© Benaki Phytopathological Institute
Hellenic Plant Protection Journal - Special Issue
80
known, it has been demonstrated to differ
from those of commercial fungicides such
as benzimidazole, demethylation inhibitor
(DMI) and strobilurin. Cyflufenamid is high-
ly active on a wide range of powdery mil-
dews, with preventative, residual and cu-
rative activity. On the plant, it has contact,
translaminar and vapour properties. The
combination of difenoconazole and cyflufe-
namid in Dynali 60/30 DC provides a broad
spectrum foliar and bunch fungicide to con-
trol
Erysiphe necator
(powdery mildew),
Guignardia bidwellii
(black rot) and
Pseudo-
pezicula tracheiphila
(syn.
Pseudopeziza tra-
cheiphila
) (rotbrenner), with excellent crop
safety. The curative properties of the triaz-
ole difenoconazole are enhanced by the cu-
rative activity of cyflufenamid. The curative
activity is extremely useful in practice, even
in the broadly recommended preventative
spray programmes. Under field conditions,
especially under very high disease pressure,
purely preventative action is frequently not
enough to provide reliable control because
several stages of the pathogen are simulta-
neously present. For powdery mildew man-
agement it is strongly recommended that a
mixture of products is used as well as alter-
nating products with different modes of ac-
tion, in order to avoid the selection of strains
that are resistant to single site active sub-
stances. For this reason the availability of
new products is essential in order to design
efficient and long-lasting effective crop pro-
tection programmes.
O
RAL
& P
OSTER
P
RESENTATIONS
Study of the inherent risk of resistance to dicarboximides and
phenylpyrroles by
Alternaria solani
Ε.L. L
AFKA
, Α.Α. M
ALANDRAKIS
and Α.Ν. M
ARKOGLOU
Pesticide Science Laboratory, Agricultural University of Athens, 75 Iera Odos Str., GR-
118 55 Athens, Greece
Mutants of
Alternaria solani
moderately
(RF: 15, based on EC
50s
) and highly (RF: 150
to >1000) resistant to phenylpyrroles were
isolated at high mutation frequency af-
ter UV-mutagenesis and selection on me-
dia containing fludioxonil. Cross resistance
studies with other fungicides showed that
the mutation(s) that conferred resistance
to fludioxonil also reduced the sensitivity
of mutant strains to the aromatic hydrocar-
bon (quintozene) and dicarboximide (iprod-
ione and vinclozolin) fungicides. No effect
of phenylpyrrole resistance mutation(s) was
observed on the fungitoxicity of the triaz-
ole flusilazole, the imidazole imazalil, the
carboxamide boscalid and the QoIs pyra-
clostrobin and azoxystrobin. Furthermore,
an increased sensitivity (RF: 0.5-0.07) of the
mutant strains to the anilinopyrimidine fun-
gicide pyrimethanil was observed in all flu-
dioxonil-resistant strains tested. Interesting-
ly, a significant reduction in the sensitivity
of a mutant strain to pyraclostrobin was ob-
served. Study of fitness determining param-
eters showed that the mutation(s) confer-
ring resistance to phenylpyrroles did not
affect, or only slightly affected, the myceli-
al growth rate, osmosensitivity, pathogenic-
ity and conidial germination in most mutant
strains tested. On the contrary, most of the
fludioxonil-resistant strains produced few-
er conidia than the wild type strain. Almost
all fludioxonil-resistant strains retained their
resistance levels even after 9 subcultures on
fungicide-free medium. The above data in-
dicate that there is a considerable inherent
risk of
Alternaria solani
resistance to fludiox-
onil and that appropriate anti-resistance
strategies should be implemented to avoid
future control failures.
