Understanding the Science

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Frequently asked questions

Q: What is AR37?
A: AR37 is a novel endophyte developed by AgResearch. It is a fungus that lives inside seed, and plants that grow from that seed. It is a natural organism with no genetic modification or engineering.

Q: What are the advantages of AR37?
A: Compared with a ryegrass of the same cultivar infected with AR1 or standard endophyte (SE) that were sown in 11 trials over 4 years, AR37 provided ryegrass plants with protection from a wider range of insect pests; increased dry matter production (average of 12% annually); larger and deeper root mass; and better persistence. (Hume et al 2004: In Proceedings of the 5th International Symposium on Neotyphodium/Grass Interactions; Hume et al 2007: Proc NZ Grassland Assn, 69: 201-05)

Q: What insects does AR37 protect against?
A: Like the AR1 endophyte, AR37 provides protection from Argentine stem weevil larvae and pasture mealy bug with better control of black beetle. (Popay & Thom: Proc NZ Grassland Assn, 71: 121–27). AR37 controls the life cycle of Black Beetle at the adult stage rather than the larval stage. AR37 also protects plants from root aphid, and in laboratory trials has been shown to be both a deterrent and toxic to porina. (Jensen & Popay 2004: NZ Plant protection 57: 323-28) In a field trial no porina were found in plots of AR37 whereas endophyte free and AR1 plots measured 10 larvae/m2. (AJ Popay Unpublished data)

Q: What is the risk of ryegrass staggers?
A: While AR37 does not produce the alkaloid lolitrem B it can cause ryegrass staggers in grazing livestock. In grazing trials at Lincoln the incidence of ryegrass staggers on pure ryegrass with AR37 has been less frequent and usually only as half as severe as on ryegrass with standard endophyte. However these trials have shown that spasmodically AR37 can cause serious staggers. (Fletcher & Sutherland 2009: Proc NZ Grassland Assn, 71: 127-33).

To date, no ryegrass staggers have been observed with any class of cattle on AR37 in trials or on commercial farms. Due to the fact that no trial work has been undertaken on deer or horses, pastures with AR37 are currently not recommended for these livestock classes or other untested species.

Q: How well do animals perform on AR37?
A: The performance of sheep on pure ryegrass pastures have been better on AR37 than on the same ryegrass cultivar infected with Standard Endophyte. This is greatest in the summer and autumn when endophyte toxins are likely to be the highest. Growth rates on AR37 are similar to the same ryegrass cultivar without endophyte or AR1 and superior to Standard endophyte when the average ryegrass staggers score is less than 2 (Fletcher & Sutherland, 2009: NZ Grassland Assn, 71: 127-33). The DairyNZ trial on Scott Farm (Waikato) compared Commando perennial ryegrass-based pasture infected with AR37, AR1, Standard (HE) or without endophte (Nil). The project aimed to measure ryegrass persistence and pasture yields and to assess any effects of the AR37 endophyte on cow health and milk production. In the fourth and final milking season white clover was removed to test the effect of endophyte/ryegrass association in isolation from any effect on clover content of pastures. The following bullet points present a summary of results from the four seasons.

Overall conclusions:

  1. AR37 ryegrass was clearly more persistent than either AR1 or Standard (HE) ryegrass. This supports findings from previous work.
  3. There was no sign of ryegrass staggers or any other animal health issues in cows grazing AR1 or AR37 pastures – even at times when cows grazing HE were affected by ryegrass staggers.
  4. With ryegrass/white clover pastures, there was a trend for slightly lower milksolids (MS) production over summer from cows grazing AR37 or HE compared with AR1. With pure ryegrass pastures there were no significant differences in MS production. These results suggest that the higher clover content of the AR1 mixed pasture was a contributing factor to the observed MS production differences.
  5. Where pasture persistence is the top priority then AR37 will clearly deliver benefits. Where persistence of AR1 ryegrass is not a problem, continuing to sow AR1 is advised. DairyNZ cannot envisage any situation in which farmers should sow HE ryegrass.

Q: Is there any difference in palatability with AR37 and AR1
A: There have been no palatability differences noted between AR1 and AR37 pastures.

