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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 zuüruckInhaltvor