Walnut Twig Beetle (Coleoptera: Curculionidae: Scolytinae) Colonization of Eastern Black Walnut Nursery Trees

Abstract Phytosanitary treatments for logs and barked wood products are needed to mitigate the spread of thousand cankers disease through the movement of these commodities. The disease threatens eastern black walnut (Juglans nigra L.) populations in the United States. It is caused by repeated attacks by the walnut twig beetle (Pityophthorus juglandis Blackman) and subsequent canker development caused by the fungal pathogen Geosmithia morbida M. Kolařík et al. Methyl bromide (MB) fumigations were evaluated for efficacy against P. juglandis and G. morbida in J. nigra bolts. Fumigation with 82 mg/L MB for 24 h at 4.5° C eliminated P. juglandis in J. nigra, but was ineffective against G. morbida. Subsequent experiments focused on eliminating G. morbida, but results were inconclusive because of low rates of pathogen recovery from naturally infested control bolts. Final experiments used J. nigra bolts artificially inoculated with G. morbida. Fumigations with 240 and 320 mg/L MB for 72 h at 10° C were effective in eliminating G. morbida from J. nigra bolts. Results confirm that the USDA fumigation treatment schedule for logs with the oak wilt pathogen will also mitigate the risk of spreading the thousand cankers disease vector and pathogen by movement of walnut bolts and wood products.

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USE OF MICROSATELLITE MARKERS TO DEVELOP NEW EASTERN BLACK WALNUT CULTIVARS IN MISSOURI, USA

Acta Horticulturae ◽

10.17660/actahortic.2011.918.27 ◽

2011 ◽

pp. 221-226 ◽

Cited By ~ 3

Author(s):

M.V. Coggeshall

Keyword(s):

Microsatellite Markers ◽

Black Walnut ◽

Eastern Black Walnut

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Black Walnut (Juglans nigra L.) Agroforestry – Its Design and Potential as a Land-use Alternative

The Forestry Chronicle ◽

10.5558/tfc67213-3 ◽

1991 ◽

Vol 67 (3) ◽

pp. 213-218 ◽

Cited By ~ 17

Author(s):

H. E. Garrett ◽

J. E. Jones ◽

W. B. Kurtz ◽

J. P. Slusher

Keyword(s):

Cover Crops ◽

Management Practices ◽

Black Walnut ◽

Early Years ◽

Specialty Crops ◽

Christmas Trees ◽

Investment Returns ◽

Nut Production ◽

Economic Analyses ◽

Eastern Black Walnut

Integrated forestry-farming (agroforestry) management typically involves the planting of trees at a wide spacing with intercrops grown in alleys between trees. A program initiated in Missouri, USA in 1965 establishes eastern black walnut on a 40- × 10-foot spacing with row intercrops (wheat, milo, soybeans etc.) for the first 10-to-12 years followed by cover crops of cool-season forages thereafter. Specialty crops of Christmas trees, balled and burlapped landscaping species, small berry crops and vegetables are also grown during the early years of plantation establishment. Contrary to conventional management of black walnut, short, clear boles (8 to 16 feet in length) with large full crowns for nut production are developed for maximization of profits. Economic analyses show the highest investment returns associated with management practices combining nut and wood production within an agroforestry regime. Key words: Forestry-farming, agroforestry, eastern black walnut, economics

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Discovery of Walnut Twig Beetle, Pityophthorus juglandis, Associated with Forested Black Walnut, Juglans nigra, in the Eastern U.S.

Forests ◽

10.3390/f5061185 ◽

2014 ◽

Vol 5 (6) ◽

pp. 1185-1193 ◽

Cited By ~ 13

Author(s):

Gregory Wiggins ◽

Jerome Grant ◽

Paris Lambdin ◽

Paul Merten ◽

Katheryne Nix ◽

...

