Apple Scab Research Articles

Apple leaf wettability variability as a function of genotype and apple scab susceptibility

An important group of fungal diseases, such as apple scab on Malus x domestica leaves, perform infection only by remaining wetted by liquid water for a sufficient time, making leaf wetness duration (LWD) a crucial variable in epidemiological risk assessment. LWD is affected by the leaf wettability, i.e. the geometry of a liquid on a leaf as a consequence of the interaction between molecules of water and structural and physicochemical properties of the leaf surface. The variables describing wettability are the contact angles, which result from a genotype's physical and chemical properties. Accordingly, we assumed that wettability could be a direct expression of the genetic resistance of apple genotypes, thus influencing the physicochemical properties of the surface. In order to verify that hypothesis we measured static and dynamic contact angles on seven different Malus x domestica genotypes with various apple scab susceptibilities. The measured contact angle hysteresis was very high (from 58.8° to 82.6° among genotypes), leading to a high variability in possible values of static contact angles of water drops on leaf surface. The results obtained by mimicking both dew like and rain like water depositions during experiments, emphasize the importance of the water deposition process on the static contact angle of a water droplet on a leaf. A positive correlation between dew like droplets and the apple cultivar susceptibility to apple scab was observed and is discussed. This study is valuable for new LWD modeling approaches taking into account the leaf wetting properties.

Kaolin-based particle film sprays reduce the incidence of pests, diseases and storage disorders and improve postharvest quality of ‘Delicious’ apples

Several pests and diseases infest apple during production, potentially causing heavy losses. Numerous pesticides are used to control pests and diseases, sprays of which contaminate the environment and result in pesticide residues. Among Good Agricultural Practices (GAPs), particle film technology (PFT) is promising for organic fruit production. Now some kaolin-based PFs such as Surround WP®, EclipseT, Anti-stress-500®, Parasol® have been developed which are available worldwide for commercial use. In India, preliminary research work was conducted for observing the effect of one kaolin-based PF (Surround WP®) on ‘Delicious’ apple. Five sprays of Surround WP® (3%) were applied to 20-randomly selected ‘Delicious’ apple trees each year during 2015–16 and 2016–17. The sprays were applied, starting on June 15 every year at fortnightly intervals and 20 unsprayed trees served as controls. Surround WP® reduced the incidence of San Jose scale (by ~ 64%), apple scab (by ~ 87%) and powdery mildew (by ~78%) significantly but increased the incidence of woolly apple aphid (by ~ 23%) compared to the control. Surround WP®- treated apples developed a better red color (Hunter ‘a’ value = 53.42 ± 0.42), increased anthocyanin content and improved appearance score. Surround WP® - treated apples were 35.4% firmer and contained a 49.9% higher Ca content compared to untreated fruit. Surround WP® treatment also showed significant improvement in soluble solids (increased by 10.5%) and ascorbic acid content (increased by 10.8%) with significant reduction in storage disorders such as bitter pit (reduced by 90.8%), brown core (reduced by 73.3%) and water core (reduced by 88.4%). Based on this study, Surround WP® can be recommended for organic production of ‘Delicious’ apples in Himachal Pradesh, India.

Aerobiology, epidemiology and management strategies in apple scab: science and its applications

Apple Scab, caused by Venturia inaequalis (Cke.) Wint. (anamorph Spilocea pomi Fr.), is considered to be one of the most important fungal diseases of apple, which occurs almost every year in severe epidemic form under favourable environmental conditions wherever apple is cultivated. The disease has two distinct phases in its life cycle i.e. the primary saprophytic stage on the fallen dead leaves and the secondary parasitic phase on the trees. The intensity of the disease varied with the environmental conditions, cultivar and orchard management practices. Yield losses during epidemic years in 1996, 2008 and 2013 in the Gangotri fruit valley of Dist. Uttarkashi went up to 84%. Among the environmental parameters, temperature, moisture and relative humidity have the highest influence on the epidemic development. The formations of pseudothecia and ascospore discharge were associated mainly with late autumn (October) infection. Urea @ 5% concentration had a significant effect on breaking of the life cycle of V. inaequalis in overwintered leaves. The pseudothecia formation takes 32–48 days more after sexual reproduction at temperature around 8–10 °C and this process completes between February and March every year. The maximum ascospores productivity was recorded at fruit development stage (pea size to walnut size) of apple with ascospore productivity of 1, 23,000/ml and thereafter declined gradually. The ascospore emission period was 64–78 days and mean numbers of cumulative degree days for 50 and 95% spore release were 456 and 960, respectively. Data accumulated over 17 years were analyzed for validation of Mills criteria to establish its relevance in rescheduling fungicide applications under monitored spray programme. On examination of the primary infection period from Gangotri valley, some differences were observed between our results and Mills table for ascospores infection. Potential ascospore dose is a useful tool for predicting the total amount of inoculums in an orchard and has been shown to effectively improve apple scab management. PAD values were 50 times higher in the poorly managed orchards than in the integrated orchards. However, integrated orchards were considered well-managed in the investigated years and showed that the epidemic risk was low and medium, while it was very high in the poorly managed orchards on the basis of PAD. Based on the long term studies carried out at different locations from 1993 to 2018, a computer based warning system was developed to forewarn the farmers for adoption of suitable management practices. The information generated are passed on to the growers by blowing a characteristic signaling, local news paper, SMS, telephonic communication, Govt. organization and through personal contacts or messages flashed 4–5 times through radio stations. In addition, growing season kisan mela, press releases and newsletters are issued via the extension workers of the University and Govt. department.

