Organic Apple Orchards Research Articles

Disease incidence of Monilinia fructigena coupled with codling moth damage and mechanical injury in an organic apple orchard

In a two-year-study, disease incidence of Monilinia fructigena were quatified and the importance of certain fruit wounding agents was determined. The first infected fruits were observed at the beginning of August in 2011 and 2012. Disease development was continuous until fruit harvest in both years. Pre-harvest yield loss caused by M. fructigena amounted on average 26.3% in 2011 and 40.4% in 2012 by fruit harvest. All infected fruits were injured mainly by mechanical injury factors and codling moth (Cydia pomonella). In this study, the most important wounding agents were codling moth and mechanical injury factors in organic apple orchards. In both years, our results showed that 65-75% of the infected fruits were damaged by codling moth in organic apple production. Moreover, 5-15% of the infected fruits were mechanically injured in the two years. Our results indicated that most of the damaged fruits fell on the orchard floor before harvest and they became an important secondary inoculum source of M. fructigena. Biological and practical implications of the results are discussed.

Disease warning models for brown rot fungi of fruit crops

In this review, disease warning models for brown rot fungi, including Monilinia fructigena, M. laxa and M. fructicola, were summarized. Few studies have been made to relate epidemiology and disease warning in brown rot infection caused by M. fructicola and M. laxa in order to predict infections or develop decision support models for fungicide applications during the growing season. More recently a disease warning model and a decision support system were also performed for M. fructigena for organic apple orchards. This review gives an overview on some details of the above disease warning models and decision support system.

Control of green apple aphid (Aphis pomi De Geer) in organic apple production

The efficacy of different methods for controlling populations of green apple aphid (Aphis pomi De Geer) in organic apple orchard was compared over three consecutive years. The following three control methods were tested: a) predator activity (Coccinela septempunctata), b) predator activity (C. septempunctata) + selective spraying of trees with infestation level exceeding 10% with a botanical insecticide (NeemAzal T/S), and c) predator activity (C. septempunctata) + total spraying of all orchard trees with the botanical insecticide (NeemAzal T/S). In terms of maintaining a biological balance within an orchard, the combination of natural regulation by C. septempunctata and selective spraying of individual trees with NeemAzal T/S proved to be the most efficient method.

유기재배 사과과원의 피복작물별 잡초발생

유기 사과과원의 피복작물 선정을 위해 피복작물의 피복율과 시기별 잡초의 발생양상에 대해 조사하였다. 토양의 화학성분은 자연초생구에 비해 들묵새와 화이트클로버가 유기물 함량과 인산 함량이 다소 높게 분석되었다. 피복작물별 잡초 종의 출현은 5월에는 클로버 종류와 청보리, 호밀이 비교적 잡초 종의 출현이 억제되었고 6월에는 호밀이 가장 좋은 효과를 가져왔다. 7월에는 피복율이 낮은 톨페스큐와 켄터키블루그라스에서는 많은 잡초 종이 출현하였다. 유기 사과과원의 발생한 잡초는 총 51종으로 조사되었고 피복율을 높이기 위해서는 피복식물 보다 키가 크고 광엽인 좀명아주, 명아주, 환삼덩굴 등의 봄철 제거가 필요하다. 잡초의 건물중을 측정한 결과 피복율이 가장 낮았던 켄터키블루그라스에서 대조구와 거의 유사한 결과를 보여주었다. 잡초와 토양과의 관계에 대해 CCA로 분석한 결과 1축에서는 토끼풀과 여뀌가 유기물의 함량과 높은 상과관계를 가지며 명아주는 인산의 함량과 상관관계를 가지고 있는 것으로 분석되었다. This study was conducted to select the cover crops in organic apple orchard by estimating the coverage of each cover crops and time-periodic weed occurrence. Seeding of Festuca myuros and Trifolium repens showed high contents of soil organic matter and phosphorus as compared with control. Seeding of Trifolium sp., Hordeum vulgare and Secale cereal reduced relatively occurrence of weed in May and S. cereal among others showed the greatest effect in June. In July, seeding F. arundinaceae and Poa pratensis showed low coverage and a lot of weeds occurred in their field. Fifty one species were occurred as weeds and it needs to removal of high and broadleaf weeds such as Chenopodium ficifolium, C. album var. centrorubru and Humulus japonicus in spring to increase the rate of ground cover. P. pratensis having the lowest cover rate showed the similar dry weight of weeds as compared with control. Trifolium sp. and Persicaria hydropiper had a high correlation with contents of soil organic matter and C. album var. centrorubru had a correlation with contents of soil phosphorus by CCA analysis.