Keyword(s):

Black Walnut ◽

Juglans Nigra ◽

Pityophthorus Juglandis ◽

Walnut Twig Beetle

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De novo genome assembly of Geosmithia morbida, the causal agent of thousand cankers disease

10.7287/peerj.preprints.1671v1 ◽

2016 ◽

Author(s):

Taruna Aggarwal ◽

Anthony Westbrook ◽

Kirk Broders ◽

Keith Woeste ◽

Matthew D MacManes

Keyword(s):

Genome Assembly ◽

Fungal Pathogens ◽

De Novo ◽

Draft Genome ◽

Black Walnut ◽

De Novo Genome Assembly ◽

Evolutionary Mechanisms ◽

Geosmithia Morbida ◽

Thousand Cankers Disease ◽

Walnut Twig Beetle

Geosmithia morbida is a filamentous ascomycete that causes Thousand Cankers Disease in the eastern black walnut tree. This pathogen is commonly found in the western U.S.; however, recently the disease was also detected in several eastern states where the black walnut lumber industry is concentrated. G. morbida is one of two known phytopathogens within the genus Geosmithia, and it is vectored into the host tree via the walnut twig beetle. We present the first de novo draft genome of G. morbida. It is 26.5 Mbp in length and contains less than 1% repetitive elements. The genome possesses an estimated 6,273 genes, 277 of which are predicted to encode proteins with unknown functions. Approximately 31.5% of the proteins in G. morbida are homologous to proteins involved in pathogenicity, and 5.6% of the proteins contain signal peptides that indicate these proteins are secreted. Several studies have investigated the evolution of pathogenicity in pathogens of agricultural crops; forest fungal pathogens are often neglected because research efforts are focused on food crops. G. morbida is one of the few tree phytopathogens to be sequenced, assembled and annotated. The first draft genome of G. morbida serves as a valuable tool for comprehending the underlying molecular and evolutionary mechanisms behind pathogenesis within the Geosmithia genus. Keywords: de novo genome assembly, pathogenesis, forest pathogen, black walnut, walnut twig beetle.

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Ambered Kernels in Stenospermocarpic Fruit of Eastern Black Walnut

HortScience ◽

10.21273/hortsci.49.9.1142 ◽

2014 ◽

Vol 49 (9) ◽

pp. 1142-1147

Author(s):

Michele R. Warmund ◽

J.W. Van Sambeek

Keyword(s):

Shoot Apex ◽

Root Apex ◽

Growing Season ◽

Black Walnut ◽

Juglans Nigra ◽

Embryo Axis ◽

Successive Sampling ◽

Ambient Temperatures ◽

High Incidence ◽

Eastern Black Walnut

“Ambers” is a term used to describe poorly filled, shriveled eastern black walnut (Juglans nigra L.) kernels with a dark brown or black-colored pellicle that are unmarketable. Studies were conducted to determine the incidence of ambered black walnut kernels and to ascertain when symptoms were apparent in specific tissues. The occurrence of ambered kernels was evaluated in fruit harvested from mature ‘Football’ trees growing at three sites within a commercial black walnut orchard in 2008 to 2010. Mature walnut fruit sampled from trees at Site 2 had greater odds for ambered kernels than those on trees at two other sites within the same orchard with 27% of the walnuts sampled exhibiting symptoms when examined in October. Also, black walnut fruit in 2010 had more ambered kernels than those examined in Oct. 2008 or 2009. Cropload, soil type, ambient temperatures, or precipitation was not apparently associated with a high incidence of ambered kernels. When black walnut fruit from trees at Site 2 were examined from 25 June to 6 Oct. 2011, embryos were visible in 50% of the fruit without discoloration on the first date. Stenospermocarpy (e.g., aborted or rudimentary embryos after fertilization) was observed in fruit with discolored or ambered kernels as early as 7 July. Stenospermocarpic fruit with ambered kernels had shorter embryo axis lengths (root apex to shoot apex) than fruit with non-ambered kernels on 7 July and at successive sampling dates. Cotyledon widths of ambered kernels in stenospermocarpic fruit were narrower than those of non-ambered kernels on 21 July, but symptomatic cotyledons continued to enlarge until 15 Sept. All fruit enlarged during the growing season and nut diameters varied by only 3.4 mm at harvest. Thus, visible embryo degeneration, which was associated with ambered kernels in black walnut fruit, was detected in early July when shell hardening occurs and kernel tissues are enlarging.

