Truffles Map Europe
Tuber melanosporum (Perigord black truffle) production in Quercy, France, since 1920 (Fauconnet and Delher 1998).
However, there is mounting concern that the quantities of mycorrhizal mushrooms that can be harvested are declining. While articles with titles like "Disappearing Mushrooms: Another Mass Extinction?" (Cherfas 1991) are somewhat alarmist, it is undeniable that there have been catastrophic declines in the harvest of some mycorrhizal mushrooms over the past hundred years. For example, at the beginning of the twentieth century production of the Périgord black truffle is estimated to have been 1000-2000 tons, but modern production, even in a good year, is often less than 10 percent of this. Forty tons is considered a bad year, 150 tons a good one (Lefevre and Hall 2001, Olivier 2000). The official figures for truffle production for Quercy, France, illustrate this trend well, as do those for matsutake harvests in Japan.
Many suggestions have been advanced to explain the decline. Very likely causes are deforestation and the establishment of plantation forests with trees that are poor hosts or that are planted much closer together than occur in natural forests. Other possibilities include compaction of the soil by hordes of pickers; acid rain that can make a soil too acid for either the mycorrhizal fungus or its host plant; global warming that has gradually made climatic conditions unsuitable for the fungus or host; the loss, during two world wars, of many of the people with knowledge of where and how to harvest mushrooms (particularly so with species such as truffles that fruit underground); the underreporting of harvests by those reluctant to pay taxes; and younger generations being more inclined to spend their
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Tricholoma matsutake (matsutake) production in Japan since 1915 (Wang et al. 1997, Japan External Trade Organization 2000a, 2000b).
time behind a computer in an office than wandering around chilly forests at daybreak searching for an unpredictable income (Ciani et al. 1992, Olivier 2000).
Pickers may also be picking mycorrhizal mushrooms when they are still too small, knowing that if they leave them until the following morning to grow to a reasonable size someone else may get there first. An example of what happens when wild mushroom mania strikes comes from Christchurch, New Zealand, in the 1990s. Hagley Park in Christchurch was established in the 1850s with oaks from England that were brought out by some of the first "official" European settlers. It seems likely that around the same time these oaks were introduced porcini (Boletus edulis) also arrived, probably on the roots of the same trees. Until 1993 porcini was quietly harvested in Hagley Park by a few Europeans who knew what they were harvesting and did not intend to tell anyone else about it. Across town, on the Canterbury University campus, porcini was meeting a more ignominious fate as periodic mowing delivered shredded porcini to the compost heap. Then in 1993 an observant gardener on the university campus decided to take a couple of the fruiting bodies to Tony Cole for identification. This in turn led to exposure on television and in newspapers and scientific articles, all heralding the find. Since that time there have been dozens of collectors, rather than a few keen amateurs, and the fruiting bodies have been collected almost as soon as they show themselves above the
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Year ground. One picker even admitted going out hunting with a torch early in the morning just to make sure he found a few for his breakfast. As a consequence, the weight of porcini now harvested in Christchurch is quite probably lower today than it was in the 1980s.
The edible ectomycorrhizal mushrooms held in the highest regard are the Perigord black truffle (Tuber melanosporum), Italian white truffle (Tuber magnatum), porcini (Boletus edulis), chanterelle (Can-tharellus cibarius), and matsutake (Tricholoma matsutake). However, Caesar's mushroom (Amanita caesarea), honshimeji (Lyophyllum shimeji), Burgundy truffle (Tuber uncinatum), Oregon white truffle (Tuber gibbosum), saffron milk cap (Lactarius deliciosus), shoro (Rhi-zopogon rubescens), and many other mushrooms are also very popular in some countries.
Because of the general decline in the harvest of many edible myc-orrhizal mushrooms, prices have been steadily climbing, particularly since the 1980s. However, the price of the Italian white truffle outshines all others, with retail prices increasing fourfold from around $1000 per kilogram in 1995 to $4000 per kilogram in 1999 (Anonymous 2000a). By 2000, retail prices had jumped to $5680 per kilogram in Milano, with $13,243 per kilogram paid for a 497-g specimen at the Alba Truffle Festival (Johnston 2000). The prices of the next two most expensive species of mycorrhizal mushrooms are trivial by comparison, with Perigord black truffles produced in New Zealand and out of season to the Northern Hemisphere managing only $1450 per kilogram, about twice the 1999-2000 in-season price. It is to be wondered what price Italian white truffles would fetch if they too were produced out of season in New Zealand!