Impact of a cultivar mixture on scab, powdery mildew and rosy aphid in an organic apple orchard

The impact of a cultivar mixture within the rows including the cvs Melrouge (low susceptibility to scab) and Pitchounette (Rvi6 resistant) was assessed during 2008–2009 in an organic apple orchard located in Rhône Valley (Drôme, France), on three important pests and diseases: scab, powdery mildew and rosy apple aphid. In this area, the resistance of Rvi6 gene was effective since the orchard plantation in 2004. The impact of the cultivar mixture was assessed per se, but also associated with sanitation practices to decrease the primary inoculum of scab and mildew, and compared to disease development on pure stands of Melrouge. The cultivar mixture showed a good efficiency to decrease the scab incidence on leaves and fruits; a significant effect on scab severity was observed in 2009 for the cultivar mixture plus sanitation practices. Our data confirmed the different susceptibility levels of the two cultivars for powdery mildew. Against powdery mildew, a favourable effect of cultivar mixture, at the condition it is associated with sanitation, was observed in case of a moderate level of the disease (2008). For rosy apple aphid, a favourable effect of cultivar mixture was observed on Melrouge in 2008 when Pitchounette has a good resistance level. In the context of organic production, the impact of the cultivar mixture seemed favourable for the control of the three pests and diseases.

An Example of Post-Harvest Thermotherapy as a Non-Chemical Method of Pathogen Control on Apples of Topaz Cultivar in Storage

For establishing a new organic apple orchard, ‘Topaz’ cultivar is especially recommended due to its resistance to scab and flavour qualities [3], [15]. Bompeix and CholodowskiFaivre [2] consider that susceptibility of various apple cultivars to heat treatment is differentiated. Thus, it is of utmost importance to establish the temperature ranges and durations of water baths for particular cultivars. The aim of this paper is to assess the suitability of ‘Topaz’ apples for post-harvest thermotherapy.

The Reemergence of an Old Pest, Orchestes pallicornis (Coleoptera: Curculionidae)

Apple flea weevil, Orchestes pallicornis (Say) was a sporadic pest in the early 1900s and has reemerged as a severe pest of cultivated apple ( Malus domestica Borkh.) in Michigan. Organic apple orchards in Michigan have had outbreak population levels of apple flea weevil since 2008 and damage has resulted in up to 90% losses. Apple flea weevil is a small, 2–3-mm black weevil with enlarged high legs for jumping. The adults feed on bud and leaf tissue and heavy pressure causes bud termination. Leaf tissue is removed in multiple small circles, with the net result of the large removal of photosynthetic material. Larvae are leaf miners, developing between the upper and lower leaf cuticles while migrating from the midrib to the leaf margin where pupation occurs. Pupae develop inside a blister, an air-filled space that turns brown. Low populations of apple flea weevil are missed easily or misdiagnosed as either frost damaged from bud feeding or sulfur burn from pupal cases. Apple flea weevil is likely secondarily managed by broad-spectrum insecticides used in conventional programs. However, there are currently no proven management options for use in organic production. As broad-spectrum materials are replaced by reduced-risk compounds, it is possible that apple flea weevil will become an important pest in apple production.

