the upper portion is discolored.. Infected plants have delayed flowering. Tungro are transmitted by the green leafhoppers.

 

1.       Application of Carbofuran 3G @ 10-12 kg/acre or spraying of Imidaclorprid 200SL @ 40ml or Chloropyriphos 20 EC @ 500ml in 200 litres of water. Repeat after 7 -10 days if needed.

2.       Leaf yellowing can be minimized by spraying 2 % urea mixed with Mancozeb at 2.5 gm/lit.

3.       Instead of urea foliar fertilizer like multi-K (potassium nitrate) can be sprayed at 1 per cent which impart resistance also because of high potassium content.

Blast

Initial symptoms white to gray-green lesions or spots with darker borders produced on all parts of shoot Older lesions elliptical or spindle-shaped and whitish to gray with necrotic borders Lesions wide in the center and pointed toward either end Lesions may enlarge and coalesce to kill the entire leaves Symptoms also observed on leaf collar, culm, culm nodes, and the panicle neck node Nodal infection causes the culm to break at the infected node Few, no seeds, or whiteheads when neck is infected or rotten.

1.       Manipulation of planting time and fertilizer and water management is advised. Early sowing of seeds after the onset of the rainy season is more advisable than late-sown crops. Excessive use of fertilizer should be avoided. Nitrogen should be applied in small increments at any time.

2.       Spray  tricylazole  75% WP @ 0.6gm/ litre or Propiconazole 25% EC 1ml/ litre or Carbendazim 50% WP @ 1gm/litre of water.

Brown spot

Infected seedlings have small, circular or oval, brown lesions, which may girdle the coleoptile and cause distortion of the primary and secondary leaves Infected seedlings become stunted or die Young or underdeveloped lesions on older leaves are small and circular, dark brown or purplish brown A fully developed lesion on older leaves is oval, brown with gray or whitish center with reddish brown margin When infection is severe, the lesions may coalesce, killing large areas of affected leaves. Infected glumes with black or dark brown spots Velvety appearance of lesions on infected glumes under severe conditions

1.       Spraying of  crop at tillering and late booting stages with Carbendazim 12% + Mancozeb 63% WP @ 1gm/litre or Zineb @ 2 gm/litre of water. Repeat spray after 15 days.

False Smut

Individual rice grain transformed into a mass of velvety spores or yellow fruiting bodies Growth of velvety spores enclose floral parts Immature spores slightly flattened, smooth, yellow, and covered by a membrane Growth of spores result to broken membrane Mature spores orange and turn yellowish green or greenish black Only few grains in a panicle are usually infected and the rest are normal

1.       At Boot stage spraying of Copper oxychloride 50% WP @ 2.5 gm/liter. If disease persists spray crop with Propiconazole 25% EC @ 1ml/litre of water  after 15 days interval for effective control of disease.

Sheath Blight

Initial lesions are small, ellipsoidal or ovoid, greenish-gray and water-soaked and usually develop near the water line in lowland fields Older lesions are elliptical or ovoid with a grayish white center and light brown to dark brown margin Lesions may reach the uppermost leaf under favorable conditions Lesions may coalesce forming bigger lesions with irregular outline and may cause the death of the whole leaf Severely infected plants produced poorly filled or empty grains, especially those on the lower portion of the panicles

1.       Spray the crop with Propiconazole 25% EC @ 1ml/litre or Carbenbendazim 50% WP @ 1gm/litre  or Hexaconazole 5% EC @ 1 ml/lit of water  at booting stage. Repeat the spray after 15 days interval.

Sheath rot

Oblong or irregular spots with chocolate brown coloration may develop on boot leaf sheathYoung panicles may not emerge and rot completely or emerge only partiallyGrains inside the chocked panicles and on the partially emerged panicles may be chaffy, light to dark brown and covered by a white to light-pink mat of mycelium and spore mass.Grains may be partially or completely filled and glume discoloration is noticed

 

1.        Same as for sheath blight.

Answer 2

Sheath blight is a fungal disease caused by Rhizoctonia solani. Symptoms are usually observed from tillering to milk stage in a rice crop
Bacterial blight is one of the most destructive rice diseases in Asia and has historically been associated with major epidemic
Rice blast (Pyricularia grisea) is a fungus that feeds on the rice plant, causing severe damage usually during the seedling stage
Rice yellow mottle virus (RYMV) is a plant virus disease. The most important symptom on a rice plant is that leaves turn yellow, with alternate yellow and green stripes that give its typical mottled appearance to the plant

are the one's that I know according our bio text