Residues of diflubenzuron on horse chestnut (Aesculus hippocastanum) leaves and their efficacy against the horse chestnut leafminer, Cameraria ohridella

Residues of the insect growth regulator diflubenzuron were quantified on horse chestnut (Aesculus hippocastanum L.) leaves treated with a diflubenzuron 480 g litre^?1 SC, Dimilin. To analyse the samples, an analytical procedure was developed involving a simple extraction step followed by high‐performance liquid chromatography on an octadecyl‐modified silica column with methanol + 0.01 M ammonium acetate mobile phase. The results showed diflubenzuron to be highly stable on horse chestnut leaves; more than 4 months (127 days) after application, 38% (on average) of the insecticide still remained on/in the leaves. The data confirmed biological observations showing diflubenzuron's long‐term efficacy against the horse chestnut leafminer, Cameraria ohridella Deschka & Dimi?, which is the most important pest of the horse chestnut in Europe. The hypothesis of possible penetration of diflubenzuron into the leaf mass is explored and discussed. Copyright © 2006 Society of Chemical Industry     

Systemic applications of neem in the control ofCameraria ohridella, a pest of horse chestnut (Aesculus hippocastanum)

Systemic injection of neem (azadirachtin) was tested in the control of horse chestnut leafminer,Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae), a pest of horse chestnut trees (Aesculus hippocastanum L.: Hippocastanaceae). Three concentrations, 0.08, 0.15 and 0.25 g of active ingredient (a.i.) per cm of diameter at breast height (dbh), provided long-lasting insecticidal activity. The 0.15 and 0.25 g a.i. concentrations resulted in 100% pupae reduction in all generations; the 0.08 g a.i. concentration was effective against the horse chestnut leafminer for at least 23 weeks and led to 70–80% pupae reduction. Treated trees did not lose their leaves before winter. Neem applicationvia injection is cheap, with no environmental hazards, and thus this treatment is recommended for the control ofC. ohridella in horse chestnut trees. http://www.phytoparasitica.org posting Dec. 19, 2004.     

Einsatz der Pheromonverwirrungstechnik zur Regulierung der Rosskastanien-Miniermotte Cameraria ohridella Deschka u. Dimić (Lep.: Gracillariidae)

The horse chestnut leafminer is an introduced invasive pest that every year causes extensive damage to the leaves of the white flowering horse chestnut tree. An environmentally friendly method to control insect pests involves the use of sex pheromones for mating disruption. A large quantity of artificial pheromone is released into the insect plant system confusing males to the extend that they are unable to locate receptive females. In order to test the potential efficacy of the mating disruption technique on the horse chestnut leafminer we set up semi-field trials with closed experimental units and varying leafminer densities. We counted the number of leaf mines on pheromone treated horse chestnut trees and compared them with an untreated control. Mating disruption lead to a significant reduction in damage by more than 90% in the first and second generation of the leafminer, irrespective of the initial leafminer density. Although these results are very encouraging, high population densities of the horse chestnut leafminer in nature and the patchy distribution of horse chestnut trees in the cities will challenge the efficacy of mating disruption in the field. Further experiments are planned with open experimental units and typical horse chestnut trees in various parks and gardens.     

Parasitism of the horse chestnut leaf miner, Cameraria ohridellaDeschka and Dimic (Lep., Gracillariidae), in Serbia and Macedonia

A study concerning the parasitism of Cameraria ohridella, a pest of Aesculus hippocastanum invading Europe, has been carried out in Serbia and Macedonia in 1998 and 1999. From C. ohridella 14 species of parasitoids were reared, which are polyphagous and occur in the whole of Europe. Twelve of the species found belong to the Chalcidoidean family Eulophidae. The rates of parasitism at different sampling dates did not exceed 25%. The results, when compared with data from central Europe, showed that C. ohridella most certainly does not originate from Serbia or Macedonia – the regions in which C. ohridella was observed for the first time – as an indigenous leaf miner on A. hippocastanum.     

