Aesculus pavia foliar saponins: defensive role against the leafminer Cameraria ohridella

BACKGROUND: Recently, the leafminer Cameraria ohridella Deschka & Dimic has caused heavy damage to the white‐flowering horse chestnut in Europe. Among the Aesculus genus, A. pavia L. HBT genotype, characterised by red flowers, showed an atypical resistance towards this pest. Its leaves, shaken in water, originated a dense foam, indicating the presence of saponins, unlike the common horse chestnut tree. The aim was to isolate and identify these leaf saponins and test their possible defensive role against C. ohridella. RESULTS: Spectroscopic analyses showed that A. pavia HBT genotype leaves contained a mixture of saponins, four of which were based on the same structure as commercial escin saponins, the typical saponin mixture produced by A. hippocastanum and accumulated only within bark and fruit tissues. The mixture showed a repellent effect on C. ohridella moth. The number of mines detected on the leaves of A. hippocastanum plants treated with A. pavia HBT saponins through watering and stem brushing was significantly lower than the control, and in many cases no mines were ever observed. CONCLUSION: The results showed that the exogenous saponins were translocated from roots/stem to the leaf tissues, and their accumulation seemed to ensure an appreciable degree of protection against the leafminer. Copyright © 2010 Society of Chemical Industry     

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     

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.     

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.     

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.     

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.     

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.     

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.

     

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.     

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.     

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.      

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).      

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.     

Stem injection of a systemic insecticide to control Uraba lugens on urban Lophostemon confertus trees

BACKGROUND: Uraba lugens Walker (Lepidoptera: Nolidae) has the potential to become a serious pest of susceptible forestry and urban trees in New Zealand. Stem injection of insecticides provides a method for the control of U. lugens in public locations where foliar applications are not suitable. Field and laboratory studies were conducted in 2009 and 2010 to determine a dose response profile of U. lugens larvae to acephate injected at 0.0, 0.25, 0.50 and 1.00 g cm^?1 tree diameter measured at breast height (dbh). The concentration of the injected solution varied across years. RESULTS: The highest mortality (85–100%) of U. lugens larvae occurred at 1.00 g acephate injected cm^?1 dbh. The lower rates (0.25 and 0.50 g acephate cm^?1) were more effective in 2010 than in 2009, a factor attributed to the change in volume of injected solution. CONCLUSION: Systemic injections of acephate at rates above 0.50 g cm^?1 dbh provide a tool for the management of U. lugens in public places. It is recommended that stem injection operations for control of U. lugens larvae be timed to coincide with the emergence of first instars so that larvae are exposed to lethal insecticide doses. Copyright © 2011 Society of Chemical Industry     

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.     

Toxicity and growth-suppression exerted by diafenthiuron in the sweetpotato whitefly,Bemisia tabaci

Diafenthiuron (CGA 106 ’630), a thiourea, was sprayed prior to a 48-h infestation by adult females of the sweetpotato whiteflyBemisia tabaci Gennadius, on cotton seedlings under greenhouse conditions; it subsequently suppressed strongly progeny formation of the whitefly, resulting in approximately 50% progeny formation relative to control at 5 mg a.i./l. When the different development stages were separately sprayed directly, the larval stage was the most susceptible, resulting in 50% and 90% mortality of 2nd instars at concentrations of 6.5 and 49.2 mg a.i./l, whereas the LC50 values of adults and pupae were 23 and 45 mg a.i./l, respectively. A mild (30–35%) reduction of egg hatch was obtained at a range of 5–125 mg a.i./l. Thus the potency of diafenthiuron against various stages was in the order larvae > adults > pupae > eggs. Diafenthiuron exhibited a low vapor phase toxicity and had no translaminar effect when tested on first instars ofB. tabaci. The high potency of diafenthiuron against whiteflies described herein, against aphids and mites, as stated in the literature, and against some lepidopterous pests, render this compound an important insect control agent for pests of cotton and other crops.     

Identification and pathogenicity of Cryphonectriaceae species associated with chestnut canker in China

Cryphonectriaceae species cause serious canker diseases on chestnut, oak and eucalypt trees. Recently, canker symptoms with typical orange fruiting bodies were observed on Chinese chestnut and oak trees in Hebei, Hubei, Shaanxi and Shandong Provinces in China. In the present study, isolates of these fungi were identified based on phylogenetic and morphological evidence, and their pathogenicities were tested on detached chestnut (Castanea mollissima) branches. DNA sequence comparisons of the internal transcribed spacer (ITS) regions and two regions of β-tubulin (TUB1/TUB2) indicate that these isolates represent five species in the Cryphonectriaceae, viz. Cryphonectria japonica, Cryphonectria parasitica, Aurantiosacculus castaneae sp. nov., Cryphonectria neoparasitica sp. nov. and Endothia chinensis sp. nov. The sexual morph of Aurantiosacculus is discovered for the first time and can be distinguished from the other genera in Cryphonectriaceae by dark brown ascospores and tubiform appendages at both ends. Cryphonectria neoparasitica sp. nov. is different from the other Cryphonectria species by its aseptate ascospores. Endothia chinensis sp. nov. is the sole species in Endothia infecting the host genus Castanea. Additionally, it is much smaller than E. gyrosa and narrower than E. singularis in ascospores. The inoculation results showed that these five Cryphonectriaceae fungi isolated from chestnut or oak are all pathogenic to tested chestnut branches. Cryphonectria parasitica appears to be the most aggressive fungus, followed by C. neoparasitica sp. nov., C. japonica, E. chinensis sp. nov. and A. castaneae sp. nov.