Control Trees Research Articles

Citrus Black Spot Symptoms on Fruit Exposed to Phyllosticta citricarpa Infections at Different Developmental Stages.

Citrus black spot (CBS), caused by Phyllosticta citricarpa, is an important fungal disease of citrus. Higher CBS severity has been associated with P. citricarpa infections at the young and green stages of fruit. The length of the fruit susceptibility period may be influenced by the amount of inoculum and the climate of the citrus growing region. This study was conducted in orchards across two South African provinces to assess the intensity of CBS under two conditions: (i) unsprayed fruit of Valencia sweet orange, Nova, and Empress mandarins inoculated with P. citricarpa at 101, 103, and 105 pycnidiospores/mL at various intervals after fruit set, from October (petal fall stage) to March (for mandarins) or June (for sweet orange), and (ii) non-inoculated Valencia fruit from orchards subjected to spray programs ranging from one to nine applications between October and June. Higher CBS intensity was observed in Valencia fruit inoculated between November and January, with an average disease severity index (DSI) of 0.94, compared to a significantly lower (0.07) for fruit inoculated from February to June. Inoculations in November or December for Nova mandarins and in December for Empress with 105 pycnidiospores/mL resulted in higher CBS intensity compared to those with lower pycnidiospore concentrations. The absence of fungicide applications from October to December during the 2017-2018 season led to increased CBS intensity, with a DSI of ~0.47, a value which was not significantly different from that of non-treated control (NTC) trees. Leaving sweet orange trees unprotected from January onwards did not significantly increase the CBS intensity. These results confirm that citrus growers should focus on protecting citrus fruit, against P. citricarpa infection, in their dark green and young stages (c.15-30 mm diameter) to control CBS.

Influence of mechanical stress on biomass allocation in three species (Pachira aquatica Aubl., Sextonia rubra (Mez) van der Werff and Simarouba amara Aubl.) with contrasting posture control mechanisms

Abstract Key message The posture control in Pachira aquatica, Sextonia rubra and Simarouba amara is achieved through contrasted mechanisms involving tensile stress in wood only, bark only or both. This study evidenced that the restoration of verticality does not imply an overall cost for trees but modifies growth kinetics and biomass allocation to organs and tissues, improving the posture control of the trees in the three species. Context All trees need a motor system to correct their position through the generation of asymmetric tensile stress around the stem, leading to active bending. In angiosperms, depending on the species, tensile stress is generated either in wood (tension wood), in bark or in both. Aims Here, we investigated how gravitropic stimuli (tilted stems without any movement) may affect growth and biomass allocation and whether this process depends on the posture control mechanism of the species. Methods Tree growth kinetics, final biomass allocation and wood and bark proportion, localisation and density were measured on young tilted plants and straight plants as controls. Pachira aquatica, Sextonia rubra and Simarouba amara were selected according to the location of their their motor system within bark only, wood only or both wood and bark, respectively. Results In response to tilting, trees from the three species increased their diameter and decreased their slenderness, but the total biomass (including stem and roots) was not different from that in the control trees, suggesting that reaction to artificial tilting does not imply a specific cost for the plant. However, the species exhibited strong differences in growth kinetics, in the amount and organisation of the tissues or in biomass allocation to different organs (root vs shoot, wood vs bark), adapted to the specificity of the posture control mechanisms and improving their motor function. Conclusion Whatever the posture control mechanism, uprighting does not modify the total biomass invested. However, allocation of biomass to different organs is strongly modified to obtain an efficient control of the posture.

Characterizing Pathogen-Induced Changes in Black Walnut Volatile Organic Compounds Following Inoculation with Geosmithia Morbida, The Causal Agent of Thousand Cankers Disease.