The earliest cultivation of an edible ectomycorrhizal mushroom was achieved by Joseph Talon in the early 1800s in France (Hall et al. 1994). He found, probably accidentally, that if he transplanted oak seedlings from the rooting zones of trees that produced Perigord black truffles, eventually the transplants would also produce truffles. Despite its lack of sophistication, Talon's technique was widely used for 150 years. A similar technique has been used in Japan to produce plants infected with Lyophyllum shimeji (Fujita et al. 1990).
The main drawback with Talon's technique is that seedlings are exposed to infection by all organisms in the rooting zone of the parent tree and, consequently, may become contaminated by patho genic fungi, nematodes, and insect pests, as well as faster-growing competing ectomycorrhizal fungi that do not produce edible mushrooms. However, in the late 1970s, after much research, French and Italian scientists developed techniques that subsequently led to routine greenhouse practice for infecting plants with various species of truffles. Scientists have also had limited success infecting plants with other types of edible mycorrhizal mushrooms, including Caesar's mushroom (Amanita caesarea), porcini (Boletus edulis), chanterelle (Cantharellus cibarius), saffron milk cap (Lactarius deli-ciosus), dotted-stalk bolete (Suillus granulatus), Jersey cow bolete (Suillus bovinus), shoro (Rhizopogon rubescens), and matsutake (Tri-choloma matsutake).
Currently only a few species of Tuber, including the Périgord black truffle, Italian white truffle, and Burgundy truffle, have been produced in commercial quantities in plantations, although fruiting bodies of saffron milk cap and dotted-stalk bolete have formed in experimental plantations. This situation has partly arisen because effective techniques for infecting plants with many edible ectomycorrhizal mushrooms have yet to be devised. Also, research has not yet identified the climate and soil biological and physiochemical conditions most edible ectomycorrhizal mushrooms require, both to proliferate and fruit. Publications consolidating this type of information have only recently begun to appear.
Tuber melanosporum (Périgord Black Truffle)
Although the cultivation of the Périgord black truffle is still an inexact science, this truffle has been cultivated for much longer than any other ectomycorrhizal fungus. As a result, Périgord black truffle truffières now cover thousands of hectares in Europe (Pacioni and Comandini 2000). The cultivation of this truffle is covered in some detail in books in English, French, Italian, and Spanish, but as it provides such a useful template for other edible mycorrhizal mushrooms, the most important points are included here. Périgord black truffle cultivation is also encouraged by governments in several countries as an alternative source of income to conventional agriculture (Colinas et al. 1999, Olivier 2000).
Production of infected plants
Although Talon's technique is still used by some Périgord black truffle growers, their plants are often heavily contaminated with fast-growing and aggressive contaminants such as Scleroderma species
(Hall et al. 1994). Consequently, greenhouse techniques predominate. Many trees will host the Perigord black truffle, but hazel (Corylus avellana) is most commonly used because it can be grown relatively easily, it forms many fine roots that are readily converted to mycor-rhizas by the fungus (Chevalier 1998), and it commonly produces truffles several years earlier than other host plants (Giovanetti et al. 1994, Hall et al. 1994). Other host plants include Mediterranean hazel (C. colurna and C. heterophylla), various species of oak (Quercus), and hop hornbeam (Ostya carpinifolia), which are produced by, among others, Agri Truffe in France and the New Zealand Institute for Crop and Food Research (Chevalier 1998, Craddock 1994, Hall et al. 1994, Lefevre and Hall 2001).
Unfortunately, some producers of infected plants make no distinction between inoculated and infected states. "Inoculated" merely means that the fungus has been introduced to the plant. However, unless the fungus also produces a good infection on the plant's roots, mushroom production will not occur. Completely uninfected plants
are rare, but it is not unusual to find the roots of commercially produced plants only partly infected with the Périgord black truffle and the remainder infected with competing ectomycorrhizal fungi. Some commercial producers of truffle-infected plants assume that when their plants are placed in ideal sites any contaminating competing fungi on the roots will eventually die out, but there is little justification for this belief.