Control of Insects and Diseases with Intelligent Variable-rate Sprayers in Ornamental Nurseries

Abstract Intelligent spray technology can reduce pesticide use and safeguard the environment; however, its ability to effectively control insects and disease must be validated before its adoption by growers. Comparative tests for two different laser-guided variable-rate intelligent sprayers and the same sprayers with conventional constant-rate mode were conducted to control pests at two ornamental nurseries in two growing seasons in Ohio. Crabapple [Malus ‘Sutyzam’ (Sugar Tyme®), M. sargentii], apple (Malus pumila), maple [Acer ×freemanii ‘Jeffersred' (Autumn Blaze®), A. rubrum ‘Franksred' (Red Sunset®) and A. rubrum], birch (Betula nigra and Betula populifolia ‘Whitespire'), London planetree (Platanus ×acerifolia ‘Bloodgood') and dogwood (Cornus florida) were used as the test plants. Intelligent spray technology reduced pesticide use by 56.1% and 51.8% on average at the two nurseries, respectively. Compared to conventional air-assisted sprayers, severity of scab on apple trees and powdery mildew in dogwood was reduced on intelligent spray-treated plants at one nursery, and there were equal or fewer leafhoppers in maple trees and aphids in birch trees when sprayed using intelligent spray technology at both nurseries. These results suggest that intelligent, variable-rate sprayers achieve equivalent or greater insect and disease control in ornamental tree nurseries compared to conventional, constant-rate sprayers. Index words: aphid, apple scab, environmental protection, leafhopper, precision spray, powdery mildew, sustainable. Species used in this study: apple (Malus pumila Mill), birches (Betula nigra L, Betula populifolia Marsh. ‘Whitespire'), crabapples [Malus ‘Sutyzam' (Sugar Tyme®), M. sargentii Rehder], dogwood (Cornus florida L.), maples [Acer ×freemanii E. Murray ‘Jeffersred' (Autumn Blaze®), A. rubrum L. ‘Franksred'(Red Sunset®) and A. rubrum L.], London planetree [Platanus ×acerifolia (Ait.) Willd. ‘Bloodgood'].

Novel data augmentation strategies to boost supervised segmentation of plant disease

Annotation of images in supervised learning is notably costly and time-consuming. In order to reduce this cost, our objective was to generate images from a small dataset of annotated images, and then use those synthesized images to help the network’s training process. In this article, we tackled for illustration with agricultural material the difficult segmentation task of apple scab on images of apple plant canopy by using convolutional neural networks. We devised two novel methods of generating data for this use case: one based on a plant canopy simulation and the other on Generative Adversatial Networks (GANs). As a result, we found that simulated data could provide an important increase in segmentation performance, up to a 17% increase of F1 score (a measure taking into account precision and recall), compared to segmenting with weights initialized on ImageNet. In this way, we managed to obtain, with small datasets, higher segmentation scores than the ones obtained with bigger datasets if using no such augmentations. Moreover, we left our annotated dataset of scab available for the plant science imaging community. The proposed method is of large applicability for plant diseases observed at a canopy scale.

