Drought legacies in mixed Mediterranean forests: Analysing the effects of structural overshoot, functional traits and site factors.

Previous favorable climate conditions stimulate tree growth making some forests more vulnerable to hotter droughts. This so-called structural overshoot may contribute to forest dieback, but there is little evidence on its relative importance depending on site conditions and tree species because of limited field data. Here, we analyzed remote sensing (NDVI) and tree-ring width data to evaluate the impacts of the 2017 drought on canopy cover and growth in mixed Mediterranean forests (Fraxinus ornus, Quercus pubescens, Acer monspessulanum, Pinus pinaster) located in southern Italy. Legacy effects were assessed by calculating differences between observed and predicted basal area increment (BAI). Overall, the growth response of the study stands to the 2017 drought was contingent on site conditions and species characteristics. Most sites presented BAI and canopy cover reductions during the drought. Growth decline was followed by a quick recovery and positive legacy effects, particularly in the case of F. ornus. However, we found negative drought legacies in some species (e.g., Q. pubescens, A. monspessulanum) and sites. In those sites showing negative legacies, high growth rates prior to drought in response to previous wet winter-spring conditions may have predisposed trees to drought damage. Vice versa, the positive drought legacy found in some F. ornus site was linked to post-drought growth release due to Q. pubescens dieback and mortality. Therefore, we found evidences of structural drought overshoot, but it was restricted to specific sites and species. Our findings highlight the importance of considering site settings such as stand composition, pre-drought conditions and different tree species when studying structural overshoot. Droughts contribute to modify the composition and dynamics in mixed forests.

Leaf functional traits differentiation in relation to covering materials of urban tree pits.

BACKGROUND: Understanding the ecological strategies of urban trees to the urban environment is crucial to the selection and management of urban trees. However, it is still unclear whether urban tree pit cover will affect plant functional traits. Here, we study the response of urban trees to different tree pit covers, analyzed the effects of different cover types on soil properties and their trade-off strategies based on leaf functional traits. RESULTS: We found that there were obvious differences in the physical properties of the soil in different tree pit covers. Under the different tree pit cover types, soil bulk density and soil porosity reached the maximum under cement cover and turf cover, respectively. We found that tree pit cover significantly affected the leaf properties of urban trees. Leaf thickness, chlorophyll content index and stomatal density were mainly affected by soil bulk density and non-capillary porosity in a positive direction, and were affected by soil total porosity and capillary porosity in a negative direction. Leaf dry matter content and stomata area were mainly negatively affected by soil bulk density and non-capillary porosity, and positively affected by soil total porosity and capillary porosity. Covering materials of tree pits promoted the functional adjustment of plants and form the best combination of functions. CONCLUSION: Under the influence of tree pit cover, plant have low specific leaf area, stomata density, high leaf thickness, chlorophyll content index, leaf dry matter content, leaf tissue density and stomata area, which belong to "quick investment-return" type in the leaf economics spectrum.

Establishment of the technology of cambial meristematic cells (CMCs) culture from shoots and high expression of FmPHV (PHAVOLUTA) functions in identification and differentiation of CMCs and promoting the shoot regeneration by hypocotyl in Fraxinus mandshurica.

In Fraxinus mandshurica, we successfully isolated and identified the loose, uniform and creamy-white cambial meristematic cells (CMCs) from newborn shoots, and established a culture technology for induction, proliferation and differentiation of CMCs. In this technology, higher induction rate (83.0%, 0.57-fold to the control) was obtained by an effective pretreatment after 28-day induction culture, CMCs can be better proliferation cultured than common calli and maintain same growth states after several times of cultures and 3.3% CMCs primarily realized differentiation. Gene expressions in the differentiated CMCs revealed that, low expression of FmWOX5 (regulator in establishment of competence for shoot formation, 0.09-fold to the control) and high expressions of FmWOX4 (cambium stem cell regulator, 16.7-fold to the control) and 9 key genes in shoot regeneration (2.4-fold-72.1-fold to the control) function in CMCs differentiation. In addition to the function of high expression of PHAVOLUTA (FmPHV) in CMCs differentiation (5.4-fold-157.3-fold to undifferentiated CMCs), functions of high expression of FmPHV in CMCs identification (22.4-fold to common calli) and generating more shoots (2.3-fold to the control) by significantly changing expressions of key regulators in HD-Zip Class III related shoot regeneration networks in positive transgenic plants through the hypocotyl transforming system in F. mandshurica, were further revealed. These works were of profound significance in providing the culture technology of CMCs from newborn shoots in F. mandshurica for the first time and revealing the positive functions of FmPHV in CMCs identification and differentiation in F. mandshurica and promoting the shoot regeneration by hypocotyls.

