--- title: Stem Weevil canonical: https://gardensuperstore.com.au/problem-solver/stem-weevil/ dateModified: 2026-08-07 09:54:47 summary: "Argentine stem weevil larvae tunnel inside grass stems and crowns, weakening turf and pasture grasses across cooler parts of Australia." type: article keywords: [Stem Weevil, Listronotus bonariensis] --- # Stem Weevil > Argentine stem weevil larvae tunnel inside grass stems and crowns, weakening turf and pasture grasses across cooler parts of Australia. *Listronotus bonariensis* The adult Argentine stem weevil is a small greyish-brown beetle about 2-3mm long, with the typical weevil snout and a mottled, speckled appearance that helps it blend into thatch and soil surface debris. Adults are active fliers and crawlers, often found low in the turf canopy or in thatch during warmer months. Eggs are laid inside the leaf sheath, and the larvae that hatch are legless, creamy-white grubs with a darker head, growing to around 4-5mm before pupating. It is this larval stage that causes the real damage, as the grubs tunnel inside grass stems, crowns and leaf sheaths, feeding on internal tissue as they move from one tiller to the next. This pest is a significant problem in ryegrass-based turf and pasture, and it has become more prominent in areas where endophyte-free ryegrass varieties are grown, since natural endophyte alkaloids in some ryegrass cultivars deter larval feeding. It is most active in the cooler, temperate regions of southern Australia, including Victoria, Tasmania, and parts of New South Wales and South Australia, where ryegrass is a dominant turf or pasture species. Populations build through the year with multiple overlapping generations possible, and damage tends to be most visible in late autumn through spring when larval feeding is active and grass growth is otherwise slow, making thinning more obvious. Warm, moist conditions favour egg-laying and larval survival, while very hot, dry summers can reduce numbers. Management in turf situations relies on maintaining healthy, actively growing grass through good irrigation, mowing and fertility practices, since vigorous swards recover from larval feeding more readily. Where ryegrass is being renovated or oversown, choosing cultivars with endophyte protection is a key long-term strategy, as endophyte-free ryegrass is considerably more susceptible to sustained weevil damage. Monitoring for adult activity and early larval tunnelling helps determine whether intervention is warranted before damage becomes severe. ## How to identify - Yellowing, thinning or dying tillers, particularly in ryegrass-dominant turf, with affected stems easily pulled from the crown due to internal tunnelling - Small, ragged notches or window-pane feeding marks on leaf blades caused by adult weevils feeding at the leaf surface - Hollowed-out stems and crowns when cut open, sometimes containing a small creamy-white legless larva inside - Patchy, uneven thinning across the turf rather than distinct circular bare patches, often more noticeable after periods of stress or slow growthTo confirm an infestation, part the turf canopy and check the base of tillers and crowns for adult weevils, which are small, dull greyish-brown and about 2-3mm long, or split open discoloured stems to look for the pale larvae feeding inside. A simple soap flush (a mix of dishwashing detergent and water poured over a marked turf section) can help bring adult weevils and other surface-active insects to the top for easier counting. Stem weevil damage can be confused with drought stress or general nutrient deficiency, since both cause similar yellowing and thinning; the key difference is the presence of hollowed stems and larvae on close inspection. It can also resemble early lawn armyworm or sod webworm damage, though those pests cause more obvious chewed leaf blades and larger caterpillar larvae rather than internal stem tunnelling. ## Registered products we stock - [Acelepryn GR Granular Lawn Insecticide | 6-Month Grub Protection](https://gardensuperstore.com.au/acelepryn-gr-granular-lawn-insecticide-6-month-grub-protection/) — Syngenta - [Acelepryn Liquid | 6-Month Lawn Grub & Armyworm Protection](https://gardensuperstore.com.au/acelepryn-liquid-6-month-lawn-grub-armyworm-protection/) — Syngenta - [AntStar | Granular Insecticide](https://gardensuperstore.com.au/antstar-granular-insecticide/) — PCT SureFire - [Fivestar | Insecticide](https://gardensuperstore.com.au/fivestar-insecticide/) — PCT SureFire - [Termiticide & Insecticide](https://gardensuperstore.com.au/termiticide-insecticide/) — PCT SureFire - [Biff 100SC | Insecticide](https://gardensuperstore.com.au/biff-100sc-insecticide/) — Colin Campbell Chemicals - [Tempo XTRA | Turf & Ornamental Insecticide](https://gardensuperstore.com.au/tempo-xtra-turf-ornamental-insecticide/) — Envu - [Provaunt | Turf Insecticide](https://gardensuperstore.com.au/provaunt-turf-insecticide/) — Syngenta - [Scarlet Trio | Advanced Insecticide](https://gardensuperstore.com.au/scarlet-trio-advanced-insecticide/) — ProForce - [Spinner | Turf Insecticide](https://gardensuperstore.com.au/spinner-turf-insecticide/) — Syngenta - [Tetrino | Turf Insecticide](https://gardensuperstore.com.au/tetrino-turf-insecticide/) — Envu - [Venom Professional 240SC | Insecticide](https://gardensuperstore.com.au/venom-professional-240sc-insecticide/) — Adama ## Image credits - [Photo: Landcare Research New Zealand Ltd. via Wikimedia Commons (CC BY 4.0)](https://commons.wikimedia.org/wiki/File:Listronotus_bonariensis_lateral.jpg) - [Photo: Landcare Research New Zealand Ltd. via Wikimedia Commons (CC BY 4.0)](https://commons.wikimedia.org/wiki/File:Listronotus_bonariensis_dorsal.jpg)