Terminal Buds Research Articles

A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry method for determination of phytohormones in the medicinal plant saffron.

Saffron (Crocus sativus L.) is a valuable Chinese herb with high medicinal value. Saffron pistils are used as medicine, so increasing the number of flowers can increase the yield. Plant hormones have essential roles in the growth and development of saffron, as well as the response to biotic and abiotic stresses (especially in floral initiation), which may directly affect the number of flowers. Quantitative analysis of plant hormones provides a basis for more efficient research on their synthesis, transportation, metabolism, and action. However, starch (which interferes with extraction) is present in high levels, and hormone levels are extremely low, in saffron corms, thereby hampering accurate determination of plant-hormone levels in saffron. Herein, we screened an efficient and convenient pre-treatment method for plant materials containing abundant amounts of starch. Also, we proposed an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the quantification of abscisic acid (ABA) and auxin (IAA). Then, the method was applied for the detection of hormone-content differences between flowering and non-flowering top buds, as well as between lateral and top buds. Our method showed high sensitivity, reproducibility, and reliability. Specifically, good linearity in the range 2-100 ng ml-1 was achieved in the determination of ABA and IAA, and the correlation coefficient (R2) was >0.9982. The relative standard deviation was 2.956-14.51% (intraday) and 9.57-18.99% (interday), and the recovery range was 89.04-101.1% (n = 9). The matrix effect was 80.38-90.50% (n = 3). The method was thoroughly assessed employing various "green" chemistry evaluation tools: Blue Applicability Grade Index (BAGI), Complementary Green Analytical Procedure Index (Complex GAPI) and Red Green Blue 12 Algorithm (RGB12). These tools revealed the good greenness, analytical performance, applicability, and overall sustainability alignment of our method. Quantitative results showed that, compared with saffron with a flowering phenotype cultivated at 25 °C, the contents of IAA and ABA in the terminal buds of saffron cultivated at 16 °C decreased significantly. When cultivated at 25 °C, the IAA and ABA contents in the terminal buds of saffron were 1.54- and 4.84-times higher than those in the lateral buds, respectively. A simple, rapid, and accurate UPLC-MS/MS method was established to determine IAA and ABA contents. Using this method, a connection between the contents of IAA and ABA and the flowering phenotype was observed in the quantification results. Our data lay a foundation for studying the flowering mechanism of saffron.

Daylength effects on black spruce bud dormancy release change during endo- and ecodormancy

The effects of daylength on bud dormancy release varied throughout the dormant period in black spruce (Picea mariana (Mill.) B.S.P.) seedlings. In phase one of this trial, seedlings exposed to 8 h photoperiods to induce terminal buds were then intermittently transferred to 12, 16, 18 or 24 h photoperiods to determine dormancy status, evaluated by observing rates of terminal budburst. Buds were in a state of endodormancy initially after short-day induction, as indicated by their inability to quickly break bud when placed in longer daylengths. The time required for budburst decreased as time after bud initiation increased. Time to terminal budburst also decreased linearly with longer photoperiods. In phase two of the investigation, beginning 9 weeks after terminal bud initiation, seedlings began receiving chilling at +5°C to promote the transition from endo- to ecodormancy. During chilling, groups of seedlings were periodically removed from the cold and placed into warm temperatures at 8, 12, 16, 18 or 24 h photoperiods to observe the rate of budburst. Time to budburst in an 8 h photoperiod decreased logarithmically with the duration of chilling, decreasing more rapidly over the first four weeks of chilling and thereafter more slowly. Photoperiod always affected the rates of budburst: with eight weeks of chilling, longer photoperiods resulted in faster rates of budburst; in contrast, after 16 weeks of chilling, budburst was faster in shorter photoperiods. These results are of practical significance in tree nurseries where controlling bud dormancy release is important. In addition, this trial provides empirical observations of bud dormancy release that contribute to the understanding of environmental control of this aspect of the tree developmental cycle, which may affect tree phenology as the climate changes.