Wood Ant (Formica polyctena) Services and Disservices in a Danish Apple Plantation

Ants possess properties that can be used to optimize plant production in agricultural systems. Ant services can be herbivore and pathogen protection and fertilization of their plant partners. They may, however, also harm plants by facilitating ant-attended herbivorous homopterans. To assess whether wood ants can be used in IPM-systems to improve apple production, we transplanted wood ants into a Danish apple plantation and tested whether ants (i) reduced the number of herbivores, (ii) led to higher amounts of leaf nutrients, (iii) controlled apple pathogens, (iv) increased homopteran abundance and (iv) whether these effects affected apple yields. During a two year study, we found that the wood ants significantly reduced the numbers of winter moth larvae, increased magnesium content in apple leaves (but did not affect 10 other nutrients), reduced the number of apples infected with apple brown rot and apple scab (on one apple variety) and increased aphid infections. In the first year, this led to higher apple production on ant trees, whereas ants had no effect on yields in the second year. It was evident that ants provided both services and disservices. If mutualistic ant-homopteran interactions can be disrupted, this would favor plant growth and open for the use of wood ants in sustainable plant management. We discuss how this may be accomplished. Alternatively, ants may be used short term to knock down pest outbreaks (before building up homopteran populations) or used in crops that do not host ant-attended homopterans.

Impact of Exclusion Netting Row Covers on 'Honeycrisp' Apple Trees Grown under Northeastern North American Conditions: Effects on Photosynthesis and Fruit Quality.

Exclusion nets have been used successfully to protect fruit from insect pests of apples under various conditions, but the effect of each particular netting system on the plant itself has rarely been investigated. In this study, a complete exclusion system—in which the soil is also excluded—was used to grow ‘Honeycrisp’ apples for six years in southern Quebec, Canada. Abiotic conditions, as well as plant photosynthesis and fruit quality characteristics (colour, firmness, size, sugar content, number of seeds, ripeness and skin integrity) and yield were estimated yearly and compared in netted (either with or without a rainproof top) and unnetted row units. Although annual variations were high and results showed little or no difference between netted and unnetted rows for all measured variables, with the following exceptions; colour (increased red surface on fruits from unnetted rows some years), size (fruits from unnetted rows were smaller) and maturity (fruits from unnetted rows matured slightly faster). Fruits produced under nets had fewer microcracks at the surface than fruits produced without nets. Reduced cracking possibly helped decrease sooty blotch and flyspeck incidence and severity. Impacts for pest control and prospects for pesticide-free production are discussed.

Test of fungicide Farmaiod, GS for apple tree viral diseases control

In the Krasnodar Territory, on the Renet Simirenko apple variety, symptoms corresponding to the manifestation of viral diseases were found: chlorotic leaf spot, dark green depressed spots on the fruit, which manifest themselves at the end of ripening before harvesting and during storage. Identification of pathogens was performed by Enzyme Immunoassay (ELISA). Samples were tested for the presence of apple chlorotic leaf spot virus (ACLSV), apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), and apple mosaic virus (ApMV). As a result of the analysis, viruses of chlorotic leaf spot of the apple tree (ACLSV) and pitted of apple tree wood (ASPV) were detected. To protect the apple tree from viruses, the drug Farmaiod, GS, whose active ingredient is iodine, was tested. The first treatment was carried out during the 2014 leaf fall period with a consumption rate of 1.0 l/ha and continued in the following 2015 in the phenophase "green cap" and "fruit diameter 10-20 mm" in two versions with consumption rates of 0.5 and 1,0 l/ha. With the onset of leaf fall in the same areas, the treatment cycle was repeated according to the same scheme. Accounting was carried out by the method of visual diagnostics, in addition, at the end of the first and second seasons, virological analyzes were performed by ELISA. As a result of research, it was noted that 3-fold use of the drug Farmaiod, GS in apple trees of the variety Renet Simirenko restrained the development of the apple tree acle virus (ASPV) and completely suppressed the apple leaf chlorophyll virus (ACLSV). The weather conditions of 2016 test triggered a strong manifestation of scab on leaves and fruits. In the experimental variants, it was noted that the drug at 78.3-83.1 % inhibits the development of apple scab. Treatment with Farmaiod, GS also fostered harvest increase and premium output. The maximum results regarding restraints of infectious processes as well as harvest increase were received when applying the preparation with consumption rate of 1,0 l/ha.