Q: What benefits can I expect from AR37?
A: While the average advantage in ryegrass growth of AR37 over Standard Endophyte in the same cultivar is 12% across 11 trials across the country over four years, farms will experience advantages both higher and lower than this.

The benefits will vary from farm-to-farm due to the wide range of insect populations, climatic stress and pasture management. Generally, trials have shown greater benefits the further north they are in the country, though AR37’s improved performance where porina exists compared to AR1 and nil endophyte means that it will have a key role in some South Island environments (AJ Popay, Unpublished Data). Trials have also shown that the greatest advantages exist where insect populations are higher (Hume et al 2007: Proc NZ Grassland Assn, 69: 201-05).

In most environments, the advantages in pasture growth will increase over time. This has been shown in trials where small advantages show up in the first year, but advantages are greater in the second and third years. This is likely to be due to insect populations building after establishment, and the increasing pasture production advantages resulting from greater ryegrass persistence.

While the average annual dry matter production advantage to AR37 is 12%, the average advantage in summer is 15% and 21% in autumn (Hume et al, 2007: Proc NZ Grassland Assn, 69: 201-05).

Q: Who should use AR37?
A: Farmers who want improved pasture production, persistence and animal performance from their pastures should use AR37, especially where damaging insects are likely to be present. Trials that have been undertaken show that AR37 is a suitable pasture for dairy cows, sheep, and beef animals. Pastures with AR37 have their largest differences in dry matter results compared to the same cultivar with standard endophyte in regions from Taupo north. These regions normally experience severe insect pressure.

AR37 should be used where pasture persistence is a key factor and where improved dry matter production is likely to occur compared to other endophyte options. This is most likely to happen where pastures are under pressure from a range of insect pests and/or drought.

AR37 has been tested for agronomic and animal performance with sheep and dairy cows.

Q: How long has AR37 been around for?
A: AgResearch together with its commercial partners began work on developing the AR37 endophyte in 1995. AR37 ryegrass cultivars were released commercially in autumn 2007.

Q: Which ryegrass cultivars have AR37?
A: AR37 is available in a range of ryegrass cultivars from Agricom, PGG Wrightson Seeds and NZ Agriseeds. To find out what will work best for you, contact:

Agricom | Ph: 0800 183 358

PGG Wrightson Seeds | Ph: 0800 805 505

NZ Agriseeds | Ph: 03 318 8514

Commercial cultivars available with AR37 endophyte:


Q: How should pasture with AR37 be established?
As with new AR1 pastures, all existing ryegrass plants should be removed from the paddock (using spraying and/or ploughing), and old ryegrass seed buried or germinated (following multiple spray applications or cropping) before planting ryegrass with AR37. Re-establishment of old ryegrass plants will not result in failure but can reduce animal performance (if old ryegrass has standard endophyte), pasture production and possibly persistence.

Q: Do AR37 pastures require insect protection at establishment?
A: AR37 pastures require the same level of insect protection as other endophyte options during the establishment phase. This is because in all establishing plants containing endophyte there is a lag period (approximately six weeks) before the endophyte is present in sufficient concentrations to provide protection. A seed treatment such as Superstrike will provide protection during establishment.

Q: AR37 is not the perfect endophyte - so what is?
A: At the moment AR37 endophyte provides ryegrass with much better dry matter production and persistence than any other commercially available endophyte.

While AR37 does not produce the alkaloid lolitrem B it can cause ryegrass staggers in grazing livestock. In grazing trials at Lincoln the incidence of ryegrass staggers on pure ryegrass with AR37 has been less frequent and usually only as half as severe as on ryegrass with standard endophyte. However these trials have shown that spasmodically AR37 can cause very serious staggers. (Fletcher & Sutherland, 2009: Proc NZ Grassland Assn, 71: 127-33).

While it is acknowledged there is a risk of ryegrass staggers in using AR37, there are significant other benefits from the technology for farmers. Research is ongoing in looking to develop an endophyte that removes this risk but like many issues until such a development there will always be some compromise with endophyte technology.


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