Yield response, pest damage and fruit quality parameters of scab-resistant and scab-susceptible apple cultivars in integrated and organic production systems

In a 4-year Hungarian study, 10 apple cultivars (5 scab-resistant and 5 scab-susceptible) were evaluated for yield, scab incidence, codling moth injury, soluble solid concentration, and calcium content of fruit in high-density integrated and organic apple orchards. Yield was significantly higher in the integrated plots compared to the organic ones in all years (mean values were 18 and 13kgtree−1, respectively). Yield was significantly lower on the younger trees (5–6years old) compared to the older ones (13–14years old) in both production systems (mean values were 14 and 17kgtree−1, respectively). Mean final scab and codling moth incidences were considerably higher in the organic than in the integrated production system, except for the resistant cultivars which had no fruit scab symptoms. Fruit of all cultivars was protected in the integrated production system (mean fruit scab and codling moth incidences were below 2.5 and 4%, respectively). Only the scab-susceptible cultivars were moderately or highly infected by harvest in the organic production system (mean fruit scab incidence was above 5%), while all cultivars (including scab-resistant ones) were highly damaged by codling moth by harvest in the organic production system (mean incidence was above 20%). Mean soluble solid concentrations and calcium contents were significantly higher in the organic production system only in one year compared to the integrated one (mean values were 17 and 16%, and 204 and 191mgkg−1, respectively), and cultivars of scab-susceptibile vs scab-resistant had significant effect on soluble solid concentrations and calcium contents also in one year (mean values were 16 vs 17kgtree−1, and 202 vs 175kgtree−1, respectively). Our results indicated that a multiscale selection approach is required for choosing cultivars for integrated, and especially for organic growing methods in order to facilitate successful apple growing in environmentally benign production systems.

Can minor compaction increase soil carbon sequestration? A case study in a soil under a wheel-track in an orchard

In an organic apple (Malus domestica Borkh., Braeburn on MM.106 rootstock) orchard in New Zealand we observed that the soil's carbon concentration in 0–0.1m depth directly below a wheel-track in the grassed alley-way was significantly higher than under the grassed tree-row. By using a literature review and direct measurements, we systematically exclude two explanations for the possible accumulation of soil carbon under the wheel-track. Firstly, we discard the possibility of higher carbon inputs to the wheel-track compared to the tree-row area. The tree-row received more carbon inputs by the regular application of compost, and the growth of roots was not impeded by compaction. Secondly, we directly measured the monthly dynamics of microbial biomass and respiration rates per unit of soil carbon over a year, and based on 3D X-ray computed tomography (CT) images we modelled the gas exchange close to water saturation. A restricted gas exchange under wet conditions would be an indication that soil carbon mineralization is reduced under wet conditions. We found that both the microbial carbon decomposition dynamics and the gas exchange under wet conditions were similar in the tree-row and under the wheel-track. The most probable explanation for the enhanced carbon sequestration under the wheel-track is a reduction in carbon losses. The water infiltration rates into the wheel-tracks were significantly smaller than in the tree-row. This means that the carbon loss with water flow in the form of dissolved carbon is probably smaller under the wheel-track. Additionally, a reduction in meso- and macro-faunal activities exporting particulate organic matter from the soil volume is probable under minor compaction. We conclude that a minor compaction like under a wheel-track can be a physical protection mechanism for soil carbon.

Entomological and functional role of floral strips in an organic apple orchard: Hymenopteran parasitoids as a case study

Habitat manipulation techniques improve the availability of resources required by natural enemies to increase their effectiveness. This study focused on the effects of floral strips on Hymenopteran parasitoid presence. The experiments were conducted during spring 2007 in one organic low-input apple orchard located in south-eastern France. The density and the diversity of parasitic wasps collected from sown floral strips were higher than those from mown plants. The family of parasitic wasps of Braconidae was strongly dominant, followed by Mymaridae and Pteromalidae. By studying 26 flowering species, the greatest diversity and density of parasitic wasps were collected from Potentilla reptans, Achillea millefolium, Trifolium repens and Torilis arvensis. In terms of the early flowering plants, the most important results were observed in Euphorbia helioscopia, Senecio vulgaris and Veronica persica. To give an idea of the functional role of these plants, we studied the parasitic wasps of the diapausing larvae (cocoon) of codling moth Cydia pomonella. We recorded three emerged species: Ascogaster quadridentata, Pristomerus vulnerator and the hyperparasite Perilampus fulvicornis. However, none of these species have been observed on the 26 studied plants. Hence, this result may be suggesting that the studied plants do not have a functional role concerning these parasitoids. These studies may be advantageous for biological control programs in order to select flowering plant species attracting parasitic wasps specific to fruit pests.