Parasitism of the horse chestnut leaf miner, Cameraria ohridellaDeschka and Dimic (Lep., Gracillariidae), in Serbia and Macedonia

A study concerning the parasitism of Cameraria ohridella, a pest of Aesculus hippocastanum invading Europe, has been carried out in Serbia and Macedonia in 1998 and 1999. From C. ohridella 14 species of parasitoids were reared, which are polyphagous and occur in the whole of Europe. Twelve of the species found belong to the Chalcidoidean family Eulophidae. The rates of parasitism at different sampling dates did not exceed 25%. The results, when compared with data from central Europe, showed that C. ohridella most certainly does not originate from Serbia or Macedonia – the regions in which C. ohridella was observed for the first time – as an indigenous leaf miner on A. hippocastanum.     

Acute spread in France of an invasive pest, the horse chestnut leafminer Cameraria ohridellaDeschka & Dimic (Lep., Gracillariidae)

The horse chestnut leafminer, Cameraria ohridella Deschka & Dimic (Lepidoptera, Gracillariidae) spread over the last 10 years from central Europe to western Europe and was observed for the first time in 2000 in the east of France and near Paris. This study presents the results of surveys carried out in France in 2001 to investigate the distribution and infestation level of the leafminer. One year after its first discovery, the moth was present in a large part of the country and for the first time has been observed in Paris. The spread of the moth is due mainly to natural dispersal and to passive dispersal by human activities.     

Acute spread in France of an invasive pest, the horse chestnut leafminer Cameraria ohridellaDeschka & Dimic (Lep., Gracillariidae)

The horse chestnut leafminer, Cameraria ohridella Deschka & Dimic (Lepidoptera, Gracillariidae) spread over the last 10 years from central Europe to western Europe and was observed for the first time in 2000 in the east of France and near Paris. This study presents the results of surveys carried out in France in 2001 to investigate the distribution and infestation level of the leafminer. One year after its first discovery, the moth was present in a large part of the country and for the first time has been observed in Paris. The spread of the moth is due mainly to natural dispersal and to passive dispersal by human activities.     

Zur Kenntnis der Blattminen-MotteCameraria ohridella Desch. & Dim. (Lep., Lithocolletidae) anAesculus hippocastanum L. in der Tschenchischen Republik

Cameraria ohridella was recorded first in 1985 in Macedonia. It gradually expanded to north and west and at present it is a serious pest of Horse ChestnutAesculus hippocastanum in the Czech Republic, having been established at about 80 localities. There are 4–5 overlapping generations with sizes of the larvae of 0.4–4.0 mm. The larva develops inside the leaf tissue in the upper parenchym layer of the leaflet and causes a mine, the size of which is broadened with growing larva. First adults start to fly at the end of April. After mating the females lay single eggs on the leaves. Larval development lasts 25–30 days followed by the prepupa I and II. The latter spins a cocoon in which the pupa of the last generation hibernates. The development from L4 to the prepupa lasts for 3–6 days at 22°C. During the summer it is possible to find all larval and prepupal stages in attacked leaves. FourAesculus species:A. parviflora Walk,A. carnea Haey.,A. glabra Walk andA. indica J. Hobb. were found to be resistent toC. obridella. A. lutea H. J. was liftle andA. pavia L. was heavily attacked. The parasitization ofC. o. larvae was very low. Only 2 parasites were found in 1500 mines in the first and second generation ofC. o., and 40 parasites in 1000 mines of the fourth and fifth generation. The highest mortality takes place in moths, eggs and young larvae. It was found in all 4 generation that there were i. m. 50 eggs/leaflet from which i. m. 3 hibernating pupae resulted. Supposing 2 moths (1♀, 1♂)/leaflet emerged in spring which produced 50 eggs (75 eggs/♀—33% moth mortality), the density of eggs in the first generation after hibernating being the same as in the last (fourth) generation before hibernating. As to the whole populations density in this case we can calculate as following: 3 pupae/leaflet on the tree=3000 pupae/leaflets pro m² on the soil=2000 emerging moths pro m²=50,000 moths (25,000 ♀♀) pro tree (namely 25 m² projecting area of the tree crown×2000 moths).      

