Diseases Of Maize

By TamilNadu Agricultural University on 07 Nov 2016 | read
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1. Downy mildew / Crazy top

Causal organism: Peranosclerospora sorghi

Symptoms: Chlorotic streaks appear on the leaf and white fungus growtH his seen on both the surfaces of leaf. Affected plants become stunted and exhibit bushy appearance due to shortening of inter nodes. Sometimes leafy growths in the tassel and proliferation of axillary buds on the stalk of the tassel are noticed.

Favourable Conditions : Low temperature (21-33˚C);High relative humidity (90 per cent) and drizzling;Young plants are highly susceptible.265

2.Rust

Causal organism: Puccinia sorghi

Symptoms: On both the surfaces of the leaf, brown pustules are seen.These represent the uredosori of the fungus. The alternate host is Oxaliscorniunlata. Cool temperature and high relative humidity favors the disease

3. Leaf Blight

Causal organism: Exserohilum turcicum & Helminthosporium maydis

Turcicum Leaf Blight Symptoms:The fungus affects the crop at young stage. Early symptoms are oval, water-soaked spots on leaves. Mature symptoms are characteristic cigar shaped lesions that are 3 to 15cm long.Lesions are elliptical and tan in color, developing distinct dark areas as they mature that are associated with fungal sporulation. Lesions typically first appear on lower leaves, spreading to upper leaves and the ear sheaths as the crop matures. Under severe infection, lesions may coalesce,blighting the entire leaf.

Maydis Leaf Blight Symptoms:: Small yellowish round or oval spots appear on the leaves. These spots enlarge become elliptical and the center becomes straw colored with a reddish brown margin. Conidiaand conidiophores are formed in the center.

Favourable Conditions : Optimum temperature for the germination of conidia is 8 to 27˚C provided with free water on the leaf;Infection takes place early in the wet season.

4.Charcoal rot

Causal organism: Macrophomina phaseolina

Symptoms: The pathogen affects the plant mostly after flowering and the disease is named as Post Flowering Stalk Rot (PFSR). The stalk of the infected plants can be recognized by greyish streak. The pith becomes shredded and greyish black minute sclerotia develop on the vascular bundles. Shredding of the interior of the stalk often causes stalks to break in the region of the crown. The crown region of the infected plant becomes dark in color. Shredding of root bark and disintegration of root system are the common features. High temperature and low soil moisture(drought) favors the disease

5.Bacterial Stalk rot

Causal organism: Erwinia dissolvens

Symptoms: The basal internodesdevelop soft rot and give a water soaked appearance. A mild sweet fermenting odor accompanies such rotting. Leaves some time show signs of wilting and affected plants topple down in few days. Ears and shank may also show rot. They fail to develop further and the ears hang down simply from the plant

B.Disease Management

1.Seed treatment: Carbendazim @ 2 g/kg or Thiram @ 4g/kg or Metalaxyl @ 3g/kg of seed

2. Downy mildew or Crazy top

Use resistant TNAU maize hybrid CO-6 Rogue out affected plants.Spray Metalaxyl+ Mancozeb @ 1000g, Mancozeb 1000g/ha at 20 days after Sowing

3.Leaf blights

Spray Mancozeb or Zineb @2 -4 g/litre at 10 days interval after first appearance of the disease

4.Post Flowering Stalk rot

Follow crop rotation

Avoid water stress at flowering time reduced disease incidence

Avoid nutrient stress. Apply potash @ 80 kg/ha in endemic areas

Soil application of P. fluorescens (or) T. viride @ 2.5 kg / ha + 50 kg of well decomposed FYM or sand at 30 days after sowing

 

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