viticola (100'000 sp/ml) per leaf (elicitor screening)
or spraying of whole plants with a sporangia suspension
(fungicide screening). Subsequently, plants
were incubated during 24 h at 100% RH and 21°C
and then grown 6 d at 60-80% RH at 20°C (light
regime: 16h day/8h night). Plants were incubated
for 12 h at 100% RH and darkness prior to disease
assessment. The standard disease assessment included
disease incidence (proportion of leaves showing
symptoms) and disease severity (proportion of
infected leaf surface) and/or lesion diameter.
The field experiments were carried out in the
screening-vineyard of FiBL in Frick, Switzerland. The
plot consists of 576 plants of the susceptible grapevine
varieties ‘Riesling-Sylvaner’ (‘Müller-Thurgau’)
and ‘Chasselas’ (‘Gutedel’). Twelve different treatments
were arranged in a „Randomized Block Design“,
with four replicates, each consisting of six
plants per variety. Besides an untreated control, a
copper treatment (‘Kocide DF’) and a systemic fungicide
(‘Aliette’), the test products and strategies
were deployed weekly. The plants were treated with
an air assisted knapsack sprayer until near run-off.
During the growing season, visual disease scoring
was carried out several times by recording disease
incidence (proportion of leaves with symptoms) and
disease severity (proportion of diseased leaf area) of
P. viticola on leaves and by recording disease severity
(%) on grapes (Table 4). The experiments were
carried out following the relevant EPPO-guidelines.