The Environmental Protection Authority (EPA) has confirmed that chlorpyrifos - a widely used insecticide for controlling grass grub - will be banned in New Zealand from July 2025, with an 18-month phase-out for pasture use. With other options like diazinon also on the way out by 2028, New Zealand farmers are facing a narrowing field of synthetic tools to tackle one of the country’s most persistent pasture pests: grass grub.
This shift is pushing the industry to explore biological alternatives - not just for compliance, but to build more resilient, productive soils.
One viable alternative is vermicast - the nutrient- and microbe-rich byproduct of earthworm digestion. At MyNoke, our customers have seen firsthand how a single application of high-quality vermicast can eliminate grass grub pressure in some pasture systems.
Vermicast is teeming with beneficial bacteria, fungi, and enzymes. It often contains:
- Bacillus species, which produce natural insecticidal compounds
- Entomopathogenic fungi and nematodes, which actively target soil-dwelling pests
- Microbial communities that stimulate plant health and root zone resilience
In this interview with Ged Goode - one of our a long-time vermicast customers - he explains how incorporating vermicast into his farming system eradicated grass grub in paddocks where the pest was previously a recurring problem. The outcome wasn’t the result of repeated applications or supplementary treatments - it was a clear shift following a single, well-timed dose.
While other biological products can also play an important role, their success often depends on tight application windows and supporting soil conditions. Vermicast, by contrast, is biologically complete - bringing both microbial agents and the organic matter needed to sustain them. It works in variable conditions, and its benefits extend beyond pest control, including:
- Improved soil structure and moisture retention
- Better root development and pasture establishment
- A more resilient, self-regulating soil ecosystem
As synthetic pesticides disappear from the landscape, vermicast offers a natural and practical tool for controlling grass grub and restoring soil function.
Get in touch if you would like to try MyNoke vermicast as part of your pasture renovation or pest management strategy. Whether your goal is to eliminate grass grub or build longer-term soil resilience, now is the time to take action - before the chlorpyrifos ban takes full effect.
Image: Grass Grub Beetle (Costelytra zealandica) © Brett Sandford