Lawn grubs, also called larvae, are the immature stage of insects found in your lawn. These tiny creatures can wreck your garden as they tunnel through the soil, feeding on vital soil nutrients. Typically, the summer months are when lawn grubs are most prevalent, as adult insects emerge to mate and lay eggs in the soil. Within a few weeks, the eggs hatch, and the hungry grubs begin their destructive feeding frenzy on your precious lawn.
When it comes to lawn grubs, chafer grubs are the most common type you’ll encounter. Don’t worry, though, because we’re here to help you eliminate them and prevent further damage. But before we get into the solutions, let us provide you with some valuable information about these troublesome pests.
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What are chafer grubs?
Belonging to the Scarabaeidae family, which includes dung beetles and chafers, chafer beetles boast a diverse representation of over 80 species in Britain.
Chafer grubs are the larvae of chafer beetles that reside in the soil. Their feeding habits depend on the specific chafer species: some eat decaying plant material, while others feed on plant roots. Certain chafer species that do not threaten gardens can be found in borders and compost heaps. However, others that target grass roots can harm lawns.
While many of the chafer beetles species are rare or localised in occurrence, many are dung feeders. They play a crucial role in dung decomposition and disposal. These species specialise in decomposing organic matter, others mainly target plant roots, and only a few are capable of damage in gardens.
What attracts grubs to lawns?
Chafer grubs tend to inhabit lawns, especially those with ample thatch. They thrive on sparse lawns that provide sufficient space to burrow into the soil. Lawns that receive regular dethatching, fertilisation, and overall proper care tend to have denser turf, less appealing to grubs. To prevent chafer grub issues, we recommend implementing a routine of regular raking and dethatching, combined with a consistent fertiliser schedule to maintain a dense lawn.
If your lawn is heavily infested with moss, it is advisable to remove the moss, as lawn grubs flourish in such conditions. While addressing the infestation, it is also advisable to minimise excessive watering, as it only encourages increased grub activity. Keep watering to a minimum until the infestation is under control.
How do I know if I have chafer grubs?
If you spot grubs in your lawn displaying the following traits, chances are you’re facing a chafer grub infestation. You can identify lawn grubs by the following features:
- A plump white C-shaped body
- 3 pairs of legs located at the front of the body
- A noticeable light brown/orange coloured head
What does grub damage look like?
As far as grub damage is concerned, there are a few specific signs that could be potential indicators of a grub infestation, such as:
- Browning or yellowing of the grass
- Bare patches in the lawn
- The grass pulls away easily
- Little or no growth of the grass blades
Chafer grubs, like other types of lawn grubs, are a sought-after food source for creatures such as foxes, badgers, magpies, and jackdaws. If you observe any of these animals lingering around your lawn, displaying suspicious behaviour and foraging for food, that’s likely another indication of a chafer grub’s presence.
What is the best time to treat grubs?
To effectively address chafer grubs, it’s crucial to consider their specific lifecycle and apply treatment or removal techniques at the appropriate times. The white chafer grub is most active between August and October and between mid-March and May in the spring.
The optimal time to apply treatment is when the grubs are young and actively feeding, which typically occurs in late August and September. If the soil temperature remains warm, treatment may extend into early October. Treatment can also be applied during spring, but the soil temperature must be above 12°C. Keep in mind that spring applications may have a lower success rate than autumn treatments, as the grubs become hardened over winter.
Here’s a breakdown of the chafer life cycle:
- August: Chafer beetles lay eggs just beneath the grass, which hatch into chafer grubs that immediately feed.
- September to October: The white chafer grubs feed on lawn roots and surface growth.
- Mid-November to mid-March: With cooler temperatures, grubs burrow deeper into the soil and become less active.
- Mid-March to May: As the soil temperature rises, the grubs resume feeding on roots and surface growth.
- May to June: The chafer grubs transform into pupae.
- Late May to June and early August: Adult chafer beetles emerge and lay eggs, typically in August, completing the life cycle.
By considering the lifecycle and targeting the periods when the grubs are actively feeding, you can maximise the effectiveness of treatments for chafer grub control.
