DOKTORI (PhD) - Nyugat-Magyarországi Egyetem Mezőgazdaság

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Using the swarming curve of the horse-chestnut leafminer, we made an
attempt to determine how densities of different larval instars changed in the
leaves during the investigation. The calculated time for the full development of
a moth generation (67 days) and the calculated main swarming time of the next
generation (July 13) squared with the facts, showing raison d’étre for the
calculation method.
From the parasitoids that emerged in relatively high abundance, swarming
times of Pediobius saulius and Baryscapus nigroviolaceus were closest to the
appearance of mature larval instars of the moth. The abundance of B.
nigroviolaceus was decreasing during the years which implies that, despite of
its favourable swarming time, it failed to increase its level of adaptation to the
new host.
Pnigalio agraules swarms somewhat earlier than Pediobius saulius what
can be part of the reason why it prefers younger moth larvae.
5. Relation between parasitism of C. ohridella and the intensity of
parasitoid attack
We determined how the attack intensity of the most abundant parasitoids
changed in Hédervár during the year 2004. P. saulius was most active at the end
of August what resulted in high parasitism rates of the moth after September 18.
Similarly, the high willingness of P. agraules to lay its eggs in September 4-11
yielded high parasitism rates in early October.
6. The infestation level of the horse-chestnut leaves
During the investigation period, there were considerable differences in the
number of moths that hatched from a given amount of horse-chestnut leaves.
When the number of the moths per leaf increased from one year to the other, the
rate of parasitism decreased and the opposite almost at all instances. For some
reason, parasitism was higher in years that were unfavourable for the horsechestnut
leafminer. However, the changes in the infestation levels were not the
result of parasitoid action, as rates of parasitism were too low to be the main
factor in determining abundance of C. ohridella.
There were no significant differences in infestation levels in the four
locations studied. Fluctuation in the population density of the moth was similar
in all locations in spite of their good distance. Low mean daily amounts of
precipitation combined with high average temperatures and longer daily
sunshine duration probably reduces the population density of the moth.
The number of the moth individuals, which were reared from a given
number of top-of-the-tree leaves, was always lower than the number of the moth
individuals reared from low-level samples of equivalent quantity. Our