Although the inoculation procedure is an important step in producing plants infected with Périgord black truffles, the critical phase is the subsequent six to twenty-four month incubation period. During this time, incorrect watering, air or soil temperatures, light levels, soil pH, nutrient concentrations in the potting medium, and, not least, contaminating ectomycorrhizal fungi, can all upset the infection process. Saprobic fungi may also cause problems, sometimes forming a loose weft of hyphae around the host plant's uninfected root tips, perhaps attracted by sugars leaking out. This presents a significant barrier to infection by the Périgord black truffle. Inoculated plants can also become contaminated with major pathogens. For this reason, plants infected with the Périgord black truffle that are produced in Europe cannot be imported into Australia, North America, New Zealand, or South Africa unless treated with chemicals that render them useless. In some cases infected plants have been smuggled into countries via a back door with no regard to the devastation a major pathogen riding piggyback on the host plants might have on a country's forests and plantation forest industry. Needless to say, the penalties these people face if caught are significant.
Soils and climate
It is critical that infected plants are placed in areas where the ecological conditions suit both the host plant and its fungal partner. In France, Italy, and Spain extensive surveys have determined where the ideal truffle-growing areas are located. These have well-aerated, well-drained, alkaline soils rich in calcium carbonate and with a carbon-nitrogen ratio of about 10:1, and they experience warm summers and cool winters. In Europe these areas are found to the west, south, and east of the Massif Central in France, in the southwest corner of France, northeastern Spain, and northern Italy (Hall et al. 1994). Somewhat surprisingly, of the eight productive Périgord black truffle truffières outside Europe, all but one have been established on naturally acidic soils that have been limed so that the pH is closer to the pH 7.9 optimum for the Périgord black truffle.
Planting and maintenance
A wide range of planting arrangements has been suggested by researchers (Hall et al. 1994). They usually recommend an alternating arrangement of several species of host plants, as one might be better suited to the ecological conditions than another, and as some species, like hazels, may produce early in the life of a truffière while others, like oaks, may start producing later but continue for longer. Planting two or more host species, such as hazels and oaks, also affords some protection against pathogens, which are unlikely to affect dissimilar species.
While expensive, artificial windbreaks have been used in some truffières. This involves surrounding the young trees with protectors such as Tree Guards, strong plastic tubes 10-15 cm across and 60-100 cm high. These are usually successful in preventing desiccation and damage by wind and browsing animals, at least for the first year or two. After planting, irrigation is often necessary to prevent plant death. Careful aeration of the ground in spring, particularly in areas where the soil has a poor structure, is also important in assisting spread of the truffle fungus and producing large, well-formed truffles (Lefevre and Hall 2001).
Once fruiting starts, perhaps ten years after planting, soil moisture must again be maintained, particularly from midsummer onward, to ensure that young truffles do not die. The trees are usually pruned to a cone shape (with the point downward) to ensure that the soil is heated sufficiently by the sun in spring and autumn and protected from losing too much moisture during the heat of the day in summer. Laying branches on the soil around the trees and adding various mulches have also been used as ways to conserve moisture. The ancient French adage "Water in July, truffles at Christmas" clearly embodies an understanding of the importance of soil moisture.
Plant health is critical to successful truffle growing. In Europe, the pests and diseases of host trees cause major problems, and books have been published offering advice on how to control them (for example, Sourzat 1994). Iron deficiency in plants growing on very alkaline soils can cause yellowing of leaves and, in severe cases, death, with oaks more susceptible than hazels. This condition can be treated by placing chelated iron, such as Ferri-Chel Microgranular, in the rooting zone. Alternatively, a solution of chelated iron, such as Sprint 138, can be sprayed onto the foliage from bud break onward, with repeat sprayings every ten to fourteen days. Weeds around the trees can be treated with various herbicides, but Roundup has been used most frequently. The very poisonous desiccant herbicide Paraquat has also been used in the past, but Buster is a much safer option.
