Young Orchards Research Articles

Identification of Fusarium Wilt Disease Causal Agents in Pistachio Fields and Determination of Efficacy of Some Fungicides Controlling of The Disease

Pistachio (Pistacia vera) propagation is commonly carried out by seedlings and new orchards are mostly set by in situ grafting of rootstocks. Pathogenic and molecular characterization of wilt and desiccation agents observed in nurseries and young orchards were carried out and the causal species were identified as Fusarium oxysporum and F. solani. In vitro inhibition of mycelial development and conidia germination were carried out with seven fungicides selected against the disease. The plant protection product containing Prothioconazole + Spiroxamine was found to be 100% effective in mycelial growth trials in F. oxysporum isolates from 20 mgL-1 and in F. solani from 100 mL-1 at all increasing doses. . The fungicide containing phosphoric acid was found to be 18.3%-33.3% effective on both species at 2.5 times the recommended dose. On conidial germination, Prothioconazole + Spiroxamine and Captan provided 100% inhibition even at the lowest doses in all isolates tested. The EC50 values of Prothioconazole + Spiroxamine, which was determined as the most effective chemical in mycelial development and conidial germination, were 3.67 ml and 3.72 ml in F. oxysporum isolates and 56.83 ml in F. solani, respectively.

The influence of soil depth and tree age on soil enzyme activities and stoichiometry in apple orchards

The indispensable role of soil microorganisms in apple orchards, impacting soil quality, nutrient cycling, and crop productivity, cannot be overstated. Nonetheless, as apple trees mature, the potential for soil nutrient imbalances arises, affecting apple growth and yield. Research on how deep soil properties evolve with tree age is limited. Soil samples were gathered from apple orchards of various ages, utilizing the microplate fluorescence method to examine soil enzyme activity, microbial stoichiometry, and their correlation with soil nutrients. Results reveal that soil properties, microbial biomass, and enzymes are influenced by both tree age and depth. Microbial biomass decreases with depth, peaking in young orchards with the highest MBN:MBP ratio. Initially declining, microbial entropy nitrogen rises with tree age. Redundancy analysis identifies OP as pivotal in explaining extracellular enzyme activity. The enzyme C:N ratio exhibits a negative correlation with the MBN:MBP ratio. Additionally, ratios of ln(NAG) to ln(BG), ln(AKP) to ln(BG), and ln(AKP) to ln(NAG) demonstrate positive correlations. Enzyme activity ratios for C, N, and P transformation deviate from the global ecosystem ratio, indicating nuanced nutrient dynamics. Soil vector angles are influenced by tree age, suggesting limitations on microbial metabolism by carbon and phosphorus. Structural equation modeling unveils that soil depth negatively impacts pH, AKP, and Enzyme N:P, while tree age adversely affects Enzyme N:P. Furthermore, MBN:MBP is directly influenced by AKP and soil depth, indirectly by tree age and pH. This study underscores the significance of microbial stoichiometry in evaluating soil resource ecology relations, offering insights into soil microbe-orchard ecosystem dynamics.

DURIAN STEM CANKER STATUS AND RELATIVE SOIL PROPERTIES IN PENINSULAR MALAYSIA

The arising stem canker issues can be devastating when new durian orchards are developed without proper disease management strategies. Hence, this study aims to obtain the current durian stem canker incident rates in Peninsular Malaysia including soil properties. 15 plots (2,500 m2 per plot) of durian orchards were evaluated and composite soil samples were analysed. Results showed that the greatest disease incidence (100%) was in old orchards (> 10 years), with a severity of 63% whereas young orchards (< 10 years) are at risk of severe stem canker with 71% of incidence and 43% of severity. There was a negative correlation (r = –0.220) between the incidence of stem canker and soil pH which indicated that durian trees grown in acidic soil (pH < 5.0) were more prone to disease dispersion in the orchards. Moreover, severely infected trees were observed more in durian orchards with a higher proportion of finer sand particles in the soil (DI/ r = 0.199 & DSI/r = 0.206) compared to coarse particles of clay and silt. Our work will play a crucial role in advancing real-time monitoring of durian stem cankers and enabling the prediction of potential disease outbreaks for the implementation of preventive measures.