Apple Scab Disease Severity in the Sais Region of Morocco and its Sensitivity to Three Commercial Fungicides

Apple scab, Venturia inaequalis (Cooke) G. Winter, results in numerous fungicide applications in the Sais region of Morocco. We conducted the study to determine the susceptibility of cultivars through field survey and to evaluate the sensitivity of V. inaequalis to three fungicides using both in vitro and in vivo methods. We surveyed 100 apple orchards and collected two samples. Disease survey showed that the cultivars were highly susceptible to apple scab (grand mean of leaf scab: Golden Delicious, 40.31%; Starking Delicious, 20.45%; and Gala, 18.92%). Results underlined no significant differences between isolates in term of inhibition rate of mycelial growth and averaged disease severity. However, both treatment and concentration were statistically significant. EC50 values ranged from 2.33 µg/ml to 7.40 µg/ml and resistance factor (RF) values of 0.55, 1.02 and 1.79 were obtained for difenoconazole, trifloxystrobin and thiophanate-methyl, respectively. In vivo tests at a concentration of 10 µg/ml on the isolate ViIF using a curative method showed a high efficacy of trifloxystrobin (96.38%), and low efficacy of thiophanate-methyl (29.65%) and difenoconazole (24.62%). V. inaequalis was most sensitive to trifloxystrobin followed by difenoconazole and thiophanate-methyl, respectively. From this work, it was recommended testing more isolates and contact fungicides in order to develop a baseline sensitivity of the pathogen population against commonly used fungicides to treat the disease, as continued usage over time and the introduction of new fungal races may result in a decrease in fungicide efficacy.

Comparison of wetness sensors and the development of a new sensor for apple scab prognosis

Apple scab prediction is based on the model of Mills which describes the risk of Venturia inaequalis infection using leaf wetness duration and air temperature data. The quality of prognosis relies on sensor quality. Six brands of commercially available leaf wetness sensors were compared at the Julius Kuehn-Institute (Germany) apple orchard from 2011 to 2013. Also a new wetness sensor was developed and optimized from 2009 to 2015 in cooperation with Thies Clima company. The Thies-wetness sensor was equipped with a glass–ceramic surface, an adjustable heating system to avoid dew and an adjustable cooling system to prolong wetness duration of sensor surface. Prototypes were tested in climate chamber before exposition in the orchard to achieve sensor settings with drying properties broadly similar to apple leaves. The market-ready prototype showed suitability for prognosis in field assays in primary seasons of 2015–2017 and maybe integrated into prognosis of apple scab without further modeling. The Thies-sensor was shown to be more reliable, uniform, sensitive and more suitable for forecasting than the purchased models.

Efficacy of Sterol-Inhibiting Fungicides on the Control of Scab Disease (Venturia Inaequalis) in Apple Tree

Apple scab, caused by Venturia Inaequalis is one of the most problematic diseases of apples in Korça region. The control of this disease requires different applications of fungicides. The aim of the study was the estimation of efficacy of sterol-inhibiting fungicides such as myclobutanil and penconazole on the control of scab disease. The effectiveness of fungicides was evaluated for two cultivars Golden Delicious and Starking and the minimum and the maximum recommended doses were applied. The obtained results showed that scab prevalence in leave ranges from 79.2% to 85.6% respectively in untreated trees of Golden Delicious and Starking cultivars. The scab prevalence of leaves in apples treated with pesticides ranges from 18.1% in Golden Delicious cultivar to 22.2% in Starking cultivar, meanwhile the scab prevalence in fruit varies from 4.2% in Starking cultivar to 6.1% in Golden Delicious cultivar. The disease index of leave in untreated control varies from 38.4% to 40.1% respectively for Golden Delicious cultivar and Starking cultivar, while the severity of fruit in untreated trees varies from 45.6% in Starking cultivar to 49.0% in Golden cultivar. Therefore, the data showed that the uses of sterol-inhibiting fungicides were effective in the control of scab disease.

Efficacy of Sterol-Inhibiting Fungicides on the Control of Scab Disease (Venturia Inaequalis) in Apple Tree

Apple scab, caused by Venturia Inaequalis is one of the most problematic diseases of apples in Korça region. The control of this disease requires different applications of fungicides. The aim of the study was the estimation of efficacy of sterol-inhibiting fungicides such as myclobutanil and penconazole on the control of scab disease. The effectiveness of fungicides was evaluated for two cultivars Golden Delicious and Starking and the minimum and the maximum recommended doses were applied. The obtained results showed that scab prevalence in leave ranges from 79.2% to 85.6% respectively in untreated trees of Golden Delicious and Starking cultivars. The scab prevalence of leaves in apples treated with pesticides ranges from 18.1% in Golden Delicious cultivar to 22.2% in Starking cultivar, meanwhile the scab prevalence in fruit varies from 4.2% in Starking cultivar to 6.1% in Golden Delicious cultivar. The disease index of leave in untreated control varies from 38.4% to 40.1% respectively for Golden Delicious cultivar and Starking cultivar, while the severity of fruit in untreated trees varies from 45.6% in Starking cultivar to 49.0% in Golden cultivar. Therefore, the data showed that the uses of sterol-inhibiting fungicides were effective in the control of scab disease.

