Black Walnut Plantation Research Articles

Fungal, host andnon‐hostvolatiles modify attraction of the walnut twig beetle,Pityophthorus juglandis, to pheromone lures

AbstractThousand Cankers Disease (TCD) of walnut trees is caused by the pathogenic fungusGeosmithia morbidavectored by the walnut twig beetle (WTB)Pityophthorus juglandis. Monitoring efforts for WTB rely on pheromone‐baited traps, but lures are likely effective at attracting beetles only over short distances. Fungal‐derived kairomones may increase the efficacy of current lures, while additional volatiles may repel beetles from valuable trees.The objective of this study was to determine the extent to which fungal, host and non‐host volatiles modify the attraction of WTB to pheromone‐baited traps. A trapping study that combined fungal, host‐associated and non‐host compounds with WTB‐pheromone lures was conducted over three years in black walnut plantations experiencing a TCD outbreak in Walla Walla, WA.Traps baited with pheromone andG. morbidavolatiles (i.e., isoamyl and isobutyl alcohol) consistently attracted more WTB, while other fungal volatiles inconsistently increased attraction compared to those baited with pheromone lure alone. This is the first field study that demonstrates fungal volatiles can increase the attraction of a bark beetle to its pheromone in a hardwood system.One fungal (benzyl alcohol) and two additional volatiles (limonene, piperitone) repelled WTB from pheromone‐baited traps. Although limonene is known to repel WTB, this is the first demonstration that benzyl alcohol and piperitone repel a bark beetle.Fungal volatiles may increase the efficacy of monitoring efforts and may play an important role in management tactics for WTB, especially in detecting the introduction and establishment of nascent populations and protecting trees from colonizing beetles.

Genetic Identification of Hybrid Walnuts (Juglans × intermedia Carr.) in Hungary, the Hidden Potential for Future Breeding

The question of the hybrid walnut (Juglans × intermedia Carr.) is still under debate in the Central European region. There is not simply just an underutilization, rather, even the existence of these hybrid forms is not broadly accepted. On the contrary, there is an intensive cross-breeding activity in the western part of Europe resulting in commercially available hybrid clones. In Hungary, several individuals have been reported with intermediate morphology from different old black walnut plantations. Due to the lacking information, a preliminary study was conducted in order to prove the difference of these selected trees and to test the hybrid state. For this purpose, DNA fingerprinting was used by applying 13 simple sequence repeat (SSR) markers for the identification of 22 hybrid genotypes selected from one study plot. A comparative analysis with a reference sample set of the ‘parental’ species and other known hybrids was performed as well. The genetic analysis resulted distinct, unique genotypes for all of the samples. Based on the genetic pattern, the analyzed hybrid group was clearly distinguishable from the other two walnut groups. The result of this study also highlights the hidden potential in walnut breeding in the Central European region. Future concepts concerning hybrid walnut utilization in plantation forestry, agroforestry or as breeding material are also discussed.

Managing Thousand Cankers Disease in High-value Plantings of Black Walnut (Fagales: Juglandaceae) in Washington State

Abstract The health and productivity of black walnut (Juglans nigra L.) is currently threatened by Thousand Cankers Disease (TCD), a pest complex comprised of an insect vector, the walnut twig beetle (WTB) (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae), and associated pathogenic fungi (Geosmithia morbida Kolařík, Freeland, Utley, and Tisserat) (Hypocreales: Bionectriaceae). There is an urgent need for tools to manage TCD and avoid catastrophic losses in high-value plantations of black walnut. In this case study, we evaluated the efficacy of IPM strategies in three TCD-infested black walnut plantations in Walla Walla, WA. At the beginning of our study, average weekly captures of WTB per trap varied across sites; low (~32), moderate (~111), and high (>1,300). Each site received a separate management tactic: 1) girdled trap trees alone; 2) the insecticide emamectin benzoate alone or in combination with the fungicide propiconazole to protect healthy crop trees with superior form; and 3) the combination of girdled trap trees and chemically-protected crop trees. Walnut twig beetle populations remained at consistently low levels at both plantations after girdled trap trees were deployed. In plantations where crop trees were treated, the crown condition of those that received emamectin benzoate alone matched or exceeded that of trees treated with the combination of emamectin benzoate and propiconazole and the untreated control trees. Our findings suggest that using both trap trees and emamectin benzoate in an integrated approach has the most potential to reduce WTB populations and protect valuable crop trees in black walnut stands threatened by TCD.

