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.

Crow damage

Crow damage

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.

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Crow damage

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.

Crows doing the damage.

Crows doing the damage.

More crows, more damage.

More crows, more damage.

 

Damage control

Damage control

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.

Racoon damage

Racoon damage–just a little.

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Same site, different angle.

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.

Lots and LOTS of racoon damage.

Lots and LOTS of racoon damage.

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. (EdThis 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 nematodesThese 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.

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A Primer On Soil Characteristics–Part 1

What’s your soil like?

Here are some of the possibilities:

Clay-ish: rich in nutrients, but very fine particles, so it clumps together so much that there’s no air spaces between particles. Doesn’t drain very well.

Sandy-ish: almost no nutrients, but very large particles, so drains very well. So well in fact it’s hard to keep plants hydrated.

Loamy-ish: this is your preferred quality, a combination of both clay and sand, so enough fine particles to hold onto water, and enough course particles to let it go.

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Notice the happy little worm in the middle of the pic enjoying the combination of loam and organic matter.

(All pictures are enlargeable by clicking on them.)

I’ve posted two short videos here to demonstrate nice loamy soil that sticks together weakly, and slightly too sandy soil that I bought as garden soil amendment.

Then there’s organic matter.

Organic matter bulks up soil making it “fluffy”. It is also what attracts earthworms and microorganisms, both of which do the real work of making soil healthy. Earthworms eat small portions of food and plant material, leaving behind “castings”–earthworm poo, aka “black gold” (not to be confused with “black gold–Texas Tea”). And bacteria and fungi are able to take molecules of nitrogen that are unavailable to plants and convert it to ammonium and nitrate that is available to plants.

Optimal soil is loamy and rich in organic matter. But really, we have what we have, and trying to change it can be an exercise in major frustration!

Wendy tells me she has clay soil.

Her backyard is flat, at the bottom of a hill, and in the winter the turf is VERY soggy. In the summer it’s so dry it’s like straw; she figures that because there isn’t enough depth of topsoil on top of the clay so it’s difficult for the grass to put down deep roots.

Really sounds like she’s got it right. Unless you’ve got at least 6″ of topsoil, preferably 8″ of topsoil, grass will not do well. There just isn’t enough depth for a reservoir of moisture and nutrients deeper than the roots, so they don’t reach downward. And if underneath that not-quite-deep-enough layer of topsoil is predominately clay, the clay creates a barrier underneath the layer of topsoil allowing a pool of water to collect when it’s wet. Roots of plants that aren’t really “bog-tolerant” will either rot, or just stay shallow. When the rains stop the pool of water eventually dries out, but the grass roots are still petty shallow and suffer from the relative drought. Even if you water the lawn regularly, there’s still that clay barrier just a few inches away preventing proper drainage.

Wendy thought she would like to  dig it all out, put a better layer of topsoil, and seed a new lawn.

What do you think? What would you advise Wendy to do?

For those who are interested, here’s an excellent short article on managing turf on clay soils.

There seems to be no one solution to improving the site. If you scrape and replace, you’ve still got the layer of clay underneath, and sooner or later end up with the same results. If you regularly add layers of organic matter on top, eventually the worms will do a great job of incorporating the OM with the clay without the damage that rototilling would do. Do you want to work on this project for 5 years or so? (I would.) If you already have large shrubs or trees, they have adapted to the current level of the ground, and their superficial roots would surely not appreciate several inches of material on their heads, effectively suffocating them. So if you do choose the “top dressing” option, keep those layers less than about 2-3″.

Now here’s a couple other options, and both involve abandoning any attempt to have a grassy lawn:

1. Substitute your grass turf with another lawn alternative.

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Thanks to A Small Green Space for her picture of a clover lawn.

Dutch White Clover will grow from seed on your clay patch, and if you already have grass “growing” there, the clover will happily coexist. If the site is bare, sow a lot of clover.

Sedges are another option, such as Carex “Hime Kawasuga” or C. pennsylvanica, short growing, underground spreading, infrequently mow-able clumping grasses.

I’ll do another post exclusively on lawn alternatives, so stay tuned…

2. Raised beds. Instead of trying to manage the whole yard, build several raised beds with pathways in between. These can be your typical 2×8″ boards filled with compost and soil, or something a lot more attractive and creative-looking like dry-stack stones in less rectangular shapes.

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Dry-stack bricks, not dry-stack rocks, but still very cool.

This has been an overly long post, so I’ll stop here and save the rest for a future post.

Do you have soil that is less than Ideal? In fact, how do I even know if it is less than ideal, or if it’s my less-than-optimal technique that’s responsible for under-performing plants?

Leave a comment, share this to your favourite social network site, ask questions. You don’t need to suffer with a garden space that doesn’t meet your needs. Let’s get things working better!