Nachernte-Behandlung von Äpfeln mit Calciumchlorid

From 2003 to 2006 the efficacy of post-harvest dips in calcium chloride solution was investigated for apples. Aim of these investigations was to find out the influence of different factors on the Ca-uptake of apples after harvest. The Ca-uptake of the fruit was influenced by following factors:

• the calcium chloride concentration of the dip solution,
• the duration of the dip,
• the duration of fruits' wetting,
• the apple cultivar,
• the addition of a wetting agent and
• the maturity of the fruit.

To get an appreciable Ca-uptake, the addition of a wetting agent is necessary. For a dip time of two minutes calcium chloride concentrations of 7 or 7.5% are needed. Apparently injuries of the apple skin don't appear. An elongation of the dip time or the duration of wetting increased the Ca-uptake. Cultivar and maturity of the fruit affect the Ca-uptake. The increase of the Ca-content can proved only close to the apple skin (skin to 2?cm depth).     

Pyramidisieren von Schorfresistenzen in der Apfelzüchtung

High quality disease resistant apples are the main breeding objective in the programme at Agroscope Changins-Wädenswil (ACW). Apple scab caused by the fungus Venturia inaequalis is still the most important disease in apple production. To ensure the durability of scab resistance we are combining different resistance genes (pyramiding). Moreover, we are incorporating also resistances against powdery mildew (Podosphaera leucotricha) and fire blight (Erwinia amylovora). Principles and methods of resistance breeding are outlined and pyramiding of resistances is illustrated by analysing crosses between two cultivars carrying different scab resistance genes (Vf and Vh2). Crosses are being analysed applying marker-assisted selection (MAS) to detect plants carrying multiple resistances. Phenotypic screening of seedlings for scab symptoms and MAS results are compared and the observed segregations into resistant and susceptible progenies discussed.     

Vergleich von Anbausystemen beim Apfel in Abhängigkeit von Sorte und Unterlage: Schlanke Spindel und Güttinger-V-System

To the 11th leaf the influence of two planting systems on yield and fruit size of apple cultivars ‘Golden Delicious, Weinsberg’ and ‘Jonagold, Rubinstar’ grafted on the dwarfed rootstocks M 9 and P 16 was investigated. The planting systems “Slender Spindle” (3.25 × 1.25 m) and “Güttinger-V-System” (3.50 × 0.60 m) were compared. In average of both cultivars and rootstocks the “Güttinger-V-System” let to significantly higher yields than the planting system “Slender Spindle”. The difference between the planting systems amounted to 121.7 t/ha from the 3rd to the 11th leaf. In this period the annual per-hectare yield of the “Güttinger-V-System” was in average 13.5 t higher than the yield of the “Slender Spindle”. The simple fruit weight of the 3rd to the 11th leaf was affected by the planting system. For both rootstocks and cultivars the simple fruit weight of the “Slender Spindle” was significantly higher than that of the “Güttinger-V-System”. However the fruit size sorting showed for both cultivars no mentioning differences between the planting systems. To the additional yield of the “Güttinger-V-System” face additional costs for the installation of the orchard and for the formation of crown. Thus the decision for this planting system will be influenced in a high measure from the producer price.     

Vergleich von Anbausystemen bei der Birne in Abhängigkeit von Sorte und Unterlage: Schlanke Spindel und Güttinger-V-System

To the tenth leaf the influence of two planting systems on yield and fruit size of pear cultivars ‘Conference, 202’ and ‘Alexander Lucas’ grafted on the rootstocks Quince A (MA) and Quince C (MC) was investigated. The planting systems “Slender Spindle” (3.25?×?1.25 m) and “Güttinger-V-System” (3.50?×?0.60 m) were compared. The “Güttinger-V-System” led to higher yields than the planting system “Slender Spindle”. In average of both cultivars and rootstocks the difference between the planting systems amounted to 75.9 t/ha from the third to the tenth leaf. To the additional yield of the “Güttinger-V-System” face additional costs for the installation of the orchard and for the formation of crown. Thus the decision for this planting system will be influenced in a high measure from the producer price.     

