Black Beetles in Lawns: The Smart Way to Stop the Damage Before It Starts

Black beetles and curl grubs can wreak havoc on lawns across Australia. Learn how to control them effectively with well-timed insecticide applications using Acelepryn or Bifenthrin-based products for safe, long-lasting protection.

In Short

Black beetles and their larvae (curl grubs) can cause serious damage to lawns by attacking the roots, leading to brown patches and thinning turf. Most people notice the problem too late—once the damage is already done and the larvae are too mature to treat effectively. This article explains why prevention is the best strategy, particularly in late August to early September when beetle eggs are hatching. It outlines two chemical treatment options: Acelepryn, which provides long-lasting, low-toxicity protection against larvae only, and Bifenthrin, a short-term solution that targets both adult beetles and larvae. You'll also learn when and how to apply each product for maximum effectiveness, and which is best suited to your situation—whether you're ahead of the problem or already seeing signs of beetle activity. If you want to protect your lawn without unnecessary chemicals and confusion, this guide will give you a clear, practical path forward.

The Beetle Problem

Black beetles (Heteronychus arator) are a notorious problem in turfgrass. While the adult beetles can be a nuisance, it’s their larvae—curl grubs—that do the real damage. These small white grubs live below the surface, feeding on grass roots and cutting off the turf’s water and nutrient supply. The result: brown patches, thinning turf, and weakened lawns that are more susceptible to pests, diseases, and weeds.

Don’t Wait for the Damage

Many homeowners act too late—running to the hardware store once brown patches appear. But by that point, the larvae have already matured and done their damage. Worse still, mature curl grubs are often too large to be effectively treated with insecticides.

The solution? Get ahead of the problem with preventative maintenance.

The Right Time to Act

The ideal treatment window is late August to early September. This aligns with the time beetle eggs begin hatching. Applying a preventative insecticide during this window ensures that the larvae are controlled before they start feeding—protecting your lawn before it even looks stressed.

What to Apply

There are two chemical treatment options, and the best choice depends on whether you're dealing with larvae only or both larvae and adult beetles.

Option 1: Acelepryn – Long-Lasting Larval Control

If your main concern is curl grubs (larvae) and you’re applying preventatively—before damage appears—then Acelepryn is the ideal solution.

• Controls only the larvae, not the adult beetles.
• One application lasts up to 6 months, covering the entire beetle season.
• Very low environmental impact—safe for pets, birds, bees, fish, and humans.
• Available in two forms:
  • Yates Grub Kill & Protect (for home gardens)
  • Acelepryn GR (for larger or commercial turf)

Acelepryn is best used as a preventative in late August to early September, before larvae start feeding on turf roots.

Option 2: Bifenthrin – Short-Term, Broad-Spectrum Control

If you’re already seeing adult black beetles active on your lawn alongside signs of larval damage, then a product containing Bifenthrin, such as Surefire Fivestar Insecticide, may be more suitable.

• Controls both adult beetles and larvae, offering a broader spectrum of action.
• Fast knockdown of visible beetles.
• Shorter residual activity—typically lasts 6 to 8 weeks in the soil.
• Not as environmentally gentle as Acelepryn—follow label directions and safety precautions.

This is the better option if you're in mid to late Spring and missed the preventative window.

How to Apply

Both Acelepryn and Surefire Fivestar (Bifenthrin) are easy to apply at home or on commercial lawns—just be sure to choose the right product for your situation.

If you're using Acelepryn (Yates Grub Kill & Protect or Acelepryn GR):

• Apply the granules evenly over the lawn surface using a spreader or by hand.
• You can apply it on its own or blend it with fertiliser for a two-in-one treatment.
• Water in thoroughly after application—this activates the product and moves it into the root zone where larvae are feeding.

• One application in late August to early September is usually enough to protect your lawn for the full beetle season.

If you're using Surefire Fivestar (Bifenthrin):

• Apply as a liquid treatment. apply with a sprayer, following label rates, and ensure even coverage across the affected area.
• Bifenthrin offers fast knockdown of both adult beetles and larvae but only lasts 6 to 8 weeks, so a follow-up treatment may be needed if pest activity continues.

No matter which product you use, thorough watering after application is essential—this ensures the active ingredient reaches the zone where beetles and their larvae are active. Always follow the manufacturer's instructions on application rates and safety, and choose your product based on whether you're tackling a known infestation or aiming to prevent one before it starts.

The Bottom Line

Black beetles and their larvae can be devastating for lawn health—but they don’t have to be. By acting before the damage is visible and choosing the right product at the right time, you’ll enjoy lush, pest-free turf with a single targeted treatment each season.

FAQ

Q: What time of year should I apply beetle control?
A: Late August to early September is ideal, just before the larvae hatch. This is when preventative treatment is most effective.

Q: How do I know if I have black beetles or curl grubs?
A: Common signs include brown patches, thinning turf, or turf that pulls up easily. You might also see the beetles or grubs themselves near the surface.

Q: What’s the difference between Acelepryn and Bifenthrin?
A: Acelepryn targets larvae only and lasts up to 6 months. Bifenthrin controls both adult beetles and larvae but only lasts 6–8 weeks.

Q: Will this harm my pets or local wildlife?
A: Acelepryn has extremely low toxicity and is safe for pets, birds, bees, and fish. Bifenthrin should be used with care and according to label instructions.

Q: Can I mix these products with fertiliser?
A: Yes. You can apply them on their own or mix with fertiliser. Either way, water in thoroughly after application.

Q: Is one treatment enough for the year?
A: With Acelepryn, yes—one treatment covers the full season. Bifenthrin may require a follow-up if pest pressure remains high after 6–8 weeks.