Monitoring of the species composition and number of insects and mites on the apple trees in the Right Bank Forest Steppe of Ukraine

Goal. To monitor the species composition and abundance of insects and mites on apple trees in the Right-Bank Forest-Steppe of Ukraine.
 Methods. Field, laboratory, microscopic, mathematical, statistical and calculation methods. The research was carried out according to generally accepted methods in entomology and plant protection, starting in early spring (late April — early May before harvest).
 Results. Monitoring of the number of insect pests and mites on apple trees in three types of plantations was carried out: a young orchard on stunted rootstocks with an intensive protection system; an old orchard on tall rootstocks with a protection system; an old orchard without treatments (long-term control).
 Conclusions. Monitoring of species composition and dynamics of pests number makes it possible to study and substantiate the patterns in the structure of insect and mite populations, to predict their harmfulness and to improve the protection system of apple trees or its individual components.

High-resolution satellite imagery to assess orchard characteristics impacting water use

Most Orchards throughout the Mediterranean basin rely heavily on irrigation, a dependency increasing due to climate changes. Assessing the water requirement (WR) is crucial and depends on different factors, including orchard age, tree density per field, inter-row management. This study proposes new methods to evaluate these characteristics with remote sensing (RS). Various remote sensors providing high and very high spatial resolution images are investigated and their accuracy is assessed. The final objective is to assess WR using variables derived from remote sensing compared to data provided by water managers and from the FAO method. A typical Mediterranean watershed was selected in South-Eastern France, with orchards having various agricultural practices. Original methods were developed with Sentinel 2 (S2) data (2016–2023), 1 Pleiades image (2022) and the extraction of Google-satellite-hybrid images (GSH, 2017), and assessed using a large ground observation dataset (information on water use collected on 366 fields). Five orchards were monitored by capacitive sensors to assess the water balance. Irrigation durations ranged from 3–300 hours/year, with decision influenced by tree density and plot age. To identify young orchards, a thresholding approach on S2 derived NDVI effectively identified young orchards achieving a 98% accuracy rate. Grassed and non-grassed orchards were mapped using two methods, with a random forest classification using three spectral bands with 72% accuracy and a supervised approach yielding 81% accuracy for GSH and 57% for Pleiades. The performance depends on the acquisition date of images. A pattern detection algorithm applied to GSH and Pleaides determined tree density, showing a high correlation (r²=0.9) with observed data. These RS derived variables allowed to compute orchard water requirements at the watershed scale, ranging from 70 to 550 mm annually depending on management practices. The proposed methods can be extrapolated to other territories and are implemented using open access softwares.

Survey on Latent Infection of Canker-Causing Pathogens in Budwood and Young Trees from Almond and Prune Nurseries in California.

Almond band canker and prune Cytospora canker have become more severe in the last decade, especially in young orchards, in California. To test our hypothesis that young trees from nurseries could carry the canker-causing pathogens at latency phase to new orchards through transplanting, a multiyear survey on latent infection of canker-causing pathogens of budwood and young trees of almond and prune nurseries in California was conducted. A total of more than 1,730 samples including shoots of rootstocks and scions and grafting union cuttings were collected from 11 nurseries. A real-time quantitative PCR assay was applied to quantify the latent infection levels by six canker-causing pathogen taxa: Botryosphaeria dothidea and species of Cytospora, Diplodia, Lasiodiplodia, Neofusicoccum, and Phomopsis. For almond, the average incidences of latent infection caused by Lasiodiplodia spp. (43.6%) and Neofusicoccum spp. (24.2%) were significantly greater than those by the other four pathogen taxa. The molecular severity (MS) of latent infection caused by Neofusicoccum spp. (3.6) was significantly greater than those caused by other pathogen taxa, except for Lasiodiplodia spp. (2.6). For prune, the average incidence of latent infection caused by Cytospora spp. (13.5%) was significantly higher than those caused by B. dothidea (1.5%) and Diplodia spp. (1.3%) but not significantly higher than those caused by Lasiodiplodia spp. (6.9%), Neofusicoccum spp. (6.3%), and Phomopsis spp. (7.7%), respectively. Moreover, the average MS values caused by Cytospora spp. (3.8) and Neofusicoccum spp. (3.2) were the highest followed by those caused by B. dothidea (1.4), Lasiodiplodia spp. (2.2), and Phomopsis spp. (2.3). Different almond varieties showed various levels of susceptibilities to different canker-causing pathogens. This study concluded that Lasiodiplodia and Neofusicoccum are the predominant pathogen species in almond, and Cytospora is the most important canker-causing pathogen species in prune in nurseries. These findings confirmed the observations of predominancy of canker-causing pathogens in almond and prune orchards in California.

