Help, My Lawn Has Been Thrashed!

CHAFER BEETLE DAMAGE

Female chafers lay 20-40 eggs over their lifespan. They are laid singly, 5–10 centimetres (2.0–3.9 in) deep in moist soil, and take 2 weeks to hatch. The grubs hatch by late July. In frost zones, the grubs feed until November, then move deeper into the soil. In frost-free areas, the larva will feed all winter. Vigorous feeding occurs from March through May. In early June, the grubs again move deeper, from 5–25 centimetres (2.0–9.8 in), to form earthen cells and pupate. The pre-pupal and pupal stages last 2–4 days and 2 weeks, respectively. By June, the new beetles begin emerging. (Wikipedia)

Thanks Wikipedia.

If you live in Metro Vancouver you have seen this, probably in your own neighbourhood, and possibly in your own lawn. This is European Chafer Beetle damage, caused not only from the beetle grubs, but even more from the predators that feed on the grubs.

The C-shaped really disgusting-looking grubs (how could anything called a “grub” be anything other than disgusting-looking?) started the damage by feeding on the roots of mostly turf. Some sources say they’ll feed on other vegetation roots if there’s a shortage of turf, but that doesn’t seem to be an issue yet, since we have lots of lawn. So you will seldom see this kind of damage in a lawn that is thick and green–it’ll have nice long roots preventing the animals and birds from pulling up the turf. You can see in the pictures that the undamaged areas still look pretty patchy. Of course, it is winter…

Then once the predators know the grubs are big enough to provide a tasty morsel, they start to dine–seems to be Fall through Spring. And since the grubs have already eaten away at the roots, the turf is now more like a carpet laid on the soil, so the crows, racoons and skunks don’t have to work very hard to get the turf out of their way.

 

Trying to keep the “carpet” pinned down will have limited success, since the critters can easily pick away in the spaces. Enlarge the above picture and you can see patchy areas that may have been damaged before the netting went down, or since.

This was what I found one morning in early December. I’ve had crummy turf, but no CB damage for the 7 years I’ve been here, but since I wasn’t going out of my way to make my lawn really healthy (I keep vacillating on replacing it with…something), an infestation was inevitable–I was disappointed but certainly not surprised. Why racoon damage instead of crow damage? Who knows–I guess because there are racoon families in some of our neighbourhood Douglas-firs.

THIS did surprise me though.

Between waking up (in the dark) last Monday morning (I like to look out the front window while I’m brushing my teeth–sometimes I’ll see skunks or racoons ambling by) and leaving the house (in the dark) 45 minutes later, the racoons had had breakfast.

I guess I should be grateful to the racoons, not only have they probably decimated my chafer beetle population, they’ve also made me stop procrastinating making a new design for my front yard. I’m checking out Houzz “lawn alternatives” page.

PREVENT DAMAGE:

I’d like to see your lawn protected from this damage in the first place. We’ve got the invasive beetle here in Metro Vancouver, so either you prevent a devastating infestation, or you clean up the mess. Hoping it won’t happen is ineffective management!

The following is taken straight from the City of Richmond “Chafer Beetle” site, a nice concise lawn management guide:

Minimize lawn damage caused by chafer grubs by keeping your turf healthy and thick with proper lawn care practices:

* Increase mowing height to 8-10 cm (3-4 in). Longer grass blades mean a longer root system that is more resilient to the larvae feeding. (Ed. It may also help prevent the female from laying here eggs in your lawn, since apparently she prefers shorter grass blades.)
* Fertilize regularly by top dressing twice a year with compost or by using organic, slow-release fertilizers. Leaving grass clippings on the lawn, rather than bagging and disposing of them (grasscyling), also naturally fertilizes your lawn with nutrients after each mow.
* Water your lawn deeply: 2 to 3 cm (½ to 1 inch) once a week to promote a lush lawn with deep roots that better resist insect damage and drought. Follow the water use restrictions in effect from June 1 to September 30.
* Overseed your lawn annually with a grass seed mix will contribute to maintain a dense, healthy, and weed-free lawn. (Ed. This can be done with the “top dressing” of compost.)
* Lime your lawn in fall and spring to counteract the soil’s natural acidity. Acidic soil prevents grass from taking up key nutrients necessary for its optimal growth and health.

If you’ve experienced the damage already, you can, like me, plan a new design that doesn’t include grass turf–or very little of it. If it’s Jan 6 and your turf looks like mine, there’s not much you can do until the weather warms up a bit. For now, you can clean up the mess and cover the bare soil with mulch, and in Feb or early March, if you’re hoping to keep lawn in this area, you can heavily grass-seed the area.

Besides the above maintenance regime, there’s a biological control, Heterorhabditis bacteriophora, or nematodes. These are a microscopic round worm that actually feeds on the the CB eggs before they turn into larvae. So it has only a short window of applicability–the latter half of July, after the eggs have been laid, and before they hatch into grubs. You can get nematodes at any nursery, and they’ll give you instruction on how to use them. They’re not cheap, and depending on your lawn maintenance you may need to repeat every year, so it may be another reason to consider removing your lawn.