R Zasso, I Pertot, A Sztjenberg
Powdery mildew (Sphaerotheca macularis f.sp. fragariae) causes severe losses in
strawberries. The aims of the study were to test several alternatives to chemical fungicides of
strawberry powdery mildew and to compare two populations of S. macularis, one from a temperate
climate (Northern Italy) and the other form a Mediterranean climate (Israel) in their sensitivity to the
control agents. A wide selection of BCAs (Ampelomyces quisqualis, Trichoderma harzianum T39,
Bacillus subtilis, Bacillus sp. F77, Cladosporium tenuissimum), chemical fungicides (azoxystrobin,
kresoxim methyl, penconazole, hexaconazole, miclobutanil, tetraconazole, triadimenol, nuarimol,
fenarimol, pyraclostrobin + nicobifen, mancozeb + famoxadon, pirifenox, pirazofos, polyoxin Al,
sulphur, sulphur + pinolene, ultrafine oil), plant extracts (Milsana – an extract of giant knotweed,
neem oil, Agribioprop – a plant extract), resistance inducers (acylbenzolar-s methyl, harpin), salts and
mineral nutrients (potassium bicarbonate, sodium bicarbonate, potassium phosphate monobasic,
calcium carbonate, iron chelate, mineral nutrients solution) were tested in conidial germination tests.
Several control agents were more effective on leaves than on glass (acylbenzolar-s methyl, harpin, T.
harzianum T39 and Bacillus sp. F77). Salts better influenced germ tube elongation than germination.
All the chemical fungicides were effective in inhibition of germination and/or the rate of germ tube
elongation. The chemicals that had no significant effect on germination were tetraconazole and
triadimenol, but they reduced germ tube elongation. Kresoxim methyl was the only chemical that had
a different effect in Italy if compared with Israel, probably because of the presence of resistant strains
in Israel and not in Italy, where it is not yet registered for the use on strawberry. The role of the plant
tissue in the mechanism of action of some biocontrol agents and resistance inducers can be
hypothesised. Although RAPD PCR analysis of genomic DNA with arbitrary primers and apPCR with
primers specific to microsatellites show that pools of isolates randomly collected in Italy and Israel
were different, the Italian and Israeli S. macularis populations can be considered similar in sensitivity
to the tested control agents, except for chemicals that are already known to select resistant strains.
R Zasso, I Pertot, A Sztjenberg
Powdery mildew (Sphaerotheca macularis f.sp. fragariae) causes severe losses in
strawberries. The aims of the study were to test several alternatives to chemical fungicides of
strawberry powdery mildew and to compare two populations of S. macularis, one from a temperate
climate (Northern Italy) and the other form a Mediterranean climate (Israel) in their sensitivity to the
control agents. A wide selection of BCAs (Ampelomyces quisqualis, Trichoderma harzianum T39,
Bacillus subtilis, Bacillus sp. F77, Cladosporium tenuissimum), chemical fungicides (azoxystrobin,
kresoxim methyl, penconazole, hexaconazole, miclobutanil, tetraconazole, triadimenol, nuarimol,
fenarimol, pyraclostrobin + nicobifen, mancozeb + famoxadon, pirifenox, pirazofos, polyoxin Al,
sulphur, sulphur + pinolene, ultrafine oil), plant extracts (Milsana – an extract of giant knotweed,
neem oil, Agribioprop – a plant extract), resistance inducers (acylbenzolar-s methyl, harpin), salts and
mineral nutrients (potassium bicarbonate, sodium bicarbonate, potassium phosphate monobasic,
calcium carbonate, iron chelate, mineral nutrients solution) were tested in conidial germination tests.
Several control agents were more effective on leaves than on glass (acylbenzolar-s methyl, harpin, T.
harzianum T39 and Bacillus sp. F77). Salts better influenced germ tube elongation than germination.
All the chemical fungicides were effective in inhibition of germination and/or the rate of germ tube
elongation. The chemicals that had no significant effect on germination were tetraconazole and
triadimenol, but they reduced germ tube elongation. Kresoxim methyl was the only chemical that had
a different effect in Italy if compared with Israel, probably because of the presence of resistant strains
in Israel and not in Italy, where it is not yet registered for the use on strawberry. The role of the plant
tissue in the mechanism of action of some biocontrol agents and resistance inducers can be
hypothesised. Although RAPD PCR analysis of genomic DNA with arbitrary primers and apPCR with
primers specific to microsatellites show that pools of isolates randomly collected in Italy and Israel
were different, the Italian and Israeli S. macularis populations can be considered similar in sensitivity
to the tested control agents, except for chemicals that are already known to select resistant strains.