GRASS COVER, TREE DENSITY, AND LEAF DEVELOPMENT OF MEDITERRANEAN ORCHARDS FROM HIGH RESOLUTION DATA

Abstract. The study focused on Mediterranean orchards and aimed to explore different remote sensing data (Sentinel 2 data (2016–2023), 1 Pleiades image (2022) and the extraction of Google-satellite-hybrid images (GSH,2017)) to compute key variables affecting water requirements such as tree age and density per plot, leaf development, the inter-row management. Surveys were conducted on 22 farms where accurate information on agricultural practices was collected. The results have shown that a thresholding on the NDVI Sentinel 2 in the summer period allowed the identification of young orchards with an accuracy of 98%. The analysis of temporal profiles of FAPAR allowed the identification of key phenological stages such as flowering and fruit set. Supervised classification was employed to separate grassed and non-grassed plots using three spectral bands of Sentinel 2. Classifications performed from GSH images gave more accurate results (81% well classified) compared with Sentinel 2 (79%) and Pleiades (57%) when identifying grassed plots. The methods presented in this study propose methods easily accessible based on free-to-download data, making them applicable in diverse orchard contexts.

Towards use of life cycle–based indicators to support continuous improvement in the environmental performance of avocado orchards in New Zealand

PurposeA life cycle assessment (LCA) study was undertaken for the orchard stage of the NZ avocado value chain, to guide the development of indicators for facilitating continuous improvement in its environmental profile.MethodsThe functional unit (FU) was 1 kg Hass avocados produced in NZ, up to the orchard gate. The baseline model assessed avocados produced in fully productive orchards, using input data collected from 49 orchards across 281 ha in the three main avocado growing regions of New Zealand. In addition, the non-productive and low production years of avocado orchards were assessed using data from four newly established avocado operations spread across 489 ha. Climate change, eutrophication, water use, freshwater ecotoxicity and terrestrial ecotoxicity results were calculated for each orchard. Finally, national scores were calculated for each impact category from the weighted averages of the individual orchard results in the baseline sample of the three studied regions.ResultsThere was significant variability between orchards in different input quantities, as well as impact scores. The impact assessment results showed that fuel use and fertiliser/soil conditioner production and use on orchard were consistently the main hotspots for all impact categories except water use, where impacts were generally dominated by indirect water use (irrespective of whether the orchards were irrigated or not). When considering the entire orchard lifespan, the commercially productive stage of the orchard life contributed the most to all impact category results. However, the impacts associated with 1 kg avocados, when allocated based on the total impacts across the orchard lifespan, were 13–26% higher than the baseline results which considered only the commercially productive years of the orchard life.ConclusionThe study identified the priority areas for focussed improvement efforts (in particular, fertiliser and fuel use for all impact categories, and agrichemical use for the ecotoxicity impacts). Second, the regional- and national-level impact scores obtained in this study can be used as benchmarks in indicator development to show growers their relative ranking in terms of environmental performance. When using the indicators and benchmarks in a monitoring scheme, consideration should be given to developing separate benchmarks (using area-based functional units) for young orchards. It will also be necessary to develop a better understanding of the reasons for the variability in inputs and impacts so that benchmarks can be tailored to account fairly and equitably for the variability between orchards and regions.