Once the fungus has become well established around its host tree, it kills many of the weeds in the rooting zone, leaving bare areas around the truffle-infected trees. In France this area is called the brûlé, and its development is said to herald the start of truffle production. Prior to the formation of the brûlé, weed control is often done by hand to avoid root damage, but in large truffières machinery or the careful application of herbicides is essential. In France once the brûlé has developed the truffière can be intensively managed with spring tilling, tree pruning, and irrigation, which, in combination, lead to early fruiting. This system is called the Pallier method (Chevalier 1998) and the techniques are similar to those used in New Zealand (Hall et al. 1994). The alternative is the Tanguy method, in which mowing replaces tilling and trees are left unpruned. In France the additional costs associated with the Pallier method have been estimated to be the equivalent of 8 kg of truffle per hectare (Olivier 2000). The cost is likely to be smaller in Southern Hemisphere countries because of the
Two closely planted oaks (Quercus) infected with Tuber melanosporum (Périgord black truffle). Notice the strong brûlé. (Hall)
higher returns from the sale of truffles, which are out of season to the Northern Hemisphere harvest.
Unlike most edible mycorrhizal mushrooms that form above the ground, black, rough-walled, potato-like Périgord black truffles are formed just at the soil surface or below ground. Finding them can, therefore, be a bit of a problem. One way is to get down on hands and knees and sniff them out. However, using this method, the owner of even a modest-sized truffière would probably spend more on trousers than could ever be made from collecting truffles. Another technique, developed out of desperation by a dogless New Zealand owner of a productive truffière, was to walk around in bare feet. Because the soil did not contain any stones, she reasoned that a hard spot under the soil surface represented a truffle. She then went down onto her hands and knees and sniffed to confirm whether the truffle was ripe or not before claiming her prize. What is really needed, however, is a more mobile nose—preferably one much more sensitive than that of a human. The traditional solution is a female pig, which has not only a nose even better than a dog's but also a natural yearning for truffles.
To select a pig, simply walk into a litter of piglets with a truffle in your hand, or tucked into your sock, and buy the one that shows the most interest. Train the piglet to walk on a lead. When she finds a truffle, persuade her that a piece of turnip, bread, or cheese is a fair swap—a bargain that may have to be reinforced with a couple of prods with a sharp stick. With piglets this is perhaps not too difficult, but it can pose something of a problem when the piglet grows to twice your own weight and does not discriminate between truffles and fingers. Consequently the majority of truffle hunters now use specially trained dogs, which, incidentally, fit better on the back seat of a car and are a bit less obvious when taken truffle poaching.
Under ideal conditions Périgord black truffle production can begin three years after inoculated trees are planted (Giovanetti and Fontana 1982), but generally the owner of a truffière will have to wait five to ten years or more before the first, often elusive, truffle is found. In artificial truffières, yields are often considerably higher than the 10 kg per hectare that might be expected from a forest that naturally produces Périgord black truffles. Yields in excess of 40 kg per hectare are infrequent, primarily because contaminating fungi often partially or completely occupy the roots of many of the trees (Chevalier 1998, Hall et al. 1994). However, several eleven- to fourteen-year-old French truffières have produced up to 150 kg per hectare (Chevalier 1998).
A truffle is just an elegant bag of spores, so those not eaten by a pig, dog, or human are not wasted: they eventually rot in the ground, release their spores, and await the arrival of a root from the right host plant. Similarly, the spores in truffles that were eaten by a pig will eventually find their way back to a well-manured patch of soil, probably some distance from the original host, where they may wait, perhaps for years, until conditions are right for germination.
Cultivation outside Europe
In the early 1980s many truffières were established in the United States using plants that were imported from Agri Truffe in France (Picart 1980). While truffles have never been harvested from the vast majority of these truffières and many have now fallen into disrepair, one near Ukiah in northern California began producing Périgord black truffles around 1988 (B. Hatch, personal communication). Truffles were also found in a truffière on Franklin Garland's property near Hillsborough, North Carolina, in 1993, when a group of students was
casually invited to have a look for themselves (F. Garland, personal communication).
