Notes on Blueberry Insects
White grub complex

Identification

White grubs are C-shaped, with a tan or brown head capsule and six prominent, spiny legs. White grubs are the larval stage of beetles that include the June beetle, European chafer, rose chafer and Japanese beetle. The larvae feed on roots and can be pests in blueberry plantings, especially in light soil types. Symptoms of white grub feeding include stunted growth and a decline in plant vigour. Bushes are poorly rooted and can be easily pulled from the soil. Infested roots are often associated with mealy bugs and ants.

Japanese beetle and rose chafer adults also feed on blueberry foliage and fruit.

C-shaped white grub larvae

Japanese beetle adults

Period of activity

Adults lay eggs in grassy places. The eggs hatch into larvae or white grubs and feed on plant roots. Feeding by European chafer larvae and Japanese beetle takes place in late summer and again in the spring until adults emerge. June beetle larvae remain in the soil for three seasons, feeding on plant roots throughout each growing season.

Monitoring and thresholds

Do not establish new plantings for two years after sod or pasture crops. Keep grassy weeds away from the bushes to make the habitat less favourable for white grubs. Clean cultivation between rows may reduce the populations over time.

• Admire 240F was recently labelled for control of European chafer and Japanese beetle larvae in blueberries. It should be applied before eggs hatch but not within 14 days of harvest.
  
• Grass parking lots can serve as a large reservoir for the build-up of grubs. Treat these grass areas like turf or lawns but do not treat inside the planting. If 5 grubs/ft.2 are found, treat with an insecticide labelled for turf.
  
• There are no pesticides labelled to control rose chafer or Japanese beetle adults on blueberries. Insecticides for other insect pests may temporarily reduce their numbers.
  
• For more information on white grubs, see OMAFRA Factsheet, Grubs in Lawns, Order No. 97-023.
  

Management notes

• Do not establish new plantings for two years after sod or pasture crops. Keep grassy weeds away from the bushes to make the habitat less favourable for white grubs. Clean cultivation between rows may reduce the populations over time.
  
• Admire 240F was recently labelled for control of European chafer and Japanese beetle larvae in blueberries. It should be applied before eggs hatch but not within 14 days of harvest. See Table 8-9. Products Used on Blueberries, on page 152.
  
• Grass parking lots can serve as a large reservoir for the build-up of grubs. Treat these grass areas like turf or lawns but do not treat inside the planting. If 5 grubs/ft.2 are found, treat with an insecticide labelled for turf.
  
• There are no pesticides labelled to control rose chafer or Japanese beetle adults on blueberries. Insecticides for other insect pests may temporarily reduce their numbers.
  
• For more information on white grubs, see OMAFRA Factsheet, Grubs in Lawns, Order No. 97-023.
  
  

Learn more...

• Notes on Blueberry Diseases and Insects
• Insects and Pests of Field Crops: European Chafer (White Grub), Publication 811
• Grubs in Lawns, OMAFRA Factsheet 97-023
• OMAFRA Publication 360 Blueberry Calendar
• OMAFRA Publication 360 Fruit Production Recommendations
• OMAFRA Berry Crops Index page