Thousand cankers disease (TCD) is a pathosystem comprised of Juglandacea spp., a pathogenic fungus Geosmithia morbida, and an insect vector, the walnut twig beetle (WTB) (Pityophthorus juglandis). Of the North American Juglans species, Juglans nigra is the most susceptible to TCD and has resulted in significant decline and mortality of urban and plantation trees in the western United States. Geosmithia morbida causes necrotic cankers in the phloem, and infected trees may release an array of volatile compounds that act as important chemical cues to WTB. Here, we aimed to determine how J. nigra volatile profiles respond to G. morbida infection as these changes can offer valuable insights into plant defense mechanisms and potentially influence WTB behavior, thus impacting disease transmission dynamics. In this study, we collected a series of bark and leaf volatiles from J. nigra seedlings inoculated with one of three isolates of G. morbida and a sham-inoculated control. Our results suggest J. nigra bark responds to G. morbida infection, with the western United States isolate (RN-2) eliciting a distinct volatile response compared to other treatments. We identified six out of fourteen compounds that contribute to 80% of the dissimilarity between RN-2 and sham-inoculated control trees. Inoculation with isolate RN-2 elicited the largest change in volatile profiles and resulted in the smallest cankers in the phloem, suggesting these compounds my play important defensive roles in J. nigra against the fungal pathogen that causes TCD.

Acceleration of Breaking Buds Dormancy on Apricot Trees by Using Alternatives of Hydrogen Cyanamide (Dormex) and Assessment of Resulting Fruits Quality

The purpose of this research was to determine the effectiveness of alternatives of dormex on apricot budbreak and their effect on apricot fruit quality. Our study was carried out on five-years old “Canino” apricot at Badr district, El Behira Governorate, Egypt, during the two seasons 2022 and 2023, respectively. Twenty-four uniform apricot trees were selected and sprayed to the runoff once on 20 and 25 January during 2022 and 2023, respectively, by following treatments: control, mineral oil at 2%, low pyrite urea at 2%, ammonium nitrate at 1.5%, potassium nitrate at 2%, mineral oil combined with low pyrite urea at the same concentration of 2%, mineral oil at 2 % combined with ammonium nitrate at 1.5 %, mineral oil combined with potassium nitrate at the same concentration of 2%. For each of the treatments that were used, 0.05% (v/v) of the non-ionic surfactant tween 80 was applied. In both seasons, the use alternatives dormex chemicals resulted in better budbreak than control trees especially the formulation of mineral oil at (2%) plus potassium nitrate (2%).

Evaluation of olfactory and visual cues for conservation biological control of crape myrtle bark scale in urban landscapes.

Acanthacoccus lagerstroemiae (crape myrtle bark scale, CMBS) is an exotic scale insect that feeds on the sap of crape myrtle trees. Heavy infestations of CMBS reduce flowering and honeydew promotes sooty mold growth on the leaves and branches, reducing the aesthetic value of crape myrtle trees in urban landscapes. Lady beetles (Coleoptera: Coccinellidae) are generalist predators that feed on CMBS. Several laboratory and field studies have demonstrated the attraction of lady beetles to olfactory and visual cues. We evaluated lady beetles' responses to olfactory lures and yellow visual attractants on infested potted and landscape trees to increase natural enemy recruitment and reduce dependence on chemical control methods. Gas chromatography mass spectrometry analysis showed that limonene is the dominant volatile compound released by crape myrtles infested with CMBS. Limonene and methyl salicylate lures, alone or in combination, failed to reduce CMBS or recruit additional lady beetles to infested trees in all experiments. Yellow rectangular panels placed 1 m above the base of an infested tree recruited up to twofold more lady beetles than control trees; however, this was not statistically significant. A significant reduction in CMBS was observed on infested trees with yellow rectangular panels placed in the canopy. Yellow rectangular panels are more likely to recruit lady beetles than limonene or methyl salicylate lures in an urban landscape. Management of CMBS is currently achieved using systemic insecticides. This study provides a basis for conservation biological control of CMBS through the recruitment of lady beetles, a significant advancement toward integrated management of this exotic pest. © 2024 Society of Chemical Industry.

Impact of crown architecture on light availability, gas exchange, flowering and fruiting in jamun (Syzygium cumini [L.] Skeels)