Dynamische Absenkung des Sauerstoffgehaltes bei der Lagerung von Äpfeln

The influence of dynamic controlled atmosphere (DCA) with stepwise oxygen reduction in comparison to conventional ultra-low oxygen (ULO) storage (1.4% O₂) was examined with apples belonging to the cultivars ‘Elstar’, ‘Holsteiner Cox’ and ‘Boskoop’. In order to avoid fruit-damaging fermentation processes, regular analyses of fruit samples for fermentation products were carried out by headspace gas chromatography. The effect of storage methods on fruit quality was quantified after fruits had been removed from DCA or ULO conditions, and again after incubation in different post-storage conditions. The results showed significant improvements in fruit flesh firmness in ‘Holsteiner Cox’ and ‘Boskoop’ after removal from DCA storage and also after post-storage for three weeks under cold storage condition, as compared to ULO storage. The occurrence of skin spots on ‘Elstar’ apples was also significantly reduced by DCA storage.     

Untersuchungen zur Lagerung von Erdbeeren unter Berücksichtigung verschiedener Verpackungsmaterialien

In order to reduce the loss of quality of freshly harvested strawberries during storage, the effects of different packaging materials were examined with regard to storage time and temperature regime (20°C with relative humidity 75%, 4°C with relative humidity 88%). Strawberry containers (500?g) were used differing in form, alignment and number of ventilation openings, top and material. It was found that a drop in temperature to 4°C preserved the quality of strawberries longer in all packaging variants. Nevertheless, the used packaging material had different effects on the quality parameters. The packaging material made of polypropylene, which was closed with a lid and was equipped only with little ventilation openings, yielded the best results, e.?g. the transpiration losses were strongly reduced, thus favouring the preservation of pulp consistency and colour stability of the fruits. On the other hand, the fresh mass during storage was reduced by the materials polyethylenterephthalat, polyactid and groundwood. The quality loss was less dependent on the material, but more dependent on the number of ventilation openings. The results showed that with increasing numbers of ventilation openings the transpiration losses increased and the consistency and colour stability of the fruits decreased. In this context, a strong reduction of pathogenic infestation in relation to the ventilation openings could not be observed. As such, the loss of freshness was lowest with the packaging material of polypropylene, followed by the polyethylenterephthalat, polyactid and groundwood. Moreover, it was found that the kind of packaging material and the ventilation openings had an effect on the amount of pressure marks and the discharge of cell sap of the strawberries. The uneven ground surface of the materials made of polyethylenterephthalat and polyactid increased the punctual pressure on the strawberry fruits, which led to pressure marks and injuries of the fruit surface. Sharp-edged ventilation openings close to the ground surface of these variants favoured injuries and cell sap discharges of the packaging.     

Mikroskopische Methode zum Nachweis pathogener Pilze auf Fruchtmumien von ?pfeln

Underdeveloped aborted fruits (fruit mummies) may remain attached to the trees of certain table apple varieties such as ??Elstar?? or crabapples such as ??Golden Hornet?? for more than 12 months, rendering them suitable substrates for fungi. A method to examine the colonisation of such fruit mummies by important fungal fruit-rot pathogens was developed. Within 30 minutes?? incubation of dried fruit mummies in water, spores of Diplodia seriata, Phacidiopycnis washingtonensis, Neofabraea alba, N. perennans, Neonectria galligena and Colletotrichum acutatum were released in sufficient quantity for microscopic detection. Whereas P. washingtonensis was found almost exclusively on mummies of ??Golden Hornet??, the remaining fungi occurred predominantly on ??Elstar??. Advantages of this method include the possibility of demonstrating the presence of pathogens throughout the year in a quantitative manner, an easy shipment of dried fruit mummies, and their storage for several years as herbarium material prior to or following examination.     