Status quo of insect pests – a decade of survey in Groundnut ecosystem

Groundnut, Arachis hypogea L. is an important oilseed crop and the insecticides to manage these pests increase the plant protection cost much if not taken at right time and also result in ecological imbalance. In order to minimize the cost of management and economic sustainability, real time management of the pests is the need of the hour. In this regard, monitoring of incidence of insect pests in groundnut ecosystem was carried out at Main Agricultural Research Station, University of Agricultural Sciences, Raichur, Karnataka for a period for over a decade (2012-2022). The pooled data showed that the maximum damage by Spodoptera litura Fab, and leaf miner was noticed during 45-75 days of crop growth wherein, spodoptera damage ranged from 10-25 percent while, the leafminer damage ranged from 5-20 percent. However, there was negligible damage by Helicoverpa armigera Hubner. Meanwhile, The leafhopper activity started from 35th standard week and the peak activity was noticed at the 43rd standard week with a foliage damage of 10-15 per cent which continued up to 45th standard week. Later on, the per cent foliage damage due to leafhopper gradually declined. Similarly, the peak activity of thrips was noticed during 40th standard week (4.0/ terminal bud) which continued till 43th standard week and thereafter the population declined.

Lectotypification of the name Actinotinus sinensis (Adoxaceae)

The specimen, Henry 4058, the type of Actinotinus sinensis was found through the trick prepared by one of Henry’s collectors who has artfully inserted an inflorescence of Viburnum into the terminal bud of an Aesculus. According to the Code operating prior to 1975, the name Actinotinus and A. sinensis must be abandoned, but they may be available for use under the current Code. The application of the names Actinotinus and A. sinensis are confusable. To clarify the confused situation, the part of inflorescence and flowers is chosen as the lectotype for the name A. sinensis for the purpose of maintaining the nomenclatural stability.

Histomorphogenesis of sublingual salivary gland of Indian sheep

ABSTRACT The primordial anlage of sublingual gland was first noticed as a solid epithelial bud from oral epithelium at the 24th day of foetal development. The terminal buds were arranged in the form of clusters with undifferentiated epithelial cells and terminated in a bulb-like structure in the 30-day-old sheep foetus. On the 37th day, lumenization and branching of the main cord was noticed. The primary septa were observed from the 55th day onwards which resulted in the formation of lobulation on the 60th day. The capsule formation was initiated by aggregation of mesenchymal tissue on the 63rd day. On the 100th day, terminal tubules differentiated to form secretory end pieces. Tubular portions formed intercalated and striated ducts. Predominantly mucous type of acinar cells was seen from the 110th day onwards with myoepithelial cells. The number of lobules increased with increase in parenchyma from 130th day onwards. Micrometrical studies revealed that the mean diameter of acini, intercalated, striated and large ducts was increased with advancement of age and significant differences were observed between groups. Localization of acidic and neutral mucopolysaccharides were observed in mucous and goblet cells. Fine lipid droplets were observed in intralobular and interlobular connective tissue however, phospholipids were observed in cell membrane of acini and ducts. The current investigation provides microstructural standards for the organogenesis of the sublingual gland of miniature sheep and can lay the foundation for further studies in the morphological investigation of salivary gland development.

Molecular Cloning and Expression Analysis of CONSTANS-LIKE 2 in Mucuna bracteata in Different Tissues and at Low Temperature

Mucuna bracteata is a leguminous cover crop that is planted in Malaysian oil palm and rubber plantations. This legume can grow well locally but is unable to produce flowers. Non-flowering M. bracteata plants presumably do not perceive the flowering signals to initiate the reproductive phase due to environmental differences. This study is on cloning a putative flowering gene, CONSTANS-LIKE 2 (COL2), from leaves of M. bracteata. To understand the molecular regulation of this gene in locally grown M. bracteata, we analysed its expression profile in different tissues of M. bracteata seedlings and response to low temperature using real-time polymerase chain reaction. The MbCOL2 gene was identified to be expressed in all selected tissues; leaf, terminal bud and stem of 2 months, 6 months and 12 months-old seedlings in different patterns. The MbCOL2 expression was the highest in the leaf tissue. Meanwhile, the expression of MbCOL2 was increased due to the low temperature. Physicochemical properties of MbCOL2 and its orthologues were also defined to analyse their protein functional properties. Outputs from this study can assist to better understand the molecular regulation of growth and development in M. bracteata.