Experiments were conducted to assess the impact of crown architecture on light availability beneath the trees, flowering, fruiting, yield and quality of jamun (Syzygium cumini [L.] Skeels). Trees were maintained as control, palmette and open centre crown. Impact was evaluated for three consecutive years, i.e. 2017–2019. Diffuse light beneath the trees ranged from 69.7 ± 2.22 to 45.9 ± 1.45%, whereas direct light varied from 30.4 ± 0.97 to 54.1 ± 1.78%. At flowering and fruit development stage (June), photosynthesis rate (A) in control trees was 12.5 ± 0.43 μmol CO2/m2/s; however, at fruit maturity and dormancy (August), it was only 9.5 ± 0.35 μmol CO2/m2/s. Similarly, in palmette and open centre trees, photosynthesis rate at flowering and fruit development stage was 13.5 ± 0.46 and 15.7 ± 0.54 μmol CO2/m2/s, respectively; whereas at fruit maturity and dormancy, photosynthesis rate dropped to 10.5 ± 0.39 and 11.7 ± 0.43 μmol CO2/m2/s, respectively. Substantial variation in stomatal conductance (gs), vapour pressure deficit (VPD) and transpiration rate (E) was also found. Days to start flowering ranged from 92 ± 0.33 to 98 ± 0.33. Similarly, days to end flowering varied from 99 ± 0.07 to 107 ± 0.36, days to fruit set 132 ± 0.33 to 139 ± 0.33 and days to fruit maturity 176 ± 0.48 to 184 ± 0.63. Significant variation in fruit length, fruit width and fruit weight was also found. Total soluble solids in fruit pulp varied from 9.0 ± 0.15 to 12.2 ± 0.149°Brix and fruit yield 62.3 ± 1.5 to 86.7 ± 1.33 kg per tree. Noteworthy variation in fruit quality traits was also recorded. This study illustrates that crown architecture has considerable impact on gas exchange parameters, flowering, fruiting, yield and quality of jamun.

The role of urban trees as nature-based solutions for stormwater runoff control

The soil cover of urban areas drastically reduces infiltration rates and increases the risk of stormwater flooding. In this context, nature-based solutions (NBS) are well-acknowledged strategies for sustainable stormwater management and water cycle restoration. As NBS, urban trees provide significant benefits to hydrological balance through rainfall interception, evapotranspiration, and water storage in the underlying soil. This paper proposes an analytical-probabilistic model to evaluate the performance of urban trees for stormwater control. The study investigates the effects on the surface runoff of the main hydrological and environmental variables involved, in particular the infiltration rate into the soil, and the impermeable contributing areas. The reliability of the analytical-probabilistic approach to estimate the surface stormwater runoff (in terms of both runoff probability and average value) was validated through its application to a case study in the city of Lecco (Italy). The results confirmed that the beneficial impact of urban trees on stormwater control is greater during leaf-on season (late spring-summer at Lecco latitude) and when a proper infiltration rate into the soil beneath the tree is ensured.

Secure Search of Smart Home Data Based on Access Control Encryption

Abstract: In recent years, the increasing variety of smart home devices, such as smart locks, surveillance cameras, and various sensors, has led to a significant rise in related data. To facilitate the sharing of smart home data, manufacturers store these data on the Internet of Things (IoT). However, since IoT servers are not fully trustworthy and the data often contain sensitive commercial information, any leakage could result in a commercial crisis for manufacturers. To address security concerns, manufacturers encrypt the data before storing them on the IoT. A challenge arises: how can users search for target data in encrypted form? This paper proposes a new search encryption scheme for smart home data, addressing the limitations of existing attribute-based encryption (ABE) searchable encryption schemes. The proposed scheme integrates access control trees and bilinear mapping technology, supporting multiple access policies including AND gates, OR gates, and threshold gates. Experimental results demonstrate a comprehensive analysis of the attribute-based searchable encryption protocol under a multi-authority architecture, covering four dimensions: correctness, security, complexity, and real-world application scenarios. In specific scenarios, when a data user, out of privacy concerns, is unwilling to reveal all attribute information to a single authority during a query for shared datathus avoiding identity disclosureor when the users identity information is managed by multiple independent authorities, this protocol proves highly effective. It ensures smooth data sharing while maintaining data security for both data owners and users, fully safeguarding data privacy and shareability.

Scab Intensity in Pecan Trees in Relation to Hedge-Pruning Methods.

