In the years 2005 to 2007 a plastic cover was tested in a testing area planted with

apricots and operated according to the regulations for organic production.

Compared to the untreated control, fruit below the plastic cover showed decreased

coloration. Monilia laxa infestations below the plastic cover could not be fully

prevented, but were reduced considerably also by copper applications during

flowering in 2007. Yield of the variant treated with copper, however, remained below

average.

Losses due to rot during storage were smallest with the covered variant

Urschler, W.

Wurm, L.

English

Organic Eprints

116Influence of plastic cover on fruit-quality and monilia laxa infestations with organically produced apricots L. Wurm1 and W. Urschler1AbstractIn the years 2005 to 2007 a plastic cover was tested in a testing area planted with apricots and operated according to the regulations for organic production. Compared to the untreated control, fruit below the plastic cover showed decreased coloration.  Monilia  laxa  infestations  below  the  plastic  cover  could  not  be  fully prevented,  but  were  reduced  considerably  also  by  copper  applications  during flowering in 2007. Yield of the variant treated with copper, however, remained below average.Losses due to rot during storage were smallest with the covered variant.Keywords: apricot, organic production, Monilia laxa, plastic coverIntroductionIn integrated apricot production clear tendencies can be recognized: For the fresh market  Orangered,  Goldrich  and  Bergeron  are  established  varieties,  Pinkcot, Sylvercot, Kioto and Bergarouge will gain importance in the future. Ungarische Beste is the first choice, if one wants to offer processing products of highest quality, and it is also  the  number  1  variety  with  ex-farm  and  drive-by  sales  in  the  Wachau.  Yield losses due to Monilia laxa twig blight or other diseases have become rare, since sufficiently effective plant protection agents are available. Fruit quality enhancing measures, like manual fruit thinning, have become standard treatments. While integrated apricot production is increasing, there is practically no organic cultivation of apricot in Austria because of two reasons: On the one hand the prices  which  can  be  obtained  with  integrated  production  are  rather  high  at  the moment,  on  the  other  hand  there  is  hardly  an  efficient  plant  protection  method against Monilia laxa twig blight, an enormous risk for organic apricot cultivation. Material and Methods In order to investigate, whether an economic organic farming of apricots is possible, an apricot orchard (planting year 1998) of the LFZ Klosterneuburg was changed over to organic farming conditions in 2005. The cultivars Ungarische Beste, Goldrich and Bergeron, both trained as spindle (4 x 2 m) and hedge (4 x 4 m), were tested. In the winter 2004/2005 in this test orchard a frame was built as a basis for a plastic cover (Brändlin  system).  In  the  following  years  it  was  used  for  covering  some  rows  of apricots  with  plastic  from  the  balloon  stage  on.  2005  and  2006  the  plastic  cover remained until harvest in some rows, in the remaining rows it was rolled up at the beginning of June. In 2007 plastic covers were already taken off of all the rows at the end of May. The temperature gradient under and outside of the plastic cover was measured  by  means  of  calibrated  thermohygrographs.  The  mechanical  tree  row management was performed with a Clemens and a Tournesol clearing plough. 1 L. Wurm, Lehr- und Forschungszentrum für Wein- und Obstbau Klosterneuburg, A-3400, lothar.wurm@hblawo.bmlfuw.gv.at 1 W. Urschler, Lehr- und Forschungszentrum für Wein- und Obstbau Klosterneuburg, A-3400Archived at http://orgprints.org/13655/117Influence of plastic cover on fruit-quality and monilia laxa infestations with organically produced apricots L. Wurm1 and W. Urschler1AbstractIn the years 2005 to 2007 a plastic cover was tested in a testing area planted with apricots and operated according to the regulations for organic production. Compared to the untreated control, fruit below the plastic cover showed decreased coloration.  Monilia  laxa  infestations  below  the  plastic  cover  could  not  be  fully prevented,  but  were  reduced  considerably  also  by  copper  applications  during flowering in 2007. Yield of the variant treated with copper, however, remained below average.Losses due to rot during storage were smallest with the covered variant.Keywords: apricot, organic production, Monilia laxa, plastic coverIntroductionIn integrated apricot production clear tendencies can be recognized: For the fresh market  Orangered,  Goldrich  and  Bergeron  are  established  varieties,  Pinkcot, Sylvercot, Kioto and Bergarouge will gain importance in the future. Ungarische Beste is the first choice, if one wants to offer processing products of highest quality, and it is also  the  number  1  variety  with  ex-farm  and  drive-by  sales  in  the  Wachau.  