Control Garden Leaf Beetles in your Home Garden – Garden Chafer Beetles can become unwanted pests of your garden. We show you how to accurately identify as well as control garden leaf beetle infestations.
Beetle larvae are considered a delicacy in Vietnam, but they are regarded as a problem in many regions of western countries. That’s also true for larvae of the garden leaf beetle, which, like the May beetles, June beetles, belong to the leaf horn beetles family (Scarabaeoidea).
They feed on lawn grassroots from June – September finally leaving behind patchy lawns which are damaging in sports complexes, parks, and home gardens. To prevent such damage, garden leaf beetle traps as well as other biological techniques can be applied.
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Identify Garden Leaf Chafer Beetles
The garden chafer beetle (Phyllopertha horticola) is also referred to as foliage beetle or Leaf Beetle and it is a member of the leaf horn beetle family. The larvae of all leafhopper beetles are termed as grubs. To identify it from other closely related beetles, like cockchafer, June beetle, and Japanese beetle, it should be properly identified.
You can recognize the garden leaf beetle by these characteristics:
Size: 8 mm – 11 mm
Body: Very densely haired
Color: Light brown
Neck shield: Metallic green color
Antennae: Short and ending in three lamellae
To avoid misunderstanding it with the now rare May beetle, June beetle or Japanese beetle, you must first look at the size of the beetle. The garden leaf beetle is quite smaller compared to its other counterparts.
May beetle have a body length of roughly around 20 to 30 millimeters, while June, as well as Japanese beetles, have a size of around 15 to 18 millimeters. However, unlike the garden chafer, the body of the cockchafer beetle is not hairy, and also the antennae finish in six lamellae instead of two.
The Japanese beetle likewise has a green neck shield but is distinguishable from the garden foliage beetle by the tufts of white hairs on the side of its body.
Damage Caused By Garden Chafer Beetle Larvae
Control of the garden leaf beetle is advisable in exceptional situations. The feeding of the garden chafer insects on leaves of oaks, hazels, birches, roses, and cherries barely does any damage to the plant.
Only the larvae of the garden leaf beetle which is the main concerning pest can harm a green lawn cover in particular situations. This is seriously annoying in places like sports facilities as well as on golf courses. The larvae of the garden leaf beetle feed on lawn grass roots, among other things, whereby the grass in the lawns and gardens withers away and becomes patchy.
Secondary damage which is caused by birds pecking at the larvae in the lawn is also unfavorable to sporting activities. To prevent such damages, garden leaf beetle traps can be utilized – they provide information on how many insects are flying to mate.
Three weeks following the mating flight, the larvae hatch and start migrating upwards in the soil and start feeding on plant roots in mid-July. Control of the white larvae is recommended when there are around 100 or more larvae per square meter. To control garden leaf beetle larvae biologically, nematodes can be utilized.
#Tip: To figure out how many foliage beetle larvae are currently in your lawn, you can simply cut out a piece of grass starting around mid-July and count them. If you find 50 larvae in half a square meter or 25 larvae in a quarter of a square meter, you should choose one of the control measures provided below.
How to Get Rid of Garden Leaf Beetles and Larvae
The following are some of the most successful methods to control chafer beetles and their larvae in your garden.
Using Leaf Beetle Traps
Adult garden leaf beetle populations are monitored with garden beetle traps. In order to attract prey, they use attractants that are dispersed by the wind. Garden leaf beetles, both sexes, fly against a yellow baffle before landing in a hopper.
Traps can be hung or placed outside starting in mid-May. There is a 100 square meter range for the attractant, and it can be renewed annually separately.
It’s recommended to use nematodes for the current season if the funnel is filled quickly to limit the spread of the garden leaf beetle. That’s because garden leaf beetle traps aren’t actually useful for controlling the pest; instead, they just keep track of where it goes on its journey.
Using Nematodes to Combat Chafer Foliage Beetles
Nematodes are small micro organisms also called eelworms. Some genera of these nematodes parasitize beetle larvae like the garden chafer beetle larvae. They work in a host-specific manner, therefore there is no harm from them to warm-blooded organisms, humans, and plants. The usage of nematodes is easy and effective when utilized correctly.
Which nematodes can be used against garden leaf beetles
The nematode belonging to the Heterorhabditis bacteriophora species specifically enters body cavities of the garden leaf beetle larvae and secretes a bacteria. This bacterium kills the chafer beetle larvae within two to three days.
After infection, reproduction of the nematodes against the white larvae occurs. Once the white larvae is killed and consumed, the nematodes depart their host in search of a new food source (host).
Best Time to use Nematodes
The garden leaf beetle’s beetle mating flight takes place starting mid-July towards the end of September. Almost six weeks later, the nematodes are sprayed against the larvae. The soil temperature must be at least 12 °C. As long as the worms locate food sources (host), they survive and multiply.
In dry conditions, they die, and that is why the soil should always be maintained moist during the whole process of using nematodes.
#Tip: Because nematodes have a limited shelf life, they should be purchased right before usage and should be used quickly. After shipment, generally, these nematodes can be stored unopened for roughly six weeks in the refrigerator.
How to Apply Nematode Treatment to kill Garden Leaf Beetle Larvae
The deployment of nematodes against garden leaf beetle larvae is relatively uncomplicated, however, several crucial factors should be noted. Since the nematodes are sensitive to the effects of UV radiation, it is best to apply them in the evening hours or when the sky is cloudy.
To achieve this, first produce a stock suspension by adding the powdered nematodes to a little water and then it stirring according to the provided instructions. Partial quantities of this stock suspension are stirred into the water and dispersed – this results in multiple watering cans filled with nematode suspension.
For relatively small areas and quantities, the preparation of a stock suspension might be skipped. Either a standard watering can or a nematode sprayer can be utilized for application. The nematode suspension should be administered fully. Overdosing will not have a harmful effect.
Then the remaining nematodes clinging to the grass blades can be flushed into the soil by pouring two to five liters of water per square meter. In dry weather conditions, this should be done within 30 minutes, as nematodes can not survive drought. It is also crucial to maintain the soil moist at all times throughout the following six weeks.
To quickly summarize the nematode application process:
- Select the proper time for nematode application: July – September
- Soil temperature of at least 12 °C.
- Mix nematodes with water as per to instructions and dilute further if necessary.
- Apply nematode suspension in the evening hours or in the early mornings.
- Keep soil moist for the next four to six weeks.
Prevent Garden Leaf Beetle Infestation
Garden leaf beetles love sandy soil and dry sections of lawn to deposit their eggs, so keep your lawn thick and well-watered. Check out our related special article to know how to properly maintain your grass throughout the year.
Mowing the lawn a little higher during the beetle mating flight in May reduces the larvae by 40 to 70 percent. Vegetable and flower beds can be used in place of lawns if you enjoy planting.
Even if the garden leaf beetle is rare in one’s area, extra care should be taken while planting a new one so as not to introduce too many host plants for it.
Host plants of the garden leaf beetle include:
- Apple trees
- Mountain ash trees
In your own backyard, moles and birds are natural predators of chafer beetle larvae. Garden leaf beetles can be collected from flowers and leaves manually or with the help of beetle traps as a preventative precaution.