Apple Scab Infection Research Articles

Classifying early apple scab infections in multispectral imagery using convolutional neural networks

Multispectral imaging systems combined with deep learning classification models can be cost-effective tools for the early detection of apple scab (Venturia inaequalis) disease in commercial orchards. Near-infrared (NIR) imagery can display apple scab symptoms earlier and at a greater severity than visible-spectrum (RGB) imagery. Early apple scab diagnosis based on NIR imagery may be automated using deep learning convolutional neural networks (CNNs). CNN models have previously been used to classify a range of apple diseases accurately but have primarily focused on identifying late-stage rather than early-stage detection. This study fine-tunes CNN models to classify apple scab symptoms as they progress from the early to late stages of infection using a novel multispectral (RGB-NIR) time series created especially for this purpose.This novel multispectral dataset was used in conjunction with a large Apple Disease Identification (ADID) dataset created from publicly available, pre-existing disease datasets. This ADID dataset contained 29,000 images of infection symptoms across six disease classes. Two CNN models, the lightweight MobileNetV2 and heavyweight EfficientNetV2L, were fine-tuned and used to classify each disease class in a testing dataset, with performance assessed through metrics derived from confusion matrices. The models achieved scab-prediction accuracies of 97.13 % and 97.57 % for MobileNetV2 and EfficientNetV2L, respectively, on the secondary data but only achieved accuracies of 74.12 % and 78.91 % when applied to the multispectral dataset in isolation. These lower performance scores were attributed to a higher proportion of false-positive scab predictions in the multispectral dataset. Time series analyses revealed that both models could classify apple scab infections earlier than the manual classification techniques, leading to more false-positive assessments, and could accurately distinguish between healthy and infected samples up to 7 days post-inoculation in NIR imagery.

Scab Resistance in some Apples Genotypes from the UASVM Collection Cluj-Napoca

Apple is one of the most consumed fruits in the world and as well one of the most important crops in temperate areas. Apple scab, caused by Venturia inaequalis is damaging diseases that affects apple species and causes up to 70% yield losses depending of cultivar’s resistance. In order to control this disease, costly chemical pesticides are necessary, which increase the pollution of environment by their toxicity. This study is focused on checking the behaviour of certain apple varieties from the pomological collection at UASVM Cluj-Napoca against apple scab infection. Nine apple cultivars ('Fuji Kiku', 'Red Cap', 'Lena', 'Katja', 'Gala Mitchgla', 'Fiesta', 'Yellow', 'Pinova' and 'Reinette du Canada'), were analysed in terms of behaviour to scab attack on leaves and fruits. Visual observations were completed by molecular analyses for the potential presence of the Vf gene in some cases. Combining results from visual observation and molecular assays, the 'Lena' and 'Pinova' cultivars were noted as resistant to scab in our field trial conditions. This indicates a good opportunity to bring them into apple breeding programs for resistance to apple scab.

Synergism and phytotoxicity: The effects of tank‐mix additives on the biological efficacy of Cu2+ against Venturia inaequalis and Podosphaera leucotricha

AbstractThe wetting behaviour of the spray and the biological efficacy of Cu2+ active ingredients in agrochemical formulations may be enhanced by tank‐mix additives. We investigated how three BREAK‐THRU® additives (BT301: biodegradable, BT133 and BT420: bio‐based and biodegradable) tank‐mixed with commercial copper preparations influenced the spray distribution, leaf uptake and biological efficacy of copper additive mixtures against apple scab and apple powdery mildew under controlled conditions. We quantified the synergetic effects of these additives in foliar applications. In addition, we determined the phytotoxic potential and evaluated their impacts on photosynthetic activity, non‐photochemical quenching and ROS activity. The additives BT301 and BT420 strongly reduced surface tension and contact angle of copper treatments. The fluorescence observations revealed that BT301 achieved better spreading of copper formulation with more complete coverage of the leaf surface than BT420 and BT133, whereas ‘coffee‐ring’ spreading was observed with BT133. The additive BT301 showed an increase in relative fluorescence area, indicating higher ROS production as a signal of intra‐cellular tissue activity. The photochemical efficiency of photosystem II (Fv/Fm) was not negatively influenced by copper or additive treatment. Thus, we observed no phytotoxic effects of copper‐additive mixtures on apple leaves at treatment doses of 4 g Cu2+ L−1. All copper treatments reduced apple scab infections significantly, by 53%–76%. Interestingly, addition of BT301 to copper preparations showed the strongest biological efficacy (83% reduction) against Venturia inaequalis, whereas addition of BT420 showed the strongest effect against Podosphaera leucotricha (89% infection reduction). The synergetic effects of additives on the biological efficacy without phytotoxic effects on plants may have potential for reducing copper loads in horticultural production systems.

