In organically cultivated orchards of the LVWO Weinsberg in the years 2006 and 2007

trials were carried out about new products and their efficacy against apple scab. In the

year 2006 (variety ‘Gala’) Armicarb and BioPluss sprayed preventively during primary

ascospore season could not convince, also not in combination with lime sulphur as stopapplication.

Armicarb showed at ‘Gala’ a tendency to increase russetting of the fruits. In

the year 2007 (Variety ‘Elstar’) different combinations of wetting sulphur with yuccasaponin

and stop-applications (lime sulphur, Armicarb) were tested with focus on the time

immediately after blossom. The effect of Armicarb as stop-application was weaker than of

lime sulphur at an infection-period with extreme high ascospore potential. The differences

between the tested combinations were low. Wetting sulphur+yucca-saponin showed

interesting tendencies in the year 2007, but should not be combined with lime sulphur as

stop-application because of significantly increased reticular russetting of the apples

Pfeiffer, B.

English

Organic Eprints

41Results from scab trials with Armicarb in the years 2006 and 2007 B. Pfeiffer 1AbstractIn organically cultivated orchards of the LVWO Weinsberg in the years 2006 and 2007 trials were carried out about new products and their efficacy against apple scab. In the year  2006  (variety  ‘Gala’)  Armicarb  and  BioPluss  sprayed  preventively  during  primary ascospore season could not convince, also not in combination with lime sulphur as stop-application. Armicarb showed at ‘Gala’ a tendency to increase russetting of the fruits. In the  year  2007  (Variety  ‘Elstar’)  different  combinations  of  wetting  sulphur  with  yucca-saponin and stop-applications (lime sulphur, Armicarb) were tested with focus on the time immediately after blossom. The effect of Armicarb as stop-application was weaker than of lime sulphur at an infection-period with extreme high ascospore potential. The differences between  the  tested  combinations  were  low.  Wetting  sulphur+yucca-saponin  showed  interesting tendencies in the year 2007, but should not be combined with lime sulphur as stop-application because of significantly increased reticular russetting of the apples. Keywords: Venturia inaequalis, apple, potassium bicarbonate, yucca-saponin IntroductionIn the last few years the search for alternatives to copper as important plant protection agent  against  apple  scab  was  going on  at  many  institutes  in lab  and  in  field  trials  on organic cultivated orchards (Kollar&Pfeiffer, 2003 e.g.). Promising results were published about preparations based on potassium carbonate and additives like saponins (Tamm et al.  2006,  Kelderer  et  al.  2006,  Heijne  et  al.  2006).  The  way  to  a  satisfactory  plant protection strategy against apple scab including new preparations is long, because the products must be registered as plant protection agents and also interactions with other standard applications in organic cultivation should be assessed. Material and Methods In experiment 1 different preparations were tested during primary ascospore-season 2006 with  and  without  stop-applications  with  lime  sulphur.  The  trial  was  carried  out  in  an organically grown orchard, where in the past often scab-trials were done, so the infection potential was high. The trees of the variety ‘Gala’ were planted in spring 2002 with 3,5 m x 1,2 m distance. Two replications were set up, so that about 35 trees per treatment were sprayed (the exact number of trees changed a little bit depending from losses by Nectriagalligena per row). At the beginning of growing season (19.03.06) the first application was done  with  15  lime  sulphur/ha  over  all  trees  of  the  plot  to  minimize  infection  risk  from overwintering  conidia  on  the  wood.  The  treatments  and  the  abbreviations  used  in  the figures are described in table 1. Armicarb is a formulation of. potassium bicarbonate and BioPluss consists of a combination of 60 plant extracts and micronutrients. On the trees of untreated control the first symptoms of scab on the leaves were found still on May 5th,shortly before full blossom.                                                 