sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

Cumulative mortality (%)
100
50
0
SDÜ ORMAN FAKÜLTESİ DERGİSİ
0 2 4 6 8 10 12
Days
197
Control-OIL-25-fall
Mycotal-OIL-25-fall
Beauveria-OIL-25-fall
Figure 2: Cumulative mortality of Cryptococcus fagisuga exposed to Lecanicillium
muscarium (Mycotal®), Beauveria bassiana and control over a period of 11 days.
A higher mortality level of scale insects treated with L. muscarium was
observed on samples collected in winter, compared with the fall samples. The
winter mortality may have been caused by very cold temperatures (-35°C)
measured in February (Environment Canada). Also, the measured mortality rate
with L. muscarium was increasing much faster, reaching 50% in only 7 days
compared with 10 days in the previous fall tests (Figure 3). Our observations are in
agreement with Crosby and Bjorkbom (1958), who consider that severe winter
temperatures of -35 o F (-37 o C) or lower are lethal to beech scale insects.
Eggs treated with L. muscarium showed very low mortality, but the treatment
slowed down their development (Figure 4). Fifty percent hatching was reached
after 8 and 12 days respectively for the L. muscarium treatment and control. The
fungus was observed to colonize only the external surface of the egg chorion.
However, when they hatch, first instars become rapidly infected by the fungus
already present on the egg chorion.
Cumulative mortality (%)
100
50
0
0 2 4 6 8 10 12
Days
Control-OIL-25-fall
Mycotal-OIL-25-fall
Control-OIL-25-winter
Mycotal-OIL-25-winter
Figure 3: Mortality of scale insects over a period of 11 days from samples collected in
the fall and winter, after treatment with Lecanicillium muscarium (Mycotal®) and control.