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Wheat: Pests, Diseases and Disorders

Wheat, an agricultural commodity that is part of almost everyone’s out of the 7.8 billion people in this planet diet.  Was also one of the crops responsible for the establishment of humanity as a productive society throughout plan domestication.

During the great drought in the Middle East, a historical period in which the human being had no choice but to cultivate his own food, they began the process of bringing the agricultural resources to themselves (water, seeds, etc.), breaking the standard behavior of feeding only from what was possible to find naturally in that area.

With this cultivation, the domestication of plants by man began unconsciously. After a harvest of wheat – main crop at the time and in the region- the larger, more vigorous and better flavored seeds were selected to be planted in the next season, and thus, the selection and improvement of the species began, allowing for the first time in history, that the human being had some control of nature, and not just live with it, starting the the agriculture we have today.

Nowadays, we have genetically improved and very productive wheat varieties and our goal is to ensure we explore all of its potential. For that, it is essential to know and control some major causes of stress for this crop, them being infesting weeds, pests and diseases.

Different types of wheat flour. Picture by: CHBAGRO

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The three main wheat crop weeds are Ryegrass (Lolium multiflorum), Radish (Raphanus raphanistrum and R. sativus) and Sourgrass (Digitaria insularis). In general, to avoid the appearance of these weed problems during cultivation, it is important to invest in pre-sowing management.

More specifically, to understand the management of each species, it is important to know about its behavior. The Ryegrass (Lolium multiflorum) is a weed of great importance for wheat, because it is used as a cover or forage crop, it was disseminated in several areas. The reproduction of this plant is via seeds. It can reduce the grain yield of the crop by 62%. Glyphosate+graminicide is used for the management, it is recommended to be done before sowing the wheat. Radish (Raphanus raphanistrum and R. sativus), are annual erect plants, that also reproduce by seeds. To manage it in wheat field it, the recommendation is to use glyphosate, 2,4-D, metribuzin and metsulfuron pre-planting.

Finally, Sourgrass (Digitaria insularis) is a perennial cycle, herbaceous, erect, clumping plant that produces rhizomes. The predominant control is herbicide application in the initial stages of development, because if the production of rhizomes happens its ability to regrowth after an herbicide injury is very high.


We can divide the major wheat pests in three groups: aphids, defoliating caterpillars and storage pests.

The main aphids that attack wheat are: The Bird Cherry-oat Aphid (Rhopalosiphum padi), Rose-grain Aphid (Metopolophium dirhodum), Wheat Cob Aphid (Sitobion avenae), and the English Grain Aphid (Schizaphis graminum). Aphids cause direct damage by sap suction, reducing the germination potential of seeds, the number of grains per ear, size and weight of grains. They can also be vectors of diseases. For its control, IPM is recommended, made with parasitoids and predators. Pyrethroids and neonicotinoids products are used for chemical control.

Defoliating caterpillars are also critical pests, as they attack every stage, from the seedlings to the spikes of the plant and can cause significant damage. The Ear-cutting Caterpillar (Pseudaletia adultera), Wheat Armyworm (Pseudaletia sequax) and the Fall Armyworm (Spodoptera frugiperda) are all from the Noctuidae family. It is ideal to monitor the crop through weekly samplings. Management decisions should be made while the caterpillars are still small. Biological control, both natural and applied, will effectively reduce the defoliating caterpillars of the crop. Insecticides are recommended if necessary.

Fall Armyworm on wheat. Picture by

As for stored wheat, some relevant pests are The Maize Weevil (Sitophilus zeamais), Rice Weevil (Sitophilus oryzae) and the Lesser Grain Borer (Rhyzopertha dominica). Its control can be done by purging phosphine-based products.


In closing, the most common wheat diseases are the Leaf Rust, Powdery Mildew and th Yellow Leaf Spot. Leaf rust caused by Puccinia triticina is the most common disease for crop, leading up to 50% of productivity losses in. It can manifest itself during all crop cycle, through small rounded orange points at the top of the leaves. It can be eradicated through genetic control, crop rotation, elimination of voluntary plants and chemical control.

Powdery mildew (Blumeria graminis) might cause up to 60% of crop loss. The wheat leaves start showing powder like white spots, following by tissue death, vigor lost, and reduction of the number of ears and weight of the grains. The control for this disease is by using resistant cultivars and spraying it with fungicides.

The Yellow Leaf Spot is found in places that practice no-tillage with monoculture. It can cause losses of up to 50% in wheat. Its agent is the fungus Drechlera tritici-repentis, which causes symptoms such as small chlorotic spots that evolve and expand to straw-colored spots, surrounded with a yellow halo. To control it is necessary to treat seeds with fungicides, crop rotation, and the elimination of voluntary plants.

Interested in knowing more about this crop? Keep reading the articles we post weekly and have a look at the forums on wheat at Knowledge Hub!


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