In organic apple growing the woolly apple aphid (Eriosoma lanigerum) is still an unsolved

problem. Various approaches to use beneficial insects were not really effective. Only

winter treatments with mineral oils showed partial and fluctuating success.

In 2006 and 2007 field trials were carried out to evaluate the efficacy of winter treatments

to control woolly apple aphids. The efficacy of several products (different mineral oils, lime

sulphur, and lime sulphur + mineral oil) was tested in comparison to an untreated control,

and possible side effects on the population of predatory mites were investigated. The

study furthermore aimed at establishing the best timing of the application against the target

pest

Casera, Claudio

Kelderer, Markus

Lardschneider, Ewald

English

Organic Eprints

196Winter treatments against the woolly apple aphid (Eriosoma lanigerum):products and timing of applications Markus Kelderer1, Ewald Lardschneider 1,Claudio Casera1Abstract In organic apple growing the woolly apple aphid (Eriosoma lanigerum) is still an unsolved problem.  Various  approaches  to  use  beneficial  insects  were  not  really  effective.  Only winter treatments with mineral oils showed partial and fluctuating success.In 2006 and 2007 field trials were carried out to evaluate the efficacy of winter treatments to control woolly apple aphids. The efficacy of several products (different mineral oils, lime sulphur, and lime sulphur + mineral oil) was tested in comparison to an untreated control, and  possible  side  effects  on  the  population  of  predatory  mites  were  investigated.  The study furthermore aimed at establishing the best timing of the application against the target pest.Keywords: apple, organic farming, woolly apple aphid. Introduction In organic farming the woolly apple aphid is very difficult to control due to its biology (Van Frankenhuyzen  et  al.,  2002)  and  its  protective  mechanisms.  This  pest  is  therefore becoming  a  major  problem  especially  in  orchards,  which  have  been  under  organic management for several years. Even though measures aimed at supporting beneficials and  releases  of  natural  enemies  such  as  the  parasitoid  Aphelinus  mali  and  earwigs provided good control in some cases, the efficacy of these control strategies is strongly related  to  specific  climatic  and  local  conditions,  and  can  therefore  not  be  ensured (Hetebrügge et al., 2006; Scheer et al., 2006). Applications of contact insecticides during the  summer  months  show  short-term  and  limited  efficacy  because  of  the  tough  waxy covering (colonies resemble tufts of wool) and the considerable reproductive potential of the woolly apple aphid. Furthermore, negative side effects of the treatments on beneficials can not be excluded. Anticipating the application of the treatments to early spring may be useful, because aphids are not yet protected by their waxy covering and the development of the summer generations has not yet started (Häseli et al., 2006). Material and MethodsTo investigate the efficacy in suppressing the woolly apple aphid of different products, applied just prior to and after the beginning of inflorescence emergence vegetative growth, several  open-field  trials  were  conducted  in  2006  and  2007.  To  ensure  that  the  sprays would reach also aphids hiding in bark crevices, all treatments were applied with a spray gun.1 VZ-Laimburg, 39040 Post Auer, Südtirol, Italien; Markus.Kelderer@provinz.bz.it (corresponding author)Archived at http://orgprints.org/13676/197Study sites:Trials were conducted in two different apple orchards.  