Discuss maize diseases, symptoms and their control measures

1.Maize streak disease
Caused by a virus transmitted by leaf hoppers (Cicadilunambila).
Symptoms:
-The virus causes a white to yellowish streaking on the leaves.
-The streaks are very narrow, more or less broken and run parallel along the leaves.
-Eventually the leaves turn yellow with long lines of green patches
-Plants infected at early stage usually do not produce any cobs.
-Yield losses in East Africa vary between 33 and 55% under natural infection conditions
-Death of young plants in severe attack.
Control:
-Use of tolerant /resistant maize varieties e.g H629
-Intercropping and crop rotation to break the life cycle of leaf hoppers.
-Destruction of alternative hosts.
-Rogueing of infected plants to reduce source of inoculum.
-Use of insecticides e,g malathion to control the vector.
-Eradication of grass weeds
-Avoid overlap of two maize crops
-Crop rotation
-Use certified maize seed

2.Leaf Blight
-Caused by fungus called Setosphaeriaturcica(Exserohilumturcicum) which was formerly known as Helminthosporiumturcicum.
-Disease development is promoted by prolonged wetness on foliage, extended dew, Relative Humidity (97-100%) and relatively warm temperatures (24-35° C).
Symptoms:
-Boat-shaped greyish lesions which develop in a few days at each affected part. Severe in young plants.
-Small yellow dots that become elongated between veins appear. They later become brownish to creamy white in colour with reddish to purplish brown borders. The spots may join together and result in blighting of entire leaves.
-Silks, portions of the husks and cobs may turn black. A black mould may develop on cobs.
-Cause damage up to 70% .
Control:
-Use appropriate fungicide
-Use of tolerant / resistant varieties
-Good field sanitation (removal of crop residue after harvest or deep ploughing of crop residues)
-Use certified seeds
-Crop rotation
-Grey leaf spot(Cercosporazeae-maydis).
-This disease is favoured by prolonged periods of high relative humidity. It can cause yield losses of 30 to over 50%.
Symptoms
-Symptoms are similar to leaf blight but the spots are much narrower.
-They are initially light brownish in colour, and with age they bleach to ashen grey surrounded by narrow light-brownish border.
-When wet, spore mass is formed on the spots with a light shade.
Control
-As for leaf blight

3.Maize rusts(Pucciniasorghi)
Damage/symptoms
-Highland rust produces yellow brown linear pustules on leaves while lowland rust produce light brown pustules on upper leave surface.
Control
-Use of resistant varieties
-Crop rotation
-Deep ploughing of crop residue
-Destruction of weed Oxalis sp. (an alternate host)

4.Maize Smuts
(Common & Head smut)
Damage/Symptoms
-The first symptoms become evident when tassels and cobs (ears) appear.
-Large white to black galls on stalks, tassels and ears.
-Masses of Black spores are released if galls are opened
-The infested plant to do not produce any grains
Control
-Use certified seeds
-Crop rotation
-Use resistant varieties
NB: Read the rest of diseases

5.Maize lethal necrosis disease (MLND)
-It is as a result of two viruses attacking maize at the same time (Double infection). The maize chlorotic virus (MCMov) and any of the cereal viruses in the potyviridae group like Sugarcane mosaic virus (SCMV), wheat streak mosaic virus(WSMV) or maize Dwarf Mosaic Virus (MDMV). The double infection of the two viruses gives rise to MLND also called Corn Lethal Necrosis (CLN).
Symptoms
-Mild to severe mottling of the leaves, usually starting from the base of young leaves in the whorl and extending upwards.
-Stunting and premature aging of the plants.
-Drying or necrosis of the leaf margins that progress to the mid-rib and eventually the entire leaf.
-Necrosis of young leaves in the whorl before expansion leading to dead heart and eventual plant death.

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Titany answered the question on August 16, 2021 at 08:11