Effect of surface disinfectants on fruit blemishes (Sooty blotch & Flyspeck) and quality of apple (Malus domestica Borkh.) cv. Banky during cold storage

Different surface disinfectants were used to control the fruit blemishes caused by sooty blotch (SB) and flyspeck (FS). Treatments included sodium hypochlorite (200, 500 and 800 ppm), copper sulphate (100, 200 and 300 ppm), hydrogen peroxide (100, 360 and 480 ppm) and potassium bicarbonate (200, 500 and 800 ppm) were used to maximize the storage life of apple fruits. Apple fruits after application of treatments were stored at 2°C and 80-85% RH for 90 days. The highest control of fruit blemishes was observed with 800 ppm sodium hypochlorite which was non-significantly (P > 0.05) different with 500 ppm sodium hypochlorite after 90 days of storage. Weight loss was less in fruits treated with 500 ppm sodium hypochlorite (30%) as compared to control fruits (85%). Further, apple fruits treated with 500 ppm sodium hypochlorite showed the best results in terms of total soluble solids, titratable acidity, sugars and sensory evaluation as well. Fruits treated with other surface disinfectants also showed good results but not as effective as 500 ppm sodium hypochlorite treatment did. Thus, it could be concluded from present study that 500 ppm sodium hypochlorite treatment have the potential to be used in controlling apple fruit blemishes and maintain fruit quality up to 90 days. Keywords: Apple; Fruit blemishes; Physical quality; Sensory evaluation http://dx.doi.org/10.19045/bspab.2019.80054

Stealth Pathogens: The Sooty Blotch and Flyspeck Fungal Complex.

Sooty blotch and flyspeck (SBFS) fungi produce superficial, dark-colored colonies on fruits, stems, and leaves of many plant genera. These blemishes are economically damaging on fruit, primarily apple and pear, because they reduce the sale price of fresh fruit. Fungicide spray programs can control SBFS but are costly and impair human and environmental health; thus, less chemically intensive management strategies are needed. Although the scientific study of SBFS fungi began nearly 200 years ago, recent DNA-driven studies revealed an unexpectedly diverse complex: more than 100 species in 30 genera of Ascomycota and Basidiomycota. Analysis of evolutionary phylogenetics and phylogenomics indicates that the evolution of SBFS fungi from plant-penetrating ancestors to noninvasive ectophytic parasites was accompanied by a massive contraction of pathogenicity-related genes, including plant cell wall-degrading enzymes and effectors, and an expansion of cuticle-degradation genes. This article reviews progress in understanding SBFS taxonomy and ecology and improving disease management. We also highlight recent breakthroughs in reconstructing the evolutionary origins of these unusual plant pathogens and delineating adaptations to their ectophytic niche.

Reducing apple scab and frogeye or black rot infections with salicylic acid or its analogue on field-established apple trees

Apple scab (Venturia inaequalis) (AS) and frogeye leaf spot or black rot (Botryosphaeria obtusa) (FLS or BR) are two diseases of apples that affect developing foliage and fruit during summer and cause significant losses in the field and during storage. In this 3-year study (2014–2016), salicylic acid (2-hydroxybenzoic acid) or its analogue (Benzothidiazole or Actigard®) were applied to field-established apple ‘Honeycrisp’ at the tight cluster stage of flower bud development and at late pink bloom as either trunk injection or foliar sprays and to ‘Cortland’ (injection only). AS and FLS leaf infections were assessed 1, 2, and 3 weeks after the second treatment while infections on fruit were assessed at harvest. Main treatment effects were significant (P = 0.05) and both salicylic acid and Actigard® showed less infections on foliage due to AS in 2014 and 2016, and only salicylic acid showed less BR infections on fruit in both years. The cultivar effects were also significant, showing consistently less AS infections on the foliage and fruit of ‘Honeycrisp’, and less FLS infections on ‘Cortland’ foliage. Injection and spray treatments of salicylic acid and Actigard® showed no differences in infections by AS and FLS or BR on foliage or fruit. The method of application × treatment interactions were only significant in 2014; both salicylic acid and Actigard®-treated ‘Cortland’ trees showed less FLS infections on foliage and less BR infections on fruit, and only salicylic acid-treated ‘Honeycrisp’ trees showed less percentage of AS and BR infected fruit. In 2015, both salicylic acid and Actigard® treatments showed less infections of FLS on foliage and lower BR-infected fruit on ‘Cortland’. In 2016, both these treatments reduced incidence of AS and FLS on ‘Cortland’ foliage, and only salicylic acid reduced AS infections on ‘Honeycrisp’ foliage. Further studies are needed to integrate salicylic acid or Actigard® treatments into an apple foliar disease management program with registered fungicides.

