White grubs in the genus Phyllophaga are also known as "perennial"
white grubs or "true" white grubs. Several common species occur
in Illinois. Adults are the large May and June beetles that range in length
from to 1 inch and vary in color from tan to dark brown.
White grub adult and larva.
Adults of common species range from 1/2 to
1 inch (12 - 25 mm) in length;
C-shaped larva may exceed 1 inch in length.
Females deposit eggs in soil during late spring or early summer; they
especially prefer grass sod near wooded areas for egg-laying. As a consequence,
damage caused by larvae is greatest in crops grown on sites that were
grass-covered the previous season. Newly-hatched larvae feed on crop roots
throughout the summer, then burrow deep in the soil to overwinter. The
following year they again migrate to the root zone to feed. These larger
larvae cause much greater damage than they did the year before. After
overwintering again well below the soil surface, white grubs pupate early
in the following summer, and adults emerge from pupal cells in the spring
three years after the cycle began.
Because very few strawberry plantings are now placed on ground that was
used for sod, pasture, or grass set-aside the previous year, white grubs
are not common in Illinois strawberries. For a list of insecticides that
might be used for grub control in strawberries, see the up-to-date edition
of the Illinois Commercial Small Fruit and Grape Spray Guide.
Banding insecticides over the row reduces the amount and cost of insecticide