Zum Auftreten der Robinien-Miniermotte,Phyllonorycter robiniella (Clem.) und der Ro?kastanien-Miniermotte,Cameraria ohridella Desch. & Dim. (Lep., Gracillariidae) in Südtirol

Zusammenfassung  An 2 Gracillariiden,Phyllonorycter robiniella undCameraria ohridella, wird gezeigt, wie rasch importierte Sch?dlinge sich ausbreiten k?nnen: Die RobinienblattmotteP. robinella wurde in Südtirol erstmals 1991 festgestellt und trat 1996 bereits in Massenbefall bei Brixen an Robinien auf.—Die Ro?kastanienminiermotteC. ohridella war hier erstmals 1992 im Pustertal bei Toblach festgestellt worden (Butin & Führer, 1994). Neueste Untersuchungen im Herbst 1997 zeigen, da? sie nun bereits im gesamten Eisacktal zwischen Franzensfeste und Bozen an Ro?kastanien (Aesculus hippocastanum) verbreitet ist (Tab. 1); hingegen wurde im Etschtal südlich und westlich von Bozen bisher noch kein Befall festgestellt.

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On the occurrence of the robinia-leafminer,Phyllonorycter robiniella (Clem.) and the horse-chestnut- leafminer,Cameraria ohridella Desch. et Dim. (Lep., Gracillariidae) in South Tyrol

The examples of two species of Gracillariidae,Phyllonorycter robiniella andCameraria ohridella, show how fast the expansion can take place: The robinia-leafminerP. robiniella was first noticed in South Tyrol in 1991 and an outbreak occured on False Acacias near Brixen, already in 1996.—The horsechestnut leafminerC. ohridella was first noticed in the Pusteria Valley near Toblach-Dobiacco, in 1992 (Butin & Führer, 1994). The latest research, of autumn 1997, shows that they are now distributed on Horse Chestnut Trees (Aesculus hippocastanum) in the whole Isarco Valley, between Fortezza and Bozen-Bolzano (Tab. 1), whereas in the Adige Valley at south and west of Bolzano no occurrence could be found as yet.

     

Analysis of the natural infection of European horse chestnut (Aesculus hippocastanum) by Pseudomonas syringae pv. aesculi

Pseudomonas syringae pv. aesculi (Psa) is an emerging bacterial pathogen responsible for a recent epidemic of bleeding canker of European horse chestnut (Aesculus hippocastanum) in northwest Europe. Very little is known about the infection biology of this pathogen, which can cause lethal cankers in the branches and stem of its host. In this study, branches and whole trees of European horse chestnut naturally infected with Psa were subjected to detailed morphological and histological examination to identify the primary infection sites, the time of infection, and the patterns of subsequent lesion expansion within the host. Lesions developed during the host dormant season on the 2003–2009 extension growth increments and were centred mainly on lenticels, leaf scars and nodes. The oldest lesion developed in the 2004/2005 dormant season and the number of new lesions increased in each subsequent year. The lesions developed in the cortex and phloem and extended into the cambium to cause cankers, but there was no evidence of necrosis in the xylem. All lesions on the branches were discrete and apparently contained by a necrophylactic periderm, although there was evidence that Psa could survive within such periderms and subsequently breach them. Examination of two whole 30‐year‐old trees revealed extensive, continuous cankers in the phloem and cambium which had formed within a single growing season. Thus, the success of Psa as a tree pathogen and the causal agent of a large‐scale epidemic may in part reflect an ability to infect the aerial woody parts of its host directly.     

