Grubs

By: John Degroot

April 26 2008

            Grubs are doing a number on Lambton’s lawns this spring and the symptoms are not pretty.  Irregularly shaped patches of dead grass appear sporadically throughout the lawn.  Size of the patches range from just a few inches up to several feet in diameter.  In many cases, grubs cause damage so severe that the dead grass can be rolled up like sod. Where grubs are plentiful, raccoons, skunk and crows dig unsightly holes in search for the tasty treats.

            Grubs come in several sizes and types.  European Chafer is the worst one for our area. 

            To control grubs effectively, it is helpful to know the grub’s life cycle.  Adult beetles lay eggs in turf in late spring.  The eggs hatch within a few short weeks and the tiny new grubs begin feeding on grass roots.  Damage at this stage is minimal because the grubs are small.  By the end of summer and fall damage becomes more evident because the grubs are bigger and hungrier.  When winter arrives, the grubs find a home deep in the soil.  In spring they come to the surface and immediately resume eating.  In early May the grubs quit eating and transform into the pupae stage.  A few weeks later the pupae transforms into an adult beetle.  The beetle wastes little time and lays eggs in the soil, usually in early to mid June.  The eggs hatch and begin to feed in early July through summer. By fall the grubs begin digging themselves deeper into the soil to prepare for winter.

            The most effective time to control grubs is in summer, just after the eggs have hatched.  By late fall and early spring control measures are rarely effective because grubs are mature. 

            The best control for grubs is preventative.  Grubs rarely damage a healthy lawn that is well fertilized and watered when necessary. 

            If control measures are warranted, you can tackle the problem in one of three ways.  For chemical control apply Sevin insecticide in mid summer.  Alternatively you can hire a lawn care company to apply Merit, an insecticide that can only be applied by licensed applicators.  The friendliest method of controlling grubs is with the use of nematodes which are microscopic worms that search out and kill grubs. 

            Since nematodes are living organisms, it is important to apply them carefully to maximize results.  Apply nematodes in July through early September.  Water the lawn prior to application because nematodes have difficulty traveling in dry soil.  Keep the lawn moist for 2 or 3 days after application.  For best results apply nematodes in on a cloudy day or in the evening when the sun is down. 

            To repair a lawn that has been damaged by grubs or other winter damage, rake up the debris and make a level surface.  Add a thin layer of topsoil, triple mix or top dresser mix.  Choose the Canada #1 grass seed mix suited for your lawn and sow the seed at the rate of one pound over 250 square feet.  Adding turf starter fertilizer is a smart move to give the sprouting seeds an extra boost.  If spring weather is dry, water frequently.

            Alternatively, for a quick catch of lawn seed, apply the following mixture known as fat grass: 5.5 cubic ft peat moss, 3 cubic ft bag vermiculite, one kg of lawn seed and 2 kg turf starter.  Mix the ingredients together and spread over 800 square feet.  Water lightly and frequently for a few weeks until the seed has sprouted.