Research

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15 pages, 17453 KiB

Open AccessArticle

Egg Morphology and Chorionic Ultrastructure of Spotted Lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae)

by Jonathan M. Powell, Laura J. Nixon, Austin P. Lourie, Tracy C. Leskey and Spencer S. Walse

Forests 2023, 14(12), 2354; https://doi.org/10.3390/f14122354 - 30 Nov 2023

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Knowledge regarding egg morphology can aid the selection of postharvest fumigants for insect control. Accordingly, scanning electron microscopy (SEM) was used to examine eggs of spotted lanternfly (SLF), Lycorma delicatula (White) (Hemiptera: Fulgoridae), a pest recently invasive to the mid-Atlantic region of the [...] Read more.

Knowledge regarding egg morphology can aid the selection of postharvest fumigants for insect control. Accordingly, scanning electron microscopy (SEM) was used to examine eggs of spotted lanternfly (SLF), Lycorma delicatula (White) (Hemiptera: Fulgoridae), a pest recently invasive to the mid-Atlantic region of the United States. As the overwintering life stage of SLF, eggs are deposited on a variety of refugia, including many forestry products that can be distributed geographically via travel, commerce, and/or trade. For fumigation to control SLF, and potentially translate into a viable strategy for limiting the spread of SLF by subject pathways, the fumigant must permeate the chorion to react with biomolecules and/or disrupt cellular processes. SLF chorion was characterized by a porous network of aeropyles localized around the operculum, in cranial and caudal relation to the developing nymph, as well as an interstice between the operculum edge and the opercular rim. The confirmation of chorionic ultrastructure that allows for ready gas exchange warrants further investigation of fumigation efficacy, even for those “non-reactive” fumigants, such as phosphine and hydrogen cyanide, which must overcome the suppression of cellular processes coincident with overwintering. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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19 pages, 9501 KiB

Open AccessArticle

Integrating the Rate of Moisture Loss into Needle Retention Testing to Improve the Selection of Balsam Fir (Abies balsamea) for Use as Christmas Trees

by Joel D. Tremblay, Ronald F. Smith and Loïc D’Orangeville

Forests 2023, 14(8), 1626; https://doi.org/10.3390/f14081626 - 11 Aug 2023

Viewed by 1115

Abstract

A study was conducted to identify balsam fir (Abies balsamea) for use in Christmas tree breeding programs in Northeastern North America. A total of sixty-four phenotypically good trees were identified from a provincial clonal seed orchard in New Brunswick, a multi-aged [...] Read more.

A study was conducted to identify balsam fir (Abies balsamea) for use in Christmas tree breeding programs in Northeastern North America. A total of sixty-four phenotypically good trees were identified from a provincial clonal seed orchard in New Brunswick, a multi-aged natural seed production area in Nova Scotia, and an operational plantation in Quebec, Canada. Trees were selected for good growth and form, numbers, and vigour of internodal branches, acceptable crown taper, needle colour, age class, branch angle, needle configuration, and freedom from insects and diseases or deformities, all traits deemed desirable in a Christmas tree. Three branches from each tree were collected at two harvest dates each year, one early and one late during the normal harvesting season in 2020, 2021, and 2022. Qualitative assessments of colour and branch pliability were performed weekly in conjunction with needle loss rub tests. A quantitative assessment of moisture loss was conducted weekly by measuring branch weights. The combination of qualitative and quantitative assessments was used to identify 7 of the 64 trees for which one or more tested branches consistently remained green and pliable, retained the majority of their needles, and lost moisture at a significantly reduced rate in all six testing periods. Grafts of the seven ‘Select’ trees are currently being integrated into seed orchards in the three participating provinces. These second-generation seed orchards are part of breeding programs designed to develop Christmas trees that will perform well under warm fall conditions, an outcome of climate change. The results from this study combined with the progeny testing of the ‘Select’ trees will be used to test for the heritability of needle retention, a key trait for the next generation of Christmas trees in the Northeast. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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14 pages, 2513 KiB

Open AccessFeature PaperArticle

Top-Leader Growth in Nordmann Fir (Abies nordmanniana)

by Bjarke Veierskov

Forests 2023, 14(6), 1214; https://doi.org/10.3390/f14061214 - 12 Jun 2023

Viewed by 904

Abstract

The growth of the top-leader in Abies nordmanniana was measured over a 6-year period, and showed a consistent growth pattern, with an initial growth phase reaching a maximum growth rate that varied between 12.0 and 22.5 mm per day, and which could be [...] Read more.