Feasibility of detecting apple scab infections using low-cost sensors and interpreting radiation interactions with scab lesions

ABSTRACT Apple scab is a disease caused by the fungus Venturia inaequalis (Cke.) Wint. which can spread rapidly throughout orchards diminishing tree productivity and causing huge losses in marketable fruit. Efficient orchard reconnaissance and early detection of infections can inform fungicide applications for effective disease control and a range of new low-cost sensors offer a means of imaging orchards as the basis of scab detection. This study evaluates the potential contribution of three imaging devices: a multispectral (VIS-NIR) camera, thermal camera and a 3D sensor, for the detection of scab on young apple plants. In a controlled experiment, apple seedings were infected with scab and disease progression was imaged daily under natural illumination conditions in a glasshouse with minimal image processing. Whilst the thermal and 3D sensors images were deemed unsuitable for scab detection, the high-resolution multispectral imagery was exceptionally effective, with the NIR band (800–1000 nm) permitting the earliest scab detection due to the substantially lower reflectance of the fungal structures of V. inaequalis relative to healthy leaf tissue. We offer a model of near-infrared radiation interactions with the fungus and leaf interactions to explain reflectance characteristics of scab-infected leaves throughout the growth cycle of the pathogen. The simple, low-cost remote-sensing approach developed here holds considerable promise for providing timely information on tree infection to improve the efficiency of apple scab disease management routines.

Ефективність застосування біологічних засобів проти хвороб на яблуні (Malus domestica Borkh.)

The author presents results of the two-year researching (2019-2020) the effectiveness of the biological means (PhytoHelp, MikoHelp, Kazumin 2L, RK, Cydox Pro, LS-1, Micro-Mineralis (universal) Plus, RK, Phytocid-r) against scab and apple fruit rot. The crop protection is limited almost as a whote to narrowing the spread and development of scab, all spraying was carried out the because of risk of the apple scab infection. The analysis of the weather conditions and instrumental monitoring of the epiphytic situation was conducted during April-August. There were 15 critical periods of the scab infection in 2019 and 2020. Respectively 5 and 4 sprays of the trees were made with experimental preparations. The analysis of the diseases spread and development the studing areas showed that all the preparations had a deterrent effect against apple scab, but higher results were obtained with the use of Kazumin, Fitohelp, MikoHelp and Fitocid-r. The development of this disease on the leaves as compared to the control variant decreased by nesrly 3-7 times( 1.4-6.1 % on the average). The efficiency of these preparations was 71-86 %. The development of scab when utilizeng LS 1 and Cydox Pro well as the fertilizers Micro-Mineralis Plus was 2.7-3 times less than in control, and their technical effectivity was 61-70 %. Casumin and Phytocid-r, which were 72-75 % effective, coped better with limiting the scab spread. With the application of Micro-Mineralis Plus worse the results were - only 41 %. The observations over fruit rot showed a low prevalence of the disease in all the experiment treatments. Nerely a few rotten fruits were defected. In the control variant without the use of where the fungicides, were fruit damage was 11 %, while in other variants this findex did not exceed 2 %, and the technical efficiency of the experimental preparations ranged from 79 to 100 %.

Temperature Influence on Pseudothecia Development Stages of Venturia inaequalis in the Western Cape of South Africa.