The invasive forest pathogen Hymenoscyphus fraxineus boosts mortality and triggers niche replacement of European ash (Fraxinus excelsior).

Determining the impacts of invasive pathogens on tree mortality and growth is a difficult task, in particular in the case of species occurring naturally at low frequencies in mixed stands. In this study, we quantify such effects by comparing national forest inventory data collected before and after pathogen invasion. In Norway, Fraxinus excelsior is a minor species representing less than 1% of the trees in the forests and being attacked by the invasive pathogen Hymenoscyphus fraxineus since 2006. By studying deviations between inventories, we estimated a 74% higher-than-expected average ash mortality and a 13% slower-than-expected growth of the surviving ash trees, indicating a lack of compensation by the remaining ash. We could confidently assign mortality and growth losses to ash dieback as no mortality or growth shifts were observed for co-occurring tree species in the same plots. The mortality comparisons also show regional patterns with higher mortality in areas with the longest disease history in Norway. Considering that ash is currently mostly growing in mixed forests and that no signs of compensation were observed by the surviving ash trees, a significant habitat loss and niche replacement could be anticipated in the mid-term.

Environmental drivers interactively affect individual tree growth across temperate European forests.

Forecasting the growth of tree species to future environmental changes requires a better understanding of its determinants. Tree growth is known to respond to global-change drivers such as climate change or atmospheric deposition, as well as to local land-use drivers such as forest management. Yet, large geographical scale studies examining interactive growth responses to multiple global-change drivers are relatively scarce and rarely consider management effects. Here, we assessed the interactive effects of three global-change drivers (temperature, precipitation and nitrogen deposition) on individual tree growth of three study species (Quercus robur/petraea, Fagus sylvatica and Fraxinus excelsior). We sampled trees along spatial environmental gradients across Europe and accounted for the effects of management for Quercus. We collected increment cores from 267 trees distributed over 151 plots in 19 forest regions and characterized their neighbouring environment to take into account potentially confounding factors such as tree size, competition, soil conditions and elevation. We demonstrate that growth responds interactively to global-change drivers, with species-specific sensitivities to the combined factors. Simultaneously high levels of precipitation and deposition benefited Fraxinus, but negatively affected Quercus' growth, highlighting species-specific interactive tree growth responses to combined drivers. For Fagus, a stronger growth response to higher temperatures was found when precipitation was also higher, illustrating the potential negative effects of drought stress under warming for this species. Furthermore, we show that past forest management can modulate the effects of changing temperatures on Quercus' growth; individuals in plots with a coppicing history showed stronger growth responses to higher temperatures. Overall, our findings highlight how tree growth can be interactively determined by global-change drivers, and how these growth responses might be modulated by past forest management. By showing future growth changes for scenarios of environmental change, we stress the importance of considering multiple drivers, including past management and their interactions, when predicting tree growth.

Analysis of Fraxinus pollen seasons and forecast models based on meteorological factors.

INTRODUCTION AND OBJECTIVE: The timings of Fraxinus and Betula flowering and pollen release overlap, which may cause increased allergic reactions in sensitive people. The aim of the present study was to characterize Fraxinus pollen seasons in Lublin (central-eastern Poland) and to identify meteorological factors that most determine the occurrence of airborne pollen of this taxon, as well as obtain forecast models for the basic characteristics of the pollen season. MATERIAL AND METHODS: The study was conducted in Lublin during the period 2001-2016, employing the volumetric method. The seasons were compared by PCA (Principal Component Analysis). To determine relationships between meteorological conditions and the pattern of pollen seasons, regression analysis was used. Data for the period 2001-2015 were used to create forecast models by applying regression analysis, while the 2016 data served to verify these models. RESULTS: Season end date and seasonal peak date were characterized by the lowest variation. The biggest differences were found for peak value and total annual pollen sum. The average dates of occurrence of ash pollen grains in the air of Lublin were between 13 April 13 - 3 May 3, whereas, on average, the pollen peak date occurred on 23 April. The factor loading values for the PC1 variable indicate that it is most strongly correlated with peak value and total pollen sum, while the PC2 variable correlated with the pollen season start date and season duration (a negative correlation). Regression models were developed for the following pollen season characteristics: season start, end and duration, seasonal peak date, and total annual pollen sum. CONCLUSIONS: The fit of the forecast models was at the level of 62-94%. Analysis of the data showed that weather conditions mainly in February were important factors controlling the Fraxinus pollen season.

