What is Structural Soil Why is it good for Trees?
Why is structural soil effective?
Structural soil is a type of soil mixed with a specific type of gap-upgraded rock (typically 75mm clear). This is a very important part of the specification; the reason structural soil works well is that the gaps created by the rock are then filled with soil, enabling penetration by tree roots. This penetration allows the tree access to a larger space underground, and has the double function of preventing the tree roots from lifting up the hard surface, i.e. the sidewalk that is on top.
How does the structural soil get tested?
The testing of structural soil is essentially a three-part process. The soil must be tested separately. The rock must be tested and sourced with a specific sieve size attached to it to determine that it is in fact a clear rock and not a minus rock. With a minus rock all of which would be filled and therefore the soil would be effective.
There is also a stabilizing compound that is used with structural support to help the soil adhere to the rock. The specifications for this material would come directly from the stabilizer supplier; there are more than one of these.
Who can make structural soil?
Like any engineered soil, structured soil is a technical process which is best done by people who understand all the specific components and have all the components readily available with testing and prior knowledge. Making good structural soil to specification is an extremely important endeavour. Structural swell that is not up to specification is a very difficult situation to remediate once it’s already in the ground.
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Life Cycle of the European Chafer Beetle
The European chafer beetle originated in continental Europe but is now an invasive species found in temperate climates in North America, where they are often called June bugs. The large grubs of the chafer feed on the roots of both wild and cultivated cool-latitude grasses, which has made them a critter-non-grata on North American lawns.
Knowing the beetle’s life cycle can help you defend your lawn against an infestation. Read on to find out more.
The chafer’s life cycle
The chafer’s life cycle is one year. The imago (adult) stage is only 1–2 weeks long, with adult beetles growing to approximately 13–14 millimetres (0.51–0.55 in) in length. The adult chafers emerge from the ground in late spring and mate in large swarms, usually on shrubs and low trees. They are most active on warm, clear nights when the temperature is over 19C (66F). The beetles come out of the ground at about 8:30 pm, mate through the night, and then return to the soil before the sun rises; they may return to the trees to mate again several times over the mating period.
Female chafer beetles lay between 20–40 eggs over their lifespan; the eggs are laid about 5–10 centimetres (2.0–3.9 in) deep in moist soil, and then take 2 weeks to hatch. The grubs hatch by late July. In frost zones, the grubs feed until November and then move deeper into the soil. In frost-free areas, however, the larva feed all winter. Intense feeding occurs from March through May. Then, in early June, the grubs move deeper again, from 5 centimetres to 25 centimetres (2.0–9.8 in), where they form earthen cells and pupate. The pre-pupal stage lasts 2–4 days and the pupal stage lasts 2 weeks. By June, the new beetles begin emerging from the ground.
Beware other critters, too
Not only do the larvae feed on roots, wreaking havoc on lawns, but they attract local fauna like crows, foxes, and raccoons, who dig up the grass in search of the grubs. So, in addition to root damage, homeowners also have to worry about destruction caused by larger creatures.
Why is it important to know about the life cycle of the Chafer beetle?
Knowing the life cycle of the Chafer Beetle helps illustrate is when the beetle is most susceptible to treatment which will help exterminate the pest. The beetle’s most susceptible time is when it is the egg form in late July. Although treatment can help in early times in the season, July is the most optimal time to apply your treatment. It’s also important to note that treatment should not be a one time thing.
In order to ensure the treatment and the extemination of the beetle, it is recommended to apply multiple treatments to your lawn or garden.
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Dealing with the Chafer Beetle – Nematode Protocol Update
Two options for addressing chafer beetle infestations
Are you or your clients having problems with the European Chafer beetle destroying lawn? We suggest the protocols described below. Please keep in mind that the insecticide must be administered by a professional with a pesticide applicator’s certificate. The rest could be done by a homeowner, but it is a procedure that is far more likely to be done by a landscaper.
The first option is to do an Imidacloprid drench. After the drench, wait a few weeks, then remove the turf and as much soil as is reasonable—a minimum depth of 2 inches. Next, add soil to required depth; the soil can either be Terraseeded, hand seeded, or lay sod. Make sure to do this in late July/early August before applying the nematodes.
By removing the turf and some soil, you’re taking out most of the grubs, even the ones killed by the Imidacloprid. The large grubs are more difficult for the nematodes to kill. Applying nematodes after egg-hatch (in mid-late July) will target the small grubs, which is more effective. It should be emphasized that nematodes should be applied annually if the Chafer Beetle continue to be a problem in their area.
There is the issue that not all jurisdictions allow the application of this insecticide. Therefore, each customer must find out what is acceptable within their jobsite and municipality.
If insecticide use is not permitted in the area, there is a second option. First, apply the nematodes at recommended rates to the soil in April through June, and then again in September through early November; the nematodes should be applied in areas of known infestation where specific lawns show signs of chafer infestation. Remember that the lawns must remain damp for at least two weeks after nematode applications.
For both options, it is very important to follow healthy lawn practices as well established lawns are more resistant to chafer damage. These practices include aeration and topdressing, watering well at appropriate intervals, consistent fertilization, and cutting to a 2-inch height (not too short).
In order to resist the chafer beetle when projects are newly installed, consider the following recommendations. First, if permissible, drench the soil with Imidaclorprid. Then, excavate and dispose of native topsoil to a reasonable depth of 2-6 inches. Replace the excavated material with compost-based soil; the type of soil should be based on specific requirements, i.e. turf. If applicable for the application, the use of grass species such as tall fescues and alternatives such as Microclover will help resist the beetle. Overseed the remediated areas at 3-4 times the suggested rates; in theory, this makes it difficult for the chafer to get to the surface. It will also make it harder for the chafer predators (birds, raccoons, etc.) to do damage. Lastly, encourage the use of any product or method that will increase turf establishment as well-rooted turf will stand a better chance.
Overall, it is important to remember that the European chafer beetle is an ongoing problem that is unlikely to be solved easily. There is no silver bullet. Providing quality products and installation combined with a willingness to maintain the remediated areas will improve the customers chance of a successful project.
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Here are some other resources we have found online that may be of help: