Most important Pest and Diseases of Maize (Zea mays)

Muhammed Alhassan

Maize is a high-yielding crop, but in order to reach its potential, the farmer should protect the health of the plants during the entire growing seaso.

Maize (corn)

Description

Maize, Zea mays, is an annual grass in the family Poaceae and is a staple food crop grown all over the world. The maize plant possesses a simple stem of nodes and internodes. A pair of large leaves extend off of each internode and the leaves total 8–21 per plant. The leaves are linear or lanceolate (lance-like) with an obvious midrib (primary vein) and can grow from 30 to 100 cm (11.8–39.4 in) in length. The male and female inflorescences (flower bearing region of the plant) are positioned separately on the plant. The male inflorescence is known as the ‘tassel’ while the female inflorescence is the ‘ear’. The ear of the maize is a modified spike and there may be 1–3 per plant. The maize grains, or ‘kernels’, are encased in husks and total 30–1000 per ear. The kernels can be white, yellow, red, purple or black. Maize is an annual plant, surviving for only one growing season and can reach 2–3 m (7–10 ft) in height. Maize may also be referred to as corn or Indian corn and is believed to originate from Mexico and Central America.

Uses of Maize

Maize and cornmeal (dried, ground maize) are staple foods in countries all over the world. The ears can be cooked and eaten from the cob as a vegetable or the kernels can be removed and either eaten as is or used to produce a wide variety of foodstuffs including cereals and flour. Maize is also a major source of starch, which can be processed into oils and high fructose corn syrup. Maize is also commonly grown as feed for livestock.

Which are the most important pests and diseases in maize?

Maize is a high-yielding crop, but in order to reach its potential, the farmer should protect the health of the plants during the entire growing season. Except for the weeds that strike early in the plant’s life, there are various pests and pathogens that can jeopardize the growth and production of maize at different times during its life cycle.

The farmer needs to be aware of them and take preventative measures or suppressive actions to avoid or limit any damage. It is highly advised for the farmer to

  • Visit the field often, observe the plants carefully and take samples-measures to define the “enemy” and its spread.
  • Be aware of the favorable factors for the spread of maize pests and the economic threshold for the crop to decide if, when, and how you need to take action.
  • Taking action before the disease or pest has infected the whole field can reduce the amount of chemicals used and increase the efficacy of crop protection.
Maize

A diseased Maize Plant Image courtesy of fwi.co.uk

 

Some Common Pests Of Maize

  • Seedcorn maggot: The maggot bore into the seeds and seedlings and may result in seedling death.
  • Seedcorn beetle: Adult attack germinating seeds and seedlings, causing stunted growth.
  • Wireworms: Wireworm feeds at the base of the young plants. It causes stunted growth and death of young plants.
  • Black cutworm: Cutworm feeds at the base of the young plants. It cuts off young plants soon after emergence.
  • Maize stalk borer: Stalk borer creates holes in young unfurled upper leaves from young larvae; older larvae bore into the stalk. It can cause the death of the plant if stalk is affected.
  • Corn root aphid: The aphids pierce plant roots and cause retarded growth. Heavily infected seedlings rarely grow taller than 25 cm.
  • Maize aphid: Attacks are on leaves as a black fungal growth (called sooty mold) often occurs on the honeydew secreted by aphids. This can lead to reduced growth.

Maize

Wireworms
Image courtesy of gardeningknowhow.com

Viruses

  • Maize streak virus (MSV) Transmitted by leafhoppers: Spread in the whole plant after transmission via insects. Reduced by retarded crop growth

Fungi

  • Common rust: Development of pustules on the upper and lower leaf surfaces.

Bacteria

  • Northern Leaf Blight: Northern leaf blight develops on the upper leaf surface. Infection that occurs during the early stage of growth may cause heavy loss in-ear fill.
  • Grey leaf spot: The lower leaves of the corn plant are most often the sites of initial infections by gray leaf spot while the upper leaves are infected afterward. Severe infestation can lead to premature plant death.
  • Ear and stem rots: Ear and stem rots infect stalks following stalk borer attack. Damage results in the failure of the ear to develop. Kernels in the ears may be infected.
Maize

Northern Corn Leaf Blight
Image courtesy of www.cropprotectionnetwork.org

Some other Pests and diseases of Maize include:

  1. Stem Borer (Busseola fusca, sesania colanistis, eldana sacharina). The insects are transmitted to the plants by butterflies, which lay eggs on corn in dry season. Damages inflicted to plants by these insects are remarkable from the holes they make in seeds, with leaves completely eaten up and galleries in stems, the whole surrounded by excrements of the insects.

