To ﬁnd new potential fungicides acceptable to organic production preventing apple scab (Venturia inaequalis) infections on leaf and fruits during primary apple scab infection period.

The trials were carried out in combination with different cover crop treatments in single-tree plots. The formerly resistant variety ‘Delorina’ on rootstock M9, planted 1995 at a planting distance of 3.3 m x 1.6 m, unfertilized and with mechanical weed cleaning in the tree row, were used. The experimental orchard is located at Research Centre Aarslev (100 27´ E, 550 18´N)

Bengtsson, Marianne

Christensen, Lars P.

Hockenhull, John

Lindhard Pedersen, Hanne

Paaske, Klaus

English

Organic Eprints

1Department of Horticulture, 2Department of Food Science, 3Department of Crop Protection,Danish Institute of Agricultual Sciences, Research Centre Aarslev, Kirstinebjergvej 10, DK-5792 Aarslev, Denmark4Section for Plant Pathology, Department of Plant Biology, The Royal Veterinary and Agricultural University (KVL),Thorvaldsensvej 40, DK-1871 Frederiksberg C, DenmarkOrganic ﬁeld-testing of compounds to control apple scab (Venturia inaequalis) in combination with alleyway cover cropsHanne Lindhard Pedersen1, Lars P. Christensen2, Marianne Bengtsson4, Klaus Paaske3 and John Hockenhull4hanne.lindhard[a]agrsci.dkAimTo  ﬁnd  new  potential  fungicides  acceptable to  organic  production  preventing  apple  scab (Venturia inaequalis) infections on leaf and fruits during primary apple scab infection period.Material and methodsThe trials were carried out in combination with different  cover  crop  treatments  in  single-tree plots. The formerly resistant variety ‘Delorina’ on rootstock M9, planted 1995 at a planting distance of 3.3 m x 1.6 m, unfertilized and with mechanical weed cleaning in the tree row, were used. The experimental  orchard  is  located  at  Research Centre Aarslev (100 27´ E, 550 18´N).In  2003,  fungicides  were  sprayed  preventively according to RIMpro warnings in the primary apple scab season, from bud break until the end of June, when  ascospore  discharge  stopped.  In  2004, weekly preventive treatments were carried out in the primary apple scab season. Application was done using a nap sac mist blower until incipient run-off.The three alleyway cover crops:1.Grass: A permanent weak grass mixture of Red fescue (Festuca rubtra) and Meadow grass (Poa pratensis).2.Clover grass: A permanent clover grass mixture consisting of White clover (Trifolium repens) and Perennial ryegrass (Lollium perénne).3.Annual:  An  annual  cover  crop  consisting  of Italian ryegrass (Lolium multiﬂorum) and Persian clover (Trifolium resupinatum) sown every year in July and mulched down the following year in April. Mechanical weed cleaning was practiced from April to July.Fig 1: Yield without apple scab for 5 treatments and 3 covercrops in 2003. 02468101214Grass clover-grassannualCover cropYield kg/tree1. Control2. Sulphur3. Plant extract E 524. C-pro.5. E15 Fig 2: Yield without apple scab for 6 treatments and 3 covercrops in 2004.024681012Grass clover-grassannualCover cropYield kg/tree1. Control2. Kumulus 3. E154. E15 and Kumulus5. E 52 6. E 52 and KumulusConclusion Sulphur, had the best effect in these trials. The use of sulphur resulted in an increase of yield, because of more and bigger fruits. Both in 2003 and 2004 the best disease control was achieved with sulphur and some control was also seen with the alternative compounds in 2003.The use of sulphur in combination with a soil treatment that reduces the level of nitrogen available to the trees increased saleable yields. An apparent correlation was found between severity of scab and the ﬂavanol content of the fruits.AcknowledgementWe  kindly  acknowledge  ﬁnancial  support  from  Danish  Research  Centre  for  Organic  Farming (DARCOF). Control of apple scabBoth in 2003 and 2004 the best disease control was  achieved  with  sulphur  (Kumulus)  (table  1 and 2) and some control was also seen with the alternative compounds in 2003. The reduction of apple scab infections was greatest on the rosette leaves. In 2004 the new compounds were tried alone and in combination with sulphur. In 2004 the alternative compounds were tried alone and in combination with sulphur, but the results were approximately  the  same  as  with  sulphur  alone (table 2).PhenolicsPhenolics  were  extracted  from  frozen  apples (fruit  and  peel)  of  the  variety  ‘Delorina’  and analysed by analytical HPLC. The major phenolics were  identiﬁed  as  chlorogenic  acid,  catechin, epicatechin, a cyanidin glycoside, rutin and three other ﬂavonol glycosides, respectively. Signiﬁcant differences in the content of ﬂavonol glycosides were  observed  between  treatments  with  the  highest content being found in the untreated apples and the lowest in apples treated with