Grass species as a living mulch – impact of sod and its weediness on apple trees

The relationship between a cover of four grass living mulches in an apple orchard and the weed cover as well as its impact on the fruit tree yield, growth, and fruit quality was estimated at the Fruit Experimental Station of the Wrocław University of Environmental and Life Sciences in Wrocław (Poland). The experiment was established in a young orchard of ‘Chopin’ cv. apple trees grafted on rootstock MM 106, i.e. one of the strongest semi-dwarf rootstock. One year after, the tree planting soil was covered by blue fescue, red fescue, Kentucky bluegrass, and perennial ryegrass in tree rows and tractor alleys. The apple trees showed a similar degree of adaptation to the changing cultivation conditions in four different living mulches despite the varied share of the area covered by weeds. However, they did not avoid competition from different grass sods and their weediness, which was reflected in their low yield and low crop efficiency coefficient. The perennial species composition and the percentage share of the most common weeds differentiated the sod of the studied grasses. Among several perennial weed species, <i>Trifolium repens</i> L. was found to be the most competitive in all grass living mulches. The dynamic development of this species in time was stimulated by a rapid increase in precipitation in the orchard. The lowest soil surface cover by the total weeds was noted soon after the perennial ryegrass emergence due to the rapid development of the grass. Red fescue spread the most efficiently among all the studied grasses, and its coverage allowed effective reduction of the presence of weeds. This cover crop also maintained high purity of grass sod, especially in the tree rows, until the end of the experiment period.

Vegetative growth and flowering of dragon fruit species according to branch pruning management and application of superabsorbent polymer

The cultivation of dragon fruit has been standing out considerably in Brazil, however, although on the rise, information onthe cultivation of this fruit, such as pruning management in young orchards and the use of superabsorbent polymer in thecrop, is scarce. In this sense, in order to remedy producers’ obstacles regarding the management of orchard formation, theobjective of this study was to evaluate the influence of pruning management and the efficiency of hydrogel in the vegetativeand reproductive development in two different species of dragon fruit (Selenicereus undatus and Hylocereus polyrhizus),in addition to defining the best dose of the polymer to be used in the crop. The work was developed at IFSULDEMINAS –Machado Campus. The design used was the randomized block design, in a factorial scheme (2x2x3), the first factor beingcomposed of the two species of dragon fruit, the second, by two cladode pruning levels (with and without pruning), and thethird, by three doses of the superabsorbent polymer Hydroplan-EB® (0; 1.5; 4.5 g plant-1). The following characteristicswere evaluated: number and length of shoots; total number of flowers; total number of fruits; number of aborted flowers;picking percentage; mean fruit mass; longitudinal and transverse diameter of fruits; peel thickness; pulp yield; peel massand productivity. The practice of cladode pruning, as well as the application of the superabsorbent polymer, did not influencemost of the characteristics evaluated. Further studies should be conducted to delve deeper into the management techniquesused in this study.

Specific and sensitive detection tools for Xanthomonas arboricola pv. corylina, the causal agent of bacterial blight of hazelnut, developed with comparative genomics.

Xanthomonas arboricola pv. corylina (Xac; formerly Xanthomonas campestris pv. corylina) is the causal agent of the bacterial blight of hazelnuts, a devastating disease of trees in plant nurseries and young orchards. Currently, there are no PCR assays to distinguish Xac from all other pathovars of X. arboricola. A comparative genomics approach with publicly available genomes of Xac was used to identify unique sequences, conserved across the genomes of the pathogen. We identified a 2,440 bp genomic region that was unique to Xac and designed identification and detection systems for conventional PCR, qPCR (SYBR® Green and TaqMan™), and loop-mediated isothermal amplification (LAMP). All PCR assays performed on genomic DNA isolated from eight X. arboricola pathovars and closely related bacterial species confirmed the specificity of designed primers. These new multi-platform molecular diagnostic tools may be used by plant clinics and researchers to detect and identify Xac in pure cultures and hazelnut tissues rapidly and accurately.

Application of living mulch in rows of the apple trees on several rootstocks – long-term evaluation

