Blueberry Fields Research Articles

Contrasting effects of landscape on nest founding and colony success of bumble bees in a mixed‐crop agroecosystem

Abstract Nest‐founding bumble bee queens search landscapes broadly for a nest site, whose later‐developed workers are constrained to foraging around the nest. Landscape could therefore have different influences on nest site selection and subsequent colony success. Additionally, the density of bumble bees in a landscape reflects the product of their nest density and nest success. To examine separate landscape effects on nest density and success, we examined nest occupancy (reflecting nest density) and colony size (reflecting nest success) using ground‐installed nest boxes placed adjacent to blueberry (Vaccinium corymbosum) fields in the Lower Mainland of British Columbia, Canada. Nest‐searching queens occupied 59% of these boxes. We classified landscapes in a 1.5 km radius of colonies using habitats of a priori relevance to bumble bees: beneficial (i.e. flowering) agriculture, non‐beneficial agriculture (NBA), forest, open semi‐natural, suburban, and their configuration (habitat edge density). Landscape strongly affected nest founding but only weakly affected colony success. Nest founding increased in landscapes with more forest habitat, more open semi‐natural habitat (and little NBA), and more habitat edge (and little NBA). Colony success increased in landscapes with more edge density (and much NBA). Overall, edge habitats enhanced bumble bee populations, but enhancement was conditional: edge increased nest occupation in landscapes with little NBA and nest success in landscapes with a lot of NBA. Populations of crop‐pollinating bumble bees might therefore best be enhanced by locally enhancing nesting: protecting forests, 2D semi‐natural habitats (when flowering crops are uncommon), and edge habitats.

Health—Promoting Properties of Highbush Blueberries Depending on Type of Fertilization

The purpose of the experiment was to demonstrate a comparison of fertilization with and without biostimulation. A study was carried out in an experimental blueberry field in central Poland (51°55′42.7″ N 20°59′28.7″ E) during the three growing seasons of 2019, 2020 and 2021, on ‘Bluecrop’ shrubs growing at a distance of 1 × 3 m. The plants were re-planted in the spring of each year and irrigated using drip irrigation. The experiment was conducted using a random block design (four fertilizer treatments × five replications × six bushes). The fruits were tested for antioxidant activity and amount of total polyphenols. Additionally, anthocyanin quantitative and qualitative analysis was performed. The results indicated a significant effect of fertilizer combinations on the values of the evaluated parameters. The positive effect of biostimulants on the content of antioxidant compounds in highbush blueberry fruit was significant. In most of the combinations in which additional biostimulants were used, higher values of the analyzed indicators (antioxidant activity and polyphenol content) were observed. The most noteworthy was the T4 fertilization program, where during treatment, soil and foliar fertilization were carried out with preparations that contained biostimulants.

Effects of Three Cultural Practices on Drosophila suzukii (Diptera: Drosophilidae) in Open Blueberry Fields in Florida.