Characterization of the VisdhC and VisdhD Genes in Venturia inaequalis, and Sensitivity to Fluxapyroxad, Pydiflumetofen, Inpyrfluxam, and Benzovindiflupyr.

Succinate dehydrogenase inhibitors (SDHI) are an important class of fungicides for management of apple scab, especially as resistance to other classes of fungicides has become prevalent in the northeastern United States. Considering their single-site mode of action, there is high risk of resistance development to SDHI fungicides. Such risk mandates the need for proper monitoring of shifts in population sensitivity. This study aims to provide a means for phenotypic and genotypic characterization of SDHI fungicide resistance for Venturia inaequalis, the causal agent of apple scab. To complement the published sequence of VisdhB, target genes VisdhC and VisdhD were identified using sequences of homologous genes in other fungal organisms and a draft genome of V. inaequalis. Using mycelial growth and conidial germination assays, baseline sensitivities and cross sensitivities of V. inaequalis were determined for several SDHI fungicides. Mean baseline EC50 values for conidial germination of benzovindiflupyr, fluxapyroxad, pydiflumetofen, and inpyrfluxam were found to be 0.0021, 0.0284, 0.014, and 0.0137 μg ml-1, respectively. Mean baseline EC50 values for mycelial growth of benzovindiflupyr, fluxapyroxad, pydiflumetofen, and inpyrfluxam were found to be 0.0575, 0.228, 0.062, and 0.0291 μg ml-1, respectively. A significant and positive correlation in sensitivity was found between benzovindiflupyr, fluxapyroxad, pydiflumetofen, and inpyrfluxam as well as penthiopyrad and fluopyram, with the highest correlation between benzovindiflupyr and penthiopyrad for mycelial inhibition of V. inaequalis (r = 0.950, P < 0.001). For inhibition of conidial germination, the highest correlation was observed between penthiopyrad and fluopyram (r = 0.775, P < 0.001). Furthermore, the sequences of the VisdhC and VisdhD genes were identified and characterized for baseline isolates of V. inaequalis. Residues of similar position to mutations found in other systems that confer resistance to SDHI fungicides were identified in baseline isolates, but no mutations were identified in baseline isolates or those previously exposed to SDHI fungicides. This study will serve as a reference for future monitoring of resistance to SDHI fungicides in V. inaequalis at both a phenotypic and genotypic level.

Investigation of Genetic Diversity in Apple Scab (Venturia inaequalis) Isolated from Two Different Geographical Areas of Turkey

Apple (Malus domestica) is a widely grown fruit in various climate types of the world and is exposed to the attack of many fungal disease agents during the growing period. One of them is Venturia inaequalis, which is probably the most important in terms of economic loss worldwide, which makes apple scab disease important in apple growing areas. In this study, the genetic diversity of apple scab in Bingol and Isparta provinces has been examined, which represent the two extremes of Turkey in terms of apple production. The 18 isolates obtained from these regions and were amplified by PCR using 7 RAPD primers. Polymorphic bands of the isolates were obtained by subjecting to agarose gel imaging. The average number of bands per primer was determined to be 3.91, with the highest polymorphic bands obtained from OPF04 encoded primer and the least polymorphic bands from OPG15 encoded primer. According to the clustering analysis, the total isolate population belongs to 5 different groups. Significant privileges were not observed between the two regions’s isolates It is thought that RAPD primers have a certain level to determine the diversity but not high levels of intra- and interregional variation in the isolates of V. inaequalis.

