Impact Of Defoliation Research Articles

The role of rehabilitating and restoration the green dam in managing the impact of invasive forest pests in Algeria

The rehabilitation of Algeria’s "Green Dam" project, a large-scale reforestation initiative, represents a key strategy for mitigating climate change, especially in semi-arid regions. This study, conducted between 2021 to 2024 in the semi-arid region of Djelfa (Algeria), evaluates the impact of defoliators in three different stands. Our findings reveal that infestation levels were significantly lower in mixed-species stands compared to monoculture stands, with monoculture plantations showing the highest infestation rates. Seasonal analysis revealed consistent stability in rehabilitated zones, with lower infestation indices throughout the year. The study highlights the role of species diversity in enhancing forest resilience to pest outbreaks, as mixed-species plantations naturally disrupt pest population dynamics and support healthier ecosystems. These results highlight the effectiveness of Green Dam’s rehabilitation in enhancing ecosystem health, increasing biodiversity, and reducing vulnerability to climate-induced disturbances, positioning it as a critical tool for ecological restoration and climate mitigation in northern Algeria. Furthermore, the project exemplifies a scientifically driven approach to combating desertification and climate change in semi-arid ecosystems. By integrating tritrophic analyses examining forest species, pest insects, and their antagonists—along with spatiotemporal monitoring, the study provides valuable insights into ecological interactions under changing climatic conditions. As expanding defoliators and xylophages pose increasing challenges, adaptive management strategies tailored to semi-arid regions are necessary. The rehabilitation of the Green Dam project emerges as a model for large-scale ecological restoration, combining reforestation efforts with scientific innovation to bolster ecosystem resilience, enhance sustainable land management, and address global issues such as biodiversity loss, desertification, and climate instability. Continued monitoring and adaptive management are essential to ensure the long-term success of reforested landscapes.

Impact of mangrove defoliation by Hyblaea puera on diversity of associated crustaceans in the Dharamtar Estuary, Maharashtra, India

Mangrove defoliation, caused by teak defoliator moth (Hyblaea puera), has been reported in India and other countries. However, research on its impact on the associated fauna remains limited. We observed extensive mangrove defoliation from August to October 2019 in the Dharamtar Estuary, Maharashtra, India. Consequently, a study was conducted to assess the impact of this defoliation on the diversity of crustaceans within the mangroves and the surrounding estuarine waters. A total of 27 crustacean species were recorded in the mangrove region exhibiting reduced species richness and abundance during the mangrove defoliation period. Whereas, a total of 32 species of crustaceans were recorded from the estuarine region, where both species richness and abundance were higher during the defoliation period. These findings indicate that the crustaceans on the mangrove floor and in the estuarine waters responded differently to the changing environmental conditions caused by defoliation. Keywords: Crustaceans, Diversity, Estuary, Mangrove defoliation, Moth infestation

Effect of Defoliation on Growth, Yield and Forage Quality in Maize, as a Simulation of the Impact of Fall Armyworm (Spodoptera frugiperda)

This study assesses the impact of defoliation applied to three developmental stages across three cropping seasons from 2021 to 2023 on growth, yield and forage quality in maize. The experimental design included three treatments: defoliation of three expanded leaves at the 3rd–4th leaf stage (DF1), the 5th–6th expanded leaves by leaf punch (DF2) and expanding leaves with the DF2 treatment (DF3) at the 6th–7th leaf stages, compared with no defoliation (control). Over three years, the most significant decrease in dry matter (DM) yield occurred in DF1 during spring sowing, while in summer sowing, the largest reduction was in DF3, both of which were correlated with changes in the number of grains per ear. The DM yields at harvest were positively correlated with plant leaf areas at the silking stage. The digestibility of forage in in vitro DM decreased concomitantly with an increase in acid detergent fiber content, indicating a decrease in forage quality. Given the frequent severe damage observed in summer sown maize and the detrimental effects of early growth stage leaf feeding on quality and quantity of spring sown maize, the application of registered insecticides is advised to reduce pest damage to maize crops.

