PlantwisePlus Blog

Wheat is a cereal grain, a staple food in many areas of the globe. It is primarily used to produce flour, which can be used to create other foodstuffs, including bread and pasta. Additionally, wheat and its by products are used to feed livestock.  

China is the world’s largest wheat producer, producing hundreds of millions of tonnes annually, followed by India and Russia. Each year, pests and diseases cause billions of dollars in losses.  

Common wheat pests 

Aphids 

Aphids are sap-sucking insects that can weaken wheat plants, causing reductions in yield and grain quality. If an infestation occurs, it can lead to the production of honeydew, which encourages the growth of mould and attracts other pests.  

Aphids can be identified by their small size (1.3-3.6mm in length) and green-yellow or reddish-brown colouring. They can usually be found on leaves, stems, or heads of the wheat plant.   

 Cereal leaf beetle 

The cereal leaf beetle is a significant pest of wheat. Larvae and adults feed on leaves, removing chlorophyll, which causes a windowpane or frosted appearance. It is native to Europe and Asia and has spread across the US.  

Adult cereal leaf beetles have a blue-black metallic head and wing covers, and a red-orange thorax and legs, they are around 5mm in length. Larvae look like slugs with yellow-brown slimy bodies.  

Wheat thrips 

These small insects are a significant threat to wheat crops in Europe and Asia. They feed on the sap of wheat plants, causing damage to the leaves and the development of the grains.  

Thrips are slim insects, between 1.5-2mm long, with fringed wings. Adults are usually dark brown or black, while the nymphs are yellowish and don’t have wings.  

Hessian fly  

The Hessian fly is a midge that affects cereal crops in America, Africa, Europe, China and New Zealand. The larvae damage the plant by feeding on its juices, resulting in stunted growth, stiffened leaves, and the plant falling over.  

Larvae start red then become white with a green stripe. They are flattened, lack a visible head capsule, and reach about 4.5mm long. Adults resemble small mosquitoes at about 3mm long and brown or black in colour.  

Flour mite 

These pests infest stored food products, including flour and grains. They contaminate and spoil food, can cause allergic reactions if inhaled or ingested, and can damage seeds. Flour mites thrive in temperate humid conditions.  

They appear as small white or pale brown oval-shaped mites, about 0.5mm in length making them difficult to see without magnification.  

Common diseases of wheat 

Rusts 

Wheat rusts are a group of fungal diseases that impact wheat production worldwide. The primary types are stem rust, leaf rust, and stripe rust, which are caused by fungi. They attack the wheat plant, disrupting its ability to photosynthesize, utilise nutrients, and produce grains properly.  

Stem rust appears as red-brown pustules on stems, leaves, and other plant parts. Leaf rust is identified by red-orange pustules on the underside of leaves, leaf sheaths, and sometimes the plant head. Stripe rust displays as yellow-orange pustules arranged in stripes across the leaves, leaf sheaths, and sometimes the awns.  

Fusarium head blight 

This fungal disease is destructive to wheat crops and other cereals. It causes plant extensive plant damage and can produce mycotoxins which are harmful to humans and animals.  

It can be identified by bleached or prematurely ripened heads, shrivelled kernels, and infected florets that can appear dark and oily. Over time, infected kernels can become covered in pink or orange fungal spores.  

Wheat blast 

Wheat blast is a fungal disease caused by a strain of the fungus Magnaporthe oryzae that also causes rice blast, leading to bleached heads and shrivelled or missing grains. It thrives in warm, humid conditions and can spread rapidly through infected seed and airborne spores. 

Symptoms include premature bleaching of heads, often with a sharp boundary between healthy and diseased tissue. Severe outbreaks can lead to total yield loss, particularly in areas with persistent moisture during flowering. 

Bacterial leaf streak 

Bacterial leaf streak, also known as black chaff, affects wheat and barley crops. It thrives in areas with high humidity or where sprinkler irrigation is used. It can spread through wind, rain, and contact, survive in crop residue, or be seed-borne.  

It can be identified through water-soaked lesions on leaves that turn into tan-brown streaks. It can also cause dark lesions on glumes and awns, which is what is referred to as black chaff.  

Wheat streak mosaic 

Wheat streak mosaic is a viral disease that is transmitted by the wheat curl mite, leading to stunted growth, shrivelled seeds, and yield reduction.  

It appears as yellow mosaic patterns on leaves, and in severe cases, the entire plant can turn yellow and dry. If wheat curl mites are feeding on the plant, it can cause the leaves to curl upwards and inwards.  

Moving forwards 

Once you have identified the problem with your wheat crops, you can use the CABI BioProtection Portal to determine if there are biocontrol or biopesticide products you can use in your country.  

You can also find management, prevention and control advice for wheat pests and diseases in your region on the PlantwisePlus Knowledge Bank. Simply search for a pest or crop and then filter the results by country.