Impact of Cameraria ohridella on Aesculus hippocastanum growth and long-term effects of trunk injection with pesticides

Defoliation caused annually by Cameraria ohridella has a considerable impact on the general condition of horse chestnut trees. We investigated the consequences of tree endotherapy against this insect. Wood samples, leaves and insect specimens were collected ten years after the treatment (injection) with pesticides. Insect invasion was manifested in all investigated trees by distinct radial growth depression. Treatment resulted in a growth upturn, while non-treated trees maintained decreased growth. The overall foliage infestation level was lower in treated trees, but pupal mass and potential fecundity of insect females were not affected. Our study revealed a long-lasting, positive effect of endotherapy on trees’ appearance and growth.     

Die Verbreitung der Ro?kastanien-Miniermotte Cameraria ohridellaDesch. & Dimic (Lepid., Gracillariidae) in der Region Südtirol-Trentino

A survey on the present distribution of the horse chestnut leafmining moth, Cameraria ohridella Desch. & Dimic 1986, in Europe and in Italy is given: In Europe, within a period of 15 years, the leafminer – recently introduced into Central Europe – has settled in an area that spreads over 13 latitudinal and about 20 longitudinal degrees; in Northern Italy, an area of approximately 50,000 km² has been afflicted in the 5 years since the leafminer's introduction in South Tyrol and Julian Venetia in 1993.The development of the distribution in the region of South Tyrol and Trentino is shown: In the province of Bozen-South Tyrol, between 1995 and 1999 the moth has spread in all the three principal valleys (Eisacktal, Pustertal, Etschtal); in the Trentino province, first local attacks began only in 1998, near Trento and Riva, but spread over the entire Etschtal/Adige Valley in 1999. While in South Tyrol C. ohridella was introduced from the North (North Tyrol), the introduction into the Trentino occured from the South (Verona).At present the attacks in Trentino province are preponderantly low (resulting heavy only in the city of Trento and in Riva del Garda) and limited to altitudes ranging from 70 to 700 in. In South Tyrol, attacks are mainly heavy in altitudes ranging from 250 to 900/950 m, while they are low in the increasingly affected higher altitudes of 1,000 to 1,230 m. Numeric attack parameters are given to show attack intensities.The number of generations per year depends on the respective climatic conditions: in lower-altitudes, usually three generations develop in a year, but in higher altitudes (800 to 1,100 m) only two generations; in the climatically favoured area around the Lake Garda a (partial) fourth generation appears possible.The question of host plants (Aesculus sp., Acer sp.) and the larval parasitism of C. ohridella is discussed. The parasitism of the larvae, principally by Eulophidae (Hym., Chalcidoidea), was ascertained already in the first years of attack: In South Tyrol, 16 species of parasitoids appeared, and 8 in the Trentino province, but only two species were dominant: Minotetrastichus sp. and Pnigalio sp. The level of parasitism reached was low, comparable to other Central European countries.     

Zusammenfassende Betrachtung der Kenntnisse über die Ro?kastanien-miniermotte,Cameraria ohridella Desch. & Dem. (Lep., Gracillariidae)

An overview of knowledge about the horse chestnut minerCameraria abridella Desch. & Dem. (Lep., Gracillariidae), a pest developing in leaf mines ofAesculus bippocastanum, spread gradually from the Ohrid-Lake (Macedonia) through Bosnia, Serbia and Croatia up to the central Europe (fig.). At present (1999) it occurs in northern Italy, Switzerland, Hungary, Czech and Slovak Republics, Austria, southern and central Germany and in southern Poland. Usually three, but up to five generations develop a year in central-European conditions.C. obridella develops also in leaf mines onAcer pseudoplatanus andA. platanoides. The parasitation is 1–8% and seems not to increase. Heavily attacked trees do not die; only rarely the dying of heavily damaged trees have been observed. Several insecticides may be used to control of this pest. The most successful was the growth-regulator Dimilin with active substance of Diflubenzurol. In the future it will be possible to control populations ofCameraria obridella by pheromones. The future development of this pest and its control is discussed.      