Experimental arid land afforestation in Central Anatolia, Turkey.

The afforestation of arid lands faces many challenges, and perhaps the most important key for success is choosing one or more species that are adapted well for local environmental conditions. We explored species that would be suitable for the steppe region of Central Anatolia. Intensive site preparation included ripping the subsoil (to 80 cm) and plowing the upper soil before planting seedlings of Elaeagnus angustifolia, Robinia pseudoacacia, Fraxinus angustifolia, and Pinus nigra were used as tree species. We also tested the success of several shrub species: Amygdalus orientalis, Calligonum polygonoides, and Spartium junceum. After five growing seasons, E. angustifolia showed the highest survival, with 80% of planted seedlings remaining. For the shrubs, A. orientalis was the most successful species with a 95% survival rate. Broad-leaved trees grew a cumulative average of 34 cm in height in 5 years, whereas P. nigra seedings grew only 9 cm. The greatest height growth occurred in the shrubs, with A. orientalis gaining 40 cm in height in 5 years. Overall, E. angustifolia and A. orientalis appeared best suited for afforestation in these areas. R. pseodoacacia and F. angustifolia may also be used as alternative species.

Seven-Year Evaluation of Insecticide Tools for Emerald Ash Borer in Fraxinus pennsylvanica (Lamiales: Oleaceae) Trees.

Emerald ash borer (EAB), Agrilus planipennis (Fairmaire; Coleoptera: Buprestidae), is decimating ash trees (Fraxinus spp.) in North America. Combatting EAB includes the use of insecticides; however, reported insecticide efficacy varies among published studies. This study assessed the effects of season of application, insecticide active ingredient, and insecticide application rate on green ash (Fraxinus pennsylvanica Marsh.) (Lamiales: Oleaceae) canopy decline caused by EAB over a 5- to 7-yr interval. Data suggested that spring treatments were generally more effective in reducing canopy decline than fall treatments, but this difference was not statistically significant. Lowest rates of decline (<5% over 5 yr) were observed in trees treated with imidacloprid injected annually in the soil during spring (at the higher of two tested application rates; 1.12 g/cm diameter at 1.3 m height) and emamectin benzoate injected biennially into the stem. All tested insecticides (dinotefuran, emamectin benzoate, and imidacloprid) under all tested conditions significantly reduced the rate of increase of dieback.

The leaf phenophase of deciduous species altered by land pavements.

It has been widely reported that the urban environment alters leaf and flowering phenophases; however, it remains unclear if land pavement is correlated with these alterations. In this paper, two popular deciduous urban trees in northern China, ash (Fraxinus chinensis) and maple (Acer truncatum), were planted in pervious and impervious pavements at three spacings (0.5 m × 0.5 m, 1.0 m × 1.0 m, and 2.0 m × 2.0 m apart). The beginning and end dates of the processes of leaf budburst and senescence were recorded in spring and fall of 2015, respectively. The results show that leaf budburst and senescence were significantly advanced in pavement compared to non-pavement lands. The date of full leaf budburst was earlier by 0.7-9.3 days for ash and by 0.3-2.3 days for maple under pavements than non-pavements, respectively. As tree spacing increases, the advanced days of leaf budburst became longer. Our results clearly indicate that alteration of leaf phenophases is attributed to land pavement, which should be taken into consideration in urban planning and urban plant management.

Optimizing Use of Girdled Ash Trees for Management of Low-Density Emerald Ash Borer (Coleoptera: Buprestidae) Populations.

