Plant Protect. Sci. Vol. 43, No. 2: 47–56 The Horse Chestnut Leafminer Cameraria ohridella: Chemical Control and Notes on Parasitisation Jelena KULDOVÁ1, Ivan HRDÝ1 and Petr JANŠTA2 1Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic; 2Faculty of Natural Sciences, Charles University, Prague, Czech Republic Abstract Kuldová J., Hrdý I., Janšta P. (2007): The horse chestnut leafminer Cameraria ohridella: chemical control and notes on parasitisation. Plant Protect. Sci., 43: 47–56. The expected high efficacy of Dimilin but also good protection by treatment with Confidor and Calypso were demonstrated. Mospilan was less effective. A high mortality of ultimate larval instars of the leafminer and their substantial parasitisation was observed in experiments with potted seedlings on Confidor and Calypso treated leaves of horse chestnut, Aesculus hippocastanum. The parasitoids found in mines with larvae and pupae of C. ohridella on A. × carnea and A. hippocastanum were recorded and determined. The most abundant species was Minotetrastichus frontalis (Chalcidoidea, Eulophidae). The possible effect of insecticide treatments on parasitisation of the horse chestnut leafminer is discussed. Keywords: Cameraria ohridella; Aesculus hippocastanum; A. × carnea; chemical control; insecticides; parasitisation At present, the horse chestnut leafminer Came- 1999a, b; Šefrová 2001; Šefrová & Laštůvka raria ohridella Deschka et Dimić (Lepidoptera, 2001; Kalinová et al. 2003). The present work Gracillariidae) has spread over most of Europe follows our previous one (Najmanová et al. 2006) (Guichard & Augustin 2002; Kindl et al. 2002). that dealt with residues of diflubenzuron and their Laštůvka et al. (1994) reported the first occur- efficacy on C. ohridella. The effect of difluben- rence of C. ohridella in the Czech Republic in zuron (Dimilin) was reported and confirmed by 1993. This monophagous species almost exclusively several authors (e.g. Buchberger 1997). With develops on white-blooming horse chestnut trees, the persistence of diflubenzuron and possible causing serious damage. As the horse chestnut selection of resistance of the repeatedly treated is one of the favourite ornamental trees in parks pest in mind, the possible efficacy of three other and other public areas, the aesthetical impact of insecticides was examined. damage together with environmental impact of prospective chemical treatment is apparent. Con- MATERIALS AND METHODS sidering the importance of this pest, the European research project CONTROCAM was initiated, in Experiments on horse chestnut seedlings. The the framework of which several studies have been samples of Dimilin 48 SC (a.i. diflubenzuron), batch carried out in the Czech Republic (Svatoš et al. # 41851001, from Crompton Uniroyal Chemical Partially supported by research project CONTROCAM QLK5-2000-01684 of the 5th Framework Programme of the European Community (the authors’ conclusions do not necessarily reflect the Commission’s view and in no way anticipate its future policy in this area), IOBC ASCR, Prague, and by the Ministry of Education, Youth and Sports of the Czech Republic (Project No. MSM 0021620828). 47 Vol. 43, No. 2: 47–56 Plant Protect. Sci. Export (Middlebury, CT, USA), Calypso 480 SC (a.i. consecutive developmental stages of the leafminer thiacloprid), batch # PF90017231 and Confidor 70 was examined at the time of the first treatment (i.e. WG (a.i. imidacloprid), batch # 233014124 from on May 11 and June 14) and then on three sequential Bayer Crop Science (Bayer Aktiengesellschaft, terms (July 24, August 25 and September 22). As Leverkusen, BRD) were used in experiments on in the previous year the infestation of untreated A. potted horse chestnut seedlings 80–100 cm high. × carnea was also determined. The upper parts of the plants (approximately half Statistics. All sets of data were converted to a of the whole foliage) were left untreated while leaf area of 50 cm2, and for each set of data and the lower parts were sprayed to run-off, using each variable (eggs, mines, pupae, imagoes) the a hand-operated sprayer, with water emulsions basic statistical characteristics were calculated. of 0.2 mg/ml Dimilin, 0.1 mg/ml Calypso and Significance of differences between individual 0.1 mg/ ml Confidor at three terms: May 29, June treatments was estimated by independent sam- 20 and July 10, 2003. The control group was sprayed ples t-test for separate variances. Transformation with water. Three plants were used for each treat- ln (x + 1), where x stands for individual variables, was ment and date. On July 11, i.e. 1 day, 21 days and used when the requirement of normal distribution 43 days after treatment, all experimental seedlings was not completed. Test of normality was based were infested with seven females and three males on skewness and kurtosis of the data treated. The from field catches; the sex ratio was in accordance program SYSTAT 5.0 was used for calculations. with that of the field population at the time of Parasitoids of Cameraria ohridella. The species infestation. The