Pecan is a valuable nut crop cultivated in the southeastern United States. Among the major yield-limiting factors in the region is scab, caused by the plant pathogenic fungus Venturia effusa. Managing scab in tall trees (15 to 25+ m) in pecan orchards is challenging because of the limitations of getting sufficient spray coverage throughout the canopy. We explored the effects of hedge pruning on scab in three orchards: 14-m-tall cv. Desirable trees winter hedge pruned on alternate sides to 11 m (site 1), 18-m-tall cv. Stuart trees hedge pruned on both sides simultaneously to 11 m (site 2), and 15-m-tall cv. Caddo trees winter hedge pruned in winter versus summer to 11 m (site 3). At site 1 and 2, hedge-pruned trees were compared with nonpruned control trees. All trees received recommended fungicide applications to control scab via an air-blast sprayer. Disease incidence and/or severity was assessed at different sample heights on shoots, foliage, and fruit during three seasons (2020, 2021, and 2022). At site 1 the hedge-pruned trees often had significantly or numerically more severe scab on foliage and fruit compared with the control trees, although the differences were mostly small. The frequency of mature fruit with scab severity <10% was greatest on control trees in 2021 and 2022. At site 2, there were few differences between hedge-pruned and control trees (on fruit, scab severity was either significantly less on hedge-pruned trees or not different from the control), but the frequency of mature fruit with scab severity <10% was consistently greatest on hedge-pruned trees. At site 3, scab intensity was low, and there were no significant differences in scab severity between winter- and summer-pruning treatments. At sites 1 and 2, there was generally more severe scab at greater sample heights compared with low in the canopy. At site 3 there was little effect of height on disease. The benefit of hedge pruning likely increases with tree height in scab-susceptible cultivars. If a tree is taller than ∼15 m, a greater proportion of the fruit will be within reach of efficacious spray coverage from air-blast sprayers.

Integration of mRNA-miRNA Reveals the Possible Role of PyCYCD3 in Increasing Branches Through Bud-Notching in Pear (Pyrus bretschneideri Rehd.).

Bud-notching in pear varieties with weak-branches enhances branch development, hormone distribution, and germination, promoting healthier growth and improving early yield. To examine the regulatory mechanisms of endogenous hormones on lateral bud germination in Pyrus spp. (cv. 'Huangguan') (Pyrus bretschneideri Rehd.), juvenile buds were collected from 2-year-old pear trees. Then, a comprehensive study, including assessments of endogenous hormones, germination and branching rates, RNA-seq analysis, and gene function analysis in these lateral buds was conducted. The results showed that there was no significant difference in germination rate between the control and bud-notching pear trees, but the long branch rate was significantly increased in bud-notching pear trees compared to the control (p < 0.05). After bud-notching, there was a remarkable increase in IAA and BR levels in the pruned section of shoots, specifically by 141% and 93%, respectively. However, the content of ABA in the lateral buds after bud-notching was not significantly different from the control. Based on RNA-seq analysis, a notable proportion of the differentially expressed genes (DEGs) were linked to the plant hormone signal transduction pathway. Notably, the brassinosteroid signaling pathway seemed to have the closest connection with the branching ability of pear with the related genes encoding BRI1 and CYCD3, which showed significant differences between lateral buds. Finally, the heterologous expression of PyCYCD3 has a positive regulatory effect on the increased Arabidopsis growth and branching numbers. Therefore, the PyCYCD3 was identified as an up-regulated gene that is induced via brassinosteroid (BR) and could act as a conduit, transforming bud-notching cues into proliferative signals, thereby governing lateral branching mechanisms in pear trees.

Artificial tree microhabitats: Wound depth and position affect saproxylic beetles attracted to freshly veteranised trees

Abstract Veteran and ancient trees are key structures sustaining biodiversity in wooded landscapes. Their value depends on tree‐related microhabitats (TreMs) such as hollows, cracks and other structures related to wounds and wood decay. Decline and loss of veteran trees results in the loss of TreMs thus threatening the biodiversity associated with them. Veteranisation, that is, interventions aimed at creating or accelerating formation of rare TreMs in live trees, are thus increasingly applied to bridge gaps in habitat continuity and sustain the biodiversity associated with veteran trees. Several studies investigated the use of artificially created TreMs by various organisms. No study has, however, investigated saproxylic beetles attracted to freshly veteranised trees, and how different veteranisation techniques affect attractivity of veteranised trees to saproxylic beetles. We veteranised 48 sessile oaks using two types of deep and two types of shallow cuts and trapped saproxylic beetles on the veteranised and control trees in the first season after the intervention. The sampling yielded 280 species (6171 individuals) of saproxylic beetles, including 64 that are threatened. Veteranised trees attracted more abundant and diverse communities than control trees. Community composition differed between shallow and deep cuts and between the two types of deep cuts. Freshly veteranised trees thus attract diverse and abundant communities of saproxylic beetles consisting mainly of species potentially exploiting the wounds. The high proportion of threatened species, often associated with old oaks, suggests that veteranised trees benefit even some threatened saproxylic biodiversity already during the first year after the veteranisation.