Pseudothecia development stages of Venturia inaequalis (apple scab) were investigated in two climatically different regions in the Western Cape of South Africa. The aim was to determine the pseudothecial density (PD; pseudothecia per fertile lesion [p/f]) and ascal density (AD; asci per pseudothecium [a/p]) that contributes to defining the potential ascospore dose in a common prediction model of the apple scab infection risk. The PD and AD were compared between Elgin (EL), now considered a warm winter apple-growing region because of climate warming, and Koue Bokkeveld (KB), a cold winter region. In 2012 and 2013, scabbed apple leaves were collected during leaf-drop in KB and EL and overwintered either in their region of origin or in the other region. PD was significantly higher in scabbed leaves collected and overwintered in KB (mean, 24.11 p/f) than in leaves collected in KB and overwintered in EL (mean, 17.11 p/f; P < 0.001). PD of scabbed leaves collected and overwintered in EL (mean, 15.27 p/f) or collected in EL and overwintered in KB (mean, 16.07 p/f) did not differ significantly. Ascal density did not differ significantly in any treatment or season. We concluded that the significantly higher PD of scabbed leaves collected from the cooler region of KB and overwintered in KB compared with scabbed leaves collected in EL or KB and overwintered in EL could be caused by adaptations of V. inaequalis populations to the respective climates. This implied long-term effects of climate warming on apple scab epidemiology and management.

Relationship between Incidence of Apple Scab and Early Infection before the Bloom Stage in Iwate Prefecture

Relationship between Incidence of Apple Scab and Early Infection before the Bloom Stage in Iwate Prefecture

Overview of the decision support system and fruit growth stages to predict the action threshold in order to control the apple scab in Kosovo

The apple scab caused by the fungal pathogen Venturia inaequalis (Cooke) G. Winter is a continuous problem for apple farmers in Kosovo. From this disease, the fruits become scabby brown or black spotty, losing their value. The fruit infection from A. scab requires immediate and multi time treatment. In the agricultural market, there are several plant protection products integrated in to various treatment variants provided by chemical manufacturers to control the apple scab infections. The purpose of this study was to identify the best action threshold based on the prediction of the infection risk provided by one decision support system (DSS RIMpro) and based on the empirical point of view by selecting few fruit growth stages from BBCH scale to control this disease in the research zone. Therefore, two different treatment intervals were used and eight treatment variants consisting of several fungicides were created. The research is carried out in one experimental orchard in cultivation with Starking apple cultivar. Based on analysed disease index on infected fruits, the treatment intervals were compared with each other to conclude the best action threshold for Kosovo conditions.

Prediction of the apple scab using machine learning and simple weather stations

Apple scab is an economically important pest for apple production. It is controlled by applying fungicides when conditions are ripe for the development of its spores. This occurs when leaves are wet for a long enough time at a given temperature. However, leaf wetness is not a sufficiently well-defined agro-meteorological variable. Moreover, the readings of leaf wetness sensors depend to a large extent on their location within the tree canopy. Here we show that virtual wetness sensors, which are based on the easily obtained meteorological parameters such as temperature, relative humidity and wind speed, can be used in place of physical sensors. To this end, we have first collected data for two growing seasons from two types of wetness sensors planted in four locations in the tree canopy. Then, for each sensor we have built a machine-learning model of leaf wetness using the aforementioned meteorological variables. These models were further used as virtual sensors. Finally, Mills models of apple scab infection were built using both real and virtual sensors and their results were compared.The comparison of apple scab models based on real sensors shows significant variability. In particular, the results of a model depend on the location of the sensor within the canopy. The models based on data obtained from virtual sensors, are similar to the models based on physical sensors. Both types of models generate results within the same range of variability. The outcome of the study shows that the control of apple scab can be based on machine learning models based on standard meteorological variables. These variables can be readily obtained using inexpensive meteorological stations equipped with basic sensors. These results open the way to a widespread application of precise control of apple scab and consequently significant reduction of the use of pesticides in apple production with benefits for environment, human health and economics of production.