The Effect of Different Forms of Sulphur on Incidence of Apple Scab on Apple Tree (Malus x domestica Borkh) Gloster CV.

Abstract From 2014 to 2015 the influence of foliar application of sulphur on apple trees (Gloster cv.)was investigated in the apple orchard at the Research and Breeding Institute of Pomology in Holovousy (North-East Bohemia, Czech Republic). The experiment was based on foliar applications of fertilizers containing different forms of sulphur: elemental S0, sulphate SO4 2− and thiosulphate S2O3 2− (in combination with other macro- and microelements) and fungicides with or without sulphur: Kumulus (S0 + F) and the conventional fungicide programme (F), in the respective treatments. Apple scab incidence on leaves and fruits was investigated in each experimental year according to the relevant methodology of the OEPP/EPPO standard PP1/5(3) Venturia inaequalis. Data on the incidence of apple scab correlate with the process of pathogen life cycle and risk of infection on the given dates. The incidence of apple scab was the lowest in 2014 in treatment S0 + F (10.8 % on leaves, 2.8 % on fruits) and F (15.8 % on leaves, 6 % on fruits) where conventional fungicides were used. When compared with the other treatments these treatments were the most effective even if the incidence of scab in the individual treatments in 2015 increased by 28 to 60 % due to high infection pressure. The results confirmed the efficiency of the conventional fungicide programme (S0 + F and F) against apple scab incidence on fruits. What is more, the results were slightly better in the treatment, where the conventional fungicide programme was combined with fertilizer containing elemental S (S0 + F) in comparison with fungicides applied alone (F). The effect of the other forms of sulphur (SO4 and S2O3) on apple scab control has not been confirmed. According to the results, the application of the conventional fungicide programme (S0 + F and F) is more effective against scab incidence than the inorganic forms of sulphur alone.

Postharvest quality implications of preharvest treatments applied to enhance Ambrosia™ apple red blush colour at harvest

Two approaches for enhancing red blush in Ambrosia™ apple were evaluated: (i) reflective row covers or (ii) application of foliar phosphorus-rich sprays, both applied several weeks before anticipated harvest. Two experiments were conducted, the first to evaluate a white reflective row cover versus foliar phosphorus spray, and the second to evaluate two types of reflective row cover, one made of a woven white polyethylene sheet and the other a solid silvered Mylar®. The comparative effects of these preharvest treatments on at-harvest fruit quality and quality after storage were assessed in both experiments. It was determined that foliar phosphorus sprays or one of the two types of reflective row covers resulted in similar enhancement of red blush colour, with no negative effects on at-harvest quality. However, in the first experiment it was found that after 8 mo of controlled-atmosphere storage (1 kPa O2 + 1 kPa CO2 at 0.5 °C), apples from the phosphorus foliar spray treatment developed greasiness and sooty blotch compared with those from the reflective row cover or control treatments. In the second experiment, after 5 mo of air storage at 0.5 °C, the apples from the silvered Mylar® reflective row cover treatment developed severe soft scald and soggy breakdown compared with the control and white reflective row cover treatments, which developed lower or very slight incidence of soft scald, respectively, and no soggy breakdown. These results indicate that when preharvest treatments are applied to apples, post-storage quality effects should be evaluated.

The efficacy of trunk injections of emamectin benzoate and phosphorous acid for control of obliquebanded leafroller and apple scab on semi-dwarf apple

Trunk injections reduce pesticide inputs and environmental contamination, and recent work has addressed apple production systems. Insecticides and fungicides have been demonstrated for apple tree injection, however combinations of the two have not yet been tested. Trunk injections of the systemic insecticide emamectin benzoate and systemic acquired resistance (SAR) fungicide phosphorous acid were performed on mature apple trees to combine management strategies for foliar insect pests and apple scab (Venturia inaequalis). Injections of emamectin benzoate followed by phosphorous acid into the same set of injection ports resulted in higher mortality of Choristoneura rosaceana larvae and lower incidence of apple scab compared to the control. Scab incidence on trees in which phosphorous acid was injected into the same set of ports before emamectin benzoate were not different from control trees early in the growing season. Injections of emamectin benzoate and phosphorous acid into the same holes in either order showed higher mortality and reduced larval feeding in C. rosaceana bioassays compared with products injected into separate holes. This study demonstrates that two pesticides can interact dynamically within the vascular system of a tree, which has important implications for expanding the utility of trunk injection for fruit tree management.