How to Control Argentine Stem Weevil in Your Lawn

What are Argentine Stem Weevils? 

The Argentine Stem Weevil (Listronotus bonariensis) is a notorious pest that poses a significant threat to Australian lawns, particularly in the southern states and Tasmania. This small but destructive insect can cause widespread damage, particularly in certain cool season grass varieties like Rye Grass, Bent Grass or Kentucky Blue Grass commonly found in home lawns.

Adult Argentine Stem Weevils are small, about 3-4 mm long, and have a greyish-brown body with distinct weevil snouts. Their larvae, which are the most damaging stage, are cream-coloured and legless with a brown head.

Originally from South America, these weevils have become a widespread problem in Australia, particularly in Victoria, Tasmania, New South Wales, and South Australia. They thrive in temperate climates and are most active during the warmer months.

The Argentine Stem Weevil has a complex life cycle that allows it to cause damage throughout the growing season. The adult weevils lay their eggs inside the stems of grass. After hatching, they feed on the inside of the grass stems, hollowing them out and causing the plant to die. This internal feeding makes the larvae particularly destructive, as the damage is not always visible until it’s too late.

 After feeding for several weeks, the larvae pupate in the soil, emerging as adults to continue the cycle. There can be multiple generations in a single growing season, making early detection and control essential.

How to Control Argentine Stem Weevils 

To effectively manage Argentine Stem Weevils, a combination of preventive and curative insecticides is recommended. Here are some commonly used insecticides:

Chlorpyrifos: A contact insecticide effective against both adult weevils and larvae. It is often used as a curative treatment when an infestation is detected.

Bifenthrin: Provides both contact and residual control, making it useful for both preventive and curative applications. It is particularly effective when applied early in the season.

Imidacloprid: A systemic insecticide that targets larvae feeding inside the stems. It is absorbed by the plant and kills the larvae as they feed.

Rumbler is an insecticide that contains Bifenthrin as the active ingredient, while Recruit contains Imidacloprid, and both are registered for the control of Argentine Stem Weevils amongst other common pests.

You can also use the popular residual insecticide Acelepryn in either liquid or granular form to act as an effective deterrent from Argentine Stem Weevils and other common lawn pests.

When to Apply Insecticides

Insecticides like Rumbler and Recruit are diluted into a medium like water and sprayed out over the lawn at varying rates, as specified on the packaging by the manufacturer. Apply liberally at the first sign of an outbreak, and then monitor the populations for the next seven to ten days. If the infestation persists, reapply after one week.

How Long Do Insecticides Take to Work?

The efficacy of an insecticide will be dictated by the severity of the outbreak, however it’s common to see populations dwindle within 24 hours of application, and then continue to thin out in the first seven days post-application.

How to Get Rid of Argentine Stem Weevils Naturally 

For those looking to manage Argentine Stem Weevils without relying solely on chemicals, several natural remedies can help.

It’s possible to stave off Argentine Stem Weevils through good cultivation practices, including regular mowing, fertilisation and watering; all of which will also improve the lawn’s chances of recovery in the event of an outbreak.

It’s also possible to use ‘Trap Cropping’ where a sacrificial section of susceptible lawn is used to attract the Weevils and then treated with a targeted insecticide application.

Natural methods like these are slower than chemical insecticides and might not be effective at managing large outbreaks.

 While Argentine Stem Weevils are a serious pest, it’s important to remember that they are part of the ecosystem. They serve as a food source for various birds and predatory insects, and their presence can indicate an imbalance in the lawn’s health or maintenance practices.

Rather than aiming for complete eradication, the goal should be to manage weevil populations at a level where they do not cause significant damage to your lawn. By combining chemical and natural control methods, you can maintain a healthy lawn while also supporting the broader ecosystem.

Control Argentine Stem Weevils in Your Lawn with myhomeTURF

Controlling Argentine Stem Weevil in Australian lawns requires a proactive and multifaceted approach. By implementing preventive measures, cultural controls, and, when necessary, targeted chemical treatments, homeowners can protect their lawns from the damaging effects of these pests. Regular monitoring and early detection play crucial roles in maintaining a healthy lawn, ensuring that you can continue to enjoy lush, vibrant outdoor spaces for years to come.

All products mentioned in this article are available at myhomeTURF’s online shop and if you still have questions contact us for a tailored solution to your problem.