How to get rid of chafer grubs for good
We have several timely suggestions for natural grub control. Please note that the success of these suggestions depends on the right timing. They are not suitable for implementation during the peak of the summer or winter seasons.
Use of nematodes
Nematodes, minuscule parasitic worms, play a crucial role in combating grubs as they infiltrate and eliminate them internally. In addition, nematodes can lay eggs within the grubs, which eventually hatch and release more nematodes. These newly hatched nematodes will actively seek out additional grubs to exterminate.
A small packet of nematodes contains millions of these beneficial organisms. The most beneficial part is that they pose no threat to pets, humans, children, or plants. It’s worth noting that nematodes primarily target grubs and do not harm regular garden worms or other insects. Hence, they are perfectly suitable for organic gardening.
When dealing with chafer grub infestations, nematodes prove an effective solution. There are, however, some limitations to consider:
- Proper timing is crucial, as nematodes should be applied when the grubs are active. It is not advisable to use them during the peak of summer or winter.
- Adequate watering of the lawn is essential for at least two weeks after application. Failure to do so can result in the demise of the nematodes.
- Nematodes are perishable, and it is important to utilise them promptly upon delivery or store them in the refrigerator for a few days at most.
- Multiple applications are highly likely to be necessary for optimal results.
The tarp method
The tarp method is an effective technique for managing grub infestations in small to medium-sized gardens, drawing inspiration from successful implementations on golf courses in the past. To begin, you will need a dark plastic cover, such as a tarpaulin, whose size depends on your garden area. If you have a large lawn, you can do it in stages.
Choose a sunny, warm day and ensure that you water the grass thoroughly, saturating it. It is important to avoid hot sunny days to prevent rapid water evaporation. Next, lay the tarp over the grass and secure it at the edges using pegs or heavy objects like bricks or plant pots.
Leave the tarp in place overnight and remove it early in the morning. The warm, dark, and moist environment created beneath the tarp will entice grubs to come to the surface. They can be collected by hand or swept into a container.
Repeat this process multiple times as needed, especially for larger lawns, and move the tarp around the garden in stages. The tarp method serves as an excellent approach to reducing the population of chafer grubs. It delivers favourable results when the grubs are actively causing damage.
Pheromones and traps
Please be aware that this is a beetle trap, not a grub trap. This device consists of two components: a trap and a lure containing a potent chafer beetle pheromone. The pheromone attracts beetles towards the trap, where they are captured and unable to escape. While the trap itself can be reused, the pheromone lure is designed for single use.
Timing is crucial, and it’s important to note again that this trap and lure specifically targets beetles, not grubs. Therefore, it should be applied before beetles lay their eggs. The optimal time to utilise this lure is in late May or early June since the pheromone remains active for approximately six weeks. While this product may not eliminate all beetles, even capturing a few can have a significant impact, as it prevents them from laying eggs and disrupts the beetle population.
Home gardeners do not have access to pesticide controls specifically designed for treating chafer grubs and leatherjackets in lawns. In the UK, pesticides for chafer grub treatment were discontinued in 2018, making them unavailable for purchase.
Although there are some products like Merit Turf and Acelepryn that gained government approval for emergency situations in recent years, they were strictly intended for professional use at airports, golf courses, and a limited number of other locations. As of spring of 2023 Acelepryn gained full approval, however, restrictions are still in place regarding how much area can be treated.
It’s important to note that insecticides carry risks not only for human health but also for other beneficial insects, including those that contribute to lawn well-being through pollination.
How to prevent grubs in the lawn
Preventing grubs is the second most important step. This involves regular maintenance practices and paying careful attention to any inconsistencies, such as moss and thatch.
Prioritise thoughtful consideration before mowing your lawn and ensure it stays at an appropriate height. When controlling grubs, use the highest mower setting. This practice encourages deeper and stronger root system growth for your grass.
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- In the case of perennial pests like white grubs and leatherjackets, the sooner you act, the better.
- White lawn grubs are unlikely to disappear on their own, especially before devouring your lawn.
- Known as chafer grubs, white lawn grubs are one of the most destructive lawn pests in the UK.
- A lawn with plenty of thatch tends to be inhabited by chafer grubs.
- In order for the treatment to be effective, the right timing is crucial.