Impact of defoliation at the reproductive stage in different leaves of the soybean plant

Inadequate phytosanitary management can cause a significant reduction in the leaf area of soybean, which directly impacts its yield. The aim of this study was to evaluate the impact of defoliation in the lower, middle and upper leaves of the canopy, at three reproductive stages, on soybean yield, as a tool for improving phytosanitary management. The design was randomized blocks in 3x3+1 factorial scheme, with 4 replicates. The 10 treatments resulted from the combination of 3 defoliation positions on the plant (lower, middle and upper leaves) and 3 phenological stages of the crop (R1, R3 and R5), in addition to a control without defoliation. Morphological and production components and grain yield were evaluated. The data were subjected to analysis of variance and, when a significant difference was identified, the means were subjected to the Dunnett test. It was observed that plants showed a reduction in height in treatments with defoliation in the upper leaves at R1 and R3 stages. For the variables thousand-grain weight and grain yield there was difference only when defoliation was performed at the R5 stage in the upper leaves, resulting in a 16.6% loss in grain yield compared to the control. The soybean crop tolerates a defoliation level of 33.3% up to the R4 stage, in any of the leaves, without significant reduction in grain yield. Upper leaves, from the R5 stage, should be prioritized in the applications of phytosanitary products, which aim to reduce the damage caused by defoliation.

Heatwaves do not limit recovery following defoliation but alter leaf drought tolerance traits.

As heatwave frequency increases, they are more likely to coincide with other disturbances like insect defoliation. But it is unclear if high temperatures after defoliation impact canopy recovery or leaf traits which may affect response to further stressors like drought. To examine these stressor interactions, we subjected defoliated (DEF) and undefoliated (UNDEF) oak saplings to a simulated spring heatwave of +10°C for 25 days. We measured gas exchange, leaf area recovery, carbohydrate storage, turgor loss point (ΨTLP ), and minimum leaf conductance (gmin ). During the heatwave, stem respiration exhibited stronger thermal acclimation in DEF than UNDEF saplings, while stomatal conductance and net photosynthesis increased. The heatwave did not affect leaf area recovery or carbohydrate storage of DEF saplings, but reflush leaves had higher gmin than UNDEF leaves, and this was amplified by the heatwave. Across all treatments, higher gmin was associated with higher daytime stomatal conductance and a lower ΨTLP . The results suggest defoliation stress may not be exacerbated by higher temperatures. However, reflush leaves are less conservative in their water use, limiting their ability to minimise water loss. While lower ΨTLP could help DEF trees maintain gas exchange under mild drought, they may be more vulnerable to dehydration under severe drought.

Effects of Leaf Removal on Free and Glycoconjugate Aromas of Skins and Pulps of Two Italian Red Grapevine Varieties.

Leaf removal is a cultural practice mainly aimed at improving cluster zone microclimates and impacting primary and secondary metabolites, such as volatiles. This research aimed to assess the impact of defoliation on free and glycosylated aromas of a neutral ('Nebbiolo') and a semi-aromatic ('Aleatico') red variety. Defoliation was performed at fruit set (BBCH 71) and, for 'Nebbiolo', also at berries touch (BBCH 81) phenological stages. Skins and pulps were separately analyzed by Solid Phase Extraction-Gas Chromatography/Mass Spectrometry. Results showed that the response to defoliation was variety-dependent. For 'Nebbiolo', especially when performed at the berries' touch stage, defoliation had a significant effect on the accumulation of free volatiles and glycosidic precursors. Differently, free and bound 'Aleatico' volatiles were less impacted by defoliation. Interestingly, in both grapevine varieties, defoliation significantly enhanced the accumulation of aroma precursors in grapes' skins, which is of particular relevance for red wine production and their aging potential. Moreover, results could be helpful for the management of grape quality, as defoliation is currently considered as a strategy to address climate change issues.

