Improved prevention and control of apple scab caused by Venturia inaequalis is aimed at without the use of copper containing products in the Repco-project. Substantial progress is made in selection of potential products against summer epidemics. A patent application is made for E73. New effective biocontrol agents are selected to reduce inoculum during winter. The product potassium bicarbonate has shown good efficacy and Repco contributes to the registration of this product in Europe. Earthworms tended to be stimulated to consume apple leaves treated with amino acids or beetpulp, especially when applied fresh under controlled environmental condi-tons

Bengtsson, M.

Eiben, U.

Heijne, B.

Hockenhull, J.

Jong, P.F. de

Köhl, J.

Lindhard Pedersen, H.

Paaske, K.

Speksnijder, A.G.C.L.

Tamm, L.

Trapman, M.

English

Organic Eprints

Prevention and control of apple scab  B. Heijne, P.F. de Jong, J. Köhl, A.G.C.L. Speksnijder, J. Hockenhull, M. Bengtsson, H. Lindhard Pedersen, K. Paaske, U. Eiben, L. Tamm and M. Trapman   Abstract – Improved prevention and control of apple scab caused by Venturia inaequalis is aimed at with-out  the  use  of  copper  containing  products  in  the Repco-project. Substantial progress is made in selec-tion of potential products against summer epidemics. A  patent  application  is  made  for  E73.  New  effective biocontrol  agents  are  selected  to  reduce  inoculum during winter. The product potassium bicarbonate has shown  good  efficacy  and  Repco  contributes  to  the registration  of  this  product  in  Europe.  Earthworms tended  to  be  stimulated  to  consume  apple  leaves treated with amino acids or beetpulp, especially when applied  fresh  under  controlled  environmental  condi-tons.1  INTRODUCTION In the cultivation of organic apples, crop protection is directed for a major part to the disease apple scab caused by Venturia inaequalis. Organic apple grow-ers  are  much  dependent  on  sulphur,  lime  sulphur and  copper  containing  products  to  control  the  dis-ease. Especially copper containing products are used frequently at the beginning of the season because of copper's  good  efficacy  during  cool  weather  condi-tions. As a negative side effect, copper affects soil organisms.  Therefore  the  European  Union  (EU) stimulates  reduction  in  use  of  copper  containing products  (Councel  Regulation  2092/91,  Annex  II) and funded the Repco-project. The purpose of Repco is to find, develop and implement methods for the control of apple scab without the use of copper con-taining products.   Repco targets several points in the life cycle of V. inaequalis. New active products are screened for the control  of  the  summer  epidemic  under  controlled environmental  conditions,  then  examined  in  small scale field experiments and finally tested in a stan-dard  organic  treatment  schedule.  Nearly-ready-to-market products are tested during the summer epi-demic as well. Selection of novel biocontrol agents                                                  B. Heijne and P.F. de Jong are with Applied Plant Research (PPO-fruit), NL-6670 AE Zetten, The Netherlands (bart.heijne@wur.nl and peter-frans.dejong@wur.nl).   J. Köhl and A.G.C.L. Speksnijder are with Plant Research Interna-tional, NL-6700 AA Wageningen, The Netherlands (jurgen.kohl@wur.nl and arjen.speksnijder@wur.nl).   J. Hockenhull and M. Bengtsson are with the Royal Veterinary and Agricultural University, Department of Plant Biology, DK-1871 Frederiksberg C, Denmark (johoc@kvl.dk and mvb@kvl.dk).   H. Lindhard Pedersen and K. Paaske are with Danish Institute of Agricultural Sciences, DK-5792 Aarslev, Denmark (hanne.lindhard@agrsci.dk and klaus.paaske@agrsci.dk).   U. Eiben is with Prophyta Biologischer Pflanzenschutz GmbH, D-23999 Malchow/Poel, Germany (ueiben@prophyta.com).   L. Tamm is with Research Institute of organic Agriculture (FiBL), CH-5070 Frick, Switzerland (lucius.tamm@fibl.ch).   M. Trapman is with Bio Fruit Advies, NL-4111 KT Zoelmont, The Netherlands (m.trapman@wxs.nl). are targeted at the summer epidemic. Another tar-get of Repco is the reduction of overwintering inocu-lum  of  the  fungus.  For  that  purpose,  novel  endo-phytes are selected and tested, and leaf degradation is  stimulated  by  addition  of  organic  products  to leaves in autumn and by improvement of leaf con-sumption  by  earthworms.  