The Roundup -

Watch Out For White Grubs


With the weather becoming nicer, homeowners are starting to work on their lawns and flower beds. With that being said, white grubs are starting to feed on the roots of your lawn as well. Detecting the presence of these insects might not happen until July when you see dead patches of lawn, which is easily pulled out of the ground. According to NDSU Extension Entomologist Janet Knodel, the action threshold is three to four larvae per square foot in lawns. To detect the amount of white grubs found, simply dig up a section and look for white C-shaped larva approximately 1 inch long.

White grubs have a three year life cycle, the first year adults emerge from their wintering sites, 6-18 inches in the soil and fly to willow and Poplar trees to feed and mate. After the female lays the eggs, 30-50 days later, they will hatch and the larvae will feed on grass roots and organic matter, then moving further down into the soil to hibernate for the winter.

The second year is the most damaging stage. They will feed all year long, laying no eggs. Once fall arrives they will move down into the soil to hibernate for the winter. The third year the insects are mature, they do limited feeding on grass roots The mature larvae will move down into the soil, go into a resting stage and are inactive, once spring comes again the life cycle will start over.

Systemic insecticides such as imidacloprid or halofenozide, provide effective control if applied approximately one month before the heaviest feeding times, soil applications should be made mid to late May. Neither of these will revive the dead lawn caused by the white grubs. Avoiding yard lights in your lawn or nearby will lower the amount of beetles that are attracted to those areas, helping to prevent egg laying.


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