Growth response of oaks to insect defoliation: Immediate and intermediate perspectives

In this study, we investigate the immediate and short-term consequences of defoliation by the spongy moth Lymantria dispar on secondary growth of oaks (Quercus robur L. and Quercus petraea (Matt.) Liebl.), including the interplay between defoliation and water availability during the defoliation period within a large-scale field experiment in south-eastern Germany. Furthermore, the impact of defoliation on oak secondary growth is explored retrospectively based on tree core measurements.Within the large-scale filed experiment, secondary growth of 880 oaks in 44 oak-dominated stands was monitored using permanent girth tapes over a three-year period following a spongy moth outbreak. Insecticide treatments were applied to half of the plots to obtain trees without defoliation, and canopy cover dynamics were subsequently monitored ground based and from satellites in all plots.We found that moth defoliation significantly reduced oak secondary growth by 10–60% during the outbreak year, with the impact on secondary growth being directly proportional to defoliation intensity. The negative impact of defoliation on secondary growth was aggravated by increased water availability during the outbreak year.In the post-outbreak year, secondary growth of oaks that had endured mild defoliation was no longer different from that of non-defoliated oaks. In contrast, oaks that had experienced substantial defoliation still exhibited a significant 10–30% reduction in secondary growth. Regardless of defoliation intensity, no further reduction in secondary growth was detected two years after the event compared to control trees. Our complementary retrospective analysis, utilizing core samples from oaks previously subjected to a defoliation event under distinct weather conditions, disclosed a strikingly analogous recovery of secondary growth from defoliation instigated by the spongy moth. Thus, validating that our experimental findings possess broad temporal transferability.

Insect infestations have an impact on the quality of climate reconstructions using Larix ring-width chronologies from the Tibetan plateau

Insect outbreaks are proven to harm trees, reducing their biomass accumulation due to the defoliation of leaves during the growing season. Various defoliators are responsible for the formation of extremely narrow tree rings in different tree species. In climate reconstructions based on tree-ring width, such narrow rings are often considered as noise, because their formation is not entirely caused by climatic conditions. Thus, the impact of defoliators should be removed (nullified) for unbiased climate reconstructions. This study mainly describes a statistical approach to disentangle the effects of Larch budmoth(LBM) (Zeiraphera diniana) and climate for an unbiased temperature reconstruction in the Bai-Ma mountain area in Southwest China using Larix potaninii. After applying our new approach, growth-climate relationships improved significantly (p < 0.05), especially with minimum temperature during the growing season (June-September). The resulting temperature reconstruction (BTmin) covers the period 1712–2020 CE (313 years). Our final temperature reconstruction for the Bai-Ma area showed a wiggly trend from 1712 to 1980, with some cool periods (1791–1853 and 1888–1930) and warm episodes (1724–1745, 1854–1887, 1950–1967). During the recent 50 years, BTmin reveal an alarming warming trend of up to 0.4 °C per decade. We also observed a strong coherency of BTmin with regional temperature series. Furthermore, we detected a differential effect of various climate modes, with the most substantial impact of the Atlantic Multidecadal Oscillation (AMO) on BTmin (p < 0.01). Interestingly, the Pacific Decadal Oscillation (PDO) showed a coupled effect along with AMO on BTmin. As revealed in this study, removing the LBM effect improved the chronology's climate sensitivity, leading to a more robust transfer function and in terms of insect infestations unbiased climate reconstructions. Thus, it is recommended to check ring-width data for any periodicity potentially related to insect outbreaks and correct the original data before using tree-ring chronologies for climate reconstruction.

Herbivory in southeastern Brazilian mangroves: An analysis of 11 years of litterfall monitoring