Pubertal exposure to dietary advanced glycation end products disrupts ductal morphogenesis and induces atypical hyperplasia in the mammary gland

BackgroundAdvanced glycation end products (AGEs) are reactive metabolites intrinsically linked with modern dietary patterns. Processed foods, and those high in sugar, protein and fat, often contain high levels of AGEs. Increased AGE levels are associated with increased breast cancer risk, however their significance has been largely overlooked due to a lack of direct cause-and-effect relationship.MethodsTo address this knowledge gap, FVB/n mice were fed regular, low AGE, and high AGE diets from 3 weeks of age and mammary glands harvested during puberty (7 weeks) or adulthood (12 weeks and 7 months) to determine the effects upon mammary gland development. At endpoint mammary glands were harvested and assessed histologically (n ≥ 4). Immunohistochemistry and immunofluorescence were used to assess cellular proliferation and stromal fibroblast and macrophage recruitment. The Kruskal–Wallis test were used to compare continuous outcomes among groups. Mammary epithelial cell migration and invasion in response to AGE-mediated fibroblast activation was determined in two-compartment co-culture models. In vitro experiments were performed in triplicate. The nonparametric Wilcoxon rank sum test was used to compare differences between groups.ResultsHistological analysis revealed the high AGE diet delayed ductal elongation, increased primary branching, as well as increased terminal end bud number and size. The high AGE diet also led to increased recruitment and proliferation of stromal cells to abnormal structures that persisted into adulthood. Atypical hyperplasia was observed in the high AGE fed mice. Ex vivo fibroblasts from mice fed dietary-AGEs retain an activated phenotype and promoted epithelial migration and invasion of non-transformed immortalized and tumor-derived mammary epithelial cells. Mechanistically, we found that the receptor for AGE (RAGE) is required for AGE-mediated increases in epithelial cell migration and invasion.ConclusionsWe observed a disruption in mammary gland development when mice were fed a diet high in AGEs. Further, both epithelial and stromal cell populations were impacted by the high AGE diet in the mammary gland. Educational, interventional, and pharmacological strategies to reduce AGEs associated with diet may be viewed as novel disease preventive and/or therapeutic initiatives during puberty.

A molecular landscape of quiescence/proliferation highlights the role of Pten in mammary gland acinogenesis.

Cell context is key for cell state. Using physiologically relevant models of laminin-rich ECM (lrECM) induction of mammary epithelial cell quiescence and differentiation, we provided a landscape of the key molecules for the proliferation/quiescence decision, with multiple layers of regulation at the mRNA and protein levels. Quiescence occurred despite active Fak, Src and PI3k, suggesting the existence of a disconnecting node between upstream and downstream proliferative signalling. Pten, a lipid and protein phosphatase, fulfils this role because its inhibition increased proliferation and restored Akt/mTORC1/2 and Mapk signalling. Pten and laminin levels were positively correlated in murine developing mammary epithelia and Pten localized to apicolaterally in luminal cells in ducts and near the nascent lumen in terminal end buds. Consistently, in 3D acinogenesis models, Pten was required for triggering and sustaining quiescence, polarity and architecture. The multilayered regulatory circuitry that we uncovered provides an explanation for the robustness of quiescence within a growth-suppressive microenvironment, which could nonetheless be disrupted by perturbations in master regulators, such as Pten.

Development of Flowers Buds and Mixed Buds in the Dichasial Inflorescence of Geranium koreanum Kom. (Geraniaceae).

Flower bud differentiation is of great significance for understanding plant evolution and ecological adaptability. The development of flower buds and mixed buds in the dichasial inflorescence of Geranium koreanum was described in this paper. The morphogenesis, surface structure, and organ morphology at different growth stages of G. koreanum buds were examined in detail using scanning electron microscope and stereo microscope. The development of mixed buds started from the flattened apical meristem. The stipule and leaf primordia arose first. Subsequently, the hemispherical meristem was divided into two hemispheres, forming a terminal bud and floral bud primordia, followed by lateral bud differentiation. The formation of the terminal and lateral buds of G. koreanum was sequential and their differentiation positions were also different. The floral bud primordia would develop into two flower units and four bracts. The primordia of a flower bud first formed the sepal primordia, then the stamen and petal primordia, and finally the pistil primordia. Compared to the stamen primordia, the growth of the petal primordia was slower. Finally, all organs, especially the petals and pistil, grew rapidly. When the pistil and petals exceeded the stamens and the petals changed color, the flower bud was ready to bloom.