Controle de pragas e doenças, maturação e qualidade de maçãs 'imperial gala' submetidas ao ensacamento

O objetivo deste trabalho foi avaliar a eficiência de diferentes embalagens no ensacamento de maçãs para o controle de pragas e doenças, e sua influência na maturação e qualidade dos frutos, em pomar sob sistema orgânico. O experimento foi conduzido em pomar com plantas de dez anos de idade da cultivar Imperial Gala, sobre porta-enxerto 'Marubakaido', com filtro EM-9, localizado no município de São Joaquim-SC, nas safras 2007/2008 e 2008/2009. Os frutos foram ensacados, após o raleio, com embalagens plásticas transparentes microperfuradas ou de tecido não texturizado (TNT). Frutos não ensacados constituíram o tratamento-controle. Na colheita, os frutos foram avaliados quanto aos danos provocados por mosca-das-frutas (Anastrepha fraterculus), mariposa-oriental (Grapholita molesta), lagarta-enroladeira (Bonagota salubricola) e pulgão-lanígero (Eriosoma lanigerum), incidência das doenças sarna-da-macieira (Venturia inaequalis) e podridão-amarga (Colletotrichum gloeosporioides), e atributos físico-químicos de maturação e qualidade e teor de cálcio (Ca) nos frutos. O ensacamento, independentemente do tipo de material utilizado, reduziu os danos de insetos-praga, porém não foi eficiente no controle de doenças nos frutos. O ensacamento não comprometeu o desenvolvimento de coloração vermelha na casca e o teor de Ca nos frutos. De modo geral, o ensacamento antecipou o processo de maturação, caracterizado pela redução na firmeza de polpa e na textura da casca e da polpa, e pelo aumento no índice de iodoamido.

Quantum dot transport in soil, plants, and insects

Environmental risk assessment of nanomaterials requires information not only on their toxicity to non-target organisms, but also on their potential exposure pathways. Here we report on the transport and fate of quantum dots (QDs) in the total environment: from soils, through their uptake into plants, to their passage through insects following ingestion. Our QDs are nanoparticles with an average particle size of 6.5 nm. Breakthrough curves obtained with CdTe/mercaptopropionic acid QDs applied to columns of top soil from a New Zealand organic apple orchard, a Hastings silt loam, showed there to be preferential flow through the soil's macropores. Yet the effluent recovery of QDs was just 60%, even after several pore volumes, indicating that about 40% of the influent QDs were filtered and retained by the soil column via some unknown exchange/adsorption/sequestration mechanism. Glycine-, mercaptosuccinic acid-, cysteine-, and amine-conjugated CdSe/ZnS QDs were visibly transported to a limited extent in the vasculature of ryegrass ( Lolium perenne), onion ( Allium cepa) and chrysanthemum ( Chrysanthemum sp.) plants when cut stems were placed in aqueous QD solutions. However, they were not seen to be taken up at all by rooted whole plants of ryegrass, onion, or Arabidopsis thaliana placed in these solutions. Leafroller (Lepidoptera: Tortricidae) larvae fed with these QDs for two or four days, showed fluorescence along the entire gut, in their frass (larval feces), and, at a lower intensity, in their haemolymph. Fluorescent QDs were also observed and elevated cadmium levels detected inside the bodies of adult moths that had been fed QDs as larvae. These results suggest that exposure scenarios for QDs in the total environment could be quite complex and variable in each environmental domain.

