Potato, Irish-White grub


Pest description and crop damage The term white grub is used for the larvae of any number of species of beetles in the family Scarabaeidae. Some of these are small beetles with larvae less than 0.5 inch long, while other species can be large with larvae well over 1 inch. White grubs have a pale body and brown head; they are often found curled into a 'C' shape. These beetles live in the soil and feed on roots and sometimes potato tubers, causing shallow, wide depressions in tubers. They rarely cause significant damage in potatoes in the PNW, most often being found in the spring as soil is prepared for potatoes and other crops or in soils with high organic matter.

Biology and life history Little is known about the biology of white grubs that infest PNW potato fields. Eggs are deposited in the ground and hatch as larvae that remain under the ground. They are rarely a problem in the PNW.

Management-chemical control: HOME USE

  • azadirachtin (neem oil)-Some formulations are OMRI-listed.
  • carbaryl
  • pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
  • spinosad (as a mix with insecticidal soap)-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

A few bifenthrin products applied in-furrow are labeled for control of white grubs.