Cereals: European Chafer (White Grub)

Excerpt from Agronomy Guide for Field Crops (Chapter 6)

Order OMAFRA Publication 811: Agronomy Guide for Field Crop

Table Of Contents

1. Description
2. Life History
3. Damage
4. Scouting Technique
5. Action Thresholds
6. Management Strategies
7. Updates on Cereals: European Chafer (White Grub)
8. Related links...

Description

European chafer larvae are white and C-shaped with an orange-brown head and dark posterior. This pest can be distinguished from other white grubs by its Y-shaped pattern of anal bristles known as "rasters" located on the underside of the last abdominal segment of the larva. The adult is a medium-sized, light brown, fawn-coloured, oval scarab beetle, closely resembling the native May or June beetle.

Plate 10. European chafer larvae are white with an orange-brown head and dark posterior. They are distinguished from other white grubs by the Y-pattern of the anal bristles (rasters).

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Life History

This pest overwinters as larvae or "grubs" in the soil below the frost line. In April to mid-May, these larvae migrate close to the soil surface and feed on plant roots. Larvae then pupate in mid-May to mid-June, and adult beetles emerge from the soil in early June to early July to mate. Adult chafers congregate in conspicuous mating flights and can be seen swarming at dusk. The beetles fly to tall objects along the horizon, usually trees or other landscape to mate. The adult females then locate cool, moist soil in nearby fields or lawns to lay their eggs in. Eggs hatch and newly hatched larvae begin feeding on roots in late July until the ground freezes. The grubs then migrate down, below the frost line, to overwinter. There is one generation per year.

Damage

Damage is mostly done by the larvae stage, however, adults may feed on plant leaves.
European chafers tend to feed earlier in the spring and longer in the fall than other white grub species.
Chafer grubs feed on the fibrous roots of grasses, forages, winter grains, corn, soybeans and lawns, 1^1/2-5 cm (1-2 in.) from the soil surface. Larvae feed on and prune roots, causing plants to become stunted and wilted. If the plants are larger and actively growing, damage, as in the case of soybeans, may not be apparent. Intense root feeding results in poor emergence and stunted plants.

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Scouting Technique

It is best to scout for chafers in the fall in standing soybean stubble. Scout for chafers on the sandier knolls of the field. Using a shovel, dig up approximately 1 ft of soil, about 3-4 in. deep, for five single soybean plants in each area sampled.

Action Thresholds

No thresholds are available at this time. Avoid planting winter cereals if chafer grubs are easily found.

Management Strategies

Avoid replanting with corn if chafer grub population is extreme. Cultural options include disturbing the soil by tillage or disking, which brings the grubs to the surface where they are exposed to the elements and natural enemies such as birds, skunks, racoons, etc.

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Updates on Cereals: European Chafer (White Grub)

• Field Crop Protection Guide - Publication 812
  • Cereals: European Chafer (White Grub)

Related links...

• Insects
• Cereals

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