1 Barbara Pfeiffer, Staatliche Lehr- und Versuchsanstalt für Wein- und Obstbau Weinsberg,  D-74 189 Weinsberg (Germany), e-mail barbara.pfeiffer@lvwo.bwl.de Archived at http://orgprints.org/13640/42Table 1: Dosages of preventive and stop-applications (2 m high canopy) during primary ascospore season 2006 - variety ‘Gala’ Treatment  Abbreviation  Treatment preventive*  Stop-application** 1  Con  untreated control   2 Cu+NS+SK (copper only before blossom) copper 400 g a.i./ha +wetting sulphur 3 kg/ha Lime Sulphur 15 l/ha 3  Arm  Armicarb 5 kg/ha   4  Arm+SK  Armicarb 5 kg/ha  Lime Sulphur 15 l/ha 5  BP  BioPluss 3 l/ha   6  BP+SK  BioPluss 3 l/ha  Lime Sulphur 15 l/ha * Data of applications before blossom: 07.04., 13.04., 21.04., 24.04. (only copper in Treatment 2 because of spraying of rape-seed-oil against spider-mites on the same day)  * Data of applications after blossom: 05.05., 08.05. (treatment 2: only 2 kg NS), 12.05., 15.05.  ** Stop-applications with lime sulphur: only 27.04. and 14.05. The following data were evaluated in this experiment: On May 16th 2006 scab infections on leaves of rosettes of blossom-clusters were divided in 4 classes (S0 = without lesions, S1 = 1-2 small lesions, S2 = middle infection, S3 = severe infection). For each replication 25 rosettes  were  assessed.  Clear  result  of  this  evaluation  was,  that  both  preparations (Armicarb and BioPluss), even in combination with stop-application with lime sulphur, were to weak to protect the leaves in a sufficient way during primary ascospore season. So the trial was stopped at middle of May, afterwards the whole plot was sprayed with the same strategy based on wetting sulphur up to middle of August.  Scab  lesions  on  the  apples  were  evaluated  provisionally  on  July  3rd  an  directly  after harvest  (about  200  apples  per  treatment)  in  a  similar  way  as  infections  of  the  leaves. Russetting of the fruits was divided in 4 classes: B1 = without russetting, B2 = < 10 %, B3 = 10-30 %, B4 = >30 % russetted skin. Apples of the class B3 can still be sold in organic fruit growing.Main topic of experiment 2 was to find an optimal plant protection strategy against apple scab round blooming period and in the weeks after blossom, when the young fruits are still very susceptible for russetting. The trial was carried out in 2007 at organically grown apple trees of the variety ‘Elstar’ (with interstem ‘Summerred’), planted in spring 2003 at 3,5 m x 1,2 m distance. Each treatment was replicated 3 times, per replication at least 10 trees were chosen, depending from losses of trees in the row. There were some indications to a better efficacy of Armicarb when used as stop-application or as curative spraying than as preventive spraying, so the design of the trial changed. In spring 2007 the first two applications were the same over all trees of the plot: 16.03. 15 l/ha lime sulphur, 29.03. 500 g copper (active ingredient) + 3 kg wetting sulphur/ha. From 25.03. to 04.05. nearly no rain fell (except for 0,2 mm on 04.04.07). The weather in April was very warm and dry, humidity of air was low, humidity of the soil decreased only at the end of the month, so the development of the plants accelerated heavily. On April 19th the apple trees of the variety ‘Elstar’ were in full blossom, that was very early in comparison to other years. Archived at http://orgprints.org/13640/43Other preparations were sprayed on 05.04. (Para Sommer) and on 11.04. (Neemazal + Dipel ES), the dispensers for confusion of codling moths were distributed on 23.04. In expectation of rainfall the trial started with different treatments on 03.05., when blooming time  had  ended.  