At a glance: Wheat is a vital cereal crop worldwide, but it is susceptible to damage from various pests and diseases like aphids and wheat streak mosaic virus. Biological control methods, such as microbial species and plant extracts, can help control pest populations and protect crops.
Overview
- What pests affect wheat?
- Russian wheat aphid
- Bird cherry oat aphid
- English grain aphid
- Corn leaf aphid
- Wheat stem sawfly
- Cereal leaf beetle
- Wheat curl mite
- Hessian fly
- Brown wheat mite
- Blue oat mite
- Pale western cutworm
- Wheat head armyworm
- How do I manage wheat pests?
- Summary
- FAQ
Wheat is a vital crop and ranks as the world’s second most-produced cereal, following corn. The United States and India produce 50 and 110 million tonnes of wheat per year, respectively. However, wheat crops are threatened by a variety of diseases, insects, and other small pests that impact harvest and reduce quality. This article discusses the various pests that attack wheat crops and outlines methods for reducing their impact, including the use of biological control methods.
What pests affect wheat?
Wheat is vulnerable to a range of pests, including aphids, mites, moths, and fly species. Many of these pests damage wheat by feeding directly on leaves and grain. In some cases, pests act as carriers for viruses that cause leaf discolouration and reduced growth. About 8% of global wheat crops are lost each year due to pests and diseases.
Russian wheat aphid (Diuraphis noxia)
This pest causes significant damage to several cereal crops, including wheat, by feeding on plant fluids. Adult Russian wheat aphids are pale green with oval-shaped bodies and grow to about 2 mm long. Their saliva is toxic, and when they feed on leaf fluids, it causes the leaves to develop white streaks and curl at the tips.
Bird cherry-oat aphid (Rhopalosiphum padi)
This pest feeds on plant tissue by piercing the outer layer of leaves. Adults are oval-shaped, grow up to 2 mm long, and appear in shades of white-green to dark green. In addition to feeding, it causes significant damage to cereal plants by carrying a variety of plant viruses, including barley yellow dwarf virus, which causes leaves to turn yellow.
English grain aphid (Sitobion avenae)
This pest damages wheat crops by piercing leaves and feeding on plant tissue. They appear in a variety of colours, including yellow, green, orange, brown, and red. Adults measure around 3 mm long and can be found with and without wings. The winged form typically has a slightly longer body. This species of aphid also transmits the barley yellow dwarf virus.
Corn leaf aphid (Rhopalosiphum maidis)
This insect feeds on many crops, including wheat, by piercing leaves and sucking out plant fluids. Adults are around 2 mm long with bluish-green bodies and two dark stripes on their heads. Damage appears as leaf discolouration, and this pest can also carry the barley yellow dwarf virus.
Wheat stem sawfly (Cephus cinctus)
This pest causes damage to wheat crops by boring and feeding inside stems during its larval phase. Adult wheat stem sawflies are black with three white stripes on their body and grow up to 13 mm. Females lay about 50 eggs during their lifetime. The eggs are about 1 mm long and white. Larvae are white, S-shaped, with dark brown heads, and grow to 13 mm. Damage caused by this pest appears as fallen stems and reduced seed numbers.
Cereal leaf beetle (Oulema melanopus)
This beetle causes damage to wheat plants during its late larval phase. Adults grow to 5 mm with black wing covers and red-orange bodies and legs. Its eggs are about 1 mm long and white, but grow darker close to hatching. Larvae are yellow-orange and feed directly on the leaves, creating a skeletonised pattern and causing the leaf tips to turn white.
Wheat curl mite (Aceria tosichella)
The wheat curl mite is a tiny, tube-shaped pest that damages wheat crops by transmitting a variety of plant viruses. This pest has two pairs of legs and is nearly impossible to see without a 10X lens. Severe infestations can cause complete yield loss. The wheat curl mite transmits wheat streak mosaic, high plains wheat mosaic, and triticum mosaic viruses. Symptoms include leaf discolouration and curling.
Hessian fly (Mayetiola destructor)
This pest is a species of fly that feeds on wheat plant tissue during its larval phase. Adults are brown or black and about 3 mm long. Females lay orange oval-shaped eggs on host plants. Larvae are white with a green stripe down their backs. Larvae pierce plants with specialised mouthparts and feed on plant tissue. Damage can appear as fallen stems and stunted plant growth.
Brown wheat mite (Petrobia latens)
This mite species damages plants by feeding directly on plant tissue, particularly the tips of leaves. Adults are brown-black and about 0.5 mm long. Damage appears as a discoloured stippling pattern on leaves.