Yield losses due to Monilia laxa twig blight or other diseases have become rare, since sufficiently effective plant protection agents are available. Fruit quality enhancing measures, like manual fruit thinning, have become standard treatments. While integrated apricot production is increasing, there is practically no organic cultivation of apricot in Austria because of two reasons: On the one hand the prices  which  can  be  obtained  with  integrated  production  are  rather  high  at  the moment,  on  the  other  hand  there  is  hardly  an  efficient  plant  protection  method against Monilia laxa twig blight, an enormous risk for organic apricot cultivation. Material and Methods In order to investigate, whether an economic organic farming of apricots is possible, an apricot orchard (planting year 1998) of the LFZ Klosterneuburg was changed over to organic farming conditions in 2005. The cultivars Ungarische Beste, Goldrich and Bergeron, both trained as spindle (4 x 2 m) and hedge (4 x 4 m), were tested. In the winter 2004/2005 in this test orchard a frame was built as a basis for a plastic cover (Brändlin  system).  In  the  following  years  it  was  used  for  covering  some  rows  of apricots  with  plastic  from  the  balloon  stage  on.  2005  and  2006  the  plastic  cover remained until harvest in some rows, in the remaining rows it was rolled up at the beginning of June. In 2007 plastic covers were already taken off of all the rows at the end of May. The temperature gradient under and outside of the plastic cover was measured  by  means  of  calibrated  thermohygrographs.  The  mechanical  tree  row management was performed with a Clemens and a Tournesol clearing plough. 1 L. Wurm, Lehr- und Forschungszentrum für Wein- und Obstbau Klosterneuburg, A-3400, lothar.wurm@hblawo.bmlfuw.gv.at 1 W. Urschler, Lehr- und Forschungszentrum für Wein- und Obstbau Klosterneuburg, A-3400In direct plant protection measures the European Union guideline 2092/91 and the Austrian permission regulations served as basis. Against different caterpillar-species (for  example  Operophtera  brumata)  one  to  three  treatments  with  a  Bacillus thuringiensis product and/or a treatment with a Pyrethrum product were carried out per year. At bud break and leaf fall the whole orchard was treated with copper. From the  stage  of  flowering  on  only  a  few  rows  were  treated  with  copper  (the  variant “copper”). In 2007 applications were: On March, 8th, 1000 g copper per ha and on March, 16th, 250 g copper per ha. The following factors can be differentiated: cultivar  Goldrich, Ungarische Beste, Bergeron Trainingsystemspindle (4 x 2 m), hedge (4 x 4 m) organicvariantcontrol, copper-flower-treatment (not with spindle), plastic cover Variants in all: •  Goldrich-spindle-control •  Goldrich-spindle-plastic cover •  Goldrich-hedge-control •  Goldrich-hedge-plastic cover •  Goldrich-hedge-copper-flower-treatment •  Ungarische Beste-spindle-control •  Ungarische Beste-spindle-plastic cover •  Ungarische Beste-hedge-control •  Ungarische Beste-hedge-plastic cover •  Ungarische Beste-hedge-copper-flower-treatment •  Bergeron-spindle-control •  Bergeron-spindle-plastic cover •  Bergeron-hedge-control •  Bergeron-hedge-plastic cover •  Bergeron-hedge-copper-flower-treatmentAs soon as at the beginning of April 2007 the Monilia infections became visible, the infected shoots per tree were counted, at harvest time tree weight and fruit number per tree were determined. In  summer  2007  all  organic  variants  of  a  cultivar  and  an  integrated  variant  from another orchard were stored for four days at 10 °C and afterwards three days at 20 °C. Before storage and after taking the fruit out of storage the fruit flesh firmness (Durofel  appliance),  the  contents  of  soluble  dry  substance  and  fruit  acids  were determined and each fruit was examined for fruit rot infestation.Archived at http://orgprints.org/13655/118Figure 1: apricot spindle in bloom with plastic cover  Results2005 and 2006 no Monilia laxa twig blight infections could be observed. Also other diseases or pests caused only slight damages (Operophtera brumata for example). The fruit set of all variants was high. Only varietal influence on crop quantity and fruit size could be determined. The temperature measurements during bloom showed that the minimum temperature under the plastic cover remains approx. 0.5 to 1 °C higher with calm and cloudless weather conditions. The maximum temperatures in summer with no wind increase by approx. 5 to 7 °C above the level in the open land. Plastic cover up to harvest caused decreased fruit coloration. For this reason this variant was not any longer pursued in 2007 and at the end of May the plastic cover was taken off. 2007 for the first time substantial Monilia laxa twig blight infections occured. Monilia laxa infestations under the plastic cover could not be fully prevented, but were reduced considerably also by copper applications (see Table 1 and Figure 2). Differences between spindle and hedge are due to the larger crown volume of the hedge. There was no varietal influence (Table 2). The  evaluation  of  the  fruit  yield  per  tree  shows  a  somewhat  more  differentiated picture (Table 3 and Figure 3). Again the larger crown volume of the hedge is to be considered. The plastic cover stimulated significantly increased yields, while control and the copper variants were on an equally low level. The application of copper had obviously  negatively  affected  the  fruit  set.  