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| White grubs | |
| | By: John Degroot | | April 20 2003 |
Bare patches in the lawn? It’s quite likely you have a problem with white grubs or June beetles.
The unusually warm spring of 1998 has brought about an early start for growth of grass. Lawns are greening up much sooner than normal. The other unusual thing we are finding in many lawns are large, irregularly shaped dead patches. Roll the dead sod back and you may uncover a family of ugly, juicy, gray grubs.
White grubs are the larval stage of the common June beetle. There are several varieties of grubs, randomly scattered throughout the northeastern portions of Canada and USA. Sarnia has never been a territory favored by grubs. Go to London, and the grub problem is rampant.
Grubs have an interesting life history. Adult beetles lay eggs in turf in late spring. The eggs hatch and the new tiny grubs begin feeding on grass roots. Damage at this stage is minimal, because the grubs are small and eat very little. By the end of the summer, damage becomes more apparent, because the grubs get hungrier. In the first winter the grubs find a home deep in the soil. In spring they come to the surface, and immediately resume eating. All summer long they feed on grass roots. In winter they go back to their homes deep in the soil. After spending their second season in the soil, they resume eating in spring and the larvae transforms into an adult beetle. The adult doesn’t enter the big world, but remains in the soil for another winter. The following spring, when the critter is three years old, the adult beetle lays eggs in order to begin another cycle.
Grubs are not easily controlled. Sprays containing diazinon or chlorpyrifos provide very effective control, provided the pesticide is sprayed on young larvae. But the two and three year old grubs are more difficult to eliminate. The best time of the year to apply spray is late spring or early summer, right after the new eggs have hatched.
If your lawn at this time shows the effects of grubs, I would first dig a small patch and hunt for the culprits. If there are only two or three grubs per square foot of soil, I would not bother spraying. For dead patches of grass, I would recommend applying a thin layer of new topsoil, or peat-soil mix, and sowing new grass seed to green up the bare patches.
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