Severe defoliation of mangrove species is reported in several parts of the world. We analyzed the effect of a severe defoliation event resulting from the attack of a lepidopteran caterpillar (an insect outbreak) on the litterfall production. The attack occurred between 2009 and 2010 in a mangrove in southeastern Brazil. Leaf litter production by different mangrove species between 2008 and 2019, was considered in the analysis. The infestation directly affected the species Avicennia schaueriana Stapf & Leechm in all physiographic types assessed, with a decrease in leaf litter production between 43% and 86% since the monitoring began (2009) until the year when defoliation reached the maximum (2011). A decrease in the impact of defoliation was observed along the tidal flooding gradient, with more pronounced effects in forests located in the transition zone with the salt-flat, and progressive decrease towards fringe forests. In fringe and basin forests, leaf litter production by Laguncularia racemosa (L.) decreased between 52% and 67% between 2009 and 2011, respectively, and increased 30% in transition forests. Contrarily, the contribution of Rhizophora mangle (L.) increased 7% in basin, became noticeable in transition, and decreased by 25% in the fringe forests. The time required for A. schaueriana to recover the level of debris production was 8 years, and still reflect the effect of the severe, selective defoliation process on the dynamics and ecological succession of mangrove forests. A model that determines the stages of defoliation and their direct and indirect impacts on litter was developed.

Growth and Mortality of Hybrid Poplar Short Rotation Culture (AF8 Clone) in Response to Clostera anastomosis L. (Lepidoptera: Notodontidae) Defoliation

The increasing worldwide interest in renewable energy and carbon storage has led to the development of relatively fast solutions to obtain wood biomass. The cultivation of fast-growing tree species in short-rotation crops, such as hybrid poplar clones, is one such solution, at least in temperate areas. Sometimes these monocultures are affected by disturbing factors, including severe insect defoliation, with strong destructive effects. The impact of defoliation on the growth and productivity of poplar crops is often estimated in the context of artificial defoliation. There have been few studies in which the effect of defoliation was calculated after natural defoliation. Among defoliating insect species, Clostera anastomosis L. is one of the most important defoliators of young poplars. This species developed severe defoliation in a 4-year-old poplar clone AF8 crop, from the northeastern part of Romania, in the spring and summer of 2017. The study aimed to assess the impact of defoliation both on the growth and mortality of defoliated trees and the productivity of the affected crop. To reach this goal, the height and radial growth of 150 trees with different defoliation rates (50 non-defoliated, 50 partially defoliated, and 50 completely defoliated) were measured and the defoliation symptoms and mortality were also evaluated for 4780 poplars (10% of the analyzed population). The defoliation caused a significant decrease in the annual height growth (28.6% of the partially defoliated trees and 38.5% of the completely defoliated trees) and a severe decrease in the radial growth, between 82.2% and 90.4%, respectively, depending on the defoliation rate. These strong decreases led to a significant decline in tree-level biomass accumulation, approximately 74.8% for partially defoliated trees and 83.1% for completely defoliated trees, for the year of defoliation. As a result, the loss in total biomass (for the four years of the rotation) was between 28.1% and 34.6%, respectively, depending on the defoliation rate. Therefore, the total biomass loss was 5 t·ha−1, representing approximately 70% of the forecasted production for 2017 only (approximately 7 t·ha−1).

Early Defoliation Impact on Fruitset, Yield, Fruit Quality, and Cold Hardiness in ‘Chambourcin’ Grapevines

Several winegrape cultivars grown in cool climates, including Vitis sp. ‘Chambourcin’, are highly productive and require crop regulation to ensure timely fruit maturation and improved fruit quality. Balanced pruning and cluster thinning are the cultural practices used to attain the desired crop load in ‘Chambourcin’. However, crop reduction by cluster thinning is labor intensive, costly and typically not mechanized for winegrapes. In this study, the practice of early season leaf removal was investigated as an alternate tool to reduce crop level, thereby optimizing crop load and fruit quality in ‘Chambourcin’. The specific objectives were to determine the effects of the timing of leaf removal (pre-bloom, bloom, fruitset, no removal) on yield components, crop load, fruit composition, and cold hardiness. Leaf removal at pre-bloom and bloom reduced yield and crop load (Ravaz index) as compared to control (no defoliation). However, leaf removal did not impact fruit composition. Furthermore, defoliation at pre-bloom and bloom reduced bud cold injury during the dormant season. Therefore, early season leaf removal is a viable alternative to cluster thinning as a vineyard practice for yield regulation in ‘Chambourcin’ grapevines.

Root Secondary Metabolites in Populus tremuloides: Effects of Simulated Climate Warming, Defoliation, and Genotype.