Nitrogen Recovery from Enhanced Efficiency Fertilizers and Urea in Intensively Managed Black Walnut (Juglans nigra) Plantations

Intensively managed forest plantations often require fertilization to maintain site fertility and to improve growth and yield over successive rotations. We applied urea-based “enhanced-efficiency fertilizers” (EEF) containing 0.5 atom% 15N at a rate of 224 kg N ha−1 to soils under mid-rotation black walnut (Juglans nigra L.) plantations to track the fate of applied 15N within aboveground ecosystem components during the 12-month period after application. Treatments included Agrotain Ultra (urea coated with a urease inhibitor), Arborite EC (urea coated with water-soluble boron and phosphate), Agrium ESN (polymer-coated urea), uncoated urea, and an unfertilized control. Agrotain Ultra and Arborite EC increased N concentrations of competing vegetation within one month after fertilization, while neither Agrium ESN nor uncoated urea had any effect on competing vegetation N concentrations during the experiment. Agrotain Ultra and Arborite EC increased δ15N values in leaves of crop trees above those of controls at one and two months after fertilization, respectively. By contrast, Agrium ESN and uncoated urea had no effect on δ15N values in leaves of crop trees until three months after fertilization. Fertilizer N recovery (FNR) varied among ecosystem components, with competing vegetation acting as a sink for applied nutrients. There were no significant differences in FNR for all the urea-based EEF products compared to uncoated urea. Agrium ESN was the only EEF that exhibited controlled-release activity in this study, with other fertilizers behaving similarly to uncoated urea.

Black Walnut Alley Cropping Is Economically Competitive with Row Crops in the Midwest USA

The maize-soybean rotation (MSR) dominates the Midwest United States and degrades many ecological functions. Black walnut (Juglans nigra L.) plantation forestry (PF) and alley cropping (AC) are two alternative land-uses that can enhance productivity and restore ecosystem services. Given the lack of robust market mechanisms to monetize ecosystems services, we tested whether the profitability of PF and AC could drive adoption in the Midwest. Publically available data on black walnut soil suitability, timber prices, crop productivity, and cash rents were combined in a high-resolution spatial analysis to identify regions where these alternatives can outcompete MSR. To avoid selecting an arbitrary discount rate at which to make comparisons, we determined the threshold discount rate necessary to make PF or AC economically competitive with MSR. We show that, with a 5% discount rate, PF and AC could be more profitable on 17.0% and 23.4% of MSR land, respectively. Contrary to the common assumption that woody agricultural alternatives should first be adopted in row crop areas, the economic competitiveness of PF and AC was not correlated with MSR productivity. Instead, black walnut growth rate was the central driver of PF and AC competitiveness, underscoring a necessary shift away from the current MSR-centric perspective in defining target regions for land-use alternatives. Results reveal major opportunities for landowners and investors to increase profitability by investing in PF and AC on both marginal and productive MSR land.

Black walnut alley cropping is economically competitive with row crops in the Midwest USA.

The maize-soybean rotation (MSR) dominates the Midwest United States and degrades many ecological functions. Black walnut (Juglans nigra L.) plantation forestry (PF) and alley cropping (AC) are two alternative land-uses that can enhance productivity and restore ecosystem services. Given the lack of robust market mechanisms to monetize ecosystems services, we tested whether the profitability of PF and AC could drive adoption in the Midwest. Publically available data on black walnut soil suitability, timber prices, crop productivity, and cash rents were combined in a high-resolution spatial analysis to identify regions where these alternatives can outcompete MSR. To avoid selecting an arbitrary discount rate at which to make comparisons, we determined the threshold discount rate necessary to make PF or AC economically competitive with MSR. We show that, with a 5% discount rate, PF and AC could be more profitable on 17.0% and 23.4% of MSR land, respectively. Contrary to the common assumption that woody agricultural alternatives should first be adopted in marginal row crop areas, the economic competitiveness of PF and AC was not correlated with MSR productivity. Instead, black walnut growth rate was the central driver of PF and AC competitiveness, underscoring a necessary shift away from the current MSR-centric perspective in defining target regions for land-use alternatives. Results reveal major opportunities for landowners and investors to increase profitability by investing in PF and AC on both "marginal" and productive MSR land.