The  potential  of  ascospores  had  increased  during  the  last  weeks extremely, so with the first rainfall in May severe infections were forecasted. Table 2: Dosages of preventive and stop-applications (2 m high canopy), beginning on May 3rd2007 - variety ‘Elstar’ Abbreviation  Treatment preventive  Addition  Stop-application  (only May 8th 2007) Con  untreated control     NS+SK  wetting sulphur 2-3 kg/ha    Lime Sulphur 20 l/ha NS+YS  wetting sulphur 2-3 kg/ha  Yucca-saponin  7,5 l/ha in this treatment only 2 kg wetting sulphur NS+YS+SK  wetting sulphur 2-3 kg/ha  Yucca-saponin  7,5 l/ha Lime Sulphur 20 l/ha NS+YS+Arm  wetting sulphur 2-3 kg/ha  Yucca-saponin  7,5 l/ha Armicarb 5 kg/ha NS+Arm  wetting sulphur 2-3 kg/ha    Armicarb 5 kg/ha The dates of applications were: 03.05., 07.05., 08.05. (stop-application), 10.05., 14.05. (only 2 kg wetting sulphur), 27.05., 30.05., 12.06., 21.06. (in short intervals without rain, severe  damage  of  the  tunnel  sprayer  the  day  before),  29.06.,  08.07.  (2,5  kg  wetting sulphur). The residues of that application could be seen for a long time. The evaluations were done in the same way as in experiment 1. On July 19th/20th 2007 the scab  infections  on  leaves  of  long  brunches  were  assessed,  for  each  replication  25 branches were determined. The apples were harvested at four days: 17.08., 20.08., 24.08. and 29.08. because of great differences in ripening between the treatments. Scab lesions on the apples were evaluated directly after harvest (about 900-1000 apples per treatment) in a similar way as infections on the leaves. For the russetting of the fruits 4 classes were formed: B1 = without russetting, B2 = < 10 %, B3 = 10-30 %, B4 = >30 % russetted skin. Samples of each treatment are still in storage for further assessments of storage diseases. Results and discussion - experiment 1 Figure 1 shows the result of the evaluation of infection of the leaves on May 16th 2006. The standard-treatment  (altogether  1600  g  copper  a.  i.  per  ha,  in  combination  with  stop-applications with lime sulphur) had a good effect on scab in early spring. The combination of the other preparations with lime-sulphur improved the efficacy. Armicarb and BioPluss used only in a preventive schedule were not convincing. So at that point the trial was stopped to avoid heavy secondary infections in the orchard. Archived at http://orgprints.org/13640/44Scab infections on leaves of rosettes May 16th 2006 - 'Gala' (Katzental) 020406080100Con Cu+NS+SK Arm  Arm+SK BP  BP+SK% infected leaves% S2% S1% S0Figure 1: % leaves of rosettes in different classes of scab infection on May 16th 2006,S0 = without lesions, S1 = 1-2 small lesions, S2 = middle infection A provisional evaluation about scab on the apples followed on July 3rd, the results were similar to the infection of the leaves of rosettes and to the assessments after harvest, which are described in table 3. In the untreated control nearly 95 % of the fruits were heavily infected by apple scab at harvest. The percentage of fruits without scab or with only  1-2  small  lesions  was  too  low  in  the  treatments  with  Armicarb  or  BioPluss  in comparison to the standard treatment. Table 3: % scab-infected fruits of the variety ‘Gala’ at harvest 2006 (S0 = without lesions) * Treatment  % S0     % S1      % S2  % S3 Con  0,0    a  0,9   a  4,5   ab  94,6     c Cu+NS+SK  73,4    b  22,3   b  2,6     a  1,7     a Arm  6,6    a  20,8   b  10,2   bc  62,4   bc Arm+SK  11,6    a  32,4   b  13,0   cd  43,1   bc BP  9,0    a  21,7   b  21,1     d  48,2   bc BP+SK  13,2  ab  38,6   b  13,2   cd  35,0   ab * different treatments only until middle of May, tukey-test, α = 0,05 Table 4: % fruits in 4 classes of russetting (B1 = without russetting), variety ‘Gala’ 2006* Treatment  % B1 + % B2  % B3  % B4 Con  98,7  1,3    a  0 Cu+NS+SK  96,1  3,9    a  0 Arm  65,3  31,8    c  2,9Arm+SK  69,4  26,9    c  3,7BP  80,7  18,1  bc  1,2 BP+SK  91,8  7,5  ab  0,7 * tukey-test, α = 0,05 Archived at http://orgprints.org/13640/45The  treatments  partly  were  sprayed  in  a  period,  when  russetting  of  the  apples  can increase. Within the classes B1, B2 and B4 no significant differences were found, but Armicarb showed significantly more apples with 10-30 % russetted skin (B3) than the other preparations, so this preparation seems to be not suitable for use directly after blossom. BioPluss had also some risk of increasing russetting at the variety ‘Gala’. Maybe there were interactions with other treatments like oil, too. Results - experiment 2 Because  of  the  long  period  of  dry  weather  in  April  2007  many  of  the  leaves  had  no symptoms  of  apple  scab  at  all,  as  it  is  shown  in  figure  2.  