Safety of lactational exposure to venlafaxine on the rat mammary gland development and carcinogenesis in F1 female offspring

The chronic use of selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors (SNRIs) may result in human gynecomastia, mammoplasia, galactorrhea, and elevated breast cancer risk. As antidepressants are frequently used for postpartum depression (PPD) treatment, this study investigated the adverse effects of lactational exposure to venlafaxine (VENL, a selective SNRI) on mammary gland development and carcinogenesis in F1 female offspring. Thus, lactating Wistar rats (F0) received VENL by oral gavage at daily doses of 3.85, 7.7, or 15.4 mg/kg (N = 9, each group) from lactational day (LD 1) until the weaning of the offspring (LD 21). F1 female offspring were euthanized for mammary gland, and ovary histological analyses on the post-natal day (PND) 22 and 30 (1 pup/litter/period, N = 9, each group). At PND 22, other females (2 pups/litter, N = 18, each group) received a single dose of carcinogen N-methyl-N-nitrosourea (MNU, 50 mg/kg) intraperitoneally (i.p.) for tumor susceptibility assay until PND 250. Tumor incidence and latency were recorded and representative tumor samples were collected for histopathology. The results indicate that lactational exposure to VENL did not alter the development of the mammary gland (epithelial ductal tree or the mean number of terminal end buds), or the ovary (weight and primary, secondary, tertiary, and Graafian follicles) in prepubertal F1 female offspring. In addition, VENL exposure did not influence tumor incidence or tumor latency in adult female offspring that received MNU. Thus, the findings of this animal study indicated that lactational VENL exposure, a period similar to human PPD, did not exert an adverse effect on the mammary gland development at the prepubertal phase or on chemically induced mammary tumorigenesis in adult F1 female rats.

Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl.)

The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25ºC) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25ºC) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (Tª<25ºC) during the floral transition stage.

Optimization of Genetic Transformation on Phytochrome A by Directly Differentiated Buds in Alfalfa

Background: The study showed that phytochrome A (phyA) is involved in alfalfa fall dormancy regulation. To provide the scientific basis for using fall dormancy to predict new varieties’ dormancy class from the molecular level, cultivate alfalfa varieties with cold solid resistance and weak fall dormancy and improve the fall dormancy level of existing excellent types, we could study its function through gene silencing. But the genetic transformation rate is not high, which affects the research progress. Methods: To optimize the genetic transformation system in alfalfa (Medicago sativa L.), a binary plasmid vector pART27-phyA was transferred into alfalfa in Agrobacterium tumefaciens-mediated way. To improve transformation efficiency, we optimized the mediums by screening different Kan (Kanamycin) concentrations, NAA (a-Naphthylacetic acid) concentrations and adding YE (yeast extracts). Result: The results showed that using cotyledon nodes as explants, the proper concentration of Kan antibiotics resistance screening was 100 mg/L, the appropriate concentration of NAA for inducing cotyledon node differentiation was 0.1 mg/L and 0.2 g/L YE was suitable to add on the root induction medium; The expression of phyA in terminal buds and leaves of transformed plants of T1 and T2 generations of phyA in Reindeer was significantly reduced (P less than 0.05), but the expression trend in roots and stems had decreasing trend with no significant changes.