Study site 1: Location: Tramin (South Tyrol – Italy) Cultivar/Rootstock: Morgenduft / M4,  Row x plant spacing: 4 x 5 m Year of planting: 1987Experimental design: 3 randomized blocks of 8 trees each (2 buffer trees included) Study site 2: Location: Montiggl (South Tyrol – Italy) Cultivar/Rootstock: Braeburn/M9 Row x plant spacing: 2.7 x 0.8 m Year of planting: 1996Experimental design: 3 randomized blocks of 7 trees each (2 buffer trees included) Data assessmentAssessments on woolly apple aphids: Due  to  the  differences  among  study  sites  and  pest  pressure,  different  assessment methods were used: in study site 1 (Tramin) the development of new woolly apple aphid colonies was evaluated on former sites of aphid infestation, while in study site 2 (Montiggl) the number and size of new aphid colonies was assessed in a previously selected area of each tree in order to determine the aphid infestation projected to the entire tree volume. Assessments on predatory mites: In study site 1, within each plot, 25 leaves were collected and the number of spider mites and predatory mites present on the leaves was determined according to Boller’s method. Archived at http://orgprints.org/13676/198it dna stcudorp detseTnoitacilppa fo gnimt ni 7002 dna 6002 ni detset stnemtaert eht fo yrammus :1 elbaTvitca( setis yduts tnereffid eh,tcudorp detalumrof ,tneidergni e deilppa ,recudorp  )ruhplus emiL=SL ;etad noitacilppa dna ,porc tegrat eht fo egats lacigolonehp ,etar)lh/l( etaRrecudorPtcudorp detalumroFecnatsbus evitcAetis ydutSraeY lacigolonehP)HCBB( egatsetad .cilppA6002.30.3205l 52acincetofloSmuiclaCruhplus emiL6002.30.3205l 5.2 + l 5.31reyaB + acincetofloS nicoilO + muiclaClio lareniM + SL6002.30.3205l 5.2reyaB nicoilO lio lareniM6002.30.3205l 5.2ceT ongiL32 tcesnItcudorp lio epaR6002.30.3205l 6irgaxereCloihtiloPtcudorp lio-ruhpluS6002.40.2175l 5.2reyaB nicoilO lio lareniM -  -  -  - lortnoc detaertnU7002.30.3125l 52oinesiloPoiclaC id oruflosiloPruhplus emiL7002.30.3125l 5.2 + l 5.31reyaB + oinesiloPnicoilO + oiclaC id oruflosiloP lio lareniM + SL7002.30.3125l 5.2reyaBnicoilO lio lareniM7002.30.3125l 5.2ceT ongiL32 tcesnItcudorp lio epaR7002.30.3125l 6irgaxereC loihtiloPtcudorp lio-ruhpluS7002.40.5075l 5.2reyaBnicoilO lio lareniMlortnoc detaertnU7002.30.3015l 52oinesiloPoiclaC id oruflosiloPruhplus emiL7002.30.3015l 5.2 + l 5.31reyaB + oinesiloPnicoilO + oiclaC id oruflosiloP lio lareniM + SL7002.30.3015l 5.2reyaBnicoilO lio lareniM7002.30.3015l 5.2ceT ongiL32 tcesnItcudorp lio epaR7002.30.3015l 6irgaxereC loihtiloPtcudorp lio-ruhpluSlortnoc detaertnU200620072007MontigglTraminTraminArchived at http://orgprints.org/13676/199Results At the study site 1 (Tramin) the same treatments were compared in 2006 und 2007. In both  years  the  treatments  lime  sulphur  +  mineral  oil,  rape  oil  product,  and  sulphur-oil product  showed  highest  efficacy  in  reducing  woolly  apple  aphid  infestations,  while treatments where only lime sulphur and only Mineral oil was applied at BBCH 50 showed lower  efficacies,  especially  in  2006  (Fig.  1).  A  slight  reduction  of  the  aphid  infestation compared l was observed when mineral oil was applied alone at the pink bud stage (BBCH 57) in 2006, but not in 2007. A slight reduction of the aphid infestation compared to the untreated control was observed when mineral oil was applied alone at the pink bud stage (BBCH 57) in 2006, but not in 2007. 0102030405060Lime sulphur LS + Mineral oil  Mineral oil (BBCH 50)Rape oilproductPolithiol Mineral oil (BBCH 57)UntreatedcontrolMean colony size (mm²)30 May 200610 May 2007aabbacbb ba aabab ab abFigure 1: woolly apple aphid infestation (mean colony size in mm²) in study site 1 (Tramin) in 2006 and  2007  in  the  different  treatments.  Statistics:  One-way  ANOVA,  Tukey’s  Post-Hoc  repeated comparison p=0,05 0102030405060Lime sulphur LS + Mineral oil  Mineral oil (BBCH 50)Rape oilproductPolithiol Mineral oil (BBCH 57)Untreatedcontrol)²mm( ezis ynoloc naeM30 May 200610 May 2007aabbacbb ba aabab ab abArchived at http://orgprints.org/13676/200020406080100120140Lime sulphur LS + MineraloilMineral oil  Rape oilproductPolithiol UntreatedcontrolProjected colony size (cm²/tree)9 May26 Juneabaaa aababbaaaFigure  2:  woolly  apple  aphid  infestation  (mean  projected  colony  size/tree)  in  study  site  2 (Montiggl) on 9 May and 26 June, 2007. Statistics: One-way ANOVA, Tukey’s Post-Hoc repeated comparison p=0,05In 2007, two aphid infestation assessments were conducted in study site 2 (Montiggl), one at the beginning of May and one at the end of June. In May, the infestation level was generally low in all plots, untreated control plots included, but it increased in June (Fig. 2). On both assessment dates, the treatments lime sulphur + mineral oil, mineral oil, rape oil