The growth of the top-leader in Abies nordmanniana was measured over a 6-year period, and showed a consistent growth pattern, with an initial growth phase reaching a maximum growth rate that varied between 12.0 and 22.5 mm per day, and which could be correlated with the temperature in July of the previous year. The daily growth rate always peaked in the last week of June. In late-bud-breaking plants, the top-leader became short because of a low growth rate in this first phase of growth. In the second growth phase, the daily growth rate slowly declined, but was similar in all plants, regardless of the size of the top-leader when this phase began, and the timing of the bud break. The growth in the second growth phase was correlated with the precipitation in the period. Growth cessation occurred in the basal part of the top-leader soon after bud break, and progressed slowly apically, whereby the upper 25% of a young top-leader contributed to 50% of the final length, as growth in this section continued throughout the major part of the growth season. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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15 pages, 4581 KiB

Open AccessFeature PaperArticle

Developing Integrated Strategies to Address Emerging Weed Management Challenges in Christmas Tree Production

by Greta Gallina, Bert Cregg, Eric Patterson and Debalina Saha

Forests 2023, 14(5), 881; https://doi.org/10.3390/f14050881 - 25 Apr 2023

Viewed by 913

Abstract

Weed control is an important aspect during the first few years of Christmas tree establishment, as weed competition directly relates to the rate of Christmas tree growth during this time. The objectives of this study were to evaluate the weed control efficacy of [...] Read more.

Weed control is an important aspect during the first few years of Christmas tree establishment, as weed competition directly relates to the rate of Christmas tree growth during this time. The objectives of this study were to evaluate the weed control efficacy of organic mulch and herbicide combinations and to determine their phytotoxic effects on four different species of Christmas trees during the establishment stage: Fraser fir (Abies fraseri (Pursh) Poir), blue spruce (Picea pungens Engelm.), white pine (Pinus strobus L.), and Scotch pine (Pinus sylvestris L.). Twelve weed control treatments were established in a complete randomized block design with four replications in each of five fields. Weed control treatments included cypress bark organic mulch and herbicides applied alone and in combinations as well as an untreated control. Herbicides included clopyralid, oxyfluorfen, and glyphosate. All herbicides were applied at their highest labeled rate. Data collection included visual estimations of weed control and phytotoxicity to trees at 30, 60, and 90 days after treatment (DAT). Tree growth and foliar nitrogen concentration were also measured. Mulch combined with herbicide provided 60%–100% weed control in all cases; at two farms, mulch provided a significant increase in weed control when compared to the same treatments without mulch. Combinations of mulch + clopyralid + glyphosate and clopyralid + oxyfluorfen + glyphosate resulted in the highest phytotoxicity ratings. Tree growth was decreased due to some treatments at Gobles farm, and foliar N did not differ among any of the treatments. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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15 pages, 16270 KiB

Open AccessArticle

Genetic Variation among Somatic Embryo Clones of Nordmann Fir Grown as Christmas Trees

by Jing Xu and Ulrik Braüner Nielsen

Forests 2023, 14(2), 279; https://doi.org/10.3390/f14020279 - 31 Jan 2023

Viewed by 1278

Abstract

Somatic embryogenesis (SE) cloning techniques for Nordmann fir Christmas tree production have been pursued and refined in Denmark, and three SE clonal trials with 201 SE clones from seeds of 27 Nordmann fir trees and seedlings from bulk harvest seeds in Georgia, Caucasus, [...] Read more.