Leaf Wetness Evaluation Using Artificial Neural Network for Improving Apple Scab Fight

Precision agriculture represents a promising technological trend in which governments and local authorities are increasingly investing. In particular, optimising the use of pesticides and having localised models of plant disease are the most important goals for the farmers of the future. The Trentino province in Italy is known as a strong national producer of apples. Apple production has to face many issues, however, among which is apple scab. This disease depends mainly on leaf wetness data typically acquired by fixed sensors. Based on the exploitation of artificial neural networks, this work aims to spatially extend the measurements of such sensors across uncovered areas (areas deprived of sensors). Achieved results have been validated comparing the apple scab risk of the same zone using either real leaf wetness data and estimated data. Thanks to the proposed method, it is possible to get the most relevant parameter of apple scab risk in places where no leaf wetness sensor is available. Moreover, our method permits having a specific risk evaluation of apple scab infection for each orchard, leading to an optimization of the use of chemical pesticides.

Udostępnienie systemu wspomagania podejmowania decyzji w zwalczaniu wybranych chorób roślin sadowniczych i warzywniczych w serwisie internetowym jako element integrowanej produkcji

This paper presents an analysis of the functioning of an online decision support system for integrated production in the fight against of major diseases of apple-, cherry- and bird-cherry-trees, onions, tomatoes and carrots based on the meteorological stations iMetos and disease models of the firm Pessl Instruments available at http://www.agropogoda.pl. To make this application we used disease development models based on numerous implementation experiences and scientific publications, which help to calculate the degree of risk/infection dedicated to the disease. The apple scab infection periods are defined on the basis of the model Schwabe. It has predicted Venturia inaequalis infections on the basis of the temperature and duration of the leaf wetness period. The description of the infection course made by Tamm et all. (1994) helped to determine the critical periods of brown rot of stone fruit trees Monilinia laxa. Pessl Instruments,Austria, developed the other disease models. The risk is assessed on the basis of conditions conducive to disease development. Daily weather data (air temperature, relative humidity and total precipitation) are used for calculations. The application calculates the risk on the basis of weather data collected from agro-meteorological stations and attached to them disease models. The user selects a station from the map or from the list of choices and the risk index values are presented in the graphs. Also text files with weather data are generated for selected stations. They can be used for a complex analysis of the conditions conducive to the development of the disease. Przedstawiono analizę funkcjonowania internetowego systemu wspomagania decyzji w integrowanej produkcji, w zwalczaniu najważniejszych chorób jabłoni, wiśni, czereśni, cebuli, pomidora i marchwi, opartego na stacjach meteorologicznych iMetos i modelach chorobowych firmy Pessl Instruments dostępnych pod adresem http://www.agropogoda.pl. Do budowy aplikacji wykorzystano modele rozwoju chorób opracowane na podstawie licznych doświadczeń wdrożeniowych oraz publikacji naukowych, dzięki którym wyliczany jest stopień zagrożenia/infekcji dla danej choroby. Terminy infekcji parcha jabłoni wyznaczane są na podstawie modelu Schwabe, który prognozował infekcje Venturia inaequalis na podstawie temperatury i długości okresu zwilżenia liścia. Do wyznaczenia okresów krytycznych brunatnej zgnilizny drzew pestkowych Monilinia laxa posłużyło opracowanie przebiegu infekcji przez Tamm i wsp. (1994). Pozostałe modele chorobowe opracowane zostały przez Pessl Instruments, Austria. Zagrożenie ocenia się na podstawie analizy warunków sprzyjających rozwojowi choroby. Do obliczenia służą dobowe dane pogodowe (temperatura powietrza i wilgotność względna powietrza oraz suma opadu atmosferycznego). Aplikacja oblicza zagrożenie na podstawie danych pogodowych pobranych ze stacji agrometeorologicznych oraz dołączonych do nich modeli chorobowych. Użytkownik wybiera stację z mapy lub z listy wyboru i wartości indeksu zagrożenia są przedstawiane na wykresie. Dla wybranych stacji generowane są także pliki tekstowe z danymi pogodowymi, które użytkownik może wykorzystać do kompleksowej analizy warunków sprzyjających rozwojowi danej choroby.