Simple SummaryThe spotted-wing Drosophila is an invasive pest of berry fruits in Florida. The pest is difficult to control with pesticides, and resistance is developing. The current study was carried out in north Florida to see if non-pesticidal pest control tactics using three mulching practices could reduce its population density to increase growers’ berries productivity. The experiments were conducted for two years while using two plant-based mulches (short pine needles and pine bark) and one fabric-based mulch in the open blueberry fields. In general, the fly population was reduced within the selected pine bark and black weed fabric mulches. This is the first report of such practices deployed to manage the spotted-wing Drosophila in Florida. We are confident that these selective cultural practices could be utilized in open blueberry fields before berries settings to reduce pest pressure for both conventional and organic blueberry growers in Florida. Indeed, this will increase growers’ berry production and profitability.The spotted-wing Drosophila (SWD), Drosophila suzukii, is native species in Southeast Asia. For over a decade, this invasive pest has been globally expanding. The economic losses to soft fruits and stoned fruits in the United States are increasing every year. Presently, the only viable tool to reduce the SWD population is the continued use of broad-spectrum insecticides. Pesticide resistance is appearing in the populations for the SWD. Organic farmers have limited options to control this pest in open fields. The major goal of this study was to develop cost-effective pest management strategies to manage the SWD using three types of mulches (two plant-based and one fabric-based) to reduce fly population and damage in open blueberry fields in north Florida. The study was conducted in two fruiting seasons (2017 and 2018). The study results demonstrated that the fly trap catches in 2017 shortleaf pine needle mulch had much higher populations (about 2.5-fold) of the SWD than all other treatments. In 2018, the numbers were about 1.7-fold more on shortleaf pine needle mulch than on other treatments. The fine texture of the mulch (pine needles) can easily facilitate the emergence of the SWD if the mulch is not thick enough. Although the pine needles covered the soil surface, it may have been too thin and thus allowed the SWD adults to emerge from the soil without much hindrance. In 2018, a higher population of the SWD was recorded from all the mulching practices. However, there were no significant differences in trap catches between all treatments. In general, the fly population is reduced with the use of pine bark and black weed fabric mulches. This is the first study that reports the effects of three mulches in controlling the SWD populations, which could benefit conventional and organic blueberry growers.

Identifying hair fescue in wild blueberry fields using drone images for precise application of granular herbicide

Hair fescue is a common perennial grass weed in wild blueberry fields in Nova Scotia, Canada and reduces yield if not adequately controlled. Hair fescue is typically managed with a broadcast propyzamide application which is costly for growers. Current research on the management of hair fescue in wild blueberry fields focuses on the development of a precision granular herbicide applicator with individual nozzle control. The integration of aerial images could benefit current work by providing a large-scale perspective on hair fescue location. This research suggests a new strategy to identify infield areas with hair fescue infestation, generate prescription maps, and integrate them into a widely available navigation system of heavy farming equipment to improve the processing workflow of hair fescue detection on a larger scale. This method proposes the integration of multi-resolution segmentation on multispectral (Blue, Green, Red, Red Edge, Near-Infrared) drone images to group hair fescue plants into segments with similar spectral characteristics. The best performing segmentation was classified and tested on wild blueberry fields in Nova Scotia. Results were assessed by comparing classified boundaries to reference data collected with high resolution RGB images. Findings from hair fescue and wild blueberry spectral profiles showed that hair fescue could be identified using blue, green, and red bands and showed no advantages over multispectral cameras. Results from the classification of wild blueberry and hair fescue showed high Kappa coefficient values of 0.90 and 0.94 and overall accuracy of 95 and 97% were achieved for both fields surveyed. Results also demonstrated an average potential cost saving of $CAD1246.43 ha-1 when compared to a broadcast application of granular dichlobenil. This work represents the first attempt to integrate aerial imagery and a precision granular herbicide applicator to manage important weeds in wild blueberry fields.

Evaluation of broadcast and spot herbicide applications for spreading dogbane (Apocynum androsaemifolium L.) management in lowbush blueberry fields

Spreading dogbane is a creeping herbaceous perennial weed in lowbush blueberry. Management is limited primarily to spot applications of dicamba, though recent herbicide registrations facilitate the evaluation of new broadcast and spot herbicide applications. The objectives of this research were to determine (1) the effect of sequential postemergence (POST) mesotrione application interval on spreading dogbane, (2) the effect of sequential POST mesotrione and foramsulfuron applications on spreading dogbane, (3) the effect of POST herbicide tank mixtures on spreading dogbane, (4) the effect of summer and fall spot herbicide applications on spreading dogbane, and (5) the effect of spot applications of dicamba tank mixtures with sulfonylurea herbicides on spreading dogbane. Broadcast mesotrione (144 g a.i. ha−1) and foramsulfuron (35 g a.i. ha−1) applications did not control spreading dogbane. Control was not improved by sequential applications of either herbicide. Broadcast mesotrione + foramsulfuron applications reduced non-bearing-year density and may be more effective than either herbicide applied alone. Broadcast flazasulfuron applications reduced non-bearing-year shoot density and flazasulfuron + foramsulfuron applications reduced non-bearing-year and bearing-year shoot densities. Summer spot applications of foramsulfuron and flazasulfuron caused 70% injury to spreading dogbane but did not reduce shoot density, and dicamba continues to be the most effective spot herbicide treatment. Fall spot applications did not control spreading dogbane due to early senescence of spreading dogbane shoots. Spot applications of dicamba at 0.96 or 1.92 g a.e. L water−1 provided equivalent spreading dogbane control and efficacy was not improved by tank mixture with foramsulfuron, flazasulfuron, or nicosulfuron + rimsulfuron.

