Pests in Wheat, Barley & Oats

Saddle gall midge eggs on wheat Dewar crop protection 750x499

Saddle gall midge

About the Pest

The saddle gall midge is approx 5mm in length (females are larger) and red in colour. The females can lay up to 250 blood-red eggs on the upper and lower surfaces of the leaves of cereal and grass plants. Eggs hatch to reveal white or light orange larvae within 1-2 weeks. The larvae change to bright orange as they mature. The larvae feed on the stem sheath below the leaf which produces a characteristic saddle-shaped contour on the stem. Larvae reach maturity in July before dropping from the plant and lying dormant in the soil until the following spring.

Timing of adult midge emergence varies according to temperature and soil moisture, however, the larvae usually pupate from April. Emergence can, therefore, begin at the end of April in warm conditions and usually continues for approximately 10 weeks.

Saddle gall midge eggs on wheat (© Dewar Crop Protection)

The larvae can remain in the soil for several years, allowing an unhealthy population to build up and increase damage to crops. Late sown winter crops and spring crops of wheat and barley are most at risk when the larval feeding coincides with stem extension (GS31–39) crops are at the highest risk.

Sowing winter crops early can reduce the potential damage from the pest. Introducing a non-cereal break crop may provide some benefit, and encouraging a biologically healthy soil can encourage the soil biodiversity required to enhance Integrated Pest Management.

Cereal leaf beetle

The slimy grubs of cereal leaf beetle have been reported on crops. The grub stage eats strips out of leaves.

About the Pest

Adult beetles are 5mm long, with a black head, red thorax and shining blue/green metallic abdomen. The grubs are small and slug-like with a humped back, but have 3 sets of legs near the head.

Both the grubs and the adult beetles feed on the veins on the upper leaves of the cereal or grass plant, stripping out the chlorophyll and leaving a 'window' like transparent patch along the leaf. They are a common pest amongst cereals in general, particularly oats.

Overwintering adults appear any time from April and from mid summer lay orange coloured eggs on the upper leaves of host plants. Ten days later, the larvae emerge and begin feasting on the plant. After 3 weeks the larvae move to the soil to pupate and return to feast on host plants before moving during autumn to a site to overwinter.

A rich natural biodiversity within the cropping area should provide sufficient predators to manage the pests and prevent significant damage. If the flag leaves are showing signs of being badly stripped, an insecticide can be employed to prevent significant damage.

We have more information about Integrated Pest Management within our Biodiversity section of the web site.

Pic: Adas

Wheat bulb fly (Wheat)

Wheat bulb fly is a serious pest of wheat crops. The larvae feed on the central shoot of wheat, causing it to turn yellow then die. This symptom is known as a "deadheart" symptom. The female lays eggs during the summer months (July - September), and bare soil is the preferred site. Consequently, wheat sown after potatoes, peas, oilseed rape, field vegetables, fallow and set-aside are, particularly at risk.

About the Pest

The eggs begin to hatch in January/February and may continue through to mid-March. Severe damage is only caused to crops that have yet to form multiple tillers. As a general rule, crops sown before mid-October will be less affected by this pest. Later sown crops which may only have a single shoot at egg hatch, may be completely killed by the grub feeding in the single shoot.

Treatment thresholds for wheat bulb fly are based on egg counts in soil from fields planned for winter wheat or spring barley. The threshold for late sown wheat crops is 1.25 million eggs/hectare. Winter barley is usually sown early enough to withstand any damage.

Orange blossom midge (Wheat)

This pest can cause a great deal of damage to the developing wheat grain during ear emergence. It is present in Scotland but we have seldom seen it at levels that will damage Scottish winter wheat crops. The orange midges usually appear in second or third winter wheat crops once the mean daily air temperatures exceed 15ºC and conditions are still and dry.

About the Pest

This pest can cause a great deal of damage to the developing grain during ear emergence. It is present in Scotland but we have seldom seen it at levels that will damage Scottish winter wheat crops. The orange midges usually appear in second or third winter wheat crops once the mean daily air temperatures exceed 15ºC and conditions are still and dry. The small orange midges lay eggs on the ears from early ear emergence onwards (GS51-59), and after hatching the larvae feed on the developing grain, resulting in poor yield and reduced quality of grain. The best time to look for midges is on warm, still evenings by standing in the crop and looking for the midges resting or flying around the ears of the crop.

For feed wheat crops, 1 or more midges per 3 ears are enough to justify an insecticide treatment. For milling wheat crops, 1 or more midges per 6 ears is enough to justify an insecticide treatment. There are also pheromone traps available to monitor for the presence of midges within crops.

Pests in Wheat, Barley & Oats

Saddle gall midge

Cereal leaf beetle

Wheat bulb fly (Wheat)

Orange blossom midge (Wheat)

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Pests in Wheat, Barley & Oats

Saddle gall midge

Cereal leaf beetle

Wheat bulb fly (Wheat)

Orange blossom midge (Wheat)

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Integrated Land Management Plans

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