plants were covered with sleeves diversity of parasitoids was determined during 2004. of nylon mesh from early spring on to prevent Leaves of A. hippocastanum and A. × carnea infested natural infestation, and they were kept in a garden by C. ohridella were randomly collected at the New at Prague-Zbraslav, far from horse chestnut trees. Jewish Cemetery, Prague, from the same branches The sleeves were removed on August 5. The effect (15 leaves from each group of treated and untreated of all treatments was scored on September 3, i.e. trees) and on the same date when the efficacy of 54 days after infestation. The number and size chemical treatments was scored. Ten leaves from of mines (each of four categories corresponding each group were placed into paper bags attached to to first and second, third and fourth, fifth and the necks of glass bottles and stored in laboratory lastly to sixth instar), live or dead penultimate conditions. Mines from the remaining five leaves and ultimate larvae in large mines, nondiapausing from each examined group were dissected, the stages and diapausing pupae and enclosed imagoes were of larvae of C. ohridella were determined and larvae recorded on each particular plant. and pupae infested by parasitoids were placed with Experiments on full-grown trees. The efficacy a small piece of leaf and a piece of moist cellulose of routine treatment (by the firm Gartensta) at the into perforated cellophane bags and stored under New Jewish Cemetery, Prague, was observed in 2003. laboratory conditions. After eclosion, parasitoids Mospilan 20 SP (a.i. acetamiprid) at concentration were determined and counted. 0.25 mg/ml was applied by backpack sprayer (motor- Monitoring the flight of Cameraria ohridella by ® assisted) on May 12. The scoring of leafminer was pheromone traps. Two Delta traps BIOLATRAP done on leaves randomly collected (at least five to delta 155 (ZD Chelčice, Czech Republic) with sticky six leaves from three different trees per each variant paper inserts 200 × 80 mm covered with Lonamelt of experiment) from treated and untreated foliage PS 3199/05 glue (Vetox, Praha, Czech Republic) of A. hippocastanum at three terms: September 9, baited with dispensers containing 100 ng of sexual September 23 and October 14, 2003. On the same pheromone (8E,10Z)-tetradeca-8,10-dienal (Svatoš days the infestation of untreated red-blooming horse et al. 1999a) were used for monitoring the flight of chestnut A. × carnea was also determined. C. ohridella during the 2004 season. In 2004, groups of A. hippocastanum were selected at the same locality for treatment. The first group RESULTS of trees was sprayed with 0.2 mg/ml Dimilin on May 11; treatment with 0.1 mg/ml Calypso and 0.1 Experiments on horse chestnut seedlings mg/ml Confidor was postponed to June 14 due to unfavourable weather. The same equipment was used Dimilin was registered for control of C. ohridella as in the previous year. The presence of eggs and in the Czech Republic in 2002 (Kupec 2002). Con- 48 Plant Protect. Sci. Vol. 43, No. 2: 47–56 fidor and Calypso were used in our experiments have eclosed) were found on seedlings sprayed only because of their expected mode of action and with water. It indicates that oviposition occurred recommendation for treatment of some fruit and just after infestation. The foliage was completely ornamental trees. Results of the final scoring are destroyed by the larvae of a single generation, some presented in Table 1. of which were unable to finish their development Two live larvae in large mines, seven mines with and there were no mines with younger larvae on diapausing pupae and 53 mines (from which imagoes untreated plants because of the lack of food. Table 1. The efficacy of Dimilin, Confidor and Calypso against Cameraria ohridella, Prague-Zbraslav, 2003 Size of Infestation in number Untreated seedlings for control 43 days after spraying with water mines Mines < 2 0 < 4 0 Mines with < 9 1 live/dead + parasitised* larvae > 9 1 Nondiapausing pupae 0 Diapausing pupae 7 Eclosed imagoes 53 43 days 21 days 1 day treated untreated treated untreated treated untreated Dimilin Mines < 2 0 4 0 9 0 13 < 4 0 2 0 6 0 10 Mines with < 9 0/1 4 0 1 0 0 live/dead + parasitised* larvae > 9 0/1 0/3 + 1* 0 1/2 + 5* 0 0/1 Nondiapausing pupae 0 1 0 1 0 0 Diapausing pupae 0 0 0 0 0 0 Eclosed imagoes 0 28 0 1 0 0 Confidor Mines < 2 0 24 1 47 2 37 < 4 0 1 0 19 0 13 Mines with < 9 0 0/7 0 0/10 0 2/16 live/dead + parasitised* larvae > 9 0 2/9 + 16* 0 0/82 + 34* 0 0/8 + 21* Nondiapausing pupae 0 0 0 0 0 0 Diapausing pupae 0 1 0 17 0 0 Eclosed imagoes 0 8 0 32 0 4 Calypso Mines < 2 17 35 18 64 6 39 < 4 2 6 2 28 5 30 Mines with < 9 0/1 8 0 1 0 0 live/dead + parasitised* larvae > 9 0/1 + 1* 1/16 + 25* 0 2/12 + 39* 0 0/0 + 4* Nondiapausing pupae 1 9 0 1 0 0 Diapausing pupae 0 19 0 53 0 4 Eclosed imagoes 0 24 5 98 0 17 Horse chestnut seedlings: upper parts of plants untreated, lower parts treated; infested with moths 1, 21 and 43 days after treatment, scored 54 days after infestation; *number of parasitised larvae 49 Vol.