Understand life cycles is key to controlling
Tim Gibb, Insect Diagnostician, Department of Entomology, Purdue
Each spring we receive many calls about grubs
as people find them while planting gardens or ornamental beds. These
are often large and appear menacing however do not let their
appearance cause you to worry, panic or run out to buy an insecticide
to annihilate these sinister creatures. These grubs are not feeding
actively so will not cause serious damage and are not in the
stage where they are susceptible to pesticides.
It’s important to understand the lifecycle of white grubs
before considering control. The large larvae that occur in the
springtime are preparing to enter into a pupation stage, preparatory
to emerging as adult masked chafer and Japanese beetles. When
they emerge (in June and July) the adults will mate and lay eggs.
Eggs hatch from mid-July to early August. Newly hatched grubs are
the more serious threat because they feed very actively on roots
sometimes causing damage to turfgrass as they grow.
During the fall, when the temperatures cool, the large larvae
quit feeding and move down deeper into the soil to pass the winter.
As the weather warms again the following spring, the larvae generally
move back up to within 1 or 2 inches of the surface where the cycle
It is rare that grubs cause significant damage in gardens or flower
beds. Do not be tempted to over react to their presence there. In
turfgrass, especially where grabs have caused damage in the past,
wait to apply an insecticide until late July or early August to
control the feeding larvae. This will give you the best value in
grub control for your dollar.
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only for the state of Indiana