The long-term influence of several living mulches on apple tree growth, nutrient status, yield, and fruit quality concerning the year of cover crop sowing in tree rows was evaluated in the Lower Silesia region in the southwestern part of Poland. The estimation was conducted in six apple tree ‘Ligol’ populations differentiated by the rootstock: M.26, M.9, P 60, P 2, P 16, and P 22. In experiment no. 1, one-year-old nursery stock was planted, and perennial living mulches were sown: colonial bent grass (Agrostis vulgaris With.) and white clover (Trifolium repens L.) in the same year and blue fescue (Festuca ovina L.) in the following year. In experiment no. 2, which involved two-year-old stock, the sowing of blue fescue was delayed until the second, third, fourth, and fifth years following orchard planting. The presence of the cover crop significantly affected young tree growth when one-year-old trees were planted. The sowing of the living mulch in the first or the second year after tree planting led to a significant reduction in the cumulative yield obtained from the young trees. The living mulch improved the red coloration of the fruit skin in the young orchard, but it caused a reduction in the mean fruit weight and size. However, it also contributed to decreased nitrogen concentration in the leaves of the apple trees, and the tree tolerance to living mulch increased as the orchard aged. A choice of semidwarf rootstock, postponed sowing of cover crop, and high-quality nursery stock were recognized as the most important factors for fostering apple tree tolerance to living mulches in tree rows.

Soil water depletion patterns in rainfed apple orchards and wheat fields.

Agricultural production in the Weibei rainfed highland, Northwest China, is challenged by severe drought and water shortages. While the land use pattern has shifted gradually from crop production to orchard farming in Weibei, little is known about the influence of fruit industry development on regional water resources and the rationality of planting orchards. Here, we characterized soil water depletion patterns in rainfed orchards and farmlands to evaluate the occurrence of soil desiccation under land use conversion from farmlands to orchards in Weibei. Soil moisture dynamics were monitored in the 0-150cm soil profiles of different aged Red Fuji apple orchards (young: 7 years, mature: 13 years, old: 22 years) and long-term cultivated winter wheat fields. We measured soil moisture content by oven-drying method in the middle of each month during the growing season of apple trees (March-September 2019). The over-depletion and depletion of soil water were analyzed to evaluate water stress and differential water depletion by distinct vegetation, respectively. The soil desiccation index was used to determine the occurrence of dry soil layers. Water stress was only observed at the 0-70-cm soil depths in the old orchards (mid-June) and farmlands (mid-May-mid-July). Water depletion took place at deeper depths for longer periods in the older orchards than in the younger orchards. Soil desiccation was absent in the young orchards, with mild desiccation at the 0-80-cm soil depths in the mature and old orchards in mid-June. The desiccation intensity was mild at the 0-60-cm soil depths in mid-April-mid-May, intense at the 0-150-cm soil depths in mid-June, and moderate at the 20-150-cm soil depths in mid-July. Results of this study demonstrate the mitigation of water stress and soil desiccation following conversion from wheat fields to apple orchards, which verifies the rationality of planting orchards in the rainfed highland area. Our findings provide strong support for developing a novel model of agro-industrial development, ecological construction, and sustainable economy in the vast arid and semi-arid areas of Northwest China.

Shrews Under-Represented in Fruit Farms and Homesteads.

Shrews are a less studied group of small mammals than rodents. Between 2018 and 2022, we surveyed 23 sites in Lithuania, including natural and anthropogenic habitats, with the aim to assess the proportion of Soricidae in small mammal communities and their diet based on stable isotope analysis. The average representation of Soricidae was 3.1%, about half the long-term average in other habitats in the country. The highest proportions were in meadows and farmsteads, at 4.9% and 5.0% respectively. Shrews were not trapped on farms or in young orchards, and their relative abundance was very low in intensively managed orchards (0.006 individuals per 100 trap days). Neomys fodiens and N. anomalus were unexpectedly found in homesteads, including in outbuildings. Sorex araneus and S. minutus had similar diets. The trophic carbon/nitrogen discrimination factor between invertebrates and shrew hair was 2.74‱/3.98‱ for S. araneus, 1.90‱/3.78‱ for S. minutus in the orchards. The diet of N. fodiens and N. anomalus at the homesteads requires further investigation. We propose that the under-abundance of shrews may be due to contamination by plant protection products and a lack of invertebrates under intensive agricultural practices.

Performance of Sweet Cherry Cultivars and Advanced Selections on Gisela 5 Rootstock in Young Orchards.