Carbon and Nitrogen Pools in Deep Soil Horizons at Different Landscape Positions

Core Ideas Total C and total N were greater at shoulder position for alfalfa than in the other two land uses. No observed differences for total C among land uses at backslope and footslope positions. Labile pools of C and N showed differences with land use and topographic positions. In general, labile C and N pools followed alfalfa > black walnut plantation > corn–soybean. Labile and bulk pools of carbon and nitrogen (C and N) play different functional roles in soil organic matter dynamics and nutrient cycling. The objectives of this study were to evaluate the (i) effects of land use [corn (Zea mays L.)–soybean [Glycine max (L.) Merr.], alfalfa (Medicago sativa L.), and black walnut (Juglans nigra L.) plantation] and (ii) vertical distribution of labile [potassium permanganate oxidizable carbon (POXC), water extractable organic carbon (WEOC), water extractable nitrogen (WEN)] and bulk [total carbon (TC), total nitrogen (TN)] pools of C and N in soil to a depth of 105 cm at different topographic positions within a watershed. Alfalfa had 10.02 to 14.86 Mg ha−1 greater TC than corn–soybean and black walnut plantation on the shoulder position in the surface horizon (0–15 cm), whereas the subsurface horizon (15–105 cm) showed no significant differences for TC measured at all topographic positions. Soil POXC was significantly higher in alfalfa than corn–soybean in the surface layer of 0 to 15 cm by 1748.6, 1904.03, and 2878.67 kg ha−1 at the shoulder, backslope, and footslope positions, respectively. However, no differences were observed for POXC at the shoulder position when all subsurface layers were combined at 15‐ to 105‐cm depth. In general, the labile pools of C and N showed differences with land use and topographic positions and followed alfalfa > black walnut plantation > corn–soybean. The study results suggest that for accurate assessment of land use on C and N gains and/or losses both bulk and labile pools should be measured including the entire root zone depth. Topographic differences should be accounted for assessing C and N pools at the watershed scale.

Seasonal Flight Patterns of Miridae (Hemiptera) in a Southern Illinois Black Walnut Plantation

Seasonal Flight Patterns of Miridae (Hemiptera) in a Southern Illinois Black Walnut Plantation

Seasonal Flight Patterns of Hemiptera (Excluding Miridae) in a Southern Illinois Black Walnut Plantation

Seasonal Flight Patterns of Hemiptera (Excluding Miridae) in a Southern Illinois Black Walnut Plantation

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 7. Miridae

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 7. Miridae

Seasonal and Vertical Distributions of Planthoppers (Homoptera: Fulgoroidea) Within a Black Walnut Plantation

Seasonal and Vertical Distributions of Planthoppers (Homoptera: Fulgoroidea) Within a Black Walnut Plantation

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 2. Coreoidea

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 2. Coreoidea

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 4. Cimicoidea

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 4. Cimicoidea

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 5. Lygaeoidea

Seasonal Flight Patterns of Hemiptera in a North Carolina Black Walnut Plantation. 5. Lygaeoidea

First Record of Thousand Cankers Disease Fungal Pathogen Geosmithia morbida and Walnut Twig Beetle Pityophthorus juglandis on Juglans regia in Europe.