Evaluation of amino acid–inhibiting herbicide mixtures for hair fescue (Festuca filiformis) management in lowbush blueberry

AbstractHair fescue is a perennial grass weed in lowbush blueberry fields that forms dense sods and reduces yield. As a result of natural tolerance or resistance of this grass to other currently registered herbicides growers rely on preemergence (PRE) applications of pronamide and postemergence (POST) applications of the Group 2 herbicides foramsulfuron and nicosulfuron + rimsulfuron for hair fescue management. This causes repeated application of Group 2 herbicides, which is compounded by the recent registration of flazasulfuron for POST suppression of hair fescue in lowbush blueberry. Mixtures of Group 2 herbicides with the amino acid–inhibiting herbicides glyphosate (Group 9) and glufosinate (Group 10), however, can improve weed control and may delay herbicide resistance development. This research used a factorial arrangement of Group 2 herbicides (none, foramsulfuron [35 g ai ha−1], nicosulfuron + rimsulfuron [13 + 13 g ai ha−1], flazasulfuron [50 g ai ha−1]) and mixtures (none, with glyphosate [902 g ae ha−1], and with glufosinate [750 g ai ha−1]) to identify possible mixtures that improve weed control and delay resistance development. Herbicides were applied in spring nonbearing year, fall bearing year, and fall nonbearing year, with each application timing conducted as a separate experiment. Foramsulfuron and nicosulfuron + rimsulfuron were not effective as fall applications, and spring applications of these herbicides with glyphosate or glufosinate improved hair fescue suppression. Glyphosate and glufosinate were more effective as fall rather than spring applications. Flazasulfuron was effective across all application timings, although its mixture with glufosinate generally improved hair fescue suppression. Flazasulfuron + glufosinate is tentatively recommended as an effective mixture for management of spring nonbearing-year and fall bearing-year hair fescue in lowbush blueberry.

How management practices influence vegetative and reproductive plant traits of wild lowbush blueberry species

Optimizing agricultural practices is an effective way to increase fruit productivity in commercial wild lowbush blueberry ( Vaccinium angustifolium Aiton; Vaccinium myrtilloides Michx) fields, but results from northern Quebec (Canada) are scarce. In this study, we assessed the effect of the main crop management practices, namely pruning method (mechanical and thermal), fungicide (with and without), and fertilization (mineral, organic, and without) on key vegetative and reproductive plant traits of both wild blueberry species. The experiment was conducted from fall 2016 to fall 2018, when the combination of pruning, fungicide, and fertilizing was applied. Results show that fertilizer application was the main management practice affecting vegetative and reproductive plant traits followed by fungicide application effects during pruning years only. Mineral fertilizer improved plant traits to a greater extent than organic fertilizer during the pruning phase only, and no significant differences in the second year after application (harvesting phase) suggest a delayed but similar final effect of organic fertilizer. Results also showed that V. myrtilloides produces taller stems with more leaves compared to V. angustifolium, whereas V. angustifolium produces more flower buds, a key reproductive plant trait. Results also highlight the fact that V. angustifolium needs both fertilizer and fungicide to keep leaves on the stem during late summer, whereas V. myrtilloides needs either fertilizers or fungicides. This study also shows that pruning method has no significant effect on any of the measured plant traits. However, we believe that long-term studies are still needed to assess the impact of pruning method over time.