Blue oat mite (Penthaleus major)
This mite pest also damages wheat plants by feeding directly on leaf tissue. Adults are black with red-orange legs and grow to about 1 mm. Damage gives leaves a silvery appearance, which can spread across entire growing areas with severe infestations.
Pale western cutworm (Agrotis orthogonia)
This pest is a moth species that causes damage to wheat crops during its larval phase. Adults are light grey and have a wingspan of about 3.8 cm. Females lay eggs in soil in batches of around 40. Younger larvae are grey and gradually turn more green as they grow, reaching a final length of about 3.8 cm. They feed on stems underground but can also feed on leaves. Damage appears as fallen stems and wilted leaves, and entire growing areas can be destroyed in days.
Wheat head armyworm (Dargida diffusa)
This pest is a species of moth that damages wheat crops during its larval phase. Adults are brown-yellow with a brown stripe down each forewing and a wingspan of up to 36 mm. Larvae come in shades of green and white and feed on wheat heads, with damage appearing as hollowed out kernels.
How do I manage wheat pests?
Several methods are available for managing wheat crop pests. A combination of approaches using Integrated Pest Management (IPM) practices and biological control methods works well in many cases.
Monitoring
Keep a lookout for the symptoms described above. Common symptoms of pest damage to wheat crops include discoloured leaves, including pale leaf tips and stippled yellow patterns, fallen stalks, and stunted plant growth. High numbers of adult moths or flies in the area may indicate an infestation. The appearance of sooty mould or increased ant activity in the area may indicate an aphid problem.
Cultural control
Cultural control involves using specific farming or gardening practices to lower the risk of pest infestations. You can manage the spread of viruses by removing volunteer wheat and grassy weeds from the growing area, as these can act as reservoirs for wheat streak mosaic virus. Grazing animals in volunteer wheat fields can be a helpful way to achieve this. Sowing seeds in late autumn can help to protect crops from aphids, which fly between growing areas earlier in the season. Crop rotation can also be a beneficial approach to reducing pest numbers.
Biological control
There are numerous biological products that can be used to control wheat pests. Natural products are typically derived from plants and can be used in sprays to repel or kill pests. Azadirachtin is an extract from the seeds of the neem plant and can be used to help control hessian fly numbers. Microbials, like the fungus Beauveria bassiana, can combat a huge variety of pests in their larval stage, including pale western cutworm and aphids. Macrobials are larger animals, including insects that feed on and parasitise pests. Aphidius colemani is a parasitic wasp that helps control aphid numbers. Together, these approaches help provide a more sustainable approach to pest control while limiting the impact on non-target species.
Chemical pesticides
As a world leader in nature-based pest management knowledge implementation, CABI encourages IPM as the preferred, ecologically-based approach to producing healthy crops, which allows for chemical pesticide use only as needed, and when adhering to measures that limit the exposure of people and the environment to them (see FAO, International Code of Conduct on Pesticide Management).
Before considering the use of chemical pesticides, farmers should explore all available non-chemical control solutions, such as the ones listed above. For tailored pest management advice, visit the CABI BioProtection Portal, where you can enter your location and pest problem to explore customised solutions.
In case chemical pesticides are considered for use, farmers should look to select lower-risk chemical pesticides which, when used as part of an IPM strategy, help manage pest problems while minimising harmful effects on human health and the environment. Agricultural advisory service providers can provide information on lower-risk chemical pesticides that are locally available and are compatible within an IPM strategy. These experts can also advise on the required personal protective equipment.
Summary
Wheat is a major cereal crop in global agriculture, with the United States and India among the leading countries in wheat production. Pests and diseases cause significant damage to wheat crops, resulting in small grains and substantial yield losses. Careful monitoring, combined with cultural and biological methods, can help control wheat pests and diseases, thereby protecting wheat yields. Planting resistant wheat varieties can also be an effective strategy to reduce crop damage and support sustainable production.We have also prepared extensive guides on dealing with pests such as aphids and bean flies, and protecting specific crops, including maize and rice.
FAQ
What is the most common pest in wheat?
The most common pests affecting wheat crops vary by region. The hessian fly and different aphids are common in North America. Armyworms and aphids are common pests in India.
What kind of bugs get in wheat?
Wheat is affected by a variety of small animal pests, including aphids, moth species, beetles, and mites.
How to get rid of pests in wheat?
There are several ways to manage wheat pests, but the first step is correctly identifying the pest causing the problem. This allows you to choose a targeted biological solution with reduced environmental impact.
Are wheat weevils harmful?
Wheat weevils can feed on stored wheat grains, leading to loss of yield. They are not harmful to humans or pets if consumed.
