The Mushroom Industry in New Zealand

Peter K Buchanan¹ and John Barnes^2
1 Landcare Research, Private Bag 92170, Auckland, New Zealand
² Mushroom Spawn Laboratories, P. O. Box 5696, Frankton, Hamilton, New Zealand

Production and Consumption

The New Zealand mushroom industry is based largely on the button mushroom Agaricus bisporus, with annual production of 7500 tonnes. This serves a local population of 3.8 million and a per capita consumption of 2 kg per annum. New Zealand is a net exporter of mushrooms, mainly fresh white buttons and Swiss browns to Japan, Australia, and Southeast Asia. Most imports are dried or canned shiitake, oyster, and enokitake.

Button Mushroom

Commercial Agaricus cultivation in New Zealand began in the 1930s (Brightwell 1993), flourishing in the 1960s with over 80 farms, many small, and sometimes growing in containers such as old banana boxes. Most of these farms have disappeared and only 13 significant farms remain. Mushroom production is located in semi-urban areas in both main islands where efficient transport links provide access to major centres of population. Large and mid-range white hybrids are predominantly grown, as well as pure brown strains and A. bitorquis. All large growers are members of the Commercial Mushroom Growers’ Federation (NZ) Ltd., which coordinates the industry and is funded by grower levies. Farms are levied at the rate of 12 cents (NZ$) per m²; most of the funds are used for research, with the balance used for an annual conference. The cultivation process utilises compost prepared from pre-wetted wheat or barley straw, chicken and/or horse manure, and gypsum. All New Zealand mushroom farms produce their own compost. Four small farms produce compost conventionally: materials are mixed and formed into rows that are mechanically turned during 3 weeks of composting. The remaining nine farms have installed aerated bunkers, in some cases as a result of odour complaints, or as a response to environmental legislation. Some of the bunkers are fully enclosed, and others have been sited well away from residential areas. Compost is loaded into trays, bags, or shelves, depending on the system operated by each farm, and is pasteurised at 60°C before cooling for spawning. Wooden trays, each about 2m² surface area and stacked four or five high, are the most popular growing system, and are used by seven farms. Four farms use the Dutch shelf system (including bulk pasteurisation), and two farms cultivate in plastic bags. Spawn is prepared using cereal grain as the carrying medium, and is either bought from a specialist spawn company or, for one large grower, produced by their own laboratory. Following colonisation by the spawn, or sometimes concurrent with spawning, the compost is covered with a casing medium, which is usually made from New Zealand peat, lime and bentonite. By various means growers try to achieve a wet, dense casing material that will have a positive effect on mushroom quality. Almost all farms use casing inoculum as standard practice. Growing rooms typically have temperature, humidity, and CO2 control. Mushrooms appear 14 to 18 days after casing, and two to four flushes are harvested, by hand, from each crop.

Figure 1. Popularity of the Swiss brown Agaricus strain is increasing in New Zealand.

An acceptable yield is about 20-35 kg per m² over a cultivation period of 4 to 7 weeks from casing to ‘cook-out’. Harvested mushrooms are graded by quality and maturity, and are marketed as ‘buttons’, ‘cups’, and ‘flats’. Sale is through produce auctioneers or, increasingly, direct to supermarkets, which account for the bulk of retail sales of fresh produce in New Zealand. Mushrooms are distributed to markets in chilled conditions. New Zealand consumers have traditionally purchased button mushrooms loose, allowing consumer choise of quality and quantity but risking damage to the retail product. Prepackaging in polyethylene bags or other containers is becoming more popular, and the variety of mushroom packs continues to grow. In addition to the three maturity grades, demand for the Swiss brown strain (Fig.1) has developed strongly since 1995, accounting for about 16% of all mushrooms sold in 2000. Although some are canned, most mushrooms are sold fresh and are available year-round for about NZ$7-9 per kg retail, $4-5 per kg going to the grower.

Research

The New Zealand Institute for Crop and Food Research has carried out research and development for the Commercial Mushroom Growers’ Federation (NZ) Ltd for the past 6 years. Dr John Marshall, Scott Godfrey, and others, have conducted research in the following areas: identification and monitoring of mushroom pathogens (nematodes, bacteria, fungi and viruses; e.g., Marshall et al. 1998); development of quantitiative and qualitative molecular PCR methods of detection of pathogens; determination of indicators of compost quality; fungicide resistance monitoring; ecological studies of microbial interactions in composts; and understanding of bacterial blotch at the molecular level.

Specialty Mushrooms

‘Wood ear fungus’ (Auricularia polytricha) was the first mushroom to become economically important in New Zealand. For several decades from about 1870 New Zealand exported field-collected wood ear to China. The trade was centred on the west coast of the North Island where land was being cleared of native forests for farming. Between 1872 and 1883, for example, 1888 tonnes of dried wood ear were exported. Cultivation of specialty mushrooms has developed slowly and erratically in New Zealand, but has recently gained renewed market attention (Fig 2). The first large scale cultivation of ‘shiitake’ (Lentinula edodes) began in 1985 in Auckland, where shiitake was grown on a sterilised sawdust medium in polyethylene bags. At peak production the Auckland farm harvested seven tonnes (fresh weight) per week. Most of the product was exported fresh, with little attempt made to develop a local market. Financial pressures led to this farm’s closure less than 2 years later. Since then farms of smaller capacity have been established, and fortunes have varied. Today about five companies produce shiitake, mostly for the catering trade, though fresh shiitake is now available in many supermarkets. Growers lack a cooperative approach to marketing.