Comparative effects of organic and conventional apple orchard management on soil chemical properties and plant mineral content under Mediterranean climate conditions

The effects of conventional and organic management systems on soil chemical properties and leaf nutrients under Mediterranean conditions were studied over a 2-year period on adjacent commercial apple orchards in Southern Greece. The soil in both orchards was characterised as a clay loam–clay and was uniform in morphological and physical properties. The results indicated no significant differences in soil chemical properties between the different management systems, including soil organic matter (SOM), pH, cation exchange capacity (CEC) and C/N ratio. However, soil samples from the conventional orchard exhibited significantly higher values (p< 0.01) of electrical conductivity (EC) and higher concentrations of K, Ca, Na, Cu and Zn, which were likely the result of chemical fertiliser application. Despite the fact that organic systems promote the accumulation of soil organic matter and fertility over time through the use of organic sources, in our study, the SOM values declined, suggesting that the type and the rate of organic matter input in the organic orchard were insufficient. The leaf nutrients, with the exception of P and Ca, were within the sufficiency range in both management systems. The present findings did not provide evidence of major differences in the leaf macronutrient content between conventionally and organically grown apple trees. Nevertheless, our leaf analysis revealed higher concentrations of Zn in the conventionally grown trees and opposite results for Cu, probably due to the extensive use of copper-containing fungicides in organic orchards in Greece.

Efeito do ensacamento dos frutos no controle de pragas e doenças e na qualidade e maturação de maçãs 'Fuji Suprema'

O objetivo deste trabalho foi avaliar a eficiência de embalagens de diferentes materiais para a proteção contra pragas e doenças e seu efeito sobre a qualidade físico-química, maturação e teor de cálcio (Ca) em maçãs 'Fuji Suprema'. O experimento foi desenvolvido nas safras de 2007/2008 e 2008/2009, em pomar manejado sob o sistema orgânico, localizado na região de São Joaquim (SC). O pomar era composto por plantas de dez anos de idade da cultivar Fuji Suprema, sobre porta-enxerto 'Marubakaido', com interenxerto 'EM-9'. Depois do raleio manual, aproximadamente 40 dias após a plena floração, os frutos foram ensacados com embalagens plásticas transparentes microperfuradas ou de tecido não texturizado (TNT). Os frutos foram mantidos ensacados até a colheita. A testemunha foi constituída por frutos não ensacados. Na colheita, os frutos foram avaliados quanto aos danos provocados por mosca-das-frutas (Anastrepha fraterculus), mariposa oriental (Grapholita molesta) e lagarta enroladeira (Bonagota salubricola). As doenças foram avaliadas pela incidência de sarna da macieira (Venturia inaequalis), podridão amarga (Colletotrichum gloeosporioides) e podridão carpelar (Alternaria sp., Fusarium sp.). Também foi avaliada a incidência de distúrbios fisiológicos "russeting" e "bitter pit", atributos físico-químicos de maturação e qualidade e o teor de Ca nos frutos. Independentemente do tipo de embalagem verificou-se que o ensacamento é prática eficaz na proteção contra o ataque de insetos, mas não reduz a incidência e o desenvolvimento de doenças nos frutos. Na safra de 2008/2009, o ensacamento dos frutos aumentou o teor de Ca e reduziu a incidência de "bitter pit", e aumentou a incidência do "russeting". O ensacamento dos frutos antecipou a maturação, especialmente com embalagem plástica transparente microperfurada, e reduziu a coloração vermelha, especialmente com embalagem TNT.

Development and evaluation of a model for management of brown rot in organic apple orchards