Das Potential von Apfel-Birne-Hybriden für die Kernobstzüchtung

Hybrids of apple and pear have been bred and described before, however no vital and fertile ones were found which could have been used for pome fruit breeding. Lately, the authors studied the putative hybrid bred by M. Zwintzscher in the eighties at genetic, physiological, and phenotypical levels and found it to be a true hybrid. Unlike other reports on such hybrids, this one allowed breeder H. Schimmelpfeng in the nineties to yield an offspring of five F2 plants from it as maternal plant. The F2 plants are meanwhile flowering and regularly set fruits. Three of the sister F2 lines seem to possess potential as cultivars. These vital and fertile hybrids offer the opportunity to combine various parts of the pear genome with the apple genome by classical breeding, introducing new genetic factors into the latter and enabling breeding with these. With such partial genomes of pear non-host-resistances of pear against specific apple pathogens like apple scab (Venturia inaequalis) or new genes for biosynthesis of aroma compounds could be introduced by crosses. A new project to establish such a F3 generation is presented here.     

Untersuchungen zum Auftreten von Druckstellen an Äpfeln nach der Auslagerung

Zusammenfassung Es wurde untersucht, welche Faktoren die Empfindlichkeit von ?pfeln für Druckstellen unmittelbar nach der CA/ULO-Lagerung (CA = Controlled Atmosphere, ULO = Ultra Low Oxygen) beeinflussen. Früchte der Sorten ‘Golden Delicious’ und ‘Jonagold’ wurden nach der CA/ULO-Lagerung für fünf Tage bei vier verschiedenen Nachlagerungsbedingungen (kühl in und ohne Folienbeutel, warm in und ohne Folienbeutel) aufbewahrt. Direkt nach der Auslagerung, ein Tag und fünf Tage sp?ter wurden die ?pfel mittels zwei Apparaturen unterschiedlichen Belastungen ausgesetzt, um Druckstellen zu erzeugen. Weitere gemessene Parameter waren die Fruchtfleischfestigkeit, der Gelbwert, der Gewichtsverlust, der Zellbruchpunkt und die Schalenbruchfestigkeit. Das Ausma? der Druckstellen nahm mit steigender Belastung der Früchte zu. Die warm gelagerten Früchte zeigten mit zunehmender Zeit der Nachlagerung eine geringere Druckstellenempfindlichkeit. Die kühl gelagerten Früchte der Sorte ‘Golden Delicious’ zeigten eine Zunahme der Druckstellenempfindlichkeit im Verlauf der Nachlagerung, die der Sorte ‘Jonagold’ eine Abnahme oder keine Ver?nderung. Ein Zusammenhang zwischen der Druckstellenempfindlichkeit und der Fruchtfleischfestigkeit, dem Zellbruchpunkt oder der Schalenbruchfestigkeit wurde nicht festgestellt.      

Ergebnisse der Leistungsprüfung von Kirschensorten auf wuchsreduzierenden Unterlagen in Ungarn

