Field Crops> Maize> Diseases

Maize crop suffers from different pathological maladies resulting in con-siderable loss in yield. Symptoms of important diseases and their suitable control measures are given below.

Seed Rot and Seedling Blight

General symptoms of these diseases are poor emergence or patchy growth, rotting of seed in the collar region of mesocotyle, presence of red brown lesions on radicle or mesocotyle and wilting of seedlings. To control them treat the seed with 3 g of Bavistin or Thiram per kg of seed.

Black Bundle Disease

Blackening of vascular bundles appears as black dots on the cut ends of the stalk. In severe cases, leaves dry and plants wilt. Ears may rot or may not form at all. To control this disease treat the seed with systematic fungicides like Bavistin, or Benlate at the rate of 3 g per kg seed.

Bacterial Stalk Rot

Stalk rot is caused by the bacterium Erwinia carotovora var Zea. It survives itself on diseased debris. The bacterium infects the plant, especially at the collar, at any stage of its growth period. The organism dissolves the middle lemella of the cell walls. as a result the tissues disintegrate and the plant collapses to the ground. Basal internodes become soft, discoloured and give a bad fermenting smell.

Control Measures: (1) Select well drained field or arrange proper drainage to avoid waterlogging.
(2) Avoid injury on the plants at the time of weeding and top dressing of urea.
(3) Bleaching powder should be applied along the rows at the rate of 20-25 kg per hectare.

Pythium Stalk Rot

Partial infection of any lower internode is the characteristic symptom of the disease. Infected plants become soft and at this point the plants get twisted and topple over the ground. It becomes serious if plant population is over 75 thousand plants per hectare and water accumulates during knee high to pre-flowering stage of crop growth. For its contrdl, apply Captan in poorly drained pockets of the field along the rows at the rate of 150 g per 100 litres of water.

Sugarcane Downy Mildew

Long, rather broad, yellowish or whitish stripes appear on or up to the upper leaves of the plant. Whitish coarse fungus growth is more apparent on affected leaves and may spread up to tassels. In severe cases, infected plants remain stunted and their leaves look pale yellow in colour.

Control Measures: (1) Grow tolerant varieties like hybrid Ganga safed-2, Tarun, Naveen, Kanchan etc.
(2) Rogue infected plants, which can be used as fodder.
(3) Spray Mancozeb 75 WP 1.5 kg + 0.25 kg Zinc sulphate in 500 litres of water per hectare.

Brown Stripe Downy Mildew

Characteristic symptoms are chlorotic to straw coloured stripes on the lower leaves and after sometime on upper leaves also. Find cottony growth of the fungus can be seen on the affected leaf surface during morning hours.

Brown stripe downy mildew can be controlled by three to four foliar sprays of 0.25% Zineb or Mancozeb 75 WP. Give first spray as soon as disease appears in the field. The sprays should be given between 10 to 15 days intervals depending upon the severity of disease.

Maydis and Turcicum Leaf Blights

In maydis leaf blight, individual spots are greyish, tan, up to one and a half inches in length, oval-shaped with straight zonations. Turcicum leaf spots are greyish green or straw coloured and boat-shaped. They are comparatively fewer in number and larger in size than those of maydis.

These diseases can be controlled by two to four sprayings of Zineb or Mancozeb 75 WP known as Maneb (2.5 kg in 1000 litres of water per hectare).