Comparison of Wood Mulch Particle Sizes for Wild Blueberry Management in a Changing Climate

ABSTRACT Climate change in Maine is characterized by increasing rates of warming temperatures and more intense rain events, which lead to altered growing seasons, earlier emergence of pests, increased seasonal drought and large crop losses. These changes have significant impacts on wild blueberry systems and make it more difficult for growers to manage this crop under increasingly unpredictable weather patterns. Mulching is a tool growers use to combat some of these challenges, but the comparative effects of wood mulch particle size in wild blueberry systems has not been studied. The purpose of this study was to determine the effect of wood mulch particle size on wild blueberry soil, plant development, pest pressure, and yield. This study was carried out over a 2-year period (one production cycle) in an organic wild blueberry field in Stockton Springs, ME. There was no mulch particle size treatment used in this study that demonstrated significantly greater overall mean soil moisture compared to the control at the 1.27 cm application thickness. All mulch treatments significantly reduced disease pressure, primarily Sphaerulina leaf spot caused by Sphaerulina vaccinii, compared to the control in year 1. The two finest particle size treatments, sawdust and shavings, resulted in significantly greater yields than the control, and were the least expensive materials. This suggests that growers should consider using finer particle size mulches rather than the current practice, wood chips, but may need to reapply more frequently. From this study, application of softwood mulch of any particle size is better than no application.

Detection of Management Practices and Cropping Phases in Wild Lowbush Blueberry Fields Using Multispectral UAV Data

Normalized difference vegetation index (NDVI) and normalized difference red-edge index (NDRE) are vegetation indices commonly used in agriculture to provide information on crop’s growth and health. Here, we investigated the sensitivity of both indices to management practices in lowbush blueberry fields. Images of the experimental plots were collected with a multispectral camera installed on an unmanned aerial vehicle. Both NDVI and NDRE values were significantly higher in fertilized plots than in controls (0.88 ± 0.03 vs. 0.79 ± 0.03 for NDVI, and 0.37 ± 0.01 vs. 0.33 ± 0.01 for NDRE) due to fertilization effect on vegetative growth. The increase was higher under mineral than organic fertilization during the two first phases of the cropping system (by ∼0.3 and ∼0.2 for NDVI and NDRE, respectively). NDRE was not affected by thermal pruning and fungicide application but was negatively correlated with Septoria infection level. NDVI was more strongly correlated with stem length than NDRE, but unlike NDRE, NDVI was not impacted by the development of reproductive shoots during the harvest phases. Overall, the results indicate that although both index values are correlated, their sensitivity to changes in canopy characteristics differs depending on the cropping phase. Further research must be conducted to relate these indices to blueberry’s nutrient status.

Pesticide risk to managed bees during blueberry pollination is primarily driven by off-farm exposures

When managed bee colonies are brought to farms for crop pollination, they can be exposed to pesticide residues. Quantifying the risk posed by these exposures can indicate which pesticides are of the greatest concern and helps focus efforts to reduce the most harmful exposures. To estimate the risk from pesticides to bees while they are pollinating blueberry fields, we sampled blueberry flowers, foraging bees, pollen collected by returning honey bee and bumble bee foragers at colonies, and wax from honey bee hives in blooming blueberry farms in southwest Michigan. We screened the samples for 261 active ingredients using a modified QuEChERS method. The most abundant pesticides were those applied by blueberry growers during blueberry bloom (e.g., fenbuconazole and methoxyfenozide). However, we also detected highly toxic pesticides not used in this crop during bloom (or other times of the season) including the insecticides chlorpyrifos, clothianidin, avermectin, thiamethoxam, and imidacloprid. Using LD50 values for contact and oral exposure to honey bees and bumble bees, we calculated the Risk Quotient (RQ) for each individual pesticide and the average sample RQ for each farm. RQ values were considered in relation to the U.S. Environmental Protection Agency acute contact level of concern (LOC, 0.4), the European Food Safety Authority (EFSA) acute contact LOC (0.2) and the EFSA chronic oral LOC (0.03). Pollen samples were most likely to exceed LOC values, with the percent of samples above EFSA’s chronic oral LOC being 0% for flowers, 3.4% for whole honey bees, 0% for whole bumble bees, 72.4% for honey bee pollen in 2018, 45.4% of honey bee pollen in 2019, 46.7% of bumble bee pollen in 2019, and 3.5% of honey bee wax samples. Average pollen sample RQ values were above the EFSA chronic LOC in 92.9% of farms in 2018 and 42.9% of farms in 2019 for honey bee collected pollen, and 46.7% of farms for bumble bee collected pollen in 2019. Landscape analyses indicated that sample RQ was positively correlated with the abundance of apple and cherry orchards located within the flight range of the bees, though this varied between bee species and landscape scale. There was no correlation with abundance of blueberry production. Our results highlight the need to mitigate pesticide risk to bees across agricultural landscapes, in addition to focusing on the impact of applications on the farms where they are applied.