Zusammenfassung In Ungarn gibt es ein reges Interesse an intensivem Obstanbau. Der Erfolg dieses Anbaus hängt in sehr großem Maße von den Wechselwirkungen zwischen dem Standort, den Sorten-Unterlagen-Kombinationen und dem Anbauverfahren ab.Um die Wirkung wuchsreduzierender Kirschenunterlagen aus ausländischen Züchtungsinstituten unter ungarischen Klimaverhältnissen untersuchen zu können, wurde im Forschungsinstitut für Obst- und Zierpflanzenbau Budapest-Érd ein Vergleichsversuch durchgeführt. Der Versuch wurde mit Cerasus avium C. 2493, Weiroot 13, Weiroot 53, Weiroot 72, Weiroot 154, Weiroot 158, GiSelA 5 und P-HL-A-Unterlagen 1997 in der Versuchsanstalt des Forschungsinstituts für Obst- und Zierpflanzenbau Budapest-Érd aufgepflanzt. Als Kontrolle diente die Sämlingsunterlage Cerasus mahaleb Cema, deren Anteil im ungarischen Süßkirschenanbau bei 70–80% liegt. Die Unterlagen wurden mit drei Süßkirschensorten (Germersdorfi , Linda, Katalin) und mit einer Sauerkirschensorte (Piramis) veredelt.Nach der Wüchsigkeit bis zum Ende des 8. Standjahres konnten die Unterlagen in drei Gruppen eingeteilt werden: starkwüchsige (Cerasus mahaleb Cema, Cerasus avium C. 2493, Weiroot 13), mittelstarkwüchsige (Weiroot 158, Weiroot 154, P-HL-A) und schwachwüchsige Unterlagen (Weiroot 72, Weiroot 53, GiSelA 5). Die stärkste Neigung, Wurzelschosse zu treiben, zeigten Weiroot 13 und Weiroot 154.Während der Untersuchung der generativen Eigenschaften wurde beobachtet, dass es Unterschiede in der Blütezeit der Sorten-Unterlagen-Kombinationen gibt. Auf GiSelA 5 veredelte Sorten blühten 1 oder 2 Tage früher als die Kontrolle. Es gab nur geringe Unterschiede in der Reifezeit der Kombinationen. Den größten Ertrag hatte die Sorte Linda, gefolgt von Katalin, Germersdorfi 3 und Piramis. Der größte Fruchtdurchmesser wurde bei der Süßkirschensorte Germersdorfi 3 gefunden, der größte Anteil an Früchten größer als 26 mm bei den Bäumen auf Weiroot 72 (23%), der geringste Anteil großer Früchte bei den Bäumen auf GiSelA 5. Bei Piramis wurde der größte Fruchtdurchmesser auf Cerasus avium C. 2493 gemessen.     

Multifunktioneller Charakter von Streuobstbeständen – Modell zur Analyse und Bewertung

High-stem orchards, traditionally grown on grassland, represent an important source of raw material for the processing industry and for traditional fruit processing on family-run farms such as cider, brandy, dried fruit, vinegar and apple sauce. As well as these production aspects, high-stem orchards preserve the traditional landscape and indirectly maintain the viability of rural areas. A method for the evaluation of high-stem orchards in Slovenia is presented, where, besides production functions, other aspects (e.?g. environmental) are also emphasized. This methodology enables empirical evaluation of high-stem orchards, including ecological and socio-cultural features and has been applied in the North-Eastern part of Slovenia, where the majority of these land-use systems are found.     

Auswirkungen von Ausd��nnungsma?nahmen auf Ertragsparameter, Krankheitsbefall und Fruchtqualit?t von S��?kirschen (Prunus avium L.) unter ?kologischen Anbaubedingungen

In 2010, various thinning methods were tested in an organically managed cherry orchard at the experimental farm of the Institute in Vienna. We tested a portable thinning machine (Effleureuse) and a manual method to remove flowers, and thinning of young cherries at the stage of pea size. Between beginning of flowering and full flowering we treated twice with wettable sulphur (4 %), lime sulphur (3 %), vinasse (6 %), potassium soap (Neudosan 6 %) and copper (Cuprofor 0.5 %) as well as ATS (1.8 %) as IP-standard. Additionally to the thinning effect, the impact on fruit size, fruit quality and diseases (Monilinia ssp.) was assessed. Some treatments (Effleureuse, manual thinning of young fruits, lime sulphur, ATS) showed a strong thinning effect and an increase of fruit size. Nevertheless, yield losses due to lower number of fruits caused by thinning could only partly be replaced through higher fruit size. The Effleureuse showed a high thinning effect, because of lower costs it is more suitable for farmers than hand thinning of flowers or fruits. The treatments with lime sulphur and wettable sulphur had a reducing effect on flower infestations with Monilinia laxa. No influence on fruit diseases and internal fruit quality could be found between treatments and control.     