Climate warming can influence interactions between plants and associated organisms by altering levels of plant secondary metabolites. In contrast to studies of elevated temperature on aboveground phytochemistry, the consequences of warming on root chemistry have received little attention. Herein, we investigated the effects of elevated temperature, defoliation, and genotype on root biomass and phenolic compounds in trembling aspen (Populus tremuloides). We grew saplings of three aspen genotypes under ambient or elevated temperatures (+4-6°C), and defoliated (by 75%) half of the trees in each treatment. After 4months, we harvested roots and determined their condensed tannin and salicinoid (phenolic glycoside) concentrations. Defoliation reduced root biomass, with a slightly larger impact under elevated, relative to ambient, temperature. Elevated temperature decreased condensed tannin concentrations by 21-43% across the various treatment combinations. Warming alone did not alter salicinoid concentrations but eliminated a small negative impact of defoliation on those compounds. Graphical vector analysis suggests that effects of warming and defoliation on condensed tannins and salicinoids were predominantly due to reduced biosynthesis of these metabolites in roots, rather than to changes in root biomass. In general, genotypes did not differ in their responses to temperature or temperature by defoliation interactions. Collectively, our results suggest that future climate warming will alter root phytochemistry, and that effects will vary among different classes of secondary metabolites and be influenced by concurrent ecological interactions such as herbivory. Temperature- and herbivory-mediated changes in root chemistry have the potential to influence belowground trophic interactions and soil nutrient dynamics.

Occurrence of arthropod pests associated with Brassica carinata and impact of defoliation on yield

AbstractBrassica carinata has the potential to become an economical biofuel winter crop in the Southeast U.S. An IPM program is needed to provide management recommendations for B. carinata in the region. This study serves as the first steps in the developing IPM tactics documenting pest occurrence, pest position within the canopy, and the impact of defoliation on B. carinata yield. The study was performed in Jay, FL, during the 2017–2018 and 2018–2019 winter/spring crop seasons. Pest species in B. carinata were documented by plant inspection within 16 genotypes of B. carinata, and the presence of insect pests in three canopy zones (upper, medium, and lower canopy) was documented. The defoliation impact on B. carinata was evaluated by artificial defoliation. Five levels of defoliation (2017–2018 crop season: 0%, 5%, 25%, 50%, and 100%; 2018–2019 crop season: 0%, 50%, 75%, 90%, and 100%) were artificially applied during vegetative, flowering, and pod formation stages of the commercial cultivar “Avanza64.” During the 2018–2019 crop season, two experiments were performed, a one‐time defoliation event and continuous defoliation. The plants were hand harvested and the average number of pods per plants, seeds per pod, thousand seed weight, and yield were estimated and correlated with defoliation levels. Results indicated the following species of pests associated with B. carinata: Microtheca ochroloma Stål (Coleoptera: Chrysomelidae), Plutela xylostella larvae, Pieris rapae L. (Lepidoptera: Pieridae), Diabrotica undecimpunctata Barber (Coleoptera: Chrysomelidae), Lipaphis pseudobrassicae Davis (Hemiptera: Aphididae), Leptoglossus phyllopus L. (Hemiptera: Coreidae), and Chloridea virescens F. (Lepidoptera: Noctuidae). The insect distribution within the plant canopy was not uniform. Different levels of artificial B. carinata defoliation did not affect seed weight, the number of seeds per pod, or the oil content of the seeds. The number of pods per plants and estimated yield were negatively impacted by defoliation during the vegetative and flowering stages.

Return of Lymantria dispar dispar (gypsy moth): A case report

An invasive moth, Lymantria dispar dispar, also known as the gypsy moth, originates from Europe and first came to Ontario, Canada, in 1969. The moth is a defoliator which feeds on oak and other deciduous trees, and less commonly, conifers. Outbreaks of Lymantria dispar dispar moth infestation occur every 7–10 years with rapid expansion of the population until there is a natural collapse due to pathogens and predators. In addition to the extensive environmental impact of defoliation of the tree canopy, the Lymantria dispar dispar moth larva (caterpillar) is responsible for causing a significant cutaneous eruption in exposed individuals. In our report, we describe six cases of Lymantria dispar dispar dermatitis which occurred in Ontario, Canada, in May of 2021. It is important for dermatologists to be aware of this potential diagnosis and to be aware of local infestation in affected areas.