First Report of Root Collar Canker Caused by Neoscytalidium dimidiatum on Jacaranda mimosifolia in China.

Jacaranda mimosifolia is widely cultivated as a garden ornamental tree. In July 2023, an unknown root collar canker of J. mimosifolia was discovered in green belts of Qingxiu District, Nanning, China, with a 8% incidence rate. Crowns of affected trees ranged from reddish brown leaves to deciduous or dead. Root collar tissue became necrotic matched by underbark dark brown lesions with irregular margins, and rotted at last. Six diseased plants distributed within 3000 m2 were choosed, and 24 root collar tissues were surface sterilized and placed on potato dextrose agar (PDA) plates to incubate at 28℃ for 3 to 5 days. Same colonies were consistently isolated from 18 tissues, and three isolates (M3-B1-1, M3-B1-2 and M3-B1-3) were purified for morphological and molecular determination. These isolates formed colonies with lush aerial mycelia rapidly, which covered a 90 mm plate in 72h. The colonies were initially white, then grayish-green to black. Arthrospores were colourless to light brown, short columnar, aseptate, truncate base, averaging 12.1±2.5 µm × 3.4±0.7 µm, sometimes formed arthric chains. Chlamydospores were dark brown, round or oval, aseptate, averaging 8.7±1.6 µm × 5.0±0.9 µm. Mature pycnidia and conidia produced for about 50 days on oatmeal agar medium (OMA), and conidia were colorless, oblong, aseptate, averaging 11.2±1.2 µm × 6.0±1.4 µm. These morphological characteristics were consistent with the description of Neoscytalidium dimidiatum (Penz.) Crous & Slippers (Crous et al. 2006). Genomic DNA was extracted from three isolates. The partial ITS region, TUB2 and TEF1-α genes were amplified (White et al., 1990; Glass and Donaldson 1995; Carbone and Kohn 1999). The sequences were deposited in GenBank (ITS: PP939650-PP939652; TUB2: PP942728-PP942730; TEF1-α: PP942731-PP942733). Blastn analysis revealed that ITS sequences of three isolates showed 99.8%, 100%, 100% identity (506 bp out of 507 bp, 507 bp out of 507 bp, 507 bp out of 507 bp) to N. dimidiatum C21 (KX447539), the TUB2 sequences showed 100% identity (436 bp out of 436 bp, 437 bp out of 437 bp, 437 bp out of 437 bp) to N.dimidiatum LNeo (ON099066), and the TEF1-α sequences showed 99.64% identity (276 bp out of 277 bp) to N.dimidiatum ARM230 (MK495384), respectively. Phylogenetic analysis based on concatenated ITS, TUB2 and TEF1-α sequences showed that three isolates were clustered into the same clade as N. dimidiatum. To fulfill Koch's postulates, pathogenicity of these isolates was tested on healthy two-year-old J. mimosifolia trees. Stem and root collar were wounded and placed mycelial plugs (8mm), and the inoculation sites were wrapped with parafilm or covered with nursery substrate to maintain the humidity. Four plants were inoculated with each isolate. As a control, four plants were inoculated with noncolonized PDA plugs. All treated plants were kept in a greenhouse at 28 ± 3°C and 70% relative humidity. Foliar blight and necrotic lesions around inoculation points were observed about 65 days after inoculation, and 50% of inoculated trees exhibited symptoms, whereas the control trees remained symptomless. Neoscytalidium dimidiatum was successfully reisolated from symptomatic tissue via morphological analysis. To our knowledge, this is the first report of root collar canker caused by N. dimidiatum on J. mimosifolia. Neoscytalidium dimidiatum has a wide range of hosts, including pitaya, pine, mulberry, pear, grape, locust tree (Luo et al. 2024). This finding will help in controlling of the disease epidemic.