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Eastern Black Walnut (Juglans nigra L.) Originating From Native Range Varies in Their Response to Inoculation With Geosmithia morbida

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2021.627911 ◽

2021 ◽

Vol 4 ◽

Author(s):

Rachael A. Sitz ◽

Emily K. Luna ◽

Jorge Ibarra Caballero ◽

Ned A. Tisserat ◽

Whitney S. Cranshaw ◽

...

Keyword(s):

United States ◽

Genetic Resistance ◽

Common Garden ◽

The United States ◽

Black Walnut ◽

Native Range ◽

Management Options ◽

Improvement Program ◽

Geosmithia Morbida ◽

Walnut Twig Beetle

Thousand cankers disease (TCD) is caused by the walnut twig beetle (Pityophthorus juglandis) vectoring the fungal canker pathogen Geosmithia morbida, which can result in severe dieback and eventual death to species of walnut (Juglans spp.) and wingnut (Pterocarya spp.). This disease is most devastating to the highly valued species J. nigra (black walnut). This species is primarily grown and harvested for timber production in the Central Hardwood Region of the United States, which comprises part of its native range. Management options for TCD are limited; therefore, finding resistant genotypes is needed. Initial studies on black walnut susceptibility to G. morbida documented some genetic variation and suggested potential resistance. Furthermore, G. morbida is thought to be native to the United States, which may have allowed for co-evolution. To capture the representative genetic diversity and screen for resistance to G. morbida, J. nigra families were collected from across the native range. These wild trees, in conjunction with seedlings developed in a black walnut timber improvement program, were planted in a common garden in Fort Collins, Colorado and repeatedly inoculated with G. morbida over the course of four years and three growing seasons. Improved seedlings exhibited larger cankered areas than wild J. nigra of the same provenance. Cankers induced by G. morbida in wild germplasm were smaller on J. nigra collected from the western and central portions of the native range compared to those collected from the eastern portion. Although trees from the western and central part of the range still incurred cankers, our findings indicate that variation in genetic resistance to G. morbida is present in black walnut. This study was performed with G. morbida independent of the walnut twig beetle, but our results suggest the limited G. morbida resistance observed in J. nigra will prevent the full compromise of black walnut to TCD. Results from this study should be taken into consideration in future black walnut breeding programs.

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Luther Burbank’s Contributions to Walnuts

HortScience ◽

10.21273/hortsci.50.2.201 ◽

2015 ◽

Vol 50 (2) ◽

pp. 201-204 ◽

Cited By ~ 1

Author(s):

John E. Preece ◽

Gale McGranahan

Keyword(s):

San Francisco ◽

Black Walnut ◽

Thin Shells ◽

White Meat ◽

High Quality ◽

Persian Walnut ◽

Soft Shell ◽

Juglans Hindsii ◽

Very High ◽

Eastern Black Walnut

Luther Burbank began making controlled crosses between walnut species in the late 19th century after hearing about a “supposed natural European hybrid walnut.” He crossed Juglans hindsii (northern California black walnut) × J. regia (Persian walnut) and produced progeny that he named ‘Paradox’ because of its extremely fast growth and other “anomalies.” He also crossed two American species, J. hindsii × J. nigra (eastern black walnut), producing ‘Royal’ walnut progeny that were fast-growing and prolific nut producers. A third interspecific hybrid was a cross between J. ailantifolia (Japanese walnut) × J. regia that resulted in extremely vigorous progeny but was not named. He observed segregation in the F2 populations and described giants and dwarfs as reversions to ancestral forms. Luther Burbank also made selections for walnut scion cultivars and was especially interested in thin-shelled nuts. He collected seeds from a J. regia growing in San Francisco because it produced regularly and had very high-quality nuts with relatively thin but poorly sealed shells. He selected one of its seedlings as ‘Santa Rosa Soft-Shell’ and described it as bearing large crops of nuts that were nearly white with thin shells and delicious white meat. Burbank’s contributions to the walnut industry endure to this day, especially through the widespread use of seedling and clonal ‘Paradox’ walnut rootstocks.

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