product,  and  sulphur-oil  product  showed  good  and  comparable  efficacies  in  reducing woolly aphid infestations, while lime sulphur alone was again less effective than the other treatments.020406080100120140Lime sulphur LS + MineraloilMineral oil  Rape oilproductPolithiol Untreatedcontrol)eert/²mc( ezis ynoloc detcejorP9 May26 Juneabaaa aababbaaaArchived at http://orgprints.org/13676/201010203040506070Lime sulphur LS + Mineral oil Mineral oil (BBCH 50)Rape oilproductPolithiol  Mineral oil (BBCH 57)UntreatedcontrolNo. predatory mites /25 leaves10 May26 JuneaabababababbbaaaaaaFigure 3: number of predatory mites/25 leaves in study site 1 (Tramin) in the different treatments in 2007. Statistics: One-way ANOVA, Tukey’s Post-Hoc repeated comparison p=0,05All treatments negatively affected the population of predatory mites (Fig. 3). Four months after the first treatment application (assessment date: 26 June 2007), in all the treated plots the population of predatory mites was still considerably lower than in the untreated control plots. The side effects of only mineral oil on the population of predatory mites were less harmful when the product was applied at the pink bud stage than when applied at inflorescence emergence.Discussion The  trials  conducted  in  2006  and  2007  evidenced  a  good  and  promising  efficacy  in reducing woolly apple aphid infestations of tank mixtures of mineral oil with sulphur and rape oil based products. The early application of the treatment (just prior to bud burst) seems  to  be  of  sound  importance  to  ensure  acceptable  efficacy  values.  At  this phenological stage, the overwintering aphids are already active, but their waxy covering is not yet adequately developed.  In the randomized trials the treatments were applied per hand with the spray gun. In 2007 in one side (Klotz) a practical experience (applying lime sulphur and oil with a transverse current blower) were carried out to compare the results in the randomized trail with a practical application technique. As expected the results were good, although the efficacy was something lower than in the randomized plots.In case of high pest pressure and favourable climatic conditions, the woolly apple aphid populations increased during spring in all plots, but infestation levels were considerably lower in the treated plots than in the untreated control plots. Even though all treatments showed strong negative side effects on the population of predatory mites, the presence of harmful spider mites was negligible in all plots. 010203040506070Lime sulphur LS + Mineral oil Mineral oil (BBCH 50)Rape oilproductPolithiol  Mineral oil (BBCH 57)Untreatedcontrolsevael 52/ setim yrotaderp .oN10 May26 JuneaabababababbbaaaaaaArchived at http://orgprints.org/13676/202References Hetebrügge  K.,  Fieger-Metag  N.,  Kienzle  J.,  H.  Bathon,  Zebitz  C.P.W,  J.  Zimmer.  (2006). Biological Control of Woolly Apple Aphid (Eriosoma lanigerum Hausm.) with Aphelinus maliHald.  Proceeding  to  the  12th  International  Conference  on  Cultivation  Technique  and Phytopathological  Problems  in  Organic  Fruit-Growing.  Fördergemeinschaft  Ökologischer Obstbau e.V. Weinsberg. 36 – 42. Scheer C., Trautmann M. (2006) Versuch zur Regulierung der Blutlaus mittels Ohrwurmansiedlung [Trial to control woolly aphid by earwigs]. Proceeding to the 12th International Conference on Cultivation  Technique  and  Phytopathological  Problems  in  Organic  Fruit-Growing. Fördergemeinschaft Ökologischer Obstbau e.V. Weinsberg. 43 – 44. Van Frankenhuyzen A., Stigte H. (2002). Schädliche und nützliche Insekten und Milben an Kern- und Steinobst. Ulmerverlag Häseli A. , Wyss E. , Weibel F. , Zingg D. (2000). Control of the aphid (Eriosoma lanigerum) in organic apple cultivation. Experience from three years of experiments using direct and indirect measures.  /  9ter  Internationaler  Erfahrungsaustausch  über  Forschungsergebnisse  zum Ökologischen Obstbau. Fördergemeinschaft Ökologischer Obstbau e.V. Weinsberg. 45-52. .Archived at http://orgprints.org/13676/

Winter treatments against the woolly apple aphid (Eriosoma lanigerum): products and timing of applications

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