Impacts of phosphite treatment on Phytophthora community assemblages and inoculum abundances in Phytophthora-infected forest soil

Phytophthora are causing declines in forest tree species worldwide and the chemical control treatment, phosphite, is the only treatment consistently shown to provide some protection to natural ecosystems from Phytophthora diseases. Phosphite inhibits Phytophthora growth and sporulation whilst boosting defence responses in the plant host. It is unclear, however, the extent of the impact of phosphite on Phytophthora species assemblages and inoculum abundances in soil around trees following treatment within natural ecosystems. In New Zealand, kauri (Agathis australis), an endemic and threatened foundation species, suffers from a dieback disease primarily caused by Phytophthora agathidicida. Phosphite is applied by trunk injection to kauri and has been shown to improve resin ‘bleed’ symptoms from basal trunk lesions and to promote recovery of thinned canopies. Phytophthora community and inoculum abundance were investigated in response to phosphite treatments at two field sites (Huia and Waitoki) in infected kauri stands in Auckland, New Zealand. At Huia, soil sampling and tree health surveying were conducted in November 2023 on trees treated with phosphite in 2012 as part of an earlier study. At Waitoki, the response to phosphite treatment was monitored 6 and 18 months following treatment. Phytophthora species were detected using soil baiting and metabarcoding of Environmental DNA (eDNA) from soil and quantified with qPCR of root and soil DNA. Three species were detected with soil baiting (P. agathidicida, P. cinnamomi, and P. multivora) and two additional species with metabarcoding (P. pseudocryptogea, and an unknown clade 7 species similar to P. europaea). Phytophthora cinnamomi was the most abundant species, followed by P. agathidicida. Both species were more likely to occur together than by chance alone and were associated with declining tree health. The P. europaea-like species was in approximately 50 % of the samples and was less likely to occur in roots with poorer health, or in association with P. agathidicida. The abundance of P. agathidicida inoculum was lower in the soil around the phosphite-treated trees than around the untreated control trees 1.5 years after treatment at Waitoki. Phosphite halted the lateral expansion of basal resin bleeds, and resin viscosity was reduced. Not only did phosphite treatments improve kauri dieback symptoms, but the phosphite treatments potentially had a direct impact on the epidemiology of the disease by reducing inoculum load around treated trees, with direct implications for disease management as an effective way to protect uninfected areas and minimise the spread of inoculum from infested zones.

Impact of PGRs, polyamines and potassium to improve pomegranate flowering behaviour, fruit set and fruit quality

Ever changing climate is affecting the flowering pattern in pomegranate worldwide. It is the need of the hour to find out some chemicals that can not only enhance hermaphrodite flowers and fruit set but also enhance fruit quality. The present investigation aimed to evaluate the effect of plant growth regulators (three), polyamines (two) and other chemicals (five) on photosynthesis, flowering ratio, fruit set and quality of pomegranate fruits. Pomegranate trees were treated at full leaf expansion stage. Potassium dihydrogen phosphate (5000 ppm), spermidine (1.5 ppm) and naphthalene acetic acid (NAA) (20 ppm) were the best treatments to significantly enhance hermaphrodite flowers, as the hermaphrodite to male flower ratio was 0.39, 0.37, and 0.35, respectively, compared to 0.22 in the control treatment. Except spermidine, NAA and paclobutrazol, all treatments increased the fruit setting significantly, with potassium dihydrogen phosphate (5000 ppm) being the most effective treatment with 66% fruit set compared to 43% in control trees. In mature fruits, compared to control, NAA enhanced total phenols, ascorbic acid and total antioxidants (3%, 15%, 7%, respectively) followed by ascorbic acid treatment (250 ppm); potassium dihydrogen phosphate (5000 ppm) and putrescine (44 ppm) enhanced the anthocyanin content and hence aril color significantly (11% and 10% respectively). Though the use of NAA in pomegranate production is commercial practice, two sprays of ascorbic acid can also be included to enhance the nutritional quality of fruits. Foliar application of potassium dihydrogen phosphate twice at flowering stage could be highly useful for quality pomegranate production due to the enhanced number of hermaphrodite flowers, fruit setting and fruit color. Overall, use of these chemicals can be beneficial to pomegranate farmers to get more remuneration from harvest.