Goldrich  produced  significantly  higher yields than Ungarische Beste and Bergeron (Table 4). Archived at http://orgprints.org/13655/119Table 1: average number infected shoots per tree (Tukey-HSD, Alpha = 0,05; values of a sub group differ statistically by chance) VARIANT N Sub group 1 2 3Plastic cover spindle  65 10,3Copper hedge  60 10,4Plastic cover hedge  20 18,3control spindle  35 47,0control hedge  25 98,9signifikance  0,90 1,0 1,0Table 2: average number infected shoots per tree of cultivars over all variants  (Tukey-HSD, Alpha = 0,05)cultivar N Sub group 1Goldrich 83 21,9Ungarische 62 28,9Bergeron 60 36,1signifikance  0,06copper hedgecontrol hedgeplasticcover hedgeplasticcover spindlecontrol spindleinfected shoots per tree200180160140120100806040200BergeronUngarischeGoldrichFigure 2: average number infected shoots per tree Archived at http://orgprints.org/13655/120copper hedgecontrol hedgeplastic cover hedgeplasticcover spindlecontrol spindlekg fruits per tree6050403020100BergeronUngarischeGoldrichFigure 3: yield per tree 2007 in kgLikewise a significant, positive effect of the plastic cover could be observed in the context of the storage trial (Figure 4). Considering all cultivars only somewhat more than  3%  of  the  fruit  from  plastic  cover  showed  symptoms  of  fruit  rot,  the  other variants, also the IP-variant, had more than 10%. The normally rather rot-sensitive cultivar Ungarische Beste did not differ from the two other cultivars in this attempt. An effect of the plastic cover or the copper  treatment on the fruit flesh firmness, the content of soluble dry substance and fruit acids was not given. Sensory evaluations by means of triangle test confirmed the results (no significant effect of organic variant on flavour and analyzed substances) of these investigations. However, a significant varietal influence was detected again (table 5, 6 and 7).Table 3: yield per tree 2007 in kg (Tukey-HSD, Alpha = 0,05)  VARIANT N Sub group 1 2 3Control spindle  35 8,7Copper hedge  60 12,2 12,2Plastic cover spindle  65 15,8Control hedge  25 16,2Plastic cover hedge  20 30,2signifikance  0,4 0,3 1,0Archived at http://orgprints.org/13655/121Table 4: yield per tree 2007 in kg of cultivars over all variants  (Tukey-HSD, Alpha = 0,05)cultivar N Sub group 1 2Bergeron 60 9,9Ungarische 62 12,6Goldrich 83 20,5signifikance  0,15 1,0controlplastic covercopperIP% fruits with rot symptoms403020100GoldrichUngarischeBergeronFigure 4: % fruits with rot symptoms after seven days (four days 10°C, three days 20°C) of storageTable 5: content of soluble dry substance in °Oechsle at the beginning of storage (cultivarsover all variants;  Tukey-HSD, Alpha = 0,05) cultivar N Sub group 1 2Goldrich 16 46,5Bergeron 16 48,0Ungarische 16 51,5signifikance  0,46 1,0Archived at http://orgprints.org/13655/122Table 6: content of fruit acids (calculated as tartaric acid) in g per litre at the beginning of storage (cultivars over all variants; Tukey-HSD, Alpha = 0,05) cultivar N Sub group 1 2Ungarische 16 18,8Bergeron 16 22,3Goldrich 16 22,5signifikance  1,0 0,94Table 7: fruit flesh firmness (Durofel-unit) at the beginning of storage (cultivars over all variants; Tukey-HSD, Alpha = 0,05) cultivar N Sub group 1 2Ungarische 16 53,4Bergeron 16 58,6 58,6Goldrich 16 64,4signifikance  0,23 0,16Discussion After three years organic apricot production seems to be feasible in principle. Plastic cover until approx. six weeks before harvest begins promotes the fruit set and the yield and improves the shelf-life of the fruit. Decreased coloration of the fruit becomes a  problem  only  if  the  plastic  cover  remains  until  harvest.  The  cover  does  not guarantee full protection from frosts, but a slight temperature increasing effect could be  determined.  A  combination  of  plastic  cover  and  heating  methods  could  be interesting. These advantages, however, are opposed by the high costs of a plastic cover, the work expenditure for applying and removing the plastic cover and the wind susceptibility of the tested system. By means of copper treatments into the bloom the Monilia laxa infestation could be inhibited to a large extent in 2007, fruit set, however, remained  below  average.  Further  attempts  for  the  optimization  of  the  copper treatment  and  for  testing  other  products  against  Monilia  laxa  twig  blight  are necessary.References Audubert, A., Lichou, L. (1989) : L’ abricotier. 1 Auflage -Paris: Éditions Ctifl 1989  Lichou, L. (1998) : Abricot- Les variétés, mode d’emploi. 1.Auflage -Paris: Éditions Ctifl 1998 ÖSTAT 2002 : Obstanlagen nach Produktionsrichtung 2002 und 1997 Osaer, A., Vaysse, P., Berthoumieu, J.F., Audubert, A., Trillot, M. (1998): Gel de printemps. 1.Auflage -Paris: Éditions Ctifl 1998 Süle, S. 1999: Strategies for the control of apricot decline. Mitt. Klosterneuburg 49 (6): 250-252Thomas,  A.  (2005):  Bessere  Monilia-Bekämpfung  durch  neue  Forschungsergebnisse? Tagungsband Bundessteinobstseminar 2005 DLR Rheinpfalz Archived at http://orgprints.org/13655/

Influence of plastic cover on fruit-quality and monilia laxa infestations with organically produced apricots

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