Seasonal Climate Trends across the Wild Blueberry Barrens of Maine, USA

Wild blueberries in Maine, USA are facing threats from our changing climate. While summer climate variations have been affecting this important commercial crop directly, significant climate variations in other seasons also can be potentially detrimental to blueberry production. Therefore, we analyzed annual and seasonal climate trends (temperature, rainfall, snow cover) over the past 41 years (1980–2020) for seven Maine counties (Piscataquis, Washington, Hancock, Knox, Lincoln, Kennebec, York) with large wild blueberry areas. We found that, across all blueberry production fields (or “barrens”), historical temperatures increased significantly (p < 0.05) in the fall and winter followed by summer, but not in the spring. Additionally, precipitation increased slightly (0.5–1.2 mm/year) in the winter and fall, whereas no changes were found in the spring and summer. Furthermore, we found that historical temperatures were lower in Piscataquis (north-central) and Washington (north-east) counties, whereas in south-western counties (Hancock to York) experienced a relatively warmer climate. The rate of increasing temperature was comparatively slower in the warmer barrens located towards the south-west (Hancock to York). Moreover, the growing season lengthened towards the fall season consistently in all locations, whereas lengthening towards the spring was inconsistent. These findings inform the wild blueberry growers in different locations of Maine about the seasonal shifts occurring for their crop. This knowledge may assist with land management planning in order for the growers to prepare for future impacts.

Fertility Effects on Blueberry Gall Midge (Diptera: Cecidomyiidae) in Wild Blueberry (Vaccinium angustifolium; Ericales: Ericaceae).

Blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae) is a pest in American cranberry, Vaccinium macrocarpon Aiton (Ericales: Ericaceae) and wild blueberry, Vaccinium angustifolium Aiton (Ericales: Ericaceae), and has been observed in areas of high soil and foliar nutrient levels. New management strategies, including fertilization, will need to be altered to sustain wild blueberry production under climate change and, in turn, may impact the occurrence of this pest. The purpose of this study was to measure the effect of diammonium phosphate (DAP) fertilizer application on density of infested stems and the combined effects of fertilizer application with and without infestation on wild blueberry systems. This study was conducted at two field sites in Jonesboro and Washington, ME during 2020 and 2021. Despite increases in habitat availability (blueberry cover) for the gall midge and greater infestation density, wild blueberry production benefited from DAP application. This was shown in the number of buds per stem at both sites, as well as in stem height, flowers, green fruit, blue fruit per stem, and total yield at the Washington site. Foliar nitrogen and phosphorus levels had a significant positive linear relationship with infestation density. Growers applying fertilizers should monitor blueberry gall midge field infestation levels due to our findings that DAP fertilizer impacted infestation density and the interaction of DAP fertilizer with infestation impacted wild blueberry production.

Fungicide Resistance in Alternaria alternata from Blueberry in California and Its Impact on Control of Alternaria Rot.

