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Identification:
The truffle found under pecan trees is Tuber lyonii (=T. texense).
It is the same genus but a different species as the very expensive
white or black truffles found in Europe. It has been found under
pecans in Georgia, Florida, Texas, and New Mexico, but this truffle
has been found on other tree species across eastern North America
from Mexico to Canada. The color of individual specimens varies
from light to dark brown and range in size from a buckshot up to
the size of a golf ball (occasionally larger). Some will be round
but most will have lobes and irregularities. The interior will be
very firm, lighter in color, and have a conspicuously "marbled"
appearance with alternating streaks of brown and white. They will
also have a very strong earthy aroma.
Truffle Hunting:
They are usually found in well-irrigated orchards, particularly
after a dry year such as 1999. They tend to be in more crowded,
shaded sections of the orchard. We have found them on numerous varieties
of pecans, but often in heavier clay soils. The fungus grows in
a mycorrhizal relationship with the pecan tree roots, but the truffles
will be found unattached in the top inch or two of soil. They may
be adjacent to the trunk or anywhere out to about the drip line
of the tree.  Areas
devoid of vegetation such as herbicide strips in managed orchards
are easier to search.
We have found truffles by simply raking the surface of the soil
with a stiff-tined garden rake.
Of course, a trained dog or pig would help since they are not usually
visible above ground! They can be seen sometimes following pecan
harvest where the sweepers have swept the soil surface.
Guidelines for Eating:
These truffles are generally considered edible, but as with any
wild mushroom it is an "eat at your own risk" situation.
Specimens should be fresh and have a firm texture. Avoid older,
darkened specimens, especially if they are noticeably softer than
usual. Truffles from managed pecan orchards that have been sprayed
regularly may have low levels of pesticide residue. The small quantities
consumed would reduce the potential risk, but this has not been
thoroughly evaluated. One pesticide that should be avoided is aldicarb
(Temik). This insecticide is highly toxic and is applied directly
to the soil. DO NOT CONSUME TRUFFLES FROM
ORCHARDS TREATED WITH TEMIK.
There are also other fungi that can be mistaken for truffles. Puffballs
are the most common. Features that distinguish them from truffles
include the fact that they usually are uniformly round or pear-shaped
and grow above ground. They also are often white and will have a
sterile base or stalk. Fortunately puffballs are generally edible
also, except for the genus Scleroderma which will be purple
when cut open. Potentially the most serious case of mistaken identity
would be to consume a mushroom "button" (ie. small, unexpanded
mushroom) from a highly poisonous species such as Amanita.
Slicing the specimen in half will reveal the stalk and cap instead
of the uniformly marbled interior of a truffle. As with any fungus,
it is important to know what you are eating as some species are
highly toxic. If you would like assistance in identifying truffles,
images can be submitted electronically to arachis@tifton.uga.edu
or samples can be mailed to the following address:
Dr. Tim Brenneman
Dept. of Plant Pathology
University of Georgia, CPES
Tifton, GA 31793
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