The first attempts to produce the Périgord black truffle in the Southern Hemisphere for out-of-season Northern Hemisphere markets began in New Zealand in the mid 1980s when English oak and hazel seedlings were infected with the fungus. Fortunately these experiments were successful, and the first truffières were established in 1987 (Hall et al. 1994). Oakland Truffière, near Gisborne on the east coast of the North Island, produced a few small truffles in 1993, some five years after planting. Disaster then appeared to have struck when Tuber maculatum and T. dryophilum, two less desirable truffle species, seemed to have taken over the 0.5-hectare truffière and began producing more than 100 kg of their own truffles each year. However, a new management regime was implemented, and between May and August 1997, 9 kg of Périgord black truffles were harvested, some weighing more than 1 kg. This was the first commercial harvest of a cultivated ectomycorrhizal mushroom in the Southern Hemisphere and the successful culmination of more than a decade of research. Since then, harvests have gradually increased, and although the owner of Oakland Truffière is a little reluctant to say just how much of the delicacy he is now harvesting, it is in excess of 40 kg per hectare. In 2000, three other New Zealand truffières and two Tasmanian truffières (Anonymous 2000b) between the latitudes 39°S and 43°S also began producing.
Sources of advice for growers
Throughout France and Italy, truffle societies hold parades during the truffle season and competitions are held to find the best truffle dog, which may later be offered for sale for perhaps more than $1000. Workshops and visits to truffières provide an important forum for the exchange of information between growers and scientists. Helpful periodicals such as Le Trufficulteur Français and Tartufomania are also available, while articles in popular horticultural and agricultural magazines review important topics such as choice of soil, size of harvests, and marketing (Garcia-Falces and De Miguel Velasco 1995a, Primavera 1995, Urbani 1995). Not surprisingly, elsewhere in the world similar associations are few and far between, although there is the North American Truffling Society, the New Zealand Truffle Association, and the fledgling Australian Truffle Association. Details on periodicals and societies are listed at the back of the book.
The owners of plantation forests receive almost no income during the life of a forestry plantation, apart from the sale of small amounts of timber from thinnings. They must carry the cost of establishing the plantation, plus interest charges, for twenty-five years or more before seeing a return on their investment. In many countries this has meant that only species with relatively short rotations are planted, while species with rotations longer than seventy years have been largely ignored, even though they may produce timber with superior characteristics.
Wild mushrooms are harvested from forests in many countries where their collection and sale are significant industries. For example, in 1992 the forests of Idaho, Oregon, and Washington in the United States yielded $41 million worth of wild mushrooms (Schlosser and Blatner 1995, Thomas and Schumann 1993). The edible mushrooms in these forests are there because they were either in the soil when a plantation was established or were acquired from the nursery soil where seedlings were raised. It is the exploitation of this second possibility that has excited scientists in a number of countries, including
New Zealand (Hall and Wang 1996), Sweden (Danell 1994), and England (Hall and Wang 2000).
Very expensive mycorrhizal mushrooms, like the Perigord black truffle, Italian white truffle, Caesar's mushroom, and matsutake, warrant the expense of establishing plantations dedicated to their production (Hall et al. 1994, Hall, Zambonelli et al. 1998). Because of the high costs and the not inconsiderable risks involved, it is questionable whether there is sufficient economic justification for setting up specialized plantations dedicated to the production of mushrooms with relatively low prices, such as porcini and saffron milk cap. An alternative is to produce these lower-priced mushrooms as secondary crops in plantation forests (Hall and Wang 2000).
All the main edible ectomycorrhizal mushrooms of commerce are native to the Northern Hemisphere. Only a few of these—for example, porcini (Hall, Lyon et al. 1998, Marais and Kotze 1977, Van der Westhuizen 1983), saffron milk cap, and shoro—have made the accidental journey to the Southern Hemisphere. This probably occurred on the roots of small deciduous trees that some of the early European settlers of Australia, New Zealand, and South Africa took with them as reminders of the land of their birth. Perhaps if more of the early settlers had been French or Italian instead of British, delicacies like the chanterelle, Perigord black truffle, and Italian white truffle would already be established in these countries.
Because most edible ectomycorrhizal mushrooms of commerce are available fresh only in the Northern Hemisphere for the short periods during the year in which they fruit, the chef, the gourmet, and those who would like to include one of these mushrooms in a favorite dish out of season are reliant on preserved specimens. There is, therefore, a golden opportunity to produce these fungi, such as the Perigord black truffle, in Southern Hemisphere countries in order to satisfy out-of-season demand in Northern Hemisphere markets.
Continue reading here: Collecting Wild Mushrooms
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