Zusammenfassende Betrachtung der Kenntnisse über die Ro?kastanien-miniermotte,Cameraria ohridella Desch. & Dem. (Lep., Gracillariidae)

An overview of knowledge about the horse chestnut minerCameraria abridella Desch. & Dem. (Lep., Gracillariidae), a pest developing in leaf mines ofAesculus bippocastanum, spread gradually from the Ohrid-Lake (Macedonia) through Bosnia, Serbia and Croatia up to the central Europe (fig.). At present (1999) it occurs in northern Italy, Switzerland, Hungary, Czech and Slovak Republics, Austria, southern and central Germany and in southern Poland. Usually three, but up to five generations develop a year in central-European conditions.C. obridella develops also in leaf mines onAcer pseudoplatanus andA. platanoides. The parasitation is 1–8% and seems not to increase. Heavily attacked trees do not die; only rarely the dying of heavily damaged trees have been observed. Several insecticides may be used to control of this pest. The most successful was the growth-regulator Dimilin with active substance of Diflubenzurol. In the future it will be possible to control populations ofCameraria obridella by pheromones. The future development of this pest and its control is discussed.     

Survival,cold tolerance and seasonality of infection of European horse chestnut (Aesculus hippocastanum) by Pseudomonas syringae pv. aesculi

Bleeding canker of European horse chestnut, caused by the pathogenic bacterium Pseudomonas syringae pv. aesculi (Pae), is now an established disease throughout several countries in northwest Europe after first emerging in 2001–2002. Pae infects the woody branches of horse chestnut directly via natural discontinuities in the bark, such as lenticels, leaf scars and leaf traces, and nodes. However, the timing of infection in relation to seasonality of host development, and the dispersal mechanisms of Pae, in particular its ability to survive and spread in soil and water, remains unknown. In this study, infection of freshly cut horse chestnut shoots by Pae was assessed at monthly intervals over a 12 month period. Pae infected the greatest numbers of lenticels and leaf scars of horse chestnut when inoculated onto actively elongating shoots in spring and early summer, whereas lesion extension from artificial wound sites was greatest after inoculation during early dormancy. Soil survival experiments showed that Pae was still detectable and viable after 50 weeks' incubation in sterile soil and 41 weeks' incubation in nonsterile soil in the absence of host debris. Pae also remained viable and pathogenic after 1 year's storage in King's B broth at ?20 and ?80°C, and was not killed by freeze/thaw treatments. Thus Pae is able to survive independently for extended periods in soil and water, and can tolerate lengthy periods of freezing at very low temperatures. Such information may facilitate a greater understanding of the epidemiology and spread of Pae in northern Europe.     

Induced resistance against leafminer eggs by extrusion in young potato plants

Abstract

Egg extrusion patterns were investigated as an inducible defensive mechanism in potato plants against the leafminer Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). Increased multiplication rates in leaf cells surrounding an egg of L. huidobrensis leads to its exposure through the leaf cuticle, which might increase the risk of mortality. Extrusion rates were evaluated in laboratory tests, in relation to plant and leaf age in Solanum tuberosum L. var. Spunta. Stratified field sampling was also carried out in order to assess leafminer distribution on new and old leaves. Extrusion was higher in young plants, being restricted in older ones to new, still expanding leaves. Plant reaction was independent of egg density. In the field, damage was concentrated in older foliage, in line with the extrusion results. The relevance of egg extrusion for pest management is discussed.     

Infection process of Phoma koolunga on stem and leaf tissue of resistant and susceptible field pea (Pisum sativum)