English

&nbsp; A new prediction model for the early warning of apple scab is proposed in this study. The method is based on artificial intelligence and time series prediction. The infection period of apple scab was evaluated as the time series prediction model instead of summation of wetness duration. Also, the relations of different measurements with apple scab infection time were analyzed. The important hours of duration were determined with the feature selection methods, such as Pearson&rsquo;s correlation coefficients (PCC), Fisher&rsquo;s linear discriminant analysis (FLDA) and an adaptive neuro-fuzzy classifier with linguistic hedges (ANFC_LH). The experimental dataset with selected features was classified by ANFC_LH, and predicted by an adaptive neural network (ANN) model. The proposed ANN model successfully predicts the apple scab infection time with 2 to 5% error rates compared to the traditional weather station predictions. The results show that the last 24-hour period is important to determine the apple scab infection at any time. &nbsp; Key words:&nbsp;Apple scab (Venturia inaequalis), early warning, time series prediction, feature selection, artificial intelligence.

Comparison of Penman–Monteith and non-linear energy balance approaches for estimating leaf wetness duration and apple scab infection

Leaf Wetness Duration (LWD) is the main parameter involved in the apple scab development in apple orchards. LWD values can be inferred from weather conditions by solving a non-linear energy balance equation. Such energy balance equation is usually linearized leading to the Penman–Monteith equations. However this approximation leads to significant errors in the evaporative term and by consequence in the LWD computation. In this work, consequences of the use of the Penman–Monteith equations instead of the exact solution were firstly investigated on single droplets and compared to experimental values obtained in controlled and constant conditions. For these studies, the LWD is overestimated by 12% when Penman–Monteith equations were used. The ability of LWD estimate from the linearized energy balance equation to forecast risk infection of a leaf by V. inaequalis conidia was investigated. For some conditions, the error in LWD estimate by Penman–Monteith approached 6 h, leading to an incorrect risk assessment of apple scab development.

Enzyme activity of the phenylpropanoid pathway as a response to apple scab infection

The study was performed on apple trees, ‘Golden Delicious' cv., which is a scab‐susceptible cultivar. The phenolic content of apple fruit was determined in different parts of the peel. The phenolic compounds were analysed in the scab spot, in the tissue around the spot and in the healthy tissue. We determined the concentration of various phenolic compounds and related enzyme activities. Infection with the Venturia inaequalis fungus enhanced the metabolism of phenolic compounds at the scab spot, around the spot and in healthy peel. Compared with the healthy tissue and the tissue around the spot, the scab spot showed higher enzyme activity for all tested enzymes, except for dihydrochalcone 2′‐O‐glucosyltransferase, which had lower activity in the scab spot. In comparison to the healthy peel, the scab spot showed up to 3.4 times more hydroxycinnamic acids, up to 1.1 times more dihydrochalcones and up to 1.4 times more flavan‐3‐ols. In contrast, the healthy peel showed up to 1.6 times more flavonols than the scab spot.

Hyperspectral Reflectance and Fluorescence Imaging to Detect Scab Induced Stress in Apple Leaves

Apple scab causes significant losses in the production of this fruit. A timely and more site-specific monitoring and spraying of the disease could reduce the number of applications of fungicides in the fruit industry. The aim of this leaf-scale study therefore lies in the early detection of apple scab infections in a non-invasive and non-destructive way. In order to attain this objective, fluorescence- and hyperspectral imaging techniques were used. An experiment was conducted under controlled environmental conditions, linking hyperspectral reflectance and fluorescence imaging measurements to scab infection symptoms in a susceptible apple cultivar (Malus x domestica Borkh. cv. Braeburn). Plant stress was induced by inoculation of the apple plants with scab spores. The quantum efficiency of Photosystem II (PSII) photochemistry was derived from fluorescence images of leaves under light adapted conditions. Leaves inoculated with scab spores were expected to have lower PSII quantum efficiency than control (mock) leaves. However, besides scab-induced, also immature leaves exhibited low PSII quantum efficiency. Therefore, this study recommends the simultaneous use of fluorescence imaging and hyperspectral techniques. A shortwave infrared narrow-waveband ratio index (R1480/R2135) is presented in this paper as a promising tool to identify scab stress before symptoms become visible to the naked eye. Low PSII quantum efficiency attended by low narrow waveband R1480/R2135 index values points out scab stress in an early stage. Apparent high PSII quantum efficiency together with high overall reflectance in VIS and SWIR spectral domains indicate a severe, well-developed scab infection.