Positive  results  will  be communicated rapidly to practice.   This paper gives an overview of some of the first results  of  the  different  approaches  to  prevent  and control  apple  scab  in  organic  orchards  without  the use of copper.  MATERIALS AND METHODS Individual  papers  are  submitted,  and  will  be  pre-sented at the Joint Organic Congress by participants of  Repco.  The  reader  is,  therefore,  referred  to  the more  detailed  descriptions  of  the  materials  and methods  used  in  individual  experiments  and  de-scribed  in  the  papers  by  Bengtsson,  et  al.,  2006; Heijne et al., 2006; Jong and Heijne, 2006; Köhl et al.  2006;  Lindhard  Pedersen  and  Paaske  2006; Speksnijder et al. 2006.  RESULTS AND DISCUSSION New compounds Both preventive and curative activity were tested of new  compounds  were  tested  against  V.  inaequalis. The  efficacy  was  considered  positive  if  new  com-pounds at 2.5 or 5 % dilution rates were equally or more effective than sulphur at the rate of 0.27 %. Over  100  plant  extracts  and  other  materials  were tested. Some nearly-ready-to-market products were also tested. Among them, positive results were ob-tained with eugenol (Bioxeda), potassium phospho-nate (Resistim), coconut soap (Cocana) and potas-sium bicarbonate (Armicarb). Selection resulted in a list of compounds with good efficacy and little or no phytotoxic side effects. From these, 20 and 23 com-pounds were selected for small scale field testing in 2005 and 2006 respectively.     Small scale field testing Only three out of 25 compounds showed an efficacy against  apple  scab  comparable  or  better  than  the standard  treatments  of  sulphur  or  copper  in  small scale field trials. These were rapeseed oil and com-pounds coded E73. In many cases, a marked con-trast was noted between effective compounds in the screening under controlled environmental conditions and their efficacies under field conditions. It is sug-gested that break down of compounds by ultra violet radiation from sun light might be responsible for this effect, possibly in combination with wash off by rain.   Efficacy in standard schedule Remarkable  good  efficacy  was  obtained  with  two nearly-ready-to-market  products,  potassium  bicar-bonate (Armicarb) and potassium phosphonate (Re-sistim)  in  2004.  These  products  were  applied  in combination  with  sulphur  according  to  the  scab warning system, Rimpro. The efficacy was as good as or even better than low-rate copper treatments or sulphur  applied  alone.  Similar  results  are  reported by  Heyne  et  al.,  2006,  Kelderer  et  al.,  2006  and Tamm et al., 2006. Also the compound E73 showed a better efficacy in a tank mix schedule with sulphur than  the  low-rate  copper  treatment  or  sulphur  ap-plied alone.   However,  flower  phytotoxicity  occurred  in  treat-ments  with  potassium  bicarbonate  and  potassium phosphonate. Also fruit russet was noted with potas-sium bicarbonate and E73. Non the less, both potas-sium  phosphonate  and  E73  treatments  resulted  in higher percentages of first class fruit than the low-rate  copper  treatment.  Unfortunately,  residues  of potassium  phosphonate  were  found  in  wine  from vine  yards  treated  with  this  product.  Therefore, further  research  with  potassium  phosphonate  was abandoned.   Efficacy of potassium bicarbonate (Armicarb) will be  investigated  further  to  facilitate  registration  of the product in Europe (Tamm et al., 2006).  Antagonists against conidia Various fungi  were  isolated  from leaf samples with sporulating  V.  inaequalis  lesions.  From  159  fungal isolates  tested  so  far  in  a  screening  programme, forty nine isolates were excluded from further test-ing  because  of  potential  risks  for  human  health  or because  of  low  economic  potential.  Remaining  iso-lates  are  now  being  tested  for  there  potential  to suppress sporulation of V. inaequalis.   First results showed that 13 fungal isolates sup-pressed sporulation of V. inaequalis by at least 80 % in experiments with apple seedlings under controlled conditions. This potentially creates an opportunity to slow down a summer epidemic of apple scab in fu-ture.  