Thousand cankers disease (TCD) is a disease complex caused by the fungus Geosmithia morbida Kolařik (Ascomycota, Hypocreales) and its vector Pityophthorus juglandis Blackman 1928 (Coleoptera, Scolytinae; walnut twig beetle, WTB). Since the mid-1990s, the disease was responsible for widespread mortality of many walnut species in the United States (4). After the first detection of TCD on black walnut (Juglans nigra L.) in Italy (3), an extensive survey was activated in cooperation with the Regional Phytosanitary Service. In May 2014, early TCD symptoms (4) were observed on English walnuts (J. regia L.). Canopies showed yellowing, wilting, and dieback of the youngest twigs, and a number of small brown cankers. Longitudinal and radial sections sampled through the cankers revealed gray to brown discoloration of both phloem and bark, and the presence of bark beetle galleries. Xylem discoloration was never observed. From one ~20-year-old European walnut growing in a garden neighboring an infected black walnut plantation (Santorso, Vicenza, 45°72' N, 11°40' E), a number of 1- to 2.5-cm-diameter twigs showing cankers up to 2 cm long surrounding bark beetle holes were collected. Whitish mycelium producing verticillate conidiophores was detected inside the insect galleries. From the necrotic margin of eight cankers previously surface-sterilized with 3% sodium hypochlorite, two 4-mm-wide chips per canker were placed on potato dextrose agar and incubated at 28 ± 1°C in the dark. Slow growing lobate, plane, yellowish-ocher colonies with hyaline mycelium appeared in 5 days. After subculturing to the same medium, growth features, mycelium, conidiophores, and conidia with morphological characteristics matching Kolarik's description of G. morbida (2) were observed. The ITS region of rDNA from the fungus strain LM14GM001-JR was amplified by using ITS1F and ITS4 primers and sequenced obtaining a 387-bp gene fragment. BLAST analysis showed 99% identity to the G. morbida strain U19 (GenBank Accession No. KF808301.1) for 384 bp, and 99% identity to the G. morbida strain LM13GM001-JN previously isolated from J. nigra in Italy (3). From the same samples, two emerging beetles were collected and identified as P. juglandis both morphologically (5) and genetically by DNA extraction following a standard salting out protocol. The barcode region of the mitochondrial gene cytochrome oxidase I was then amplified by using universal primers (1) and sequenced to obtain a 614-bp fragment of the gene. BLAST analysis showed 100% identity to P. juglandis based on comparison with KJ451422. A few other English walnuts with both the fungus and WTB were also found close to other infected black walnut plantations. To our knowledge, this is the first record of G. morbida and P. juglandis on J. regia in Europe, where the tree is cultivated for both fruit and timber production, as well as a traditional landscape tree. Voucher specimens are stored in the TeSAF herbarium and in the DAFNAE insect collection.

Nitrogen fertilization of black walnut (Juglans nigra L.) during plantation establishment. Physiology of production

Physiological mechanisms by which nitrogen (N) fertilization affects growth and development in temperate deciduous forest trees are not clearly understood, especially under intensive silvicultural systems. Grafted, Tippecanoe 1 cultivar black walnut (Juglans nigra L.) trees were grown in an intensively managed plantation in west-central Spain and subjected to six, fixed-nutrient-ratio complete fertilizer treatments (defined as 0, 25, 50, 75, 150, and 300 g N tree−1) delivered via daily fertigation. Leaf chemistry and morphology were evaluated from June to September, and gas exchange was measured in July. Specific leaf mass, leaflet nitrogen (N), and chlorophyll concentrations varied over the course of the growing season, yet consistently increased with increasing fertilization. Net photosynthesis at ambient (A net) and light-saturated (A max) conditions increased from the unfertilized control to lowest treatment (25 g N) but did not increase at higher fertilizer rates. Photosynthetic N and chlorophyll use efficiencies decreased with increasing fertilization, but photosynthetic phosphorus and water use efficiencies increased. Transpiration rates and dark respiration were not significantly affected by treatment. Overall, the lowest fertilizer treatment (25 g N) had the greatest photosynthetic efficiency. Interactions between N and other nutrients with increasing fertilizer application suggested potential for nutrient imbalances at high fertilization rates. Our results provide a physiological justification for the use of low-to-moderate fertilization as an efficient strategy to promote black walnut plantation establishment under intensive cultural systems.

