Grubs in the Lawn

The grub is the larvae stage of a variety of beetles. Japanese Beetle, European Chafer and June bug are the most common three. European Chafer is the worst one for destroying lawns in our area.

Damage and I.D.

Grubs feed on grass roots causing your lawn to die. The key symptom of grub invasion is irregular dead patches which will lift up easily if tugged on

These patches have had the roots severed and there is nothing to anchor the sod in place. The lawn may also have patches that have been burrowed in or been up-turned by moles, skunks or raccoons feeding on grubs. The highest concentration of grubs will be found in dead turf bordering green areas. The grub is “C” shaped with a brown head, white body and six legs on its upper half.

Grubs were first imported from the Orient in their adult stage and first discovered in North America in New York.

Life cycle

The grub’s life cycle is very simple. The grub feeds on grass roots from mid-March to mid-May, and then develops into its pupal form. The adult beetle then emerges in mid-June, mates over a two week span and retreats back into soil to lay its eggs. The grubs hatch and begin to feed in late July to August. The grubs will burrow below the frost line in the fall and stop feeding but if there is a thaw, they will resume feeding at any time, even during the winter. The grubs will continue to feed in the spring, constantly growing larger.

Control

The fall (mid-August to September) is actually the best time to apply chemical control as the larvae have just hatched and can be killed quickly due to their small size. A certain percentage of chemical must be ingested in relation to body mass, therefore, the smaller the grub the less the amount needed to kill it. They will not die with their first taste. It can take up to two or three weeks. If you don’t notice the problem in fall then you must recognize the problem and apply in the spring. If you’re going to apply in the spring, do so around mid-March to mid-April as larvae are feeding ravenously.

Certain conditions can cause unsuccessful control of the grub. These conditions are as follows. Excessive thatch build-up will absorb and hold the chemical rather than allow entry into the grub zone. Hot and dry conditions, in late July or early August prevent successful mortality rate also because the grubs will move to cooler soil below and will not be feeding. It is necessary to soak your lawn previous to application, as this will allow the chemical to be dispersed throughout the soil more easily. Watering in after application is necessary to the success because the chemical will remain on grass blades, therefore, the mortality rate may only be approximately 50 per cent of what it should have been.

If you are spraying in the fall, a spring treatment may be necessary, as all of the grubs may not have been killed the year before.

Cultural Control

When a lawn is well maintained, well watered and well fertilized, there may be grub problems but because the lawn is so vigorous, it will grow more roots as they are destroyed. You may not even detect a problem and if you do, the damage will not be as severe.

Grubs

 

 

 

 

 

 

 

 

 

 

 

 

 

This life cycle calendar may be affected by your geographic location and by seasonal fluctuations in weather.

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