Forstschutz
Aktuell Forstliche Bundesversuchsanstalt |
Nr.21/1997 Rosskastanienminiermotte |
Cameraria Ohridella
Occurrence of Cameraria ohridella in
Austria.
Cameraria ohridella was first observed in Upper Austria near Linz in
1989. Since then practically all horse chestnut trees all over the country
have been attacked by the moth. Fig. 1 shows the situation in Austria in
the year 1996. The heaviest attack occurred in the east and southeast of
Austria, mainly because of favorable climatic conditions.
Occurrence of Cameraria ohridella in
Germany.
According to the answering of a questionnaire sent to all German plant
protection organisations about the occurrence of the horse chestnut mining
moth, infested trees were observed in 1996 in the south east of Bavaria up
to Munich and around Dresden. But as the symptoms caused by the mining
moth are not so well known by now, it is possible that these symptoms are
sometimes mixed up with Guignardia aesculi fungus necrosis on the leaves.
Therefore it is assumed that the moth has also spread to other parts of
the country.
Occurrence of Cameraria ohridella in
Hungary
Cameraria ohridella was first recorded 1993 in South-Transdanubia near
the border to Austria. From there it spread quite rapidly to the more
eastern parts. Hungary is the first country where high levels of natural
parasitoids were observed.
Occurrence of Cameraria ohridella in the
Cech Republic
First findings of Cameraria ohridella occurred in autumn 1993 in south
Moravia. In 1994, rapid spreading was observed in Bohemia. During the
following year a mass outbreak occurred in the south and southwest of
Moravia, and during summer all chestnut trees were completely defoliated.
Occurrence of Cameraria ohridella in
Slovakia
The first occurrence of Cameraria ohridella in Slovakia was reported by
Matlak (1994) near the Austrian border. Fig. 1-3 show the spreading of the
horse chestnut mining moth from west Slovakia to Middle Slovakia within 3
years (1994-1996).
Biology and behavior of Cameraria
ohridella
The introduced horse-chestnut leafminer, Cameraria ohridella, has 3
overlapping generations, with adults appearing mostly in May, July, and
September. The egg stage lasts from 2 to 3 weeks, the feeding period, on
average, 4 weeks, and the pupal stage in the mine about 2 weeks, but at
least 6 months in the partial 3rd generation overwintering in the litter.
Infestations of old and young trees in the Vienna City forests, streets
and parks have been excessive during the last 5 years, with 100 %
defoliation and leaf fall occuring already at the end of the 2nd
generation in August. Possibly due to this food shortage, a few mines of
the 3rd generation have appeared on sycamore (Acer pseudoplatanus).
High mortality rates due to intraspecific competition for space and food
occurred during all 3 generations, intensified by the simultaneous
presence of a fungus disease (Guignardia aesculi) damaging the leaves.
Rates of predation and parasitism have so far been negligible.
Where does the horse chestnut - mining
moth really come from?
At present it seems quite certain, that Cameraria ohridella has been
introduced to Austria from Macedonia (by man). But the real origin of this
moth is still unknown because the insect was also introduced to Macedonia.
Cameraria ohridella is strictly connected with Aesculus. Therefore the
natural habitat could be one of the tertiar relict areas of
Hippocastanaceae in Eastern Europe, in the Far East (Himalaya, India,
etc.) or America.
First results of isozymes analysis of
Cameraria ohridella (D&D)
Samples of 6 populations of Cameraria ohridella from different locations
in Upper-, Lower Austria and Vienna (Austria) were collected and
examinated by isozyme-electrophoresis using a discontinous PAGE-system.
The first results indicate that only 3 of 12 isozymes (esterase, amylase
and malate-dehydrogenase) show polymorphism in allele frequencies. These
results and the high genetic identity detected by cluster analysis seem to
prove that there is only one motherpopulation responsible for the outbreak
of Cameraria ohridella in Austria. Although there are signs of "inbrulling",
no negative effects like epidemic occurrence of pathogens or lower rates
of reproduction could be found so far.
Tests for the control of Cameraria
ohridella by synthetic chitin synthesis inhibitors
Three different synthetic chitin synthesis inhibitors (DIMILIN, ALSYSTIN
and INSEGAR) were tested on the effectiveness of controlling Cameraria
ohridella. The application of DIMILIN and ALSYSTIN proved to be very
effective, between 98% - 100% of the larves were killed depending on the
number of applications. INSEGAR-application had lower mortality rates
Effects and non target effects of
Dimilin
Diflubenzuron is the effective chemical substance of Dimilin. It belongs
to the group of Bezoylureas which effects the chitin synthesis of the
cuticula eggs and larves. Dimilin proved to be very effective on target
insects and very ineffective on non target insects like honey bee,
parasitoides, ants, mites and others. Dimilin is registered as "not
poisonous" under the Austrian Chemical Law.
Measures against Cameraria ohridella
undertaken by the municipal of Vienna
Complete removal and compositing of the foliage is one important measure
to reduce Cameraria ohridella in Vienna. Besides, irrigation of Aesculus
hippocastanum seems to lower damage. In addition, spraying with Dimilin
provided good results.
Experiences with systemic insecticides
in the USA
Systemic insecticides have been successfully used in the USA for insect
control and nutrition in urban areas. Investigations on Lithocolletis
showed that Orthene (Acephate) should have the ability to reduce the
population of leaf miners.
Cameraria control with tree injections
with Confidor
Trials with tree injections using the systemical insecticide Confidor WG
70 in the concentration 80 mg a.i./ml solution on horse chestnut trees to
control Cameraria ohridella showed good results. The insecticide
formulation was applied not before 24 July when the first generation of
the insect had nearly finished its development inside the leafmines.
Therefore only the second and third generation could be controlled. 11
weeks after application the injected trees (3 ml per 20 cm round) showed
only about 50 % defoliation whereas the non-treated trees had more than
80% fallen leaves.
[irst experiences with tree infusions
against the horse chestnut mining moth Cameraria ohridella
Best results can be achieved when using this control-method at the
beginning of swarming of the moth in late April. Per tree (about 20 m of
height) 200 to 400 ml of Acetamiprid solution (20 % a. i.) is needed.
About the problems with the phytotoxicity of the solvent
(N-Methylpyrrolidon) which was sometimes observed and irregular dispension
of the systemic insecticide in the crown is also reported.
Possibilities of biological control of
Cameraria ohridella.
Many examples of the past have shown that the natural parasitiodes of the
original habitat have much better chances to reduce an insect population
than polyphagous enemies in the new habitat. Therefore the most important
step for biological control of Cameraria ohridella is to identify the
origin of this insect and to find out what are the main natural regulators
there.
Investigations on larval- and
pupal-parasitoids of Cameraria ohridella with regard to
laboratory-cultures.
About 6500 parasitoids (20 different species) from the fallen leaves
collected in automn and winter 1996 were examined from different sites in
Vienna. Further studies will show which of those species can be cultivated
for biological control.
How does the "Saller" method
(applied for patent) work?
The Saller Method is a control method based on two main components. Long
term and short term fertilization by soil injections and addition of
different "biological" substances against harmful leaf miners to
the soil water. Healthy trees of good condition will be more resistant to
pests than weak ones.
Deterrence of the horse chestnut-
mining moth by electronical methods
With the help of an aerial cosmic energy is collected and an information
system at the base of crystalline structure channels this energy to the
horse chestnut tree, where the attractivity of the tree for Cameraria
ohridella could be reduced
PfiA/1/12/97 |