Symptoms of maize stalk borer, Busseola fusca, damage on leaves: (A) characteristic “window panes,” (B) shot holes where tissue has been eaten away, and (D) dead

heart. Symptoms of damage to stems and cobs: (C) galleries filled with frass, (E) cobs showing frass, and (F) deposits and empty grains.

The following measures are recommended to fight against the disease: early planting, rotation of crops, pile up the stems in compost or apply Dursban 48%.1, 5l/Ha or beta-cyfluthrine 2,5% in 10 l of water /acre.

2. Maize streak virus; this disease

is transmitted by an insect called Cicadulina rubila. The disease is noticed by visible traces on leaves. 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.

Symptoms of Maize Streak Virus

To fighting against the disease, it is recommended to early plant the entire field, pull up possible infected seedlings, which could transmit the disease.

3.  Leaf spots: this disease is transmitted by a fungus called “Helmnthosporium turcicum “. This disease attacks the leaves of corn and it is seen by many large oval spots on them. It is frequent during rainy seasons

Symptoms of maize leaf spots

The following measure fight against the disease: early planting using resistant varieties and treated with Thiran and Benomyl before planting. It is recommended to compost the stems away from the field.

4. Fall Army worm

Fall armyworm (FAW) – Spodoptera frugiperda, is a pest that can cause significant damage and crop yield losses, if not well managed. Maize is its preferred host and a major staple crop for smallholders. In addition to maize, the pest has also been detected on an increasing number of other crops (e.g., sorghum and sugarcane).

 

                               

Fall Armyworms and their damage on maize leaves         Fall Armyworm with “Y”shape  between eyes

Prevention

  • Deeply ploughing the soil with the aim of discovering, removing or burying the fall armyworms,
  • Always weeding the plantation whenever weeds have emerged and keeping clean the plantation contours,
  • Removing the plants residues in the field after the harvest,
  • Boosting the plants resistance by applying well decomposed manure, recommended inorganic fertilizers and irrigation,
  • Crop rotation of cereals with legumes (beans, soybeans,..) or tubers (potatoes, sweet potatoes),
  • Regular surveillance of the plantation (at least three times a week) and check whether there is no Fall armyworm outbreak. Once you realize that there Fall armyworms are available, you should inform the concerned people (farmer promoters, facilitators and extension workers at Cell, Sector, District and RAB…)

Control

  • Collecting fall armyworms and killing them,
  • Using pesticides like:
  • Cypermethrin 4%+profenofos 40% (example: roket, target, cypro, jaket,…)   at 1-2 ml of pesticide in1l of water,
  • Lambda-Cyhalothrin 50g/l, at 1-2 ml in 1l of water,
  • Pyrethrum 5% EWC, at 8ml in 1l of water,
  • Acetamiprid 20g/l + Lambda-Cyhalothrin 16g/l, 4-6ml in 1l of water,
  • Imidacloprid 200g/l at 1ml in 1l of water.

5. Maize Lethal Necrosis Disease

Maize lethal necrosis disease is caused by co-infection of maize by Maize chlorotic mottle virus (Machlomovirus: Tombusviridae) and Sugarcane mosaic virus (Potyvirus: Potyviridae) or sometimes another cereal virus of the Potyviridae group.

Symptoms

Maize chlorotic mottle virus (MCMV) causes a variety of symptoms in maize depending upon genotype, age of infection and environmental conditions. They range from a relatively mild chlorotic mottle to severe stunting, leaf necrosis, premature plant death, shortened male inflorescences with few spikes, and/or shortened, malformed, partially filled ears (Castillo and Herbert, 1974; Castillo Loayza, 1977; Niblett and Caflin, 1978; Uyemoto et al., 1981).

     

Symptoms of MLN disease

Prevention and Control

  • Seed should not be recycled; farmers should plant certified seed only. Those seeds are available in agrodealers’ shops;
  • The best approach for the management of MLND is to employ integrated pest management practices encompassing cultural control such as closed season, crop rotation and crop diversification, appropriate spacing, fertilizer application, weeding etc…
  • Uprooting infected plants and bury them in 1m deep hole,
  • Do not grow maize nearby an infected maize plantation,
  • Crop rotating maize with other non cereal crops,
  • Grain and cobs that are rotten should not be fed to humans or animals. These should be destroyed by burning,
  • Domestic regulation can be put in place to prevent the movement of maize products from affected areas to disease-free regions.

Information supplied by COLEACP to be found at https://pip.coleacp.org 

and http://www.ehinga.org/eng/articles/maize/pests_and_diseases

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Muhammed Alhassan