For healthy potatoes - Bayer CropScience

Fusarium ear blight
Snow mould in
winter barley
In order to support this, treated seed must
satisfy a number of requirements. It must
have an adequate thousand-seed weight,
good germinability, varietal purity and last
but not least, it must be free of infection.
Given the major importance of seed to
the farmer, legal requirements designed to
guarantee seed quality were established at
an early stage. One example is the set of
requirements laid down in the seed-quality
regulations that determine the maximum
allowable levels of infection of seed crops
by various pathogens. Seed lots that satisfy
these criteria are considered to be acceptable
– but no information is available about
exact levels of infection below these
thresholds.
The major problems here are those fungal
diseases that are transmitted exclusively
via the seed, and which can therefore
only be controlled effectively through
seed-treatment. These pathogens tend to
have very short generation times, so they
are often able to build up their populations
quickly and cause extensive damage, even
if infection in the original seed crop was
within the thresholds set in the seed quality
regulations. This is why severe infections
occur regularly if seed-treatment is omitted,
even if high-quality seed has been
used: this results in serious losses in yield
and quality, and ultimately, economic
penalties. The only reliable method for
avoiding this problem remains the systematic
use of seed-treatments based on effective
crop protection compounds.
Modern active substances have
a broad spectrum-of-action
Following the ban, more than 25 years ago,
on the marketing of mercury-based crop
protectants, a whole range of new active
substances and products were developed
for use as seed-treatments. Some of these
new compounds were the first systemic
active substances; they were able to control
pathogens that had previously been uncontrollable,
or which were controllable only
through dosages so heavy that they jeopardized
the vitality and germinability of
the seed. Today, a large number of different
systemic seed-treatments are available on
the market, which can differ greatly in
their properties, as well as in price. Nor has
product development stopped in this area,
as is demonstrated by the ongoing adoption
of active substances from the strobil-
urin class into new seed-treatment products.
Seed-treatments designed to control
seed-borne pathogens, including the various
smuts, the snow mould pathogen
(Microdochium nivale), and Fusarium culmorum,
must meet certain minimum standards
in terms of percent control. Product
efficacy against seed-borne pathogens is
tested for during the biological trials that
are required under the regulatory procedure.
However, many systemic active substances,
especially those in the triazole
class, show spectra-of-action that go well
beyond the official requirements, controlling
a range of significant leaf-diseases
too. These include the pathogens that cause
mildews, net-blotch of barley, common
root rot of barley and rye, Rhynchosporium,
both species of Septoria, rusts,
Fusaria and others. One specialist area in
the use of seed-treatments is the control of
take-all of cereals. This disease is not actually
seed-borne, but as a „disease of rotations“,
it can nevertheless only be controlled
directly using the appropriate seedtreatments.
There is now a choice of seed-treatment
products on the market that are registered
for the control of these pathogens. Some of
these have certain incidental effects that
can positively influence the emergence and
early development of the cereal plant, i.e.
beyond the active substance’s direct fungicidal
effect. Although for some diseases
(e.g. smuts), there is a direct correlation
between the number of infected ears and
the extent of harvest losses, the yield benefit
associated with the use of broad-spectrum
seed-treatments is not always attributable
to the control of a specific pathogen.
As well as differing in their spectra-ofaction,
seed-treatments differ in their
potency, particularly under “worst-case”
conditions. Strong infection potential tends
to highlight a product’s reserves, or con-
Stinking smut of wheat
Loose smut of barley
2/06 COURIER 29