Somatic embryogenesis (SE) cloning techniques for Nordmann fir Christmas tree production have been pursued and refined in Denmark, and three SE clonal trials with 201 SE clones from seeds of 27 Nordmann fir trees and seedlings from bulk harvest seeds in Georgia, Caucasus, were established from 2014 to 2015. This study was the first to evaluate the genetic performance of these SE clones in different sites. In addition, the performance of SE clones and (zygotic) normal seedlings in the field was compared in this study. This study was based on three key groups of traits for Christmas tree production, measured 5 and 6 years after planting: growth, commercial tree quality, and disorder. Seedlings grew faster and had better Christmas tree quality than SE clones. There were significant family effects for all traits, indicating that a good family also produced good clones on average. Growth and disorder traits were under moderate genetic control, with estimated broad-sense heritability (H²) from 0.19 to 0.31 and from 0.20 to 0.28, respectively. Quality traits had low to moderate H², ranging from 0.09 to 0.24. Significant genotype-by-environment interactions were shown for Christmas tree quality, post-harvest needle retention, and branch angle, suggesting the importance of choosing the right clone at each site. There was no significant interaction in height among the years. Superior clones, compared to the unbred seed source, were identified by combining several important traits. Overall, the somatic clones were well established but had slower growth compared to standard seedlings. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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11 pages, 2725 KiB

Open AccessArticle

Managing Cone Formation and Leader Growth in Fraser Fir Christmas Tree Plantations with Plant Growth Regulators

by Bert Cregg, Dana Ellison-Smith and Riley Rouse

Forests 2023, 14(1), 25; https://doi.org/10.3390/f14010025 - 23 Dec 2022

Viewed by 1476

Abstract

Early cone formation is a consistent issue in Fraser fir Christmas tree plantations in the eastern United States. Growers must remove cones by hand, resulting in significant labor costs, as cones degrade the aesthetic value of Christmas trees. In this study, we conducted [...] Read more.

Early cone formation is a consistent issue in Fraser fir Christmas tree plantations in the eastern United States. Growers must remove cones by hand, resulting in significant labor costs, as cones degrade the aesthetic value of Christmas trees. In this study, we conducted two series of experiments in collaboration with several Christmas tree farms to determine the effectiveness of applying plant growth regulators (PGRs), specifically GA-inhibitors, in reducing cone formation and shoot growth in Fraser fir. In the first experiments we investigated the effectiveness of paclobutrazol, applied as a soil injection or as a foliar spray in reducing cone formation. The highest rate of soil application (300 mL of paclobutrazol per tree) reduced cumulative coning by approximately 38%. Leader growth control of soil applied paclobutrazol increased with application rate. In the second set of experiments, we compared four GA-inhibitors (paclobutrazol, chlormequat chloride, uniconazole-p, daminozide) applied as foliar sprays on coning and leader growth. Overall, paclobutrazol was the most effective compound for reducing coning and shoot growth. The results confirm earlier findings that application of GA-inhibitors can reduce, but not eliminate, coning. Likewise, PGR application can reduce shoot growth and possibly increase tree density but will not eliminate the need for shearing. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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13 pages, 3270 KiB

Open AccessArticle

Linking Changes in Fatty Acid Composition to Postharvest Needle Abscission Resistance in Balsam Fir Trees

by Gaye E. MacDonald, Rajasekaran R. Lada, Claude D. Caldwell, Chibuike C. Udenigwe and Mason T. MacDonald

Forests 2022, 13(5), 800; https://doi.org/10.3390/f13050800 - 20 May 2022

Cited by 1 | Viewed by 1515

Abstract

Balsam fir needle retention and fatty acid profile changes due to cold acclimation throughout autumn, but little is known about the relationship between these two phenomena. The objective was to examine differences in FAs in contrasting needle abscission resistant balsam fir genotypes throughout [...] Read more.