Insect defoliation is linked to a decrease in soil ectomycorrhizal biomass and shifts in needle endophytic communities.

Insect outbreaks of increasing frequency and severity in forests are predicted due to climate change. Insect herbivory is known to promote physiological changes in forest trees. However, little is known about whether these plant phenotypic adjustments have cascading effects on tree microbial symbionts such as fungi in roots and foliage. We studied the impact of defoliation by the pine processionary moth in two infested Pinus nigra forests through a multilevel sampling of defoliated and non-defoliated trees. We measured tree growth, nutritional status and carbon allocation to chemical defenses. Simultaneously, we analysed the putative impact of defoliation on the needle endophytes and on the soil fungal communities. Higher concentrations of chemical defenses were found in defoliated trees, likely as a response to defoliation; however, no differences in non-structural carbohydrate reserves were found. In parallel to the reductions in tree growth and changes in chemical defenses, we observed shifts in the composition of needle endophytic and soil fungal communities in defoliated trees. Defoliated trees consistently corresponded with a lower biomass of ectomycorrhizal fungi in both sites, and a higher alpha diversity and greater relative abundance of belowground saprotrophs and pathogens. However, ectomycorrhizal alpha diversity was similar between non-defoliated and defoliated trees. Specific needle endophytes in old needles were strongly associated with non-defoliated trees. The potential role of these endophytic fungi in pine resistance should be further investigated. Our study suggests that lower biomass of ectomycorrhizal fungi in defoliated trees might slow down tree recovery since fungal shifts might affect tree-mycorrhizal feedbacks and can potentially influence carbon and nitrogen cycling in forest soils.

Dynamic economic thresholds for the management of vegetable leafminer on glasshouse cucumber estimated by simulated defoliation

AbstractDefoliation by the vegetable leafminer, Liriomyza sativae Blanchard (Diptera: Agromyzidae), was simulated by removing known amounts of leaf area with a hole punch in a glasshouse experiment that evaluated 21 combinations of defoliation intensity, timing and duration on cucumber yields. Defoliation was quantified in cm2‐days (leaf area removed x no. days), and linear regression was used to correlate yield losses to simulated damage. The probability of erroneous decisions associated with different intensities of sequential sampling was explored. Spatial heterogeneity in leafminer infestation and the cumulative impact of defoliation over time were both considered, and the economic costs associated with wrong decisions were also assessed. Significant yield loss was observed beyond 10,000 cm2‐days of defoliation, whereas lower defoliation levels were tolerated by plants. The economic injury level (EIL) rose at an increasing rate as the onset of defoliation moved later in the season. An algorithm was used to estimate monthly EILs that farmers can use to guide leafminer management decisions in cucumber and minimize their economic risk.

Lagged effects of sawfly leaf herbivory on reproductive organs in cherry trees: Overcompensation in flower production reduces quality of fruits and seeds

Herbivores reduce plant productivity by removing part of the assimilation surface. Also, they can alter plant traits that affect plant–pollinator interactions and reproductive success. The objective of this study was to evaluate the impact of defoliation by sawfly (Caliroa cerasi) larvae on fruit production and quality in three cultivars of sweet cherry (Prunus avium). We hypothesized that the fruit production and quality is reduced as a consequence of changes in the allocation of resources within the plant in response to partial leaf removal during the previous year. Number of flowers per branch meter was higher in infested trees than in non-infested trees, while the number of fruits per branch meter was similar due to fruit abortion in all cultivars. Fruit quality was significantly affected by herbivory in different traits depending on cultivar. Infested Lapins and Van trees had significantly lower soluble solid content than non-infested trees. Titratable acidity was higher and ripening index was lower in infested Bing and Lapins trees than non-infested trees. Infested Van trees also exhibited a significant decrease in equatorial diameter and fresh fruