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White Grubs

White Grubs

What are they?

White grubs are the larvae of certain beetles, like June beetles, Japanese Beetles and European Chafers. Grubs are one of the hardest lawn pests to deal with.

Grubs are white or yellowish and have fleshy, wrinkled, C-shaped bodies with tan or brown heads and six spiny legs. They are quite small when they hatch, but when fully grown are from 2 to 4 cm (.75 to 1.5 inches), depending on the species.

The most common white grubs infesting turf in Canada are those of the European chafer and the Japanese beetle, which have been accidentally introduced into Canada. These have recently migrated further north and east, and is responsible for much of the lawn damage in recent years in eastern Ontario.

June beetle adults are shiny reddish brown, and up to 2.5 cm (1 inch) long. The adult European chafer is light brown or tan, and is about 1.3 cm (0.5 inches) long. The adult Japanese beetle is metallic green and bronze, and about 1 cm (less than 0.5 inches) long.

Should I be concerned?

Did you know?

It takes the June beetle three years to mature, while the European chafer and the Japanese beetle take only a year. On their way to maturity, there are times when they are most active and most damaging to a lawn. At one time, when we only had the June Beetle to worry about, the damage cycled every three years. Now that these new grubs are in town we have massive infestations every year.

Grubs feed on the roots of many plants but they like the fibrous roots of lawn grass best. As the roots are destroyed, turf will wilt and turn brown. Grubs also feed on potatoes and carrots in the garden. They cut the main stems or roots of plants below the soil surface, and tunnel into tubers and freshly rooted plants.

How do I know if I have a problem?

Affected areas will feel soft and spongy to walk on, and turf in these spots can be lifted up with ease. Carefully fold back the turf and note the number of grubs exposed. 4-5 grubs per square foot can damage to a non-irrigated lawn.

Damage is most severe in the spring and fall when the grubs are at their largest and heavily feeding. During the early summer the eggs are laid and larvae can be found in the soil a few weeks later. Extremely dry summers weaken the turf and newly hatched grubs. add even more pressure to the turf causing elevated damage.  Mature grubs can be found near the surface in late summer and early fall.

Often, skunks and other small mammals  will pull back the turf to feed on grubs at night and birds light crows and starlings tear up the turf during the day. The assault to your lawn comes from below by the grubs and from above by the animals digging – day and Night.  in the spring or fall.

This secondary damage to your lawn are signs of a grub infestation. If you have any of these natural predators digging at your grass, check for white grubs. Many people notice these indicators first.

Did you know?

White grubs do the most damage at these times:

June beetle grub:
  • Year 1 – August through September
  • Year 2 – April through September
  • Year 3 – April through May
European chafer grub:
  • Year 1 – August through November
  • Year 2 – April through late May
Japanese beetle grub:
  • Year 1 – September through November
  • Year 2 – April through late May

How can I get rid of grubs?

Lawn care

The best thing you can do is to make sure your lawn is healthy before any problems happen.Healthy, vigorously growing lawns can tolerate more grub feeding than stressed lawns, because damage to one grass root is made up for by others strong roots. Control excessive thatch by aerating compacted soil areas and to ensure proper drainage. Raise your summer mowing height to 6 to 8 cm (2.5 to 3 inches). Leave lawn clippings after mowing because their slow release of nitrogen encourages micro-organisms to break down the thatch. Use fertilizer with high potassium and enough nitrogen.

Nematodes are parasitic worms that kill grubs. They are very specific to which ones they feed on so be sure you are getting the ones that will control your type of grubs. The best time to apply them is mid August to mid September. After this point the grubs are too large and the soil becomes too cold for them to be effective. nematodes do not work very well in the spring due to the cold soil temperatures and the large size grubs are at that time of year.

If you notice grubs during the warm, dry periods of the growing season, water and fertilize your lawn to strengthen it and make up for the root feeding damage. Apply a top dressing of sand and manure and overseed with grass. Deep, infrequent watering encourages deep-rooted, drought-tolerant lawns. Water no more than once a week, and water until at least 2 cm (1 inch) of water collects in a container placed on your lawn or for about one hour.

Predators

Beneficial insects like ants prey on the eggs of June bugs. Certain parasitic wasps and flies also help keep June bug or Japanese beetle populations in check. Some of these are specific to a single insect, but others will control several pests in an area. Bird houses attract natural predators (like starlings and blackbirds) that feed on white grubs.

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Green Unlimited
3-2709 Stevenage Drive
Ottawa, ON
Canada
K1G 3N2

Phone: 613.744.7336
Website: http://www.greenunlimited.com
Email: info@greenunlimited.com