Balsam fir needle retention and fatty acid profile changes due to cold acclimation throughout autumn, but little is known about the relationship between these two phenomena. The objective was to examine differences in FAs in contrasting needle abscission resistant balsam fir genotypes throughout autumn and early winter. Branches from genotypes with low and high needle abscission resistance (NAR) were collected from September to January and analyzed for FA composition. High NAR genotypes retained needles 120–130% longer than low NAR genotypes and NAR increased through autumn in both genotypes. There was approximately a 3:1 ratio of unsaturated: saturated FAs, which increased by 4% in favor of unsaturated fatty acids through autumn. Palmitic, palmitoleic, and linolenic acid content was significantly higher in high NAR versus low NAR genotypes; arachidic, oleic, linoleic, pinolenic, coniferonic, icosadienoic, and sciadonic acids were lower in high NAR genotypes versus low. Linolenic acid was of particular interest because it tended to decrease throughout autumn, to the point that high NAR genotypes were significantly lower in linolenic acid than low NAR genotypes in January. These changes may be linked to an increase in abscisic acid and/or jasmonic acid synthesis depleting linolenic acid stores and promoting postharvest needle abscission resistance. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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11 pages, 3356 KiB

Open AccessCommunication

Controlling Leader Growth on Noble and Turkish Fir with S-ABA

by Chal Landgren, Bert Cregg, Riley Rouse and Judy Kowalski

Forests 2022, 13(2), 212; https://doi.org/10.3390/f13020212 - 31 Jan 2022

Cited by 2 | Viewed by 1995

Abstract

Control of leader growth in Christmas tree production is a critical and expensive component in developing quality trees. Producers typically hand trim leaders to a desired length. With noble and Turkish fir this practice frequently results in poor top development in the subsequent [...] Read more.

Control of leader growth in Christmas tree production is a critical and expensive component in developing quality trees. Producers typically hand trim leaders to a desired length. With noble and Turkish fir this practice frequently results in poor top development in the subsequent year. This study investigated the use of S-abscisic acid (S-ABA) at various rates up to 6% active ingredient (a.i.) to determine if the plant growth regulator provides predictable leader control with minimal phytotoxicity. S-ABA was effective in controlling leader extension of both noble fir and Turkish fir. Shoot growth of Turkish fir was slightly more sensitive to S-ABA than noble fir, and effective growth control was achieved at 2% a.i., versus 3% a.i. for noble fir. With Turkish fir, we achieved an 80–90% reduction in growth across all sites, depending on rate. For noble fir, we achieved a 67–88% growth reduction. The addition of a surfactant did not increase the effectiveness of S-ABA for growth control and is not recommended. Repeating S-ABA applications 2 weeks after initial application resulted in a slight increase in growth control and phytotoxicity compared to a single application at the same rate. The results suggest that S-ABA can be an effective tool in Christmas tree production to control leader growth on fir species that often produce crooked or multiple leaders in response to conventional leader pruning. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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Review

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19 pages, 748 KiB

Open AccessReview

A Review of Chemical Weed Control Practices in Christmas Tree Production in the United States

by Greta C. Gallina, Bert M. Cregg, Eric L. Patterson and Debalina Saha

Forests 2022, 13(2), 250; https://doi.org/10.3390/f13020250 - 06 Feb 2022

Cited by 1 | Viewed by 2370

Abstract

Christmas trees are sensitive to weed competition, especially during establishment. In initial stages of the tree crop, weeds can utilize available soil moisture and trees may succumb to drought stress. In later stages, weeds can even interfere with production practices. Non-chemical weed control [...] Read more.

Christmas trees are sensitive to weed competition, especially during establishment. In initial stages of the tree crop, weeds can utilize available soil moisture and trees may succumb to drought stress. In later stages, weeds can even interfere with production practices. Non-chemical weed control methods alone may not provide effective weed control. Chemical weed management strategies involve the use of preemergence and postemergence herbicides at the right timing and application rates. There are many herbicides that are used in Christmas tree production in the United States, and each has specific application guidelines and weed control spectra. Moreover, crop trees vary in tolerance by species and tree age. Growers need to be careful while applying herbicides as many of these chemicals can cause injury to Christmas trees. Repeated application of herbicides with the same mechanism of action has resulted in development of herbicide resistance among several weed species. Managing herbicide resistance has now become an important issue. More research is required on identifying and managing herbicide resistance among weed species in Christmas tree production. Future research needs to focus on herbicide and mulch combinations, herbicide rotations, and tank mixing different herbicides with different mechanisms of actions and how these affect Christmas tree varieties. Full article

(This article belongs to the Special Issue Culture, Plant Health, and Genetics of Christmas Trees in Changing Climate)

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