Figure 2. Button mushrooms and specialty mushrooms (shiitake, grey oyster mushroom, and white jelly fungus) on display in a New Zealand supermarket.

Development of ‘oyster mushroom’ cultivation was initially hindered by quarantine restrictions on importation of strains of Pleurotus ostreatus. Because this species does not occur naturally in New Zealand it is not approved for importation. Biosystematics research on the genusPleurotus (Segedin et al. 1995) recorded six species in New Zealand including P. pulmonarius, a species widely cultivated overseas, and cultivation of this species began in 1994. Currently, about five companies produce small quantities for supermarkets and the catering trade. As with shiitake, cultivation uses bags containing sterilised hardwood sawdust, and the process is not mechanised. Three to four flushes are harvested from each bag. Sciarid flies are a major local pest. ‘Enokitake’ (Flammulina velutipes) is another locally cultivated species that occurs naturally in New Zealand. With strict quarantine regulations essential to protect New Zealand’s forestry, horticultural, and livestock industries, importation of certain other edible or medicinal species, that do not occur naturally in New Zealand, is prohibited. Included among prohibited species is the medicinal ‘reishi’ (Ganoderma species).

Mycorrhizal Mushrooms

The Périgord black truffle (Tuber melanosporum) has been harvested from at least six truffle plantations (truffières) in New Zealand, with more than 50 other truffières growing truffle-infected trees (Hall et al. 2001). Seedlings of hazel (Corylus avellana) and English oak (Quercus robur) that have been infected with the truffle are planted out at sites where soil and climatic conditions resemble regions of natural black truffle occurrence in France and Italy. The first black truffles were produced in New Zealand in 1993, and Italian white truffle (T. magnatum) has also been harvested. With the exception of the field mushroom Agaricus campestris, harvest of wild mushrooms is rare in New Zealand. Knowledge of the edibility of New Zealand’s native species is poor. In pre-European times the indigenous Maori lived mainly near the coast, and generally considered mushrooms to be a poor food source (Riley 1988). There has been recent interest in collection of introduced mycorrhizal species, such as Rhizopogon rubescens under introduced Pinus radiata, and the newly recorded Boletus edulis s.l. under oak (Hall et al. 1998). There has also been recent research to cultivateTricholoma matsutake. Several isolates have been induced to form mycorrhizas with seedlings of Pinus densiflora and P. radiata (Hall and Wang 1992; Wang et al. 1997).

Future Developments

The profile of edible mushrooms in New Zealand is increasing as consumer preference moves towards healthy, organically grown fresh produce, and as the marketing of mushrooms becomes more coordinated and effective. Exposure of consumers to a range of edible mushrooms will likely increase the overall level of mushroom consumption. Vast areas of managed pine forests suggest a potential for seeding and harvest of mycorrhizal species, although research is currently in its infancy. Despite the disadvantage of distance to overseas markets, New Zealand is potentially well placed to increase production of wild mushrooms for export to the Northern Hemisphere because of its southern ‘out-of-season’ location. Expanded cultivation of a range of edible and medicinal mushrooms is also likely, helped by the country’s environmentally clean image and ready supply of waste plant materials as cultivation substrates. Productivity (per unit area) in Agaricus production continues to improve, perhaps in part due to the move to bunker composting, and the regular use of casing inoculum. However, productivity rates in New Zealand are low compared with those in Europe and North America, and it is likely that greater improvements will be made in the future. The increase in productivity has led to an increase in the supply of mushrooms, putting supermarkets in a favourable bargaining position. In this competitive environment greater emphasis has been placed on mushroom quality at the point of sale, and on marketing generally. This trend is likely to continue. Small farms tend to survive by niche marketing, e.g., growing mushrooms organically and growing specialty mushrooms. The new challenge to New Zealand’s mushroom growers is to expand domestic and export markets even further through more active marketing, and to develop more added-value mushroom products.

Acknowledgements

Funds for PKB were provided by the Foundation for Research, Science and Technology under contract no. C09X0001.

References

Brightwell, S. 1993: Feasting on fungi. New Zealand Geographic 18: 34-58

Hall, I. R.; Wang, Y. 1992: Current research on the cultivation of edible ectomycorrhizal fungi in New Zealand. Proceedings, International Symposium of Recent Topics in Genetics, Physiology and Technology of the Basidiomycetes. Japan, Chiba, Dec. 2-4, 1992.

Hall, I. R.; Brown, G. B.; Byars, J. 2001: The Black Truffle, its History, Uses and Cultivation (CD-ROM ed.). Christchurch, New Zealand Institute for Crop and Food Research.

Hall, I. R.; Lyon, A. J. E.; Wang, Y.; Sinclair, L. 1998: Ectomycorrhizal fungi with edible fruiting bodies. 2. Boletus edulis. Ecomonic Botany 42: 44-56.

Marshall, J. W.; Williams, M.; Grogan, H. M. 1998: A baseline survey of fungal pathogens and weed moulds on New Zealand mushroom farms. 7th International Congress of Plant Pathology, Edinburgh, Scotland, 9-16 August 1998. Abstract 6.28.

Riley, M. 1988: Maori Vegetable Cooking, Traditional and Modern Methods. Paraparaumu, Viking Sevenseas.

Segedin, B. P.,; Buchanan, P. K.; Wilkie, J. P. 1995: Studies in the Agaricales of New Zealand: new species, new records and renamed species ofPleurotus (Pleurotaceae). Australian Systematic Botany I: 453-482.

Wang, Y.; Hall, I. R.; Evans, L. 1997: Ectomycorrhizal fungi with edible fruiting bodies. 1. Tricholoma matsutake and allied fungi. Economic Botany51: 311-327.