Unsuitability of the gall‐inducing fly Eutreta xanthochaeta for biological control of Lantana camara in presence of other native hosts in nature

AbstractThe biological control of weeds requires the successful introduction and establishment of natural enemies into other regions, to reduce population densities of target species. Potential biocontrol agents are sought in the native region of target weed and should be highly specialized. The gall‐inducing fly Eutreta xanthochaeta Aldrich (Diptera: Tephritidae) is native to Mexico and has been brought into other regions of the world – such as Hawaii (USA), South Africa, and Australia – for the biological control of Lantana camara L. (Verbanaceae), although this not always proved to be successful. Here we investigate the trophic interactions of this fly species with two host plants inhabiting in sympatry, L. camara and Lippia myriocephala Schltdl. &amp; Cham. (Verbenaceae), evaluating its preference through infestation rates, the gall distribution in the plant architecture, as well as the indirect impact upon production of inflorescences affecting the reproductive capacity of the plants. We found that the fly was not monophagous in its native range, and under natural conditions it preferred the wild host L. myriocephala in the presence of L. camara. Moreover, we found that gall formation was linked to changes in the host architecture along with the potential for reproduction, leading to increased terminal buds and a reduction in the inflorescences produced on the twigs where galls develop. Lantana camara consists of both horticultural hybrids and wild varieties resulting in unresolved taxonomic ambiguities. Hence, there may be adaptive limitations of this fly to distinct geographic races or climatic conditions in the various regions, which needs further investigation.

Taking shape: Intercalation within the mammary terminal end bud.

In this issue of Developmental Cell, Pfannenstein and Macara leverage the experimental versatility of the mammary gland to show that intercalation within the terminal end bud is regulated by the tight junction organizing protein ZO-1 and dynamic actin cytoskeletal rearrangements to propel ductal elongation.

A junction-dependent mechanism drives murine mammary cell intercalation for ductal elongation.

The luminal epithelium of the mammary gland is organized into monolayers; however, it originates from multilayered terminal end buds (TEBs) during development. Although apoptosis provides a plausible mechanism for cavitation of the ductal lumen, it doesn't account for ductal elongation behind TEBs. Spatial calculations in mice suggest that most TEB cells integrate into the outermost luminal layer to generate elongation. We developed a quantitative cell culture assay that models intercalation into epithelial monolayers. We found that tight junction proteins play a key role in this process. ZO-1 puncta form at the new cellular interface and resolve into a new boundary as intercalation proceeds. Deleting ZO-1 suppresses intercalation both in culture and in cells transplanted into mammary glands via intraductal injection. Cytoskeletal rearrangements at the interface are critical for intercalation. These data identify luminal cell rearrangements necessary for mammary development and suggest a mechanism for integration of cells into an existing monolayer.

In vitro regeneration of Haloxylon ammodendron

Haloxylon ammodendron (C.A.Mey) Bunge is one of the important species of arid desert vegetation in China, and it is also an ideal material for studying plant stress resistance, which plays an extremely important role in protecting desert ecosystems and preventing land desertification. However, there are relatively few studies on the regeneration of the fusiform, and the genetic transformation system has not been successfully reported, which restricts the in-depth study of the molecular mechanism of shuttle propagation and stress resistance. In the present study, the seeds, hypocotyls, cotyledons, cotyledon nodes, terminal buds and fixed buds were used as explants, and a set of tissue culture and plant regeneration system was established by inducing adventitious buds, adventitious bud rooting and transplanting. The results showed that amongst different H. ammodendron explants, i.e., seeds, hypocotyls, cotyledons and cotyledon nodes, the last induced budding effect was better. The optimal medium for inducing clandine buds by cotyledon segment differentiation is 0.5 mg·L-1 NAA+0.5 mg·L-1 6-BA induced budding rate was high, reaching 61.90%, rooting medium was 1/2 MS+1 mg·L-1 NAA +1 mg·L-1 IBA + 1 mg·L-1 IAA with a rooting rate of 50%. The results of this study will provide a theoretical basis for the genetic transformation of H. ammodendron.

The experimental life cycle closure of Andricus truncicolus (Giraud, 1859) (Hymenoptera: Cynipidae: Cynipini) and taxonomic description of its sexual generation.

The life cycle of Andricus truncicolus (Giraud, 1869), a species previously known only from its asexual generation, is closed. Laboratory rearing and field sampling have revealed the sexual generation of this species, which develops in a hypertrophic degeneration of the terminal or lateral shoot buds appearing as a muddled agglomerate of leaves on Quercus, section Cerris oaks. We describe for the first time the newly discovered sexual generation of A. truncicolus and provide illustrations and diagnosis for adults and galls of both generations, further observations on biology and information on the species distribution.