Antagonists to prevent ascospore formation The  presence  of  endophytic  bacterial  and  fungal communities was demonstrated inside leaves with or without scab lesions in autumn. 16S-rRNA and ITS DGGE fingerprints of apple leaves were performed to describe the composition of these microbial commu-nities.  Sequence  types  were  correlated  with  pro-duced numbers of ascospores of V. inaequalis. Multi-variant  analysis  indicated  that  some  of  the  endo-phytic  micro-organisms  present  in  atumn-leaves were correlated with reduced number of ascospores in following spring. Moreover, the autumn treatment of  leaves  with  amino  acids  (Aminosol)  seemed  to promote  the  proliferation  of  an  endophytic  fungal sequence  type  F56.1.  Future  sequencing  of  bands from fingerprints will reveal the identity of potential antagonistic endophytes.  Leaf degradation Coniothyrium  minitans,  a  well  known  antagonist, retarded leaf degradation during winter compared to untreated leaf litter and had no effect on ascospores. Also  beet  pulp  (Vinasse),  at  a  high  dose  rate,  re-tarded  leaf degradation during the winter  of 2004-2005.  Leaf  degradation  seemed  to  accelerate  with increasing dose rate of beet pulp during the winter of 2005-2006.    Ascospore  production  of  V.  inaequalis  was  re-duced only by beet pulp treatments during autumn 2004. However, the number of produced ascospores was lower with urea than beet pulp. And also, leaf degradation was faster with the non-organic product urea than with beet pulp.   Addition of extra earthworms to small plots in the field substantially accelerated leaf degradation.  Earthworms There is a tendency that amino acids (Aminosol) and beet  pulp  (Vinasse)  promoted  leaf  consumption  by the earthworm Lumbricus terrestris under controlled environmental  conditions.  This  leaf-eating  earth-worm  is  commonly  present  in  orchards.  For  beet pulp, this was especially the case when the dose was increased  or  when  it  was  freshly  applied.  In  this way,  earthworms  might  be  stimulated  to  consume more leaves, at a faster rate in orchards and con-tribute to low inoculum orchards.  CONCLUSIONS Substantial progress is made in selection of potential products with good efficacy against summer epidem-ics. A patent application is made for E73. New effec-tive biocontrol agents are selected to reduce inocu-lum during winter. The product Armicarb has shown good efficacy and Repco contributes to the registra-tion of this product in Europe.  ACKNOWLEDGEMENT This  work  is  funded  by  the  European  Commission (Project No 501452; Repco).  REFERENCES Heyne, P., Kruse, P. and Maxin, P. (2006). In "Pro-ceedings 12th International Conference on Cultivation Technique  and  Phytopathological  Problems  in  Or-ganic  Fruit  Growing",  pp.  98-100,  edn  Förderge-meinschaft Ökologischer Obstbau e. V.: Weinsberg, Germany.  Kelderer,  M.,  Casera,  C.  and  Lardschneider,  E. (2006).  In  "Proceedings  12th  International  Confer-ence on Cultivation Technique and Phytopathological Problems in Organic Fruit Growing", pp. 93-97, edn Fördergemeinschaft  Ökologischer  Obstbau  e.  V.: Weinsberg, Germany.  Tamm, L., Amsler, T., Schärer, H. and Refardt, M. (2006).  In  "Proceedings  12th  International  Confer-ence on Cultivation Technique and Phytopathological Problems in Organic Fruit Growing", pp. 87-92, edn Fördergemeinschaft  Ökologischer  Obstbau  e.  V.: Weinsberg, Germany. 

Prevention and control of apple scab

Improved prevention and control of apple scab caused by Venturia inaequalis is aimed at without the use of copper containing products in the Repco-project. Substantial progress is made in selection of potential products against summer epidemics. A patent application is made for E73. New effective biocontrol agents are selected to reduce inoculum during winter. The product potassium bicarbonate has shown good efficacy and Repco contributes to the registration of this product in Europe. Earthworms tended to be stimulated to consume apple leaves treated with amino acids or beetpulp, especially when applied fresh under controlled environmental condi-ton

Prevention and control of apple scab

Abstract

Similar works

Full text

Available Versions

Organic Eprints

NARCIS

Name not available

Copenhagen University Research Information System