Two novel Venturia inaequalis genes induced upon morphogenetic differentiation during infection and in vitro growth on cellophane

Venturia inaequalis is a hemibiotrophic ascomycete that causes apple scab. Germ tubes, from conidia or ascospores, penetrate the leaf or fruit surface directly via appressoria-like swellings; subsequently the hyphae divide laterally to form a stroma between the cuticle and the outer wall of the epidermal cells. This morphological switch can be mimicked by growing the fungus in vitro on cellophane discs. The aim of this work was to identify genes upregulated in planta using growth on cellophane as a model. Four cDNA clones were found to be induced by growth on cellophane, and qRT-PCR showed two of these genes were up-regulated over a thousand fold in infected apple leaves compared to liquid culture. The predicted proteins for both genes possess putative signal peptides for secretion but have no similarity to sequences in publicly available databases. Both genes encode proteins with novel, imperfect repeat domain structures, the number of which vary in an isolate-specific fashion. Cin1 has seven or eight repeats of about 60 amino acids with four conserved cysteine residues per repeat, while Cin3 has four or five repeats of 32 amino acids with no cysteines. Both proteins appear to have evolved through internal duplication. Cin3, in particular, shows considerable between-strain variation in domain structure, indicating a high degree of recombination at this locus and revealing that the repeat structure has most likely arisen by unequal crossing-over. Results of this study support the hypothesis that cellophane-grown V. inaequalis mimics aspects of biotrophic infection and provide the first insights into novel fungal genes expressed during apple scab infection and their mechanisms of evolution.

A during-infection spray strategy using sulphur compounds, copper, silicon and a new formulation of potassium bicarbonate for primary scab control in organic apple production

In a field experiment conducted over two growing seasons, the effectiveness and phytotoxicity of inorganic fungicides such as sulphur, lime sulphur, copper, silicon and Armicarb (a new formulation of potassium bicarbonate) was compared with water for the control of primary apple scab infections in Belgium on high, medium and low scab-susceptible cultivars (cvs ‘Pinova’, ‘Pirouette’ and ‘Reinette des Capucins’, respectively). In order to drastically reduce the amount of fungicide applied in the orchard, two approaches were used: (1) a strategy involving spraying during the infection process, before fungal penetration and (2) a tunnel sprayer machine for treatment applications. Under field conditions highly favourable for disease, low rates of elemental sulphur (31.8 and 38.6 kg ha−1 year−1 in 2005 and 2006, respectively) combined with low rates of copper (2.1 kg ha−1 year−1 in both years) provided the best scab control and reduced scab severity on the fruits of cv. ‘Pinova’ by 97 and 98% compared with water control in 2005 and 2006, respectively. Lime sulphur was much more effective than wettable sulphur and appeared to be efficient at temperatures below 10°C, but its effectiveness against apple scab decreased if the treatments were applied 12–24 h later than in the ‘during-infection’ spray strategy. Armicarb used alone significantly reduced apple scab severity on the leaves and fruits of the three cultivars compared with the water control. Its effectiveness was as good as wettable sulphur applied using the same timing and dosage. Silicon reduced apple scab on fruits very slightly, but not on leaves. The amounts of wettable sulphur, lime sulphur, copper, silicon and potassium bicarbonate used in this experiment to control apple scab were not phytotoxic, did not increase fruit russet, did increase the yield of each cultivar and did not affect summer density of the beneficial Typhlodromus pyri. The potential and limitations of ‘during-infection’ spraying as a protection strategy against apple scab in organic farming are discussed.

