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Wednesday, January 22, 2014 - 9:13am

Ever Wonder about Shredded Lawns?

While walking my dog, I noticed many shredded tracts of lawn. I decided to find out what was going on.

Meet the Beetles

Although the lawn “rototillers” are crows during the day and raccoons and skunks at night, the reason they are shredding your lawn is because they are after grubs—beetle grubs. European Chafer beetles (Rhizotrogus majalis) were introduced to North America from Europe back in the 1940s, but were only noticed in the Lower Mainland, specifically New Westminster, in 2001 and have been spreading ever since.

Laying the Ground Work

A chafer beetle spends most of its life as a larva underground, chewing on the roots of grass and other plants. Adults emerge in June, looking like small tanned June bugs, about 13mm long. They fly off to nearby deciduous trees to mate. Once they’ve done their business, each female lays up to 50 eggs in places where the grass is short, but otherwise neglected. By July, the adult beetles will have breathed their last breath.

Beating the Spread

It doesn’t take long before the eggs hatch. The young larvae are quite vulnerable to pesticides (though these are banned in many areas) and nematodes, until early August. Nematodes are tiny worms that occur everywhere. The type used to attack chafer beetles is called Heterorhabditis bacteriophora, which carries a kind of bacteria that eats insects from the inside out. If you are calling in this ghoulish cavalry, do so on a cloudy day, because they are sensitive to strong UV light.

Underground Movement

If you fail to quell your beetle hordes, the brown-headed, C-shaped larvae will continue to devour your plant roots, grow, moult and become more resistant to pesticides or nematodes. They keep feeding through the fall and reach their third and final instar during this time. They enjoy the cool, moist conditions that Vancouver has to offer. They tend to stay within 5cm of the surface, but can burrow deeper if it gets too cold, during the winter. Those that survive, become pupae in April, before becoming adults and continuing the cycle.

Grub Grub

The uninvited landscaping occurs during the fall and winter when the beetle-baby buffet is the beefiest. In case you'd like to join the crows and raccoons, perhaps first you should try some edible insect recipes.

Please share your shredded lawn strategies… or your edible insect recipes.

Want to delve deeper into the dirt and learn more about larvae? Drop by Search: Sara Stern gallery at TELUS World of Science and check out our mealworms!


Great concise article. I

Great concise article. I particularly like the cartoon at the top. I would, however say that the idea that the chafer beetles will only target neglected or shirt cut lawns is not consistent with what I have noticed. In fact, as a landscaper in Vancouver, I, along with my staff have recently launched a project to better understand the infestations in Vancouver. We are surveying the entire west side of Vancouver on foot and uploading the information to a map on our website for all to see. While it is true that many of the lawns that are torn up are neglected, we're also seeing a high number of pristine lawns that are laid to waste. As part of our project of documenting the areas of damage we are taking pictures, which we have then uploaded to the site. If you're interested in checking it out, feel free to visit the page. It is I should say that since we're a small company, and with all the time it's taken to do the project, it's not too polished yet.

Good luck with your project,

Good luck with your project, though I suppose good luck would be for the beetles to go away, but that does not look likely anytime soon.

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