Do You Really Need Treated Seed or Endophyte?
A practical, science-based guide for New Zealand farmers
Most pasture seed sold in New Zealand today comes with something added — seed treatment, endophyte, or both. In many cases, it’s included as a default, with little discussion about whether it is actually required for the farming system, paddock history, or establishment method.
This article takes a practical, farmer-focused look at what treated seed and endophytes actually do, when they add value, when they don’t, and why in some situations non-endophyte pasture can outperform endophyte-based options in terms of utilisation, intake, and animal performance.
The aim is not to say “never use them”, but to help farmers make intentional, system-matched decisions rather than paying for insurance they may not need.
WWhat does seed treatment actually protect against during pasture establishment?
The primary purpose of seed treatment
Seed treatment is designed to provide short-term protection during pasture establishment, primarily against insect pests that attack germinating seed or young seedlings.
Common target pests in New Zealand include:
Argentine stem weevil (adult and larval stages)
Grass grub (early larval stages)
Black beetle (regionally)
Other soil-dwelling or surface-feeding insects during establishment
Importantly, seed treatment does not increase yield, improve feed quality, or enhance long-term persistence. Its role is limited to the first few weeks of establishment.
Once the seed has emerged and established leaf area and root mass, the protection from seed treatment is largely irrelevant.
When treated seed makes sense
Seed treatment can be genuinely beneficial when pasture is:
Direct drilled or oversown into existing pasture
Established where insect populations are already present and active
Competing with existing plant material during establishment
In these situations, pasture seedlings often establish rapidly and evenly, and the benefit of seed treatment is minimal.
In many cultivated paddocks, seed treatment adds little more than peace of mind, rather than measurable performance gains.
This leads to an important question:
Are insects actually likely to limit establishment in this paddock — or is seed treatment simply being applied by default?
Treating the cause, not the symptom: alternatives to seed treatment
If insect pressure is known or observed, seed treatment is not the only management option.
Targeted insect control
Targeted spray applications, including biological control options, can:
Reduce existing pest populations before sowing
Be timed to actual insect pressure
Address the problem directly at a paddock level
This approach allows farmers to deal with the root cause of pest pressure, rather than building permanent insurance into the seed itself.
In integrated pest management (IPM) systems, this often results in better long-term outcomes and more flexibility in pasture choice.
This raises another key consideration:
Is seed treatment solving a real problem, or acting as a short-term band-aid for something better managed through paddock management?
GKey pasture insect pests in New Zealand (by region)
Upper North Island (Northland, Auckland, Waikato, Bay of Plenty)
Common pasture pests include:
Black beetle – high-risk in warm summers and lighter soils
Argentine stem weevil – widespread, especially in ryegrass-dominant pastures
Armyworm – seasonal outbreaks, often linked to warm, dry periods
Black beetle pressure is one of the strongest arguments for endophyte use in this region, particularly in perennial pastures. However, pressure can vary significantly between paddocks and seasons.
Central North Island & East Coast (Taranaki, Hawke’s Bay, Manawatū, Whanganui)
Typical pest pressures include:
Argentine stem weevil
Grass grub (localised but severe in some soils)
Porina (especially hill country and lighter soils)
In many cases, pest pressure is episodic rather than constant, making paddock-level monitoring and targeted control highly effective alternatives to blanket seed protection.
South Island – Upper & Eastern Regions (Marlborough, Canterbury)
Key pests include:
Grass grub – often the dominant pasture pest
Argentine stem weevil
Porina – particularly in dryland and hill systems
Grass grub damage often appears well after establishment, meaning seed treatment offers little long-term benefit in these systems.
South Island – Southern Regions (Otago, Southland)
Common pests include:
Grass grub
Porina
Lower overall insect pressure due to cooler temperatures
In many southern systems, insect pressure is moderate and seasonal, and pasture utilisation and quality are often more limiting factors than insect damage.
What are endophytes and why are they used?
Endophytes are fungi that live within the ryegrass plant. Their primary role is to produce compounds that deter insect feeding.