Temporal development of brown rot (Monilinia fructigena) on fruits was analysed in two organic apple orchards on three apple cultivars in Eastern Hungary from 2002 to 2006. The three-parameter logistic function gave the best fit to brown rot over four non-linear growth functions in all cultivars, years and orchards. Depending on location, year and cultivar, disease increased continuously from 6 to 8 weeks before harvest up to harvest, reaching 19–37% of disease incidence. Disease variables of Y f , the final disease incidence; β, relative rate of disease progress; AUDPC S , standardized area under disease progress curve; T 1.5 , the time when disease incidence reaches 1.5% (day), and M, the inflection point were derived from the three-parameter logistic function. The disease variables of Y f , β, and AUDPC S were used in a computer simulation for predicting temporal brown rot development, and the disease variables of T 1.5 , M, and Y f were used to determine threshold values for epidemic intensity. Afterwards these were used to construct a fundamental model for developing a brown rot forecasting and management strategy (BRFMS). The fundamental model contained four parts: i) data insertion and analyses by computer simulation of pathogen submodels, ii) calculation of yield loss threshold levels based on disease incidence, iii) determination of epidemic intensity levels and iv) a decision module with suggestions for disease management practices for each epidemic intensity level. The fundamental model was supplemented with the prediction of occurrence of the first fruit rot symptoms and with the insect injury prediction related to brown rot development in order to complete a BRFMS for organic apple orchards. In a 3-year field evaluation from 2006 to 2008, season-long application of BRFMS treatments reduced the number of sprays against brown rot by 22–33% compared with the treatments of general spray schedules against brown rot.

LATEST TRENDS IN INSECT AND DISEASE MANAGEMENT IN ORGANIC APPLE SYSTEMS IN THE MIDWESTERN USA AND NEW ZEALAND

In the USA in 2005, organic apples were produced on 2788 ha in the drier climates of Colorado and eastern Washington State, but significant production also occurred in the Midwestern USA. In Midwestern organic markets, scab (Venturia inaequalis)-resistant cultivars have gained increased acceptance as the most environmentally acceptable method of organic apple production, due to concerns about copper and sulfur applications in susceptible cultivars. Typically, key pests, such as codling moth (Cydia pomonella), have been managed to damage levels below 5% through the use of codling moth granulosis virus (CMGV), mating disruption, kaolin clay, and spinosad-based insecticides. In an experimental organic apple orchard in Iowa, killing frosts in 2007 destroyed up to 80% of fruit production, leading to a resurgence of codling moth and plum curculio (Conotrachelus nenuphar) under a no-spray program. This resurgence emphasizes the need to manage pests even in low crop years. Similar pest management systems have been developed by apple-exporting countries like New Zealand in order to comply with export standards and quarantine requirements. In New Zealand, significant progress has been made in achieving greater fruit firmness after 3-month storage in advanced scab-resistant selections with 'Pinkie' background compared to 'Pinkie' or 'Liberty' apples. Future pest management strategies in organic apple production will continue to focus on the development of scab-resistant cultivars with enhanced storage capability, and the use of controlled atmosphere (CA) treatments to reduce inputs associated with negative environmental and health effects.

THE EFFECTS OF GROUNDCOVER MANAGEMENT AND NUTRIENT SOURCE DURING ORGANIC ORCHARD ESTABLISHMENT

Expansion of organic tree fruit production in the southern region of the USA has been hindered by lack of reliable, regionally appropriate, and scale-neutral technologies. In March 2006, an experimental organic apple orchard of 'Enterprise'/M26 was planted in a replicated trial to examine the effects of three organic fertilizer treatments (control, composted poultry litter and commercial pelletized fertilizer) and four groundcover treatments (shredded paper, wood chips, municipal compost and mow-blow), with the goal of developing organic management recommendations. The effects of nutrient and ground cover treatments on tree growth, canopy and root development, soil biological, chemical and physical characteristics, foliar nutrient content, and weed density were evaluated during the establishment period of the orchard as a precedent for cropping. This paper reports on the effects of these treatments on early tree growth, development, and physiology. Significant differences have been found among the organic production systems were observed after two seasons of growth. Trees grown with ground cover managed with compost or wood chips were larger than those using shredded paper or mow-blow. Both composted poultry litter and commercial fertilizer resulted in trees larger than trees which derived nutrition solely from the ground cover treatments without additional nutrients. In the third season, trees with compost or woodchip mulch had significantly more flowers, more harvested fruit, and higher fruit set than those grown with mow-blow or shredded paper. Trees that did not receive supplemental nutrition had significantly fewer flowers, fruit set, and harvested fruit, compared with those receiving poultry litter or a commercial fertilizer.