Six sweet cherry cultivars and two advanced selections of Gisela 5 rootstock were tested in 2015-2021 at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Fruit trees were planted at distances of 4.5 × 2.5 m and trained as spindles. Orchard floor management included frequently mown grass in alleyways with herbicide strips along tree rows. Cultivars 'Mindaugė' and 'Irema BS' were the most vigorous at the end of the seventh leaf. Their trunk diameter achieved 11.6 cm. The 'Merchant' cultivar had the smallest trunk diameter-9.3 cm. The average yield in 2018-2021 ranged from 2.75 t/ha for 'Vega' to 8.73 t/ha for 'Regina'. Cultivars 'Regina', 'Sunburst', 'Irema BS' and 'Merchant' had the highest cumulative yield efficiency of 0.440-0.503 kg/cm2 with respect to the trunk cross-section area (TCSA). The least productive cultivar 'Vega' produced fruits of the highest average weight-9.9 g. Fruits of 'Regina' and 'Sunburst' were large as well-8.8-9.1 g. 'Irema BS' fruits had the highest soluble solids content (SSC)-20.2%. The lowest SSC was recorded in 'Merchant' and 'Sunburst' fruits-14.7-15.8%. The yield of advanced selection, No. 102, equaled to the yield of cv. 'Regina'. No. 102 had a high fruit weight, and fruits were distinguished by attractiveness and taste.

Analysis of soil water potential characteristics of wheat croplands and apple orchards in an agroforestry ecosystem based on the van Genuchten model

Due to intense droughts and water shortages, soil water deficit limits agricultural production in arid and semiarid areas, such as China’s Loess Plateau region. Yet the effects of different cover crops on soil water in these areas have received insufficient attention. This study was conducted in the Weibei rainfed highland to investigate soil water potential dynamics in an agroforestry ecosystem comprising winter wheat (<i>Triticum aestivum</i> L.) and apple (<i>Malus domestica</i>) trees over the apple growth period (March to September of 2020). Soil water characteristic curves (SWCCs) of cropland topsoil (0 to 40 cm), orchard topsoil (0 to 40 cm), dark loessial subsoil (40 to 80 cm), and loess parent material (80 to 150 cm) were determined using the centrifuge method and water vapor equilibrium method. The van Genuchten model was used to fit SWCCs and then convert volumetric soil water content monitored in field plots to soil water potential. A quantitative analysis was conducted to evaluate soil water stress in wheat croplands and apple orchards. The model performed well in fitting SWCCs for all tested soils, yielding a robust accuracy (<i>R</i>² &gt; 0.96). Compared to apple trees, wheat was more threatened by drought. From mid-March to early July, the 0 to 100 cm soil layers of croplands all exhibited high water stress with matric suction pF &gt; 3.98, and unavailable water occurred in the 0 to 20 cm and 0 to 80 cm soil layers in late March to late April and mid-May to mid-July, respectively. Drought threat in apple orchards increased with an increase in tree age. In young orchards (&lt;10 y), high water stress was found only in surface soil layers (0 to 20 cm) in mid-March to late April and late May to early July, which spread to a depth of 70 cm in early June to early July. In mature orchards (10 to 20 y), high water stress was similarly observed in the surface soil layers in mid-March to early May and late May to early July, which extended to the 80 cm depth in late May to early July. In old orchards (&gt;20 y), high water stress initially emerged in the surface soil layers in early April to mid-April and then reached the 70 cm depth in late May to mid-July, whereas unavailable water occurred in the 0 to 60 cm soil layers in mid-June to mid-July. The results indicated that soil water stress zones with low water potential were formed intermittently at different soil depths of apple orchards depending on tree age and growth stage. However, compared to wheat croplands, apple orchards were less influenced by drought stress, so that converting croplands to orchards could alleviate drought threats in the Weibei area.

Apple tree productivity depending on planting density and rootstock variety combinations

In this article has been studied the dependence of tree planting density, variety-rootstock combinations and water- and resource-saving technologies in providing the population of our country with fresh fruits and obtaining a constant plentiful and high-quality harvest. Fruit growing is one of the most important and unique areas of agriculture. The growth, development and productivity of young orchards from seed fruits depend on the planting density of seedlings, the combination of rootstock varieties, the use of water-resource-saving innovative technologies, and agrotechnological factors. In this area, a sharp increase in fruit production, a radical improvement in quality and a reduction in cost are mainly determined by the laying of new intensive orchards and the consistently plentiful and high-quality fruits of existing orchards, including apple tree care and the use of resource-saving technologies. At present, the total area of orchards in the Republic of Uzbekistan is 216,400 ha, of which 89,100 ha or 44.0% of the total area is occupied by seed fruits. On a scientific basis, such activities as the correct formation and pruning of fruit trees, biological characteristics, intensive varieties and planting density of seedlings, modern water-resource-saving agro-care technologies used in the laying of accelerated young fruit orchards in Uzbekistan are studied in detail.