Effective survey methods to detect and monitor recently established, low-density infestations of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), remain a high priority because they provide land managers and property owners with time to implement tactics to slow emerald ash borer population growth and the progression of ash mortality. We evaluated options for using girdled ash (Fraxinus spp.) trees for emerald ash borer detection and management in a low-density infestation in a forested area with abundant green ash (F. pennsylvanica). Across replicated 4-ha plots, we compared detection efficiency of 4 versus 16 evenly distributed girdled ash trees and between clusters of 3 versus 12 girdled trees. We also examined within-tree larval distribution in 208 girdled and nongirdled trees and assessed adult emerald ash borer emergence from detection trees felled 11 mo after girdling and left on site. Overall, current-year larvae were present in 85-97% of girdled trees and 57-72% of nongirdled trees, and larval density was 2-5 times greater on girdled than nongirdled trees. Low-density emerald ash borer infestations were readily detected with four girdled trees per 4-ha, and 3-tree clusters were as effective as 12-tree clusters. Larval densities were greatest 0.5 ± 0.4 m below the base of the canopy in girdled trees and 1.3 ± 0.7 m above the canopy base in nongirdled trees. Relatively few adult emerald ash borer emerged from trees felled 11 mo after girdling and left on site through the following summer, suggesting removal or destruction of girdled ash trees may be unnecessary. This could potentially reduce survey costs, particularly in forested areas with poor accessibility.

Effect of elevated atmospheric CO2 concentration on growth and leaf litter decomposition of Quercus acutissima and Fraxinus rhynchophylla.

The atmospheric carbon dioxide (CO2) level is expected to increase substantially, which may change the global climate and carbon dynamics in ecosystems. We examined the effects of an elevated atmospheric CO2 level on the growth of Quercus acutissima and Fraxinus rhynchophylla seedlings. We investigated changes in the chemical composition of leaf litter, as well as litter decomposition. Q. acutissima and F. rhynchophylla did not show differences in dry weight between ambient CO2 and enriched CO2 treatments, but they exhibited different patterns of carbon allocation, namely, lower shoot/root ratio (S/R) and decreased specific leaf area (SLA) under CO2-enriched conditions. The elevated CO2 concentration significantly reduced the nitrogen concentration in leaf litter while increasing lignin concentrations and carbon/nitrogen (C/N) and lignin/N ratios. The microbial biomass associated with decomposing Q. acutissima leaf litter was suppressed in CO2 enrichment chambers, while that of F. rhynchophylla was not. The leaf litter of Q. acutissima from the CO2-enriched chambers, in contrast with F. rhynchophylla, contained much lower nutrient concentrations than that of the litter in the ambient air chambers. Consequently, poorer litter quality suppressed decomposition.

Larval Survival and Growth of Emerald Ash Borer (Coleoptera: Buprestidae) on White Ash and White Fringetree Saplings Under Well-Watered and Water-Deficit Conditions.

Emerald ash borer (Agrilus planipennis Fairmaire) was recently found on a novel host in North America, white fringetree (Chionanthus virginicus L.) (Oleaceae). In this study, we artificially infested 4-yr-old, naïve white fringetree and white ash (Fraxinus americana L.) saplings under well-watered and water-deficit conditions with emerald ash borer eggs. We used physiological and phenotypical approaches to investigate both plant response to emerald ash borer and insect development at 21, 36, and 61 d postinfestation. Photosynthesis was reduced in both tree species by larval feeding, but not by water deficits. Emerald ash borer larvae established and survived successfully on white ash. Both establishment and survival were lower on white fringetree than on white ash. Larvae were larger, and had reached higher instars at all three time points on white ash than on white fringetrees. Larvae grew faster in white ash under water-deficit conditions; however, water-deficit conditions negatively impacted survival of larvae at 61 d postinfestation in white fringetrees, although head size did not differ among surviving larvae. White ash showed higher callus formation in well-watered trees, but no impact on larval survival was observed. In white fringetree, callus formation was not affected by water treatment, and was inversely related to larval survival. The higher rate of mortality and slow growth rate of larvae in white fringetree as compared to white ash suggest that populations of emerald ash borer may be sustained by white fringetree, but may grow more slowly than in white ash.

Climate change and the ash dieback crisis.

Beyond the direct influence of climate change on species distribution and phenology, indirect effects may also arise from perturbations in species interactions. Infectious diseases are strong biotic forces that can precipitate population declines and lead to biodiversity loss. It has been shown in forest ecosystems worldwide that at least 10% of trees are vulnerable to extinction and pathogens are increasingly implicated. In Europe, the emerging ash dieback disease caused by the fungus Hymenoscyphus fraxineus, commonly called Chalara fraxinea, is causing a severe mortality of common ash trees (Fraxinus excelsior); this is raising concerns for the persistence of this widespread tree, which is both a key component of forest ecosystems and economically important for timber production. Here, we show how the pathogen and climate change may interact to affect the future spatial distribution of the common ash. Using two presence-only models, seven General Circulation Models and four emission scenarios, we show that climate change, by affecting the host and the pathogen separately, may uncouple their spatial distribution to create a mismatch in species interaction and so a lowering of disease transmission. Consequently, as climate change expands the ranges of both species polewards it may alleviate the ash dieback crisis in southern and occidental regions at the same time.