Erh?hung der Temperatur bei der Apfellagerung durch Einsatz von 1-MCP

The investigations should purify whether the temperature during apple storage can be increased by application of 1-MCP to decrease energy consumption and costs. The investigations were carried out over 2 years with the following treatments: Year 1: The apple cultivars ‘Elstar, Elshof’ and ‘Gala, Must’ were investigated. For both cultivars 3 different storage temperatures (1, 2 and 4°C) with and without application of 1-MCP were examined. Each temperature and 1-MCP treatment was investigated both under CA-/ULO-conditions with 1.5% O₂ and 2% CO₂ and in cold storage with normal atmosphere. Year 2: The apple cultivars ‘Jonagold, Jonica’ und ‘Golden Delicious, Weinsberg’ were investigated. For both cultivars 3 different storage temperatures (1, 2 and 4°C) with and without application of 1-MCP were examined. Each temperature and 1-MCP treatment was investigated both under CA-/ULO-conditions with 1.5% O₂ and 3% CO₂ and in cold storage with normal atmosphere. The influence of temperature, storage atmosphere and 1-MCP application on fruit firmness, soluble dry matter (sugar) and fruit acid was investigated on 6 dates (September to October in the first year) respectively on 5 dates (October to March) during the storage period. Following results were obtained:

1. In the first year storage temperature did not influence the content of soluble dry matter of both cultivars. Application of 1-MCP led to a less decomposition of soluble dry matter. In the second year the content of soluble dry matter decreased slightly with increasing temperatures. A clear positive effect of 1-MCP-application was not noticeable. Altogether an increase of storage temperature has no or only a small influence of the content of soluble dry matter. 1-MCP can slow down the decomposition of soluble dry matter.
2. An increase of storage temperature had no or only a small influence of fruit firmness. With increasing storage temperature fruit firmness decreased slightly.1-MCP application led to a higher fruit firmness, especially during cold storage in normal atmosphere. In both years all cultivars showed a same or higher fruit firmness at 4°C with 1-MCP application under CA-/ULO-conditions as at 1°C without 1-MCP application under CA-/ULO-conditions.
3. An increase of storage temperature had no or only a small influence of the content of fruit acid.1-MCP application under CA-/ULO-conditions reduced the decomposition of fruit acid. In both years usually all cultivars showed a same or higher content of fruit acid at 4°C with 1-MCP application under CA-/ULO-conditions as at 1°C without 1-MCP application under CA-/ULO-conditions.

The results show that an increasing of storage temperature under CA-/ULO-conditions and with 1-MCP application has no negative influence on fruit quality in comparison to fruits which were stored under CA-/ULO-conditions at low temperatures without 1-MCP application.     

Einfluss von Biostimulanzien und Lichtreflexionsfolie auf die Fruchtqualität und Farbentwicklung bei Apfel

The aim of this research was to improve inner and external fruit quality and fruit colouration using four-year-old apple ‘Braeburn, Hillwell’ trees on M9 (3?m × 1?m spacing) by employing reflective ground covers and biostimulants at Klein-Altendorf, nr. Bonn, Germany (50°N). Two reflective ground covers were spread on both sides of tree rows seven weeks before anticipated harvest and two biostimulants were applied two times – four and two weeks before harvest. Adjacent trees of the same row without reflective ground cover or without biostimulants served as control.Reflective ground covers significantly improved red colouration from 71°hue in the control to 49°hue with the ground cover Lumilys® and to 40°hue with Extenday®. The red colouration of the lower surface of fruits improved from 85°hue in the control to 52°hue with Lumilys® and 40°hue by Extenday®. Apple trees with Extenday® and Lumilys® produced 69% and 44% well-coloured fruit (with 75–100% fruit colouration) compared with 16–26% in the control.By contrast, an acceleration of ripening processes was not observed in plots with reflective ground covers compared with the control. There were no differences in sugar contents (°Brix) and fruit firmness (kg/cm²), but starch breakdown in fruit with reflective mulch was significantly delayed compared with the control resulting in retarded maturation.An economic analysis based on material costs and lifespan – excluding the labour costs for spreading and removing the ground covers – showed an economic advantage, if these mulches are used more than once a year.Both biostimulants showed neither effects on inner and external fruit quality nor on fruit colouration. Fruits with Wuxal®ATRiun or Sunred® did not improve the percentage of well-coloured fruits (75%–100% fruit surface with red colouration) compared with the untreated control. Similarly, inner and external fruit quality showed no significant differences in fruit firmness, sugar content and starch degradation. An economic analysis based on chemicals’ costs – excluding the labour costs for applying the biostimulants – resulted in no economic advantage. The chlorophyll – based ‘Index of Absorption Difference’ (IAD; measured non-destructively by the DA-meter) in some cases correlated positively with the Streif (maturation) index based on destructive assessment fruit firmness, sugar content and starch breakdown in an ‘ART system’.     