Maximizing the role of trees in flood control and creating resilient landscapes in Sokoto State, Nigeria: A review

Maximizing the role of trees in flood control and creating resilient landscapes in Sokoto State, Nigeria: A review

Trees have similar growth responses to first-entry fires and reburns following long-term fire exclusion

Managing fire ignitions for resource benefit decreases fuel loads and reduces the risk of high-severity fire in fire-suppressed dry conifer forests. However, the reintroduction of low-severity wildfire can injure trees, which may decrease their growth after fire. Post-fire growth responses could change from first-entry fires to reburns, as first-entry fires reduce fuel loads and the vulnerability among trees to fire effects, which may result in trees sustaining less damage during reburns. To determine whether trees had growth responses that varied from first-entry fires to reburns, we cored 87 ponderosa pine trees in the Gila Wilderness, New Mexico, USA that experienced 3–5 fires between 1950 and 2012 following long-term fire-exclusion and 67 unburned control trees from the Gila and Apache-Sitgreaves National Forests. We assessed tree growth response to fire by comparing tree-ring growth among burned and unburned trees from two years before to two years after fires. We compared growth between burned and unburned trees using a bootstrapping procedure to calculate annual median tree-ring width index values with 95 % confidence intervals. We compared post-fire growth after first-entry fires and reburns following long-term fire-exclusion. Burned trees had similar growth responses following first-entry fires and reburns, with lower growth during the fire year through two years post-fire compared to unburned controls. Burned tree growth returned to expected rates following these immediate post-fire growth reductions. Interestingly, trees had lower growth during the year before and the year of reburns compared to the first-entry fire, reflecting greater aridity before reburns. Greater aridity may have contributed to larger-than-expected growth reductions following reburns, which could explain similar growth responses to first-entry fires and reburns. Our results indicate that trees had consistent short-term growth responses to low-severity fires following long-term fire-exclusion. As trees retained vigor after multiple fires, managing fires for resource benefit is an effective approach to reduce the likelihood of high-severity fire without long-term negative effects on tree growth.

A new approach for artificial pollination in walnut trees: AirPoll

Pollination is the first step in the plant's fruit development. Therefore, fruit setting does not occur without pollination. Some problems encountered in natural pollination cause pollination not to be achieved as desired and cause significant losses in yield and fruit quality. Artificial pollination applications with drones are the best way to solve these problems. In this study, the AirPoll artificial pollination machine, which performs artificial pollination through the air using drone technology, was developed and the operating success of the machine was tested in walnut gardens. In the experiment gardens, female flowers on 18 branches of 5 trees each in the artificially pollinated area with a drone and in the control area were marked with colored strings. Control trees were selected from a distance that would not be possible to transport pollen with a drone. As a result of the study carried out in 2020 and 2021, the average fruit setting rate in trees pollinated by drone was determined as 94.61%. In control trees, 32.33% fruit setting was achieved. Thus, it was determined that the productivity increase in artificial pollination with AirPoll was 62.28%. In addition, in the study, Computational Fluid Dynamics (CFD) simulation analysis was performed using ANSYS Fluent 2024 R1 software to predict the downward air flow and pollen distribution in the walnut tree crown. The analysis was carried out in 680 iterations using drone propellers at a rotation speed of 4500 rpm, 4 m/s airflow and a k-w viscous model. In the analysis, it was observed that the pollen was distributed homogeneously with the determined height and the created artificial pollination environment. Based on the results obtained from the simulations, a convergence criterion of 5e−3 for continuity and 1e−6 for speed, k, w was determined. Considering all the results, the ease of use of the developed AirPoll artificial pollination machine and the successful results obtained in field trials reveal the effectiveness of the AirPoll artificial pollination machine.

Physiological and biochemical changes of Picea abies (L.) during acute drought stress and their correlation with susceptibility to Ips typographus (L.) and I. duplicatus (Sahlberg)