The  stop-application  with Armicarb was not as effective as that with lime sulphur. The first tendency was, that the combination of wetting sulphur+yucca saponin seemed to have a comparable effect to scab as wetting sulphur + stop application with lime sulphur under the conditions in May 2007.  The  application  on  July  8th  expecting  further  rain  after  period  of  rain  and  high humidity of the air caused heavy damages by sunburst (about 10 % of the total yield), when temperature rose up to extremes of 35 °C in the middle of July. % infected leaves (4 classes)at long brunches on July 19th/20th 20070102030405060708090100Con NS+ SK NS+ YS NS+ YS+ SK NS+ YS+ Arm NS+ Arm% S0 % S1 % S2 % S3Figure 2: % leaves of rosettes in different classes of scab infection on July 19th/20th 2007,  S0 = without lesions, S1 = 1-2 small lesions, S2 = middle infection, S3 = severe infection Table 5: % fruits in 4 classes of russetting (B1 = 0 % russetting) and scab infections, variety ‘Elstar’ 2007*Treatment  B1**  B2       B3  B4**  S0  S1  S2**  S3** Con  2,5  80,5  b  16,1  a   0,9  66,9   a  31,1   a  2,0  0 NS+SK  0,5  76,8  b  22,6  a  0  97,9   b  1,9   b  0  0,1 NS+YS  0,2  74,1  b  25,6  a  0,1  98,0   b  2,0   b  0,1  0 NS+YS+SK  0  38,0  a  62,0  b  0  92,5   b  7,5   b  0  0 NS+YS+Arm  0,3  85,8  b  13,9  a  0  94,5   b  5,4   b  0  0,1 NS+Arm  0,9  83,7  a  15,0  a  0,4  92,4   b  7,4   b  0,1  0,1 *tukey-test, α = 0,05, ** no significances found Archived at http://orgprints.org/13640/46Armicarb used as stop-application caused less russetting than in the year before, when it was  sprayed  in  a  preventive  schedule  at  the  variety  ‘Gala’.  This  first  data  showed  an increasing of russetting by the combination wetting sulphur + yucca-saponin with stop-application lime sulphur. Discussion There seems to be some effect of Armicarb when used as stop-application against scab. Respecting other results, that will be presented during conference, the new trials in spring and summer 2008 should be designed. One important question is, if Armicarb can be used as stop-application or curative spraying under cold weather conditions in spring, too, in a period when other treatments against insects or spider-mites are usual. Combinations of wetting sulphur and yucca-saponin should be tested in other concentrations and at further varieties to get more data about risk of russetting.Acknowledgements Thanks to all members of the staff of the Obstversuchsgut Heuchlingen, who helped us to carry out the trials and the assessments. References Heijne, B., de Jong, P. F. Köhl, J. (2006): EU-Projekt REPCO entwickelt neue Möglichkeiten zur Biologischen Bekämpfung von Apfelschorf. Mitteilungen des Beratungsdienstes 04/2006, 11-13. Kelderer, M., Casera, C., Lardschneider, E. (2006): First results of the use of potassium bicarbonate against scab in South Tyrol. 12th International Conference on Cultivation Technique and Phytopathological Problems in Organic Fruit-Growing 2006, conference proceeding 93-97. Kollar, A. (2000): A waterbath method for detection of potential ascospore discharge of Venturiainaequalis. Bulletin IOBC wprs, Vol. 23(12), 53-60. Kollar, A., Pfeiffer, B.(2003): Untersuchungen zum Einsatz alternativer Stoffe zur Regulierung des Apfelschorfes. Abschlußbericht des Forschungsprojektes 02OE109 des Bundesprogramms Ökologischer Landbau. Tamm, L., Amsler, T., Schärer. H. Refardt, M. (2006): 12th International Conference on Cultivation Technique and Phytopathological Problems in Organic Fruit-Growing 2006, conference proceeding 87-92. Archived at http://orgprints.org/13640/

Results from scab trials with Armicarb in the years 2006 and 2007

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