This study investigates the infection process of Phoma koolunga on field pea (Pisum sativum) stems and leaves using different susceptible and resistant pea genotypes for each tissue, viz. 05P778‐BSR‐701 (resistant) and 06P830‐(F5)‐BSR‐5 (susceptible) for stems and ATC 866 (resistant) and ATC 5347 (susceptible) for leaves. On both resistant and susceptible genotypes, light and scanning electron microscopy showed P. koolunga conidia infect stem and leaf tissues directly via appressoria or stomatal penetration, but with more infections involving formation of appressoria on stems than on leaves. On leaves of the resistant genotype, at 72 h post‐inoculation, P. koolunga penetrated more frequently via stomata (5.2 conidia per 36 893 μm²) than by formation of appressoria (1.8 conidia); yet no such difference was observed on stems of the resistant genotype. In contrast, at the same time point, the number of conidia infecting the susceptible genotype by formation of appressoria on either stems (135 conidia) or leaves (11.3 conidia) was significantly greater than via stomata (8 and 7.3 conidia, stems and leaves, respectively). Mean germ tube length of germinating P. koolunga conidia on both stems (29.8 μm) and leaves (32.9 μm) of the resistant genotype was less than on the susceptible genotype (40.5 and 63.7 μm, stem and leaves, respectively). In addition, there were differences in the number of germ tubes emerging from conidia on resistant and susceptible genotypes. These are the first insights into the nature of leaf and stem resistance mechanisms operating in field pea against P. koolunga.     

Note: Systemic effects of a spinosad insecticide onLiriomyza huidobrensis Larvae

In an effort to expand the spectrum of larvicides effective againstLiriomyza huidobrensis (Blanchard), the effect of spinosad was studied on the mortality of the leafminer under laboratory conditions. Bean plants infested with various leafminer stages (egg through third instar) were treated by dipping leaves in a liter of water containing 24, 48 or 96 mg a.i. spinosad or by drenching the soil of plants with 200 ml of water containing 12 mg, 24 mg or 48 mg a.i. spinosad. In general, leaf dipping was more efficacious and adverse effects were observed sooner than with soil drench. All concentrations of spinosad significantly reduced the number of adults that emerged except leaf dip of third instar; only the highest concentration caused significant reduction of pupae and adults. Spinosad would likely be a valuable insecticide for control of the pea leafminer,L. huidobrensis. http://www.phytoparasitica.org posting Nov. 4, 2005.     

The bionomics ofLiriomyza Trifolii on Gypsophila and Bean Leaves

A study was carried out to determine the distribution of feeding and oviposition punctures made byLiriomyza trifolii Burgess on gypsophila(Gypsophila paniculata ) and bean(Phaseolus vulgaris) leaves, and the development times of the immature stages on these plants. The absolute number of punctures per leaf area was much greater on bean leaves than on gypsophila leaves. The number of mines per leaf was also higher on beans than on gypsophila, but the ratio of mines/punctures was higher on gypsophila. Gypsophila leaves were punctured on both sides, but most of the punctures were on the distal third of the upper leaf side. On beans the punctures were dispersed uniformly on the upper side of the leaf. The larval period (±SE) at temperatures of 20, 25 and 30°C was 9.9±0.2, 4.4±0.1 and 3.7±0.1, and 5.5±O. l, 3.7±0.1 and 2.4±0.1 days, on gypsophila and bean, respectively. The pupal period at 17, 20, 25 and 30°C lasted 19.9±0.2, 14.7±0.1, 10.4±0.1 and 7.8±0.1 days, respectively.     

Tree Injection in the Management of Horse-Chestnut Leaf Miner. Cameraria ohridella (Lepidoptera: Gracillariidae)

Insect and disease problems often occur suddenly, and frequently represent a crisis that demands immediate attention. There are some problems with tree health care because application of sprays to shade trees in urban areas requires specialized, expensive equipment. Microinjection is a type of trunk injection where small amounts of therapeutic chemicals are introduced directly into a tree without any contact with the environment. We applied microinjection technology by using VIVID^®II (Tree Tech Microinjection Systems, Morriston, FL, USA) insecticide to solve the problem with horse-chestnut leaf miner (Cameraria ohridella Deschka et Dimic) on horse chestnut tree (Aesculus hippocastanum L.) in urban greenery in Slovakia. In 2006 were treated 230 host trees in 12 localities, 337 trees in 15 localities were treated in 2007. Mean efficiency of control measures was above 95%. The presence of insecticide residues were analyzed in pollen. 0.145 mg/kg of residues was detected in pollen one day after treatment. It decreased rapidly 8 days after treatment and 16 days after treatment was not detectable. In spite of these results the treatment after blossom is recommended.