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.
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.
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.