Population dynamics of bronze beetle &lt;i&gt;Eucolaspis&lt;/i&gt; spp (Coleoptera Chrysomelidae) in relation to other soil macroinvertebrates in organic apple orchards in Hawkes Bay

The population structure and dynamics of bronze beetle Eucolaspis spp and other soil macroinvertebrates were studied in eight organic apple orchards in Hawkes Bay during spring/summer 200708 Orchards with high bronze beetle population densities also had higher abundance of all types of soil macroinvertebrates than orchards with low bronze beetle populations Surfacedwelling generalist predators were more numerous (on average 536 versus 405 predators per trap) in orchards with low bronze beetle density than in orchards with high beetle density This result was mainly due to spider numbers in pitfall traps which were highest during January It may be that within orchards where surface dwelling spiders are most abundant these spiders may be predating upon newly emergent adult bronze beetles as they move from the soil to the apple foliage

The role of natural enemies on the population dynamics of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in organic apple orchards in south-eastern France

Efficient pest control using conservation strategies requires sound knowledge of the dynamics of the pest and its natural enemies (NE). But the role of natural regulation under natural conditions is not easy to prove. The rosy apple aphid (RAA) Dysaphis plantaginea is the most detrimental aphid in organic apple orchards. Our aim was to determine whether and to which point the abundance and composition of arthropod communities associated with aphid colonies affects RAA population dynamics. The present study, based on weekly observations of marked and infested apple shoots was carried out from April to June in 2008 and 2009 in one experimental insecticide-free apple orchard and four organic commercial orchards located in south-eastern France. NE populations were the most diverse (7.3 taxonomic groups for 50 shoots) and abundant (1.44 individuals per shoot) in the experimental orchard compared to organic orchards (3.8 groups for 50 shoots and 0.7 individuals per shoot). The large RAA populations per shoot (more by 1.7-fold) observed in two of the five orchards were presumably related to a lower number of NE (less by 1.9-fold) and a high abundance of ants (more by 6.2-fold). Among the main NE groups, syrphids arrived first, followed by coccinellids and earwigs. Parasitism rates, mainly due to Ephedrus sp. (Braconidae), were between 0.66% and 6.93%. Based on their precocity and abundance, syrphids appeared to be the most efficient group of NE under the study conditions. By surveying the same shoots weekly we could demonstrate that RAA population dynamics were strongly affected by the presence of NE. This predatory effect was however not sufficient to prevent damage to the apple trees. New management practices aimed at favoring natural regulation, especially augmentative approaches, need to be developed.

Temporal and spatial variability of rosy apple aphid Dysaphis plantaginea populations: is there a role of the alternate host plant Plantago major?

1 The rosy apple aphid Dysaphis plantaginea (Passerini) (Homoptera: Aphididae) is a pest of economic importance to the apple industry worldwide, particularly in organic apple orchards where no acceptable controls are available. In the Similkameen Valley of British Columbia, Canada, the rosy apple aphid population size varies widely between orchards and between years. To explain this variation, potential environmental correlates of aphid density were evaluated. The architecture of the alternate host was also evaluated for its effect on rosy apple aphid summer survival and reproduction. 2 The percentage of trees infested by rosy apple aphids among orchards was in the range 8–94% for trees having at least one cluster with more than ten aphids in 2007 and in the range 0–39% in 2008. 3 A general linear model correlating aphid densities to the environmental variables of abundance of the alternate host (plantain Plantago spp.), foliar nitrogen, tree age and planting density, and reduced by stepwise regression, indicated that foliar nitrogen and tree age explained 33% of the variation. Abundance of the summer, alternate food plant, plantain, was not related to later aphid densities on apple trees. 4 Plantain architecture, however, influenced aphid numbers and 25-fold more aphids were found on low-lying plantain leaves than on more upright leaves. Experimental manipulation of leaf angle and leaf size showed that significantly more aphids occurred on low angle, large leaves. Finally, mowing that encouraged low lying plants prior to spring aphid migration was associated with a four-fold greater number of both winged and wingless aphids on the plantain.