http://dallasfood.org/2011/06/gianduia-gianduja-nutella-part-23/
In terms of productivity on a per tree or per hectare basis, TGL is only an
average performer in Piedmont (1). However,
outside of Piedmont, the cultivar’s productivity has been
even lower.
In a series of trials conducted by Oregon State University in Corvallis, Oregon, Tonda Gentile delle Langhe had the
lowest cumulative yield (in both nut and kernel weight) of the nine cultivars tested. TGL’s yield of both nut and kernel were less than a third that of Oregon’s industry standard cultivar, Barcelona (2). TGL’s low productivity in Oregon is not unique. The cultivar has also
severely underperformed in trials in Portugal, Argentina, Sicily, and Croatia (3). Current pricing premiums for kernel quality cannot offset the
significant productivity gap between Tonda Gentile delle Langhe and other popular cultivars.
Within Piedmont, Tonda Gentile delle Langhe faces few
serious threats from bacteria, viruses, and pests that afflict hazelnuts in other growing regions, apart from a few species of insects that infest kernels (4). However, outside its native territory, it has proven to be
much more vulnerable.
Tonda Gentile delle Langhe is
highly susceptible to bud mites (
Phytoptus avellanae), which infest and feed on buds in spring, preventing flowering, and lowering yield (5).
TGL is vulnerable to gray mold (
Botrytis cinerea), a
fungal infection that damages nuts and causes them to prematurely drop. The cultivar has
little resistance to bacterial blight (
Xanthomonas campestris) and eastern filbert blight (
Anisogramma anomala), both of which reduce vigor and can ultimately kill the tree (6).