In New Zealand pasture systems, endophytes are commonly used to:
Reduce damage from Argentine stem weevil
Improve plant survival under insect pressure
Increase theoretical pasture persistence in high-risk environments
From a plant protection perspective, endophytes can be highly effective.
However, this protection does not come without trade-offs.
The trade-offs of endophyte-based pastures
While modern endophytes are often marketed as “animal safe”, they can still influence:
Palatability
Voluntary intake
Grazing behaviour
Pasture utilisation
Commonly observed issues include:
Selective grazing
Patchy paddocks
Higher post-grazing residuals
Reduced utilisation efficiency
In practical farming terms, a pasture that animals do not want to eat evenly is often less productive than one that is slightly more vulnerable to insects but fully utilised.
Endophytes and animal health: grass staggers
One of the most well-recognised animal health risks associated with some endophytes is grass staggers.
Grass staggers is more likely where:
Endophyte levels are high
Pasture makes up the majority of the diet
Magnesium status is marginal
Stress or rapid dietary changes are present
Clinical signs may include:
Nervousness and muscle tremors
Head nodding and unsteadiness
Staggering or falling
Reduced grazing time
Even sub-clinical effects can reduce intake and animal performance.
Utilisation vs persistence: the real productivity question
Many pasture decisions focus heavily on persistence, often at the expense of utilisation.
However, pasture productivity is driven by:
How much feed is grown and
How much of that feed is actually eaten
A pasture that persists well but is poorly grazed can underperform a more palatable pasture that is fully utilised.
This is where non-endophyte ryegrass can perform extremely well.
Where non-endophyte pasture still excels
In many New Zealand farming systems, non-endophyte ryegrass performs just as well — or better — especially where:
Intake and digestibility drive production
Pasture utilisation is a priority
Grazing is regular and well managed
Insect pressure is low to moderate or actively managed
Farmers commonly report:
More even grazing patterns
Higher utilisation
Strong animal preference
Improved feed conversion into milk or liveweight gain
Not because the seed is cheaper — but because animals actually want to eat it.
This isn’t about never using treated seed or endophyte
Seed treatments, insecticides, biological controls, and endophytes all have a place in New Zealand farming systems.
They are most effective when used:
Based on paddock history
Matched to establishment method
Aligned with stock class and production goals
The most expensive pasture mistakes are rarely about seed price. They are usually about choosing protection that doesn’t match the system.
Frequently asked questions (FAQ)
Do I always need endophyte in ryegrass?
No. Endophyte is most valuable where insect pressure is consistently high and damaging. In low to moderate pressure systems, non-endophyte ryegrass can outperform endophyte pasture through better palatability and utilisation.
Is treated seed necessary every time I oversow?
Not always. While treated seed can help when oversowing into existing pasture, the decision should be based on known insect presence, sowing timing, and competition — not habit.
Does seed treatment protect pasture long-term?
No. Seed treatment provides short-term protection only during establishment. It does not protect established pasture from future insect damage.
Can sprays or biological controls replace seed treatment?
In many cases, yes. Targeted insect control — including biological options — can reduce pest pressure directly and may be more effective than building insurance into the seed.
Is non-endophyte pasture less persistent?
Not necessarily. Persistence depends on grazing management, soil fertility, moisture, and utilisation. Poorly utilised endophyte pasture often underperforms well-managed non-endophyte pasture.
Final thoughts: intentional decisions deliver better outcomes
Before selecting pasture seed, it is worth asking:
What insect pressure actually exists in this paddock?
Is the pasture being oversown or fully cultivated?
Is utilisation or theoretical persistence more important in this system?
Would paddock-level pest control be more effective than built-in insurance?
Answering these questions upfront leads to better pasture performance, better utilisation, and better returns over time.
If you want to discuss what pasture options best suit your farming system, paddock by paddock, seek independent, system-focused advice rather than default settings.
Better decisions upfront almost always deliver better outcomes.