Unveiling the Predisposing Factors for the Development of Branch Canker and Dieback in Avocado: A Case of Study in Chilean Orchards

Chilean avocado orchards have been affected by branch canker and dieback, mainly associated with pathogens species of the family Botryosphaeriaceae. Producers often relate water stress to these phenomena; however, predisposing factors for these diseases in Chilean orchards have not been reported. Therefore, the objective of this study was to identify the main climate, planting, and management variables associated with branch canker and dieback in Chilean avocado orchards. Multivariable statistical analyses (PCA and PLS-DA) were performed to analyze 76 variables possibly associated with the incidence of these diseases during two consecutive growing seasons. Our findings indicated that branch canker and dieback are mainly conditioned by orchard variables such as plant age, canopy volume, trunk diameter, leaf area index, and planting density. Variables associated with aged orchards, such as high age, high canopy volume, and high trunk diameter, appeared to be more associated with high incidence levels than were younger orchards with higher planting densities and high tree vigor levels. In addition, abiotic stresses, such as frost and overirrigation, were associated as secondary factors affecting these diseases’ development in avocado orchards. Moreover, this study allowed us to determine that branch canker and dieback can develop indistinctly in the different Chilean agroclimatic zones.

Development of European apple canker on different cultivars in relation to planting time at three sites in the UK

European apple canker, caused by Neonectria ditissima, is a damaging disease of apple in many production regions worldwide. The pathogen infects apple trees through artificial or natural wounds. The most damaging phase of the disease is that cankers on main stems post-planting, most likely originating from infection in nurseries, can result in tree death in young orchards. Apple cultivars differ in their responses to the pathogen, which may be additionally affected by specific site factors. An experiment was conducted to study i) the susceptibility of seven cultivars to N. ditissima at three sites and ii) the effects of cold storage duration prior to planting on subsequent development of both main stem and peripheral cankers. Planting date had significant (albeit minimal effects) on the development of peripheral cankers only. Canker development differed greatly among the three sites and between the tested cultivars, with ‘Grenadier’ and ‘Golden Delicious’ being most resistant at all sites. The relative performance of cultivars in terms of canker development was generally consistent across the three sites. Nevertheless, the interaction between cultivar and site was still statistically significant for the development of main stem cankers, indicating that some site-specific factors may interact with cultivars to affect development of latent infections. Given the close proximity of the three sites (similar climatic conditions), the results indicate that further research is needed to investigate the effects of soil characteristics on canker development post-planting.

Providing sugar sources for ants improves the biological control of Aphis spp. in apple orchards

The green apple aphids Aphis pomi DeGeer and A. spiraecola Patch are serious pests of apple, especially in young orchards, where both species establish facultative mutualisms with ants. This study, conducted in Hungary in 2014 and 2015, manipulated the presence of the common black ant Lasius niger (L.) on colonies of Aphis spp. in apple tree canopies. To this end, two kinds of sugar dispensers (bottle dispensers and agar jelly cubes), each providing a sucrose solution with 300 g/1000 ml concentration, were deployed as alternative sugar sources for the ants, with plots lacking dispensers serving as controls. Both forms of sugar provisioning reduced the number of ants tending Aphis spp. colonies and reduced aphid populations compared to controls in both years. However, bottle dispensers demonstrated consistent efficacy in both years, whereas agar jelly cubes were less reliable in distracting the ants. Both treatments significantly increased the abundance of natural enemies at Aphis spp. colonies compared to controls. Our results indicate that the provisioning of ants with sugar in apple orchards can effectively disrupt ant-aphid mutualisms in the case of Aphis spp., by drawing ants away from aphid colonies and thus increasing natural enemy predation on aphid colonies. The use of sugar-feeding tactics to alter ant behaviour should permit reduced pesticide use in apple orchards, whether to control aphids or other pests that might serve as prey for ants, and is fundamentally compatible with biological pest control in apple orchards.