Diseases and their Management

Lentil Disease

kiran — Wed, 03 Oct 2018 04:29:38 +0000

Lentil Disease kiran Wed, 10/03/2018 - 10:14

STEMPHYLIUM BLIGHT

This is very severe in our country since 2-3 yrs. This is caused by Stemphylium botryosum f. sp. lentis. Initially disease may appear as a small back dots on young leaf but it spreads very fast covering all the leaves and flower also on steam and pods black lesions are found. When disease appear in epidemic form, the whole plant get killed.

MANAGEMENT

Some lentil variety shows horizontal resistance so bring such variety under cultivation practice
Fungicide like Iprodine and Dithane M₄₅can be used
Low plant population and good drainage reduce the severity

Category

Diseases and their Management

Wheat Disease

kiran — Wed, 03 Oct 2018 04:29:23 +0000

Wheat Disease kiran Wed, 10/03/2018 - 10:14

RUST:

It is considered to be the oldest known disease. It is the potential cause of economic loss in all wheat growing areas. It is of three types:

i)Black Stem Rust

Causative agent of this disease is Puccinia graminis tritici.This problem is high in the hills and mountains where local varities are cultivated. Due to the use of improved varities in Terai, this disease is not seen. Pustules are found on stem elongated and long brownish to black coloured. It may appear on leaves under severe condition.

ii) Brown Leaf Rust

This disease is caused by fungus Puccinia recondite. Pustules are brown in colour and scattered all over the leaves. Pustules are spherical rarely seen on leaves.

iii)Yellow Striped Rust

Causative agent of this disease is Puccinia striiformis. Pustules are yellow in color confined along in between veins. Pustules are elongated appear in linear fashion. It may also appear on leaf sheath in severe codition.

MANAGEMENT:

Use resistant varieties like WK1204, Pasang Lhamu
Use fungicides like Dithane M45 75% WP at the rate of 1.5-2 kg in 750 litres of water per hectare
Short duration varieties of wheat should be recommended
Cultivating susceptible varieties of wheat in high hills and resistant varieties in mid hills helps in controlling disease in main fields of Terai

LOOSE SMUT:

This is seen particularly in those areas where local varieties are cultivated. So this is serious in hilly areas. Causative agent of this disease is Ustilago tritici .The infected plants are slightly taller than healthy plants and develop chlorotic leaves. All the spikelets of affected pants are transformed into black powdery mass of spores. There is no grain formation. Before emergence, the smutted spikelets are covered by a thin membrane which is silvery but it breaks while emerging out the earheads. These are loosely attached and can be blown up easily.

MANAGEMENT:

Seed treatment with systemic fungicides like vitavax at the rate of 2gm per kg is effective
Solar Heat Treatment: Seeds are soaked in cold water for 4-6 hrs, dormant mycelium becomes active and seeds are spread on cemented floor on direct sunlight for 4-6 hrs
Hot water treatment at 55⁰C for 10-15 mins.
Development and use of resistant varieties

LEAF BLOTCH OR TANSPOT:

It is very common disease found throughout the Terai, Inner Terai, as well as in Hills. There is involvement of 2-3 pathogens in this disease namely Pyrenophora tritici-repentis, Bipolaris sorokiniana, Alternaria triticina. Spots appear as tan brown flecks which expand into the lens shaped and have yellowish halo around the spots. These tan blotches expand upto few mm long often with chlorotic or yellow borders. Such leisons may coalesce and become more dark brown in color.

MANAGEMENT:

Development and use of resistant varieties: Chinese variety ‘Chiria’ is used for crossing to transfer resistant gene to other variety
Chemicals like Tilt, Horizon can be used to spray. Just 2 spray can control the disease upto 95%.
Early planting can escape severity of infection and Use of short duration varieties

Category

Diseases and their Management

Maize Disease

kiran — Wed, 03 Oct 2018 04:29:10 +0000

Maize Disease kiran Wed, 10/03/2018 - 10:14

DOWNY MILDEW

It is most common diseases of maize. In Nepal 2 types are found brown stripe downy mildew and philipino downy mildew which are caused by Scleropthora rassyi var. zeae and Peronosclerospora philipinensis respectively. In brown stripe type, symptoms appear on leaf as yellowish lesion in between veins which later on change into brown color also in morning downy fungal growth appears around lesion. In philipino type, there is crazy top symptoms i.e. dwarf plant with many leaves originating from limited region also leaves become small sized with chlorotic sometimes whitish appearance.