Crown Width Extraction of Metasequoia glyptostroboides Using Improved YOLOv7 Based on UAV Images

With the progress of computer vision and the development of unmanned aerial vehicles (UAVs), UAVs have been widely used in forest resource investigation and tree feature extraction. In the field of crown width measurement, the use of traditional manual measurement methods is time-consuming and costly and affects factors such as terrain and weather. Although the crown width extraction method based on the segmentation of UAV images that have recently risen in popularity extracts a large amount of information, it consumes long amounts of time for dataset establishment and segmentation. This paper proposes an improved YOLOv7 model designed to precisely extract the crown width of Metasequoia glyptostroboides. This species is distinguished by its well-developed terminal buds and distinct central trunk morphology. Taking the M. glyptostroboides forest in the Qingshan Lake National Forest Park in Lin’an District, Hangzhou City, Zhejiang Province, China, as the target sample plot, YOLOv7 was improved using the simple, parameter-free attention model (SimAM) attention and SIoU modules. The SimAM attention module was experimentally proved capable of reducing the attention to other irrelevant information in the training process and improving the model’s accuracy. The SIoU module can improve the tightness between the detection frame and the edge of the target crown during the detection process and effectively enhance the accuracy of crown width measurement. The experimental results reveal that the improved model achieves 94.34% mAP@0.5 in the task of crown detection, which is 5% higher than that achieved by the original model. In crown width measurement, the R2 of the improved model reaches 0.837, which is 0.151 higher than that of the original model, thus verifying the effectiveness of the improved algorithm.

Topological and spatial analysis of within-tree fruiting characteristics for walnut trees

Shoot morphology and canopy position usually have a significant impact on fruiting potential, but these effects have not been fully quantified, especially at the whole tree level. This study addressed the fruit number variation as affected by shoot length and within-tree position for mature walnut trees cv. Chandler, which is a lateral bearing variety. A positive relationship was observed between parent shoot (previous-year) length and the number and length of current-year floral shoots, as well as between the length of current-year floral shoots and fruit number per floral shoot. Fruit number and spatial position in defoliated trees were manually identified based on LiDAR data, but tree architecture, including shoot length and topology, was not accurate to be reconstructed by the available software (TreeQSM). About half of fruits were located in the outer canopy, while the reminder, especially at the mid-canopy height, were equally distributed inside the canopy to a depth of about 90 cm. The topological fruit location at the whole tree level were manually quantified in relation to the length and relative node rank of parent shoots. Even though long parent shoots exhibited more lateral bearing, the majority of fruits at the whole tree level were on current-year floral shoots that developed from the terminal buds of relatively short (<=10 cm) parent shoots because these represented the vast majority (over 90%) of parent shoots on mature trees.

Refining Management of Apple Powdery Mildew in New York State with Weather-Based Fungicide Application Timing Programs.

In the absence of durable host resistance among commercial cultivars, chemical management continues to be an essential component of disease control in apple production. Apple powdery mildew, caused by the ascomycete Podosphaera leucotricha, is largely managed with regular fungicide applications from the host phenological stages of tight cluster to terminal bud growth set, with applications typically being made in a prophylactic manner irrespective of existing disease pressure. Here we evaluated two management programs that aligned fungicide applications to specific weather thresholds conducive to powdery mildew development using a rotation of single-site fungicides and sulfur. In three separate orchards among four cultivars, we compared powdery mildew disease progression over the growing season for each of the weather factor-based programs and a typical calendar-based application program. In each year of the trial, we found that management programs with weather-based fungicide applications provided levels of disease control similar to the calendar program but required 50 to 83.3% fewer mildew-specific fungicide applications throughout the growing season. Our results provide a framework with which to evaluate future weather-based management programs for apple powdery mildew management. This knowledge could be implemented in the creation of a powdery mildew disease management decision support system to better inform and aid fungicide application programs for continued sustainable apple production in the northeast United States.