Nährstoffaufnahme von Obstbäumen im 1. und 2. Standjahr

The nutrient uptake of fruit trees in the first and second year of cultivation was analyzed. The following fruit species and fruit varieties were examined: sour cherry (‘Schattenmorelle, Rheinland’, Hüttners Hochzucht 170?×?53, one year old tree), pear (‘Conference’, Quince A, two year old tree), apple on M 9 inoculated with the varieties ‘Pinova’ (two year old tree with one year old crown, two year old tree), ‘Elstar’ (one year old tree, two year old tree with one year old crown, two year old tree), ‘Jonagold’ (one year old tree, two year old tree with one year old crown, two year old tree) und Süßkirsche (‘Regina’, Gisela 5, two year old tree).

1. There was low nutrient uptake in the first and second year of cultivation.
2. In the second year of cultivation the nutrient uptake of all fruit species was clearly higher than in the first year of cultivation.
3. In average of the proved fruit varieties the nutrient uptake in the first year of cultivation was: 8?kg N/ha, 2?kg P/ha, 6?kg K/ha, 1?kg Mg/ha and 9?kg Ca/ha.
4. In average of the proved fruit varieties the nutrient uptake in the second year of cultivation was: 3?kg P/ha, 9?kg K/ha, 3?kg Mg/ha and 26?kg Ca/ha.
5. Especially in the first year of cultivation the trees of the stone fruits showed a higher nutrient uptake per tree than the trees of the pome fruits. But related to the nutrient uptake per hectar this difference reversed or became infinitely small.
6. The nutrient uptake of both the three apple varieties and the different plant materials showed only low differences.

     

Effects of methionine-induced hyperhomocysteinemia on protein C,antithrombin-Ⅲ and von willebrand factor

AIM:To observe the effects of methionine-induced hyperhomocysteinemia on protein C(PC),ant ithrombin-(AT-)and von willebrand factor(vWF).METHODS:Eighteen New Zealand rabbits were randomized as methionine group(group M,n=9)and control(group C,n=9),which were fed with methionine-rich diet(600 mg/d)and regular diet respectively for sixteen weeks.By the end of sixteen weeks,the serum biochemistry and PC,AT-and vWF in plasma were determined and vWF expression of endothelial cel s of aorta were examined.RESULTS:In group M,the levels of methionine(29.97±5.34 mol/L)and homocysteine(13.30±2.19mol/L)in serum were signif icantly higher than those(14.48±1.97 mol/L and 5.36 1.19 mol/L,respectively,P<0.01)of group C.The levels of AT-and PC of group M were signif icantly lower than those of group C(P<0.01).The level of vWF in plasma of group M was higher than that of group C(P<0.01).Immunohisto chemistry showed that vWF expression in endothelial cells of aorta was decreased.CONCLUSION:Methionine-induced hyperhomocysteinemia had promot ive ef ects on coagulat ion and inhibiting effects on antioagulation.     

Biostimulantien – von Algenextrakten bis Shrimpsschalen – eine Branche (er-)findet sich

The 2^nd World Congress on Biostimulants in Agriculture in Florence, Italy in November 2015 attracted ca. 1,200 participants with many attendees from the US, India, Asia and Brazil. The vendor section was dominated by ca. 14 mostly medium-sized Italian companies, their products and projects. The congress featured a number of molecular biology talks on gene up and down-regulation using mostly Arabidopsis, which seemed fairly unsuitable to an audience of agronomists.     