Alternaria rot caused by Alternaria alternata is one of the major postharvest diseases affecting blueberries in California. The sensitivity profiles of A. alternata from blueberry field to quinone outside inhibitors (QoIs), boscalid, fluopyram, fludioxonil, cyprodinil, and polyoxin D in California were examined in this study. EC50 values of 51 A. alternata isolates for boscalid varied greatly among the isolates, ranging from 0.265 to >100 μg/ml. EC50 values of 51 A. alternata isolates to fluopyram, fludioxonil, cyprodinil, and polyoxin D were 5.188 ± 7.118, 0.078 ± 0.021, 0.465 ± 0.302, and 6.238 ± 7.352 μg/ml, respectively. In total, 143 isolates were screened for resistance at 5 and 10 μg/ml for fludioxonil, cyprodinil, and fluopyram, 10 μg/ml for polyoxin D, and 10 and 50 μg/ml for boscalid. Based on the published discriminatory concentrations for phenotyping resistance, of the 143 isolates, all were considered resistant to boscalid; 32, 69, and 42 were sensitive, low resistant, and resistant to fluopyram, respectively; and all were sensitive to fludioxonil and cyprodinil. In a PCR-restriction fragment length polymorphism method for phenotyping, 60 out of the 143 isolates were classified as resistant to QoIs. Control tests on detached blueberry fruit inoculated with different Alternaria isolates showed that fludioxonil and cyprodinil significantly reduced disease incidence and severity; however, pyraclostrobin, boscalid, fluopyram, and polyoxin D significantly reduced only disease severity. The obtained results will be helpful in making decisions on fungicide programs to control A. alternata isolates with resistance or reduced sensitivities to multiple fungicides.

High Variation in Yield among Wild Blueberry Genotypes: Can Yield Be Predicted by Leaf and Stem Functional Traits?

Wild lowbush blueberry fields are characterized by high genetic diversity, with a large number of genotypes coexisting in every field. Yield also varies among genotypes, which could be related to the variation in physiological and structural traits, but this has not been rigorously tested. In this study, we aimed to quantify the inter-genotype variation in yield, as well as leaf and stem functional traits, and to establish the relationship between functional traits and yield-related traits in wild blueberries. To do so, we carried out a study during the 2019 harvest season measuring structural and functional traits including stem number, stem length, stem diameter, leaf chlorophyll concentration, leaf mass area, leaf area per stem, leaf number per stem, number of branches per stem, leaf temperature, soil temperature, and soil water content and yield data including yield, berry size (weight of 100 berries), number of berries per stem, and length of berry cluster from two wild blueberry farms. We found high variations in structural, functional, and yield-related traits among genotypes, but not between two fields. We also found negative associations of the leaf mass per unit area and midday leaf temperature with the yield, whereas the leaf chlorophyll concentration was positively associated with the yield. Additionally, we found a quadratic relationship between yield-related traits (weight of 100 berries, number of berries per stem, and length of berry cluster) and stem length, with the optimum stem length for yield at 25 cm. Our results suggest that several leaf and stem functional traits are related with yield-related traits; thereby, those traits can be used to predict wild blueberry yields. Our findings could help growers and breeders select better-yielding genotypes based on structural and functional traits.

Managing Botrytis blossom blight of wild blueberry through field sanitation, lime sulfur and Trichoderma application

Botrytis blossom blight is an important disease of wild blueberries (Vaccinium angustifolium) and causes substantial yield loss annually. Field trials that involve primary inoculum reduction and disease reduction techniques were conducted for the 2015/2016 and 2019/2020 growing seasons. The aim of this study was to evaluate the single and combined effects of thermal treatment, calcium polysulphide and Trichoderma harzianum T-22 application on Botrytis blossom blight development, physical plant structure and harvestable yield over the 2-year production cycle of the crop. The treatments were such that fields were thermally treated in May after pruning, followed by calcium polysulphide application in November 2015 and 2019. Trichoderma harzianum was applied in June 2016 and 2020 as single and combined treatments. Thermal treatment + calcium polysulphide + T. harzianum and thermal treatment + calcium polysulphide combinations reduced Botrytis blossom blight incidence and severity by over 50% and 74%, respectively, compared with the untreated control in both seasons. Plots receiving only the thermal treatment and calcium polysulphide as well as the calcium polysulphide + T. harzianum combination showed reductions in disease incidence of over 51, 38 and 81%, and reductions in disease severity of 55, 39 and 68%, respectively, compared with the untreated control. Plots that received thermal treatment combined with calcium polysulphide had taller stems, and a higher number of floral and vegetative buds. Results from this study have demonstrated that Botrytis blossom blight in wild blueberry fields can be adequately reduced when calcium polysulphide is used tandem with thermal treatment and biofungicides.