Predicting apple leaf emergence from degree-day accumulation during the primary scab period

The severity of primary infections of apple scab (Venturia inaequalis) is mainly determined by three components: the amount of primary inoculum, climatic conditions, and the amount of unprotected susceptible leaves. Prediction tools are available for the first two components but there are no tools to predict the emergence of apple leaves. The objective of this study was to develop degree-day models to predict emergence of both cluster and terminal shoot leaves during the primary scab period. The number of leaves per shoot was monitored during the primary infection period from 2003 to 2005 on three replicate apple trees of the cultivar Summerland McIntosh grafted on different rootstocks (M.9, MM.111, M.26) at one site and on trees of the cultivars Cortland, Empire, Lobo, McIntosh, Paulared and Spartan at two sites. There were no significant differences in the area under the leaf emergence curve (AULEC) for the different rootstocks and cultivars. The models were thus developed on data pooled over years, sites and cultivars. The rate of change in apple leaf emergence in response to degree-days (base temperature 5°C) accumulated from Apr. 01 was nonlinear with an initial lag phase followed by a linear response reaching a maximum after which the rate remained low or reached zero (no more new leaves). This response was well described by the Richards (R2 = 0.91) and the Weibull (R2 = 0.96) functions for the emergence of cluster and terminal shoot leaves, respectively. The models were tested against data not used for model development and provided an adequate prediction of the number of leaves per shoot (R2= 0.92 and 0.97). This new tool can be used to improve timing of fungicide applications against primary apple scab infections. Key words: Leaf development, phenologymodel, Malus domestica Borkh., Venturia inaequalis (Cke.) Wint

Effect of pruning on disease incidence of apple scab and powdery mildew in integrated and organic apple production

In a three-year study, the effect of two winter pruning treatments (strong and weak) on apple scab (Venturia inaequalis) and powdery mildew (Podosphaera leucotricha) was evaluated on six apple cultivars (`Rewena', `Elstar', 'Liberty', 'Gala', 'Pilot' and `Jonica') in two environmentally-benign apple production systems (integrated and organic). Results on apple scab showed that compared to the integrated production system, the pathogen caused significantly more infection on the leaves of cvs. `Elstar', 'Gala' and `Jonica' in the organic production system. The effect of pruning treatments on apple scab was mainly detectable on the cultivars susceptible to the disease such as cvs. 'Gala' and `Jonica'. The weak pruning correlated with a higher level of apple scab infection than the strong pruning, especially in the organic production system. Primary mildew infection was very low in both protection systems (below 2 %), therefore, effect of pruning on primary mildew infection could not be analysed. Low secondary mildew incidence was detected in the organically treated orchard part; however, incidence of powdery mildew was significantly higher (P&gt; 0.05) on cvs. 'Elstar', 'Pilot' and `Jonica' in the integrated orchard part compared to cvs. 'Gala', 'Rewena' and 'Liberty'. The highest incidence of mildew was on cv. 'Elstar'. Pruning had very low effect on incidence of secondary mildew infection on leaves.

Pest management benefits of compost mulch in apple orchards

The effect of compost application on weed, fungal, and insect pest management in apple orchards was investigated from 1999 to 2001. Composted poultry manure was applied in June 1999 to half of two small research orchards which had previously received little or no management. The compost provided weed control for 1 year after application. There was no effect of compost on apple scab (Venturia inaequalis) infection. In a laboratory experiment, growth of the brown rot fungus (Monilinia fructicola) was significantly slower on a compost substrate than a sterilized compost substrate. The compost significantly affected arthropod abundance during two years after application, with more predators and fewer herbivores in the compost treated plots. Populations of spotted tentiform leafminer ( Phyllonorycter blancardella) and migrating woolly apple aphid (Eriosoma lanigerum) nymphs were reduced in the compost plots. This study showed that the use of compost in an orchard ecosystem is beneficial to management of weed, fungal, and insect pests. The use of compost as a mulch in orchard ecosystems should be encouraged as a sustainable management practice because of a potential to reduce pesticide use. Published by Elsevier B.V.