Interplay of growth rate and xylem plasticity for optimal coordination of carbon and hydraulic economies in Fraxinus ornus trees.

Efficient leaf water supply is fundamental for assimilation processes and tree growth. Renovating the architecture of the xylem transport system requires an increasing carbon investment while growing taller, and any deficiency of carbon availability may result in increasing hydraulic constraints to water flow. Therefore, plants need to coordinate carbon assimilation and biomass allocation to guarantee an efficient and safe long-distance transport system. We tested the hypothesis that reduced branch elongation rates together with carbon-saving adjustments of xylem anatomy hydraulically compensate for the reduction in biomass allocation to xylem. We measured leaf biomass, hydraulic and anatomical properties of wood segments along the main axis of branches in 10 slow growing (SG) and 10 fast growing (FG) Fraxinus ornus L. trees. Branches of SG trees had five times slower branch elongation rate (7 vs 35 cm year-1), and produced a higher leaf biomass (P < 0.0001) and thinner xylem rings with fewer but larger vessels (P < 0.0001). On the contrary, we found no differences between SG and FG trees in terms of leaf-specific conductivity (P > 0.05) and xylem safety (Ψ50 ≈ -3.2 MPa). Slower elongation rate coupled with thinner annual rings and larger vessels allows the reduction of carbon costs associated with growth, while maintaining similar leaf-specific conductivity and xylem safety.

Effects of endophytic fungi on the ash dieback pathogen.

While Hymenoscyphus fraxineus causes dieback of the European ash (Fraxinus excelsior), flowering ash (F. ornus) appears resistant to the pathogen. To date, contributions of endophytic fungi to host resistance are unknown. The following hypotheses were tested: (i) endophytic fungi enhance the resistance of F. excelsior to the pathogen; (ii) resistance of F. ornus relies on its community of endophytic fungi. Two experiments were performed. (i) The effect of exudates of ash endophytes on the germination rate of H. fraxineus ascospores was studied in vitro Isolates of abundant Fraxinus leaf endophytes, such as Venturia fraxini, Paraconiothyrium sp., Boeremia exigua, Kretzschmaria deusta and Neofabraea alba inhibited ascospore germination. (ii) Ash seedlings inoculated in a climate chamber, with fungi sporulating on the previous year's leaf litter, were exposed to natural infections by the pathogen present in the forest. Non-inoculated seedlings were used as controls. Venturia spp. dominated the inoculated endophyte 'communities'. Subsequent exposure to H. fraxineus led to infection of F. excelsior leaves by the pathogen, but no differences in health status between pre-inoculated and non-inoculated seedlings were detected. Fraxinus ornus leaves experienced a low infection rate, independent of their colonization by endophytic fungi. These results did not support either hypothesis.

Sexually different morphological, physiological and molecular responses of Fraxinus mandshurica flowers to floral development and chilling stress.

Fraxinus mandshurica is considered a dioecious hardwood, and the temporal separation of the maturation of the male and female flowers is one reason that F. mandshurica has become an endangered species in China. Rainfall and low temperature influence pollen formation and dispersal and the blooming of female flowers. Therefore, low fertilization efficiency strongly influences the population of F. mandshurica. Nevertheless, few studies have investigated the sex-specific morphological, physiological and molecular differentiation of F. mandshurica during flowering and its responses to low temperature. In this study, we investigated the sexual differences in the morphological, physiological, and biochemical parameters of F. mandshurica during flowering and determined the physiological and biochemical parameters and expression levels of related genes in response to low-temperature stress induced by exposure to 4 °C (chilling stress) during pollen dispersal and fertilization. Our study supports the hypothesis that male flowers suffer more severe injuries while female flowers are more adaptable to environmental stress during flower development in F. mandshurica. The results showed higher physiological and biochemical levels of malondialdehyde, proline, and soluble sugar, as well as the expression of genes involved in calcium signaling, cold shock and DNA methylation in male flowers compared with female flowers, which suggested that male flowers suffer from more serious peroxidation than female flowers. In contrast, higher antioxidant capacity and FmaCAT expression were detected in female flowers, providing preliminary evidence that male flowers rapidly fade after pollination and further demonstrating that female flowers need a much stronger antioxidant enzyme system to maintain embryonic growth. Most peaks related to physiological and molecular responses were observed at 2-4 h and 8-10 h of exposure to chilling stress in the female and male flowers, respectively. This trend implies that female flowers have higher adaptability to low temperature during fertilization.