Are Foliar Fertilizers Beneficial to Growth and Yield of Wild Lowbush Blueberries?

Wild lowbush blueberry is an economically and culturally important crop in North America. Different fertilizer companies have been advertising their foliar fertilizer products to the wild blueberry growers, claiming better growth and production of this crop with no scientific proof. Although foliar fertilization has shown to be efficient for delivering micronutrients in deficit for different crops by reducing soil activation and environmental contamination, limited research has been done in wild blueberries. It is still unknown how foliar fertilizers affect the physiology, growth, and yield of this crop. Therefore, we tested the impacts of seven foliar treatments containing macro- and micro-nutrients and plant hormones (Seacrop16, Salvador, Agro-Phos applied in 2019 and Kali-T, Nano-Gro, Poma, Poma + Nanocellulose applied in 2020) on this crop for one crop cycle from vegetative year (2019) to crop year (2020). We tested these products against the standard soil-applied granular fertilizer called Diammonium phosphate (DAP) and control (no fertilizer) in a randomized complete block design with eight replicates in a conventional wild blueberry field in Maine, USA. In 2019, no significant differences across the applied treatments were observed in crop physiology and growth except in leaf chlorophyll concentration. In 2020, there was significantly higher leaf chlorophyll concentration in SeaCrop16 and Poma+Nanocellulose plots, but significantly lower photosynthetic rates in DAP and SeaCrop16 treated plots compared to the control. Meanwhile, no significant differences in plant height, leaf characteristics, or blueberry yield were found among the treatments. Overall, mobile nutrients (N, P, K) from soil applied fertilizers and foliar fertilizers containing other immobile nutrients (Ca) and/or plant hormones might benefit crop growth, but the impact on yield is limited. We also reveal that the wild blueberry physiological and morphological traits and leaf nutrients in the vegetative year are more related to the crop yield than those traits in the crop year. This implies that a combination of wild blueberry physiology, morphology, and leaf nutrients in the vegetative year largely impact their yield in the following crop year.

Will Climate Warming Alter Biotic Stresses in Wild Lowbush Blueberries?

As global temperatures rise, a growing need exists for understanding the impacts of warming on crop production. Warming not only changes crop physiology and growth but also the weeds, insect pests, and diseases of crops including wild lowbush blueberries, which have not been studied till now. Changes in pest pressures can cause instability in production and will require changes in management practices and the development of mitigation strategies. The objective of this study was to determine the impacts of warming on the prevalence of major weeds, insect pests, and diseases of the wild blueberry production system. We selected six genotypes of wild lowbush blueberries in a commercially managed wild blueberry field in Maine Northeast USA and used open-top-chambers (OTCs) to study the effects of warming for two years (2019 and 2020). Both active-heating OTCs (elevated monthly mean temperatures by 3.3 °C) and passive-heating OTCs (elevated by 1.2 °C) were employed and compared with ambient controls. Our results showed that warming did not change the prevalence of red leaf disease, blueberry gall midge, red-striped fireworm, or any weed species. In contrast, the incidence of Sphaerulina leaf spot, powdery mildew, and other leaf spot disease were significantly lower under warming treatments compared to the ambient control at the end of the growing season in 2020. Overall, different pests responded to warming differently, inviting further research to reveal the mechanisms. The lower overall pressure of leaf spot disease under warming was probably due to decreased air humidity.

Field bindweed control with quinclorac in highbush blueberry

AbstractField bindweed is a perennial vining weed with vigorous growth, and is commonly found in highbush blueberry fields of Oregon. It requires and integrated strategy using multiple applications of postemergence herbicides and hand weeding for adequate control. Quinclorac is a herbicide that has been shown to control field bindweed, but no information is available indicating the tolerance of blueberry to quinclorac. The objective of this study was to evaluate the response of blueberry to quinclorac and to evaluate field bindweed control with quinclorac in different mixtures. Three groups of field studies were designed to assess 1) single application control of field bindweed, 2) use of sequential treatments to control field bindweed, and 3) long-term impact of quinclorac on field bindweed. In the single application control studies, a single application of quinclorac at 210 or 420 g ai ha−1 alone or in a mixture with rimsulfuron (35 g ai ha−1) or carfentrazone (35 g ai ha−1), controlled field bindweed by 69% to 76% while reducing its biomass between 22% and 44% compared to the nontreated control (61 g m−2). In a sequential treatment study, a single application of quinclorac (420 g ai ha−1) provided 83% to 100% control of field bindweed, outperforming three sequential applications of carfentrazone. In the long-term study, a single application of quinclorac reduced field bindweed biomass by 50% to 82% in 2019 and 62% to 87% in 2020. These results indicate that quinclorac can be safely applied to highbush blueberry plants. Early spring applications of quinclorac to field bindweed will reduce or eliminate the need for subsequent applications later in the season.

Does sending honey bee, Apis mellifera (Hymenoptera: Apidae), colonies to lowbush blueberry, Vaccinium angustifolium (Ericaceae), for pollination increase Nosema spp. (Nosematidae) spore loads?

Abstract In the Canadian Maritimes, many beekeepers rent honey bee, Apis mellifera Linnaeus (Hymenoptera: Apidae), hives to growers of lowbush blueberry, Vaccinium angustifolium (Ericaceae), for pollination services. Anecdotally, hives have less vigour following pollination, potentially due to higher Nosema spp. (Nosematidae) spore loads, the microsporidian causing nosemosis. We undertook a study to determine whether sending honey bee hives to lowbush blueberry fields for pollination (blueberry hives) results in higher Nosema spp. spore loads relative to hives remaining in apiaries (home hives). Nosema spp. spore loads were quantified using light microscopy. Nosema apis and Nosema ceranae were differentiated using polymerase chain reaction and sequencing. Nosema spp. spore loads were greatest in April and May and declined to low levels from June to September. Ninety-eight per cent of Nosema detections were positive for N. ceranae. In April, blueberry hives had a lower spore load than home hives did; however, in June, spore loads were significantly higher in blueberry hives. No other differences in Nosema spp. spore loads were observed between hive types. We conclude that Nosema ceranae is the dominant Nosema species in the Canadian Maritimes and that using hives for lowbush blueberry pollination does not appear to influence long-term Nosema spp. spore loads.

Postdiapause reproduction of spotted-wing drosophila (Diptera: Drosophilidae) in realistically simulated cold climatic springtime conditions of Québec, Canada

Abstract Knowing the biology and ecology of Drosophila suzukii (Diptera: Drosophilidae) is important to predict its potential for permanent establishment in cold climatic regions. We studied the reproductive potential of postdiapause male and female flies collected in lowbush blueberry fields in late season over two years. After being submitted to a six-month cold-winter regime, survivors were exposed to a simulated springtime warming regime to monitor reproductive potential and expected population growth. Overwintered fly survivors of both sexes that were aged up to nine months after field capture reproduced successfully in spring and early summer when mated to nondiapause flies experimentally made available for mating as potential migrant colonisers from lower latitudes. Relative to control nondiapause flies, the lifetime fertility of postdiapause flies was reduced by 84% in females and 70% in males, revealing large fitness costs of reproductive diapause under cold stress. Modelling potential reproduction of overwintered flies in warming conditions using models parametrised for age-dependent fertility rate and diapause status showed that nondiapause migrant flies would be strongly advantaged over locally overwintered postdiapause flies due to precocious reproductive maturity, broader pattern of age-specific fertility, and higher lifetime fertility.