Pressemitteilung zur kritischen Stellungnahme von 30 Agrarwissenschaftlern zu den Ver?ffentlichungen von PD Dr. F. Uek?tter zur Rolle der Agrikulturchemie bei der Entwicklung der deutschen Landwirtschaft

Mitteilungen

Pressemitteilung zur kritischen Stellungnahme von 30 Agrarwissenschaftlern zu den Ver?ffentlichungen von PD Dr. F. Uek?tter zur Rolle der Agrikulturchemie bei der Entwicklung der deutschen Landwirtschaft     

Einsatz von Kennzahlen und Beratungsbriefen als Controlling-Instrument für Beratung und Gartenbaupraxis an der Niederelbe

The first business management analyses of fruit farms from the Altes Land (Lower Elbe Valley, Northern Germany) date back to the financial year 1956/57 and were published in 1958 by Prof. A. Löhden in the journal Mitteilungen des Obstbauversuchsringes des Alten Landes e.V. The data compiled by Löhden from the Agrarian Report were used by the Chamber of Agriculture of Hannover to evaluate the book-keeping of those fruit farms which it supported with business development grants. In the early 1980s the fruit advisory services had to implement a comparison of the book-keeping data of fruit farms. This business management advice has been expanded subsequently. At present, some 120 fruit farmers participate at the annual comparison of the Fruit Advisory Service and the Centre of Business Management in Horticulture. The use of this controlling instrument for evaluating key business data will be demonstrated in the current article on the basis of two examples.     

Einfluss verschiedener Ausdünnverfahren auf die Source: Sink-Verh?ltnisse und Fruchtqualit?t von Zwetschen

Chemical thinning agents for stone fruits are scarce. Hence, the objective of the present work was to improve fruit quality,viz size in plum, using mechanical and chemical thinning or combinations thereof; untreated, i.e., un-thinned plum trees of the same rows served as control. Plum trees of the medium-sized cv. ‘Ortenauer’ on dwarfing St. Julien GF 655/2 rootstock, with maximum flower intensity in 2009, were grown near Bonn, Germany. Trees were mechanically thinned in April 2009 with the blossom thinner developed by the University of Bonn with 300, 400 or 500?rpm at a tractor speed of 5?km/h. Half of the trees were additionally chemically thinned with both ammonium thiosulphate (ATS) (15?l/ha) at full bloom and an ethylene releasing compound (0.375?l/ha) 35 days after full bloom. The objective of 1/3 flower i.e. fruitlet removal was successfully achieved even with the slowest rotor speed of 300?rpm. The number of fruit per metre fruiting spur was reduced from 46 to 18–27, equivalent to a (source: sink) leaf: fruit ratio of 5:1. Mechanical thinning significantly enlarged fruit mass from 28?g in the un-thinned control to 30–32?g with rotor speeds of 400 or 500?rpm. Additional chemical thinning with ATS and an ethylene-releasing compound resulted in no further increase in fruit mass. Inner fruit quality (sugar) of the plums appeared unaffected by either mechanical or chemical thinning, except for fruit firmness. Plums thinned with an ethylene releasing compound were softer and ripened earlier than respective control fruit, possibly due to the ethylene release. The lesser fruit density per tree after thinning reduced the potential for fungal infections such asMonilia due to faster drying of the fruits after precipitation. Mechanical thinning reduced thinning by manual labour from 31?min. per tree in the un-thinned control to 24?min. by ca 25%, i.e., by 7?min. per tree; this is equivalent to a net financial gain of 400–500?€/ha, after expenditure (120?€/ha; 1.5?h/ha), for thinning. Overall, both efficacy of blossom removal and fruit mass enlargement scored best after mechanical thinning around 400?rpm, indicating that mechanical blossom thinning provides a suitable alternative for chemical and/or manual thinning or can be combined with either of those options. An additional advantage of mechanical blossom thinning is to overcome or avoid alternate/biennial bearing due to its early application at bloom time; a similar effect was observed with the ethylene-releasing compound applied 35 days after full bloom.