E15/Kumulus and Plant  extract  E52/Kumulus,  respectively  (table 2). Table 1. Control of apple scab in the variety ‘Delorina’ in 2003 with  sulphur  and  alternative  fungicides:  number  of  treatments, percentage of non-infected leaves on annual shoots, rosettes and fruits on 2nd July, two weeks after the end of the primary infection period. Yield and percentage fruits without russeting at harvest.Alternative fungicides usedNum-ber treat-ments 2003Annual shoots: % leaves without scabRosettes:% leaves without scab% fruits without scab% fruits without russeting at har-vestYieldKg/tree1.Control 0 17,5 c 28,4 d 20,8 c 82,6 a 6,2 b2.Kumulus S (0,27%) 8 51,8 a 87,8 a 71,7 a 52,9 b 12,7 a3.Plant extract E52(5,0%) 8 23,1 c 35,9 cd 35,0 bc 60,9 b 8,8 b4.C-pro (0,3%) 5 24,2 c 44,0 bc 26,7 c 83,7 a 8,2 b5.E15 (0,2%) 7 33,2 b 54,1 b 45,0 b 29,6 c 7,1 bNumbers followed by the same letters are not signiﬁcantly different for p<0,05.Table 2. Control of apple scab in the variety ’Delorina´ in 2004 with sulphur and alternative fungicides:  Number of treatments, percentage of non infected fruits on 8th July, two weeks after the end of the primary infection period and yield, fruit quality and content of Flavanols in mg compound per g fruit at harvest.Alternative fungici-des usedNum-ber treat-ments 2003% fruits without scab% fruits without russe-ting at harvestYieldKg/treeFruit sizeg/fruit% surface colourFlavanol glycosi-desMg/g1.Control   0 72,2 b 52,4 a 5,7 b    82 c 59,7 a 0,023 a2.Kumulus (0,27%)   11 90,0 a 55,1 a 10,3 a  103 a 54,7 bc 0,012 b3.E15 (0,02%)   11 77,8 ab 34,7 b 6,7 b    86 bc 51,7 cd 0,016 ab4.E15 0,02% and   Kumulus (0,27%   11 90,0 a 41,8 ab 9,6 a    98 a 50,0 d 0,011 b5.Plant extract E52 (5%)   11 72,2 b 32,2 b 6,0 b    84 bc 57,3 ab 0,016 ab6.Plant extract E52 (5%) and Kumulus (0,27%)   11 87,8 a 44,0 ab 9,2 a    95 ab 44,8 d 0,011 bNumbers followed by the same letters are not signiﬁcantly different for p<0,05.YieldApple scab control using sulphur increased the yield.  Combination  of  trees  grown  in  alleyway grass using sulphur to control apple scab had the highest yield of fruits not damaged by apple scab (ﬁg. 1 and 2).  Especially for the clover grass alleyway in 2003, the apple scab control using E15 or Plant extract E52 seems to have had a positive effect on the yield (ﬁg 1). In 2004 the use of sulphur increased the yield of not apple scab damaged fruits in the clover grass alleyway and annual cover crop (ﬁg. 2). Table 3:  Infections of powdery mildew and apple scab at the end of the primary apple scab season.Fruit colour and yield at harvest and nitrogen and potassium in leaf samples and available nitrogen in soil for the variety ’Delorina´ in 2003. Cover crop usedPowdery mildew on shoots% fruits without scab% surface colourYieldKg/tree% Ni-trogen in lea-ves% potas-sium in leavesNminin soil 0-50 cm depth1.Grass 1,6 ab 42,0 ab 57,6 a 11,6 a 2,01 1,34 26,3 b2.Clover grass 1,5 b 47,0 a 48,9 b 7,2 b 2,14 1,24 22,9 b3.Annual 1,7 a 30,5 b 49,8 b 7,0 b 2,22 1,02 51,3 aNumbers followed by the same letters are not signiﬁcantly different for p<0,05.Table 4:  Infections of powdery mildew and apple scab at the end of the primary apple scab season.Fruit colour and yield at harvest and nitrogen and potassium in leaf samples and available nitrogen in soil for the variety ’Delorina´ in 2004. Cover crop usedPowdery mildew on shoots% fruits without scab% surface colourYieldKg/tree% Ni-trogen in lea-ves% potas-sium in leavesNminin soil 0-50 cm depth1.Grass 1,96 a 78,3 a 53,0 b 10,9 a 2,44 a 1,02 a 39,3 b2.Clover grass 1,58b 83,3 a 56,4 a 5,2 c 2,53 a 1,00 a 41,8 ab3.Annual 1,81 a 83,3 a 52,2 b 7,6 b 2,44 a 0,91 a 70,4 aNumbers followed by the same letters are not signiﬁcantly different for p<0,05.Cover cropsThe annual cover crop supplied the trees with a high nitrogen level in the soil, but it only resulted in differences in uptake by the trees in 2004 (table 3 and 4). This gave a slightly higher infection of powdery mildew, a higher infection of apple scab and more green fruits (table 3). Yield was signiﬁcantly higher for trees grown in grass alleyways in both years (table 3 and 4) StopScab180805_7.indd   1 24-08-2005   13:53:19

Organic ﬁeld-testing of compounds to control apple scab (Venturia inaequalis) in combination with alleyway cover crops

Pedersen, Hanne Lindhard

Bengtsson, Marianne Vibeke

Hockenhull, John Rodney

Copenhagen University Research Information System

Organic field-testing of compounds to control apple scab (Venturia inaequalis) in combination with alleyway cover crops

Organic ﬁeld-testing of compounds to control apple scab (Venturia inaequalis) in combination with alleyway cover crops

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Copenhagen University Research Information System

Copenhagen University Research Information System