MANAGEMENT

Seed treatment with mercurial or systematic fungicide Bavistin@ 2gm/kg seed. Spraying can also be done but it is not practical in farmers level.
Use of resistant variety Rampur composite, Indian variety Ganga safeda is also resistant.

BLIGHT

Southern Leaf Blight

This is caused by two pathogens namely Drechslera maydis, Bipolaris maydis. Generally, it appears during summer season. Smaller boat shaped lesion developed in between veins which are initially chlorotic later change into brownish and finally becomes straw colored. The lesions never becomes blackish color.

Northern Leaf Blight

This is caused by multiple pathogens namely Helminthosporium turcicum, Drechslera turcicum, Bipolaris turcicum. It appears in winter season. Larger boat shaped lesion developed across the vein which are initially tan later change into brownish and finally becomes blackish.

Cercospora Leaf Blight

This is caused by Cercospora zeae-maydis and it is prevalent in hilly regions. It begins from lower leaves and moves upward. Symptoms can be seen as rectangular tan spot in between veins which later changes into brown and finally becomes straw color. In severe case, whole plant may be killed.

MANAGEMENT

See treatment with fungicide like Captan, Thiodan.
Foliar spray with Iprodine@ 0.1% (2-3 sprays at 15 days interval)
Resistant variety like Rampur composite, Ganga Safeda can be used
Removal of collateral host

STALK ROT

This is fungal and bacterial disease. The causative agent are fungus like Pythium debarianum, Fusarium moniliforme, Cephalosporium maydis, Diplodia maydis and bacteria like Erwinia carotovora, pseudomonas spp. In fungal rot, 1^st and 2^nd internode near the ground get attacked. Symptoms may appear as shrinking of attacked internodes, discoloration of pith (yellowish, reddish or brownish) and if we cut we can find dirty white fungal mycelial growth. In bacterial attack, nodes get discolored, bacterial ooze comes out from node with foul smell. In both of the cases plant get topple down even under light air blow.

MANAGEMENT

Soil treatment or soil solarization
Use of bio control agent fungus like Trichodema harzianum, Trichoderma viride, Gliocladium virens and bacteria like Pseudomonas fluorescence.
Development and use of resistant variety

Category

Diseases and their Management

Rice Disease

kiran — Wed, 03 Oct 2018 04:28:53 +0000

Rice Disease kiran Wed, 10/03/2018 - 10:13

1) RICE BLAST:

Rice Blast Disease

It is the major disease of rice throughout the world and is caused by a fungal pathogen Pyricularia oryzae. The symptoms appear on the above ground parts like leaf, leaf sheath, panicle etc. First eye shaped small spot is developed in the leaves which has ash coloured centre, brownish in margin and get yellowish colour in outer parts of margin i.e. yellowish halo. If the infection takes place in neck region, then it becomes weak and panicles are held down known as neck blast.

MANAGEMENT:

Use fungicides like Hinosan 50 EC 1.5 ml, Bavistin 50 WP 3 gm, or Dithane M45 3 gm per litre of water.

Seed treatment with Bavistin at the rate of 2.5 gm per kg of seed.

2) BROWN SPOT:

Brown spot of rice

It is caused by fungus Helminthosporium oryzae .

MANAGEMENT:

Nitrogen should not be applied more than the recommended dose

Seed treatment with hot water or Dithane M-45 or Bavistin at the rate of 3gm per kg

Spary fungicides like Dithane M-45 or Bavistin at the rate of 3gm per litre

Biocontrol agents like Trichoderma herzianum, T viridae can be used

3) BACTERIAL LEAF BLIGHT:

Bacterial Leaf Blight of Rice

This disease is caused by bacteria Xanthomonas campestris . First the edges of the leaves develop wet specks and they gradually increase in size and become yellow and light brown in colour.

MANAGEMENT: Controlled irrigation in diseased field and raise seedlings in dry field rather than muddy fields

Use disease free seeds and seedlings

4) FALSE SMUT:

It is caused by Fungus Ustilaginoidea virens

MANAGEMENT:

Fasle smut of Rice

Seed treatment with Mercuric Chloride (HgCl₂) to eliminate seed borne inoculum.

Rouging of affected panicles and use of balanced fertilizers and follow crop rotation

Category

Diseases and their Management