Plantwise Blog

Maize is an important crop, grown by smallholder farmers around the world. It is a staple food in the diets of millions and is vital for food and economic security. However, there are a number of pests and diseases that attack maize and limit yields. Below we outline four pests and diseases of maize and how to spot them.

Head smut Sphacelotheca reiliana

Head smut is a disease caused by a fungus that infects tassels, ears, and occasionally leaves. It can spread via wind and can survive for years in the soil.

The fungus lives on the maize ear, causing black masses to form there. It penetrates and develops inside the plant, but does not appear until flowering or cob formation. The black masses contain spores, or fungal seeds, that contaminate other plants.

Sphacelotheca reiliana
Head smut Sphacelotheca reiliana Image CABI

Recognising the problem

The grains of plants infected with head smut maintain their size but become dark and deformed. As a result, maize quality and yield decrease.

Head smut Pest Management Decision Guide on the Plantwise Knowledge Bank

African maize stalk borer Busseola fusca

The maize stalk or stem borer is a widespread pest, found throughout tropical and sub-tropical areas of Africa, and is one of the major pests of maize. Busseola fusca larvae damage all plant parts of the crops they attack. If farmers do not use controls then infestations can cause yield losses as high as 50%.

Maize stalk borer
African maize stalk borer Busseola fusca Image CABI

Recognising the problem

Young affected plants have holes and ‘windows’ in the leaves. Small dark caterpillars can appear at the base of the leaf. In severe attacks, the central leaves die. In older plants, the young caterpillars bore into the main stem and later move up into the cob of maize.

The caterpillar is pinkish with distinct black spots along its body. When fully grown it measures about 4cm long. It lays round eggs on the underside of leaves in columns stretching from the stem. They are white when first laid but get darker with age. They hatch into larvae after about 10 days. The larvae develop from small black caterpillars into pink caterpillars with black spots.

Management

Stalk borer Pest Management Decision Guide on the Plantwise Knowledge Bank

Fall armyworm Spodoptera frugiperda

In 2016, the Fall armyworm (Spodoptera frugiperda) was found in Africa for the first time. It is a lepidopteran pest native to the Americas that feeds in large numbers on leaves and stems of more than 80 plant species, causing major damage to maize, sorghum, sugarcane but also other vegetable crops, and cotton. The life cycle of the fall armyworm and its ability to spread and reproduce quickly makes it an incredibly successful invasive species.

Fall armyworm
Fall armyworm Spodoptera frugiperda Image,CABI

Recognising the problem

Spodoptera frugiperda larva enters the maize bud and from there eats the plant. Caterpillars feed on maize at nearly all stages of growth from when the plant is young and also on the cob.

Leaf feeding causes extensive “windowpane” damage to maize. Big caterpillars create large irregular and elongated holes on the leaves while feeding. Small caterpillars cause clear or window-like patches.

Window panes are the most common damage symptoms at the early whorl stage; however, other stem borers create similar damage. Finding and identifying the larva is the best way to confirm the damage is being caused by fall armyworm damage.

Management

Fall armyworm Pest Management Decision Guide on the Plantwise Knowledge Bank

Fall armyworm lifecycle

Maize lethal necrosis disease

Maize Lethal Necrosis Disease (MLND) can be devastating for farmers, causing low yields to total crop failure, and is an important food security issue. A combination of two viruses causes MLND, the Maize Chlorotic Mottle Virus (MCMoV) and any of the cereal viruses in the Potyviridae group, like the 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 what is known as MLND, also referred to as Corn Lethal Necrosis (CLN).

Vectors spread the disease, transmitting it from plant to plant and field to field. The most common vectors are maize thrips, rootworms, and leaf beetles.

Barren tassels caused by MLND. Image, CABI

Recognising the problem

The disease causes a variety of symptoms in maize depending upon genotype, age of infection, and environmental conditions. Symptoms include dying leaves, leading to premature plant death, failure to tassel and sterility in male plants, malformed or no ears and rotting cobs.

MLND Datasheet on the Plantwise Knowledge Bank

Plantwise Knowledge Bank

Find information on pests and diseases of maize on the Plantwise Knowledge Bank.

The Plantwise Knowledge Bank is a free online resource that gathers plant health information from across the world. Over 15,000 pieces of content, which include, pest management decision guide’s (PMDG), factsheets for farmers (PFFF), species pages, photosheets, manuals and video factsheets in over 100 languages.

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