Cryotechniques for the Long-Term Conservation of Embryogenic Cultures from Woody Plants.

Since its development in the 1960s, plant cryopreservation is considered an extraordinary method of safe long-term conservation of biological material, as it does not induce genetic alterations and preserve the regeneration potential of the stored material. It is based on the storage of explants at cryogenic temperatures, such as the one of liquid nitrogen (-196 °C), where the metabolism within the cells is suspended; thus, the time for these cells is theoretically "stopped". Cryopreservation is particularly important for embryogenic cultures, as they require periodic subculturing for their maintenance, and this, in turn, increases the risk of losing the material, as well as its embryogenic potential. Periodic re-initiation of embryogenic cultures is possible; however, it is labor intensive, expensive, and particularly difficult when working with species for which embryogenic explants are available only during a limited period of the year. Among various methods of cryopreservation available for embryogenic cultures, slow cooling is still the most common approach, especially in callus cultures from softwood species. This chapter briefly reviews the cryopreservation of embryogenic cultures in conifers and broadleaf trees, and describes as well a complete protocol of embryogenic callus cryopreservation from common ash tree (Fraxinus excelsior L.) by slow cooling.

Lethal trap trees: a potential option for emerald ash borer (Agrilus planipennis Fairmaire) management.

BACKGROUND: Economic and ecological impacts of ash (Fraxinus spp.) mortality resulting from emerald ash borer (EAB) (Agrilus planipennis Fairmaire) invasion are severe in forested, residential and urban areas. Management options include girdling ash trees to attract ovipositing adult beetles and then destroying infested trees before larvae develop or protecting ash with a highly effective, systemic emamectin benzoate insecticide. Injecting this insecticide and then girdling injected trees a few weeks later could effectively create lethal trap trees, similar to a bait-and-kill tactic, if girdling does not interfere with insecticide translocation. We compared EAB larval densities on girdled trees, trees injected with the emamectin benzoate insecticide, trees injected with the insecticide and then girdled 18-21 days later and untreated controls at multiple sites. RESULTS: Pretreatment larval densities did not differ among treatments. Current-year larval densities were higher on girdled and control trees than on any trees treated with insecticide at all sites. Foliar residue analysis and adult EAB bioassays showed that girdling trees after insecticide injections did not reduce insecticide translocation. CONCLUSIONS: Girdling ash trees to attract adult EAB did not reduce efficacy of emamectin benzoate trunk injections applied ≥ 18 days earlier and could potentially be used in integrated management programs to slow EAB population growth.

[PATHOGENIC MIKO,- AND MICROFLORA OF FRAXINUS EXCELSIOR IN PODOLYA UKRAINE].

The article summarizes our research results of pathogenic myco- and microflora, as well as harmful entomofauna on European Ash. It is shown that the most common and harmful diseaseis tuberculosis (its causal agent--bacteria Pseudomonas syringae pv.savastanoi (Smith 1908), which affects trunks, branches, twigs and buds of European Ash. It describes a number of pathogens and representatives mikofitozov malicious entomofauna that by virtue of its activities significantly weaken the growth, development and underestimate the qualitative characteristics of wood European Ash.

Efficacy of Soil-Applied Neonicotinoid Insecticides for Long-term Protection Against Emerald Ash Borer (Coleoptera: Buprestidae).

Protection of green ash trees (Fraxinus pennsylvanica Marshall) from the emerald ash borer (EAB), Agrilus planipennis Fairmaire, by soil applications of neonicotinoids (imidacloprid, clothianidin, and dinotefuran) was tested at five locations between 2005 and 2013. Application rate and spring versus fall application dates were evaluated in tests with neighborhood street trees and in one plantation of 65 ash trees. Insecticide treatments of ash trees at all five sites were initiated as the leading edge of the EAB invasion began to kill the first ash trees at each location. Trees were treated and evaluated at each site for 4 to 7 yr. Spring applications of imidacloprid were more efficacious than fall applications. Application rates of 0.8 g a.i./cm dbh or greater per year gave a higher level of protection and were more consistent than rates of 0.56 g a.i./cm dbh per year or less. The number of years between the first observation of canopy loss due to EAB and death of most of the control trees varied from three to seven years among test sites, depending on how many non-treated ash trees were nearby.