Energy biomass from the low-investment fully mechanized thinning of hardwood plantations

Agroforestry practises can accrue significant benefits to farm owners and have a good potential for expansion worldwide. Among the many possible options, Black walnut plantations are especially popular in the Temperate zone, and are often based on the association with nurse trees, to be removed within the first two decades after establishment. The authors designed and tested two low-investment fully mechanized operations for producing chips or traditional firewood from the thinning of walnut plantations. The mechanized small-scale chipping operation incurred the lowest cost and offered a dramatic improvement over manual harvesting. On the other hand, mechanized firewood harvesting was financially less effective than traditional motor-manual operations. For the price levels assumed in this study, small-scale mechanized chipping offered higher profits than motor-manual firewood production all along the tree size range. Furthermore, chipping achieved a break even with smaller trees than firewood production, allowing for financially viable early thinning, timely performed before the nurse trees overtop the crop trees.

Stand growth models for more intensive management of Juglans nigra: A case study in Croatia

The study focuses on the development of stand growth models for more intensive management of black walnut (Juglans nigra L.) plantations in Croatia. In total, 48 plots were sampled (ages between 3 and 91 years) and, on average, 28.3 trees (between 17 and 43 trees) were measured [diameter at breast height (dbh), total height, two crown diameters, increment core] on each plot. Management scenarios with rotations of 50, 60, 70 and 80 years were developed under three different management regimes: conservative (CAS), high individual tree growth (HTGS) and high stand growth (HSGS). Indicators of competition (current annual increment in dbh, basal area and crown area) were used for scheduling thinning and the intensity of interventions for the intensive scenarios. Depending on the management options and rotation, final stand densities varied between 105 and 210 trees ha−1, mean dbh between 30.4 and 46.1 cm, and total heights between 25.9 and 29.5 m. The mean annual increment in total volume varied between 7.1 and 11.0 m3 ha−1 per year under different rotations and management options, yielding in total accumulated volume of 529–666 m3 ha−1. The CAS yielded the lowest and the HSGS the highest total volume, and HTGS yielded the highest mean dbh.

Planting black walnut in southern Ontario: midrotation assessment of growth, yield, and silvicultural treatments

We established 480 remeasurement plots in plantations originally laid out by F.W. von Althen in the 1970s and 1980s for his pioneering work on hardwood planting in southern Ontario. We used 110 of these plots to summarize the growth and yield of black walnut (Juglans nigra L.) plantations in southern Ontario. Overall, walnut growth averaged only 2.3 m3·ha–1·year–1, reflecting the less than optimal soil conditions at the majority of sites. However, good growth rates (i.e., >5 m3·ha–1·year–1) were recorded at sites with well-drained loamy soils, particularly when walnut was interplanted with other tree species. We also carried out a detailed analysis of four of the original experiments of F.W. von Althen to examine the long-term impacts of silvicultural treatments applied at an early stage in plantation development. Briefly, these analyses found (i) a significant long-term effect of controlling herbaceous competition at an early point in plantation development, although there is a suggestion that lower herbicide concentrations may be adequate in the long run, (ii) that fertilization effects, which were marginal at the time of application, were not apparent at age 32, (iii) generally better walnut growth when interplanted with other woody species, but autumn olive (Elaeagnus umbellata Thunb.), the species that stimulated the best walnut growth, grew invasively throughout the study area, thus ruling it out as a nurse species, and (iv) weak evidence that an initial spacing of 3 m × 3 m is optimal for walnut development in the absence of thinning up to age 30. This study provides rare insight into black walnut growth rates and best management practices in southern Ontario, although we recognize that the scope of these findings is limited by less than optimal soil conditions at many of the study sites.

Using Poultry Litter in Black Walnut Nutrient Management

ABSTRACT Poultry litter was evaluated as a fertilizer in a young (three-year-old) and an old (35-year-old) black walnut (Juglans nigra L.) plantation in southwest Missouri. The older planting had a fescue (Festuca arundinaceae Schreb.) ground cover that is grazed by cattle. In the young plantation, weeds were mowed and sprayed with herbicides once annually in the spring. Litter was applied at rates of 6.72 Mg ha− 1 and 13.44 Mg ha− 1for one year in the spring in the young plantation and at 8.96 Mg ha− 1 for two years in the spring and once in late summer in the older plantation. Height growth and leaf nitrogen (N) concentrations were improved during the summer following litter applications in the young plantation, but neither diameter growth nor nut production increased in the older plantation. Second-year height growth treatment differences for the young plantation were not significant. The number of nuts increased in the second year, but differences between treatments were not significant.