IntroductionIn recent years, Norway spruce (Picea abies L.) forests in Central Europe have faced escalating threats from bark beetles, primarily Ips typographus (L.), and other species, such as I. duplicatus (Sahlberg). Outbreaks are partially attributed to weakened tree defense resulting from drought periods induced by climate change. This study examines Norway spruce’s physiological and metabolic reactions to acute drought stress during the growing season and evaluates its susceptibility to I. typographus and I. duplicatus.MethodologyIn order to induce drought stress, mature Norway spruces had their roots covered with a roof in April 2021, depriving them of water. Control trees were left with free access to natural rainwater. Over 5 months of the growing season, soil water potential, bark temperature, tree trunk circumference, and sap flow were monitored. Roofed trees and controls were sampled in July, August, and September and analyzed for non-structural carbohydrates and the two classes of defensive compounds, phenolics and terpenes. Furthermore, two different bioassays in tubes and boxes were performed using adult I. typographus and I. duplicatus beetles to assess host choice and acceptance.ResultsRoofed trees exhibited signs of stress as early as July, resulting in decreased tree trunk and a consequent increase in non-structural carbohydrate content. Defensive metabolites remained largely unaffected except for an increase in diterpenes in September. In bioassays, I. typographus preferred boring into the bark of roofed trees in August in tubes and in September in boxes. This increased tree acceptance correlated with increased levels of soluble carbohydrates in the phloem. I. typographus and I. duplicatus beetles showed higher mobility in boxes in August and September on roofed trees but not in July, even though bark surface temperatures were elevated in roof-covered trees during all three bioassay periods.ConclusionThe study revealed rapid physiological responses of trees to acute drought stress, although not many changes were observed in defense traits. Despite the absence of natural bark beetle attacks, drought trees were more accepted by I. typographus than naturally watered trees. This response may indicate the beetles’ preference for trees with phloem of higher nutritional quality induced by the acute drought stress conditions.

Watering the trees for the forest: Drought alleviation in oaks and pines by ancestral ditches

Traditional ditches (“acequias” in Spanish) derive meltwater and infiltrate groundwater providing ecological services downstream in the semi-arid Sierra Nevada range (SE Spain). Therefore, they may act as a nature-based solution by alleviating drought stress in trees growing near ditches by enhancing growth and reducing their intrinsic water-use efficiency (iWUE). Such a mitigation role of acequias is critical given that some oak (Quercus pyrenaica) and pine (Pinus sylvestris) stands reach their xeric distribution limits in Europe. We compared tree-ring width data and wood δ13C, a proxy of iWUE, in oak and pine stands located near or far (control) from ditches with different infiltration capacity in two watersheds. We assessed how trees responded to climate data, drought stress, and vegetation greenness through correlations and resilience indices. Oak trees located near ditches grew more and responded less to precipitation, soil moisture, a drought index, and greenness than control trees. In pines, we did not find this pattern, and ditch trees grew more than control trees only during an extremely dry year (1995). Climate-growth correlations suggested a longer growing season in ditch pines. Growth of ditch oaks from the “Acequia Nueva” (AN), with high infiltration capacity, responded more to autumn soil moisture and showed the lowest δ13C. Growth was enhanced by cool-wet spring conditions in pines and also by warm-wet conditions in the prior winter in the case of oaks. Control trees showed lower resistance to drought. Control trees presented higher wood δ13C values except for old oaks from the “Acequia Grande” (AG) site which may show long-term acclimation. Traditional ditches alleviate drought stress in oak and pine stands subjected to regional xeric climate conditions.

Integrated Pest Management: Success Stories and Key Takeaways

Integrated Pest Management (IPM) has revolutionized pest control in various agricultural settings, including orchards. By blending cultural, biological, and chemical methods, IPM aims to minimize pest damage while reducing environmental and health impacts. One of the most successful strategies within IPM is mating disruption, which uses synthetic pheromones to confuse male insects and prevent them from finding mates. This technique has been particularly effective against pests like the codling moth in apple and pear orchards, significantly reducing insecticide use by up to 90% in some regions.The implementation of IPM in orchards has numerous long-term advantages. Lower manufacturing costs, less environmental contamination, and increased worker safety have all resulted from reduced pesticide use. Furthermore, a healthier ecological balance has been promoted by the rise in natural predators and parasitoids brought about by the decrease in chemical treatments. Many growers have reported greater fruit quality due to more targeted pest control and healthier trees, despite worries that reduced use of pesticides would harm fruit quality. Important pests have also been suppressed regionally as a result of IPM's efficacy, such as the codling moth in the Pacific Northwest, whose populations have dropped to the point where little intervention is needed. Economic assessments highlight IPM's financial sustainability by demonstrating considerable long-term cost savings. According to one study, IPM adopters in apple orchards in Nova Scotia had 25% reduced pest management expenses over a ten-year period than those using conventional approaches. These results demonstrate how integrated pest management (IPM) has the ability to provide long-term, efficient pest control that is advantageous to growers, the environment, and consumers alike. IPM's widespread use attests to its effectiveness and sustainability. Integrative pest management (IPM) ensures the long-term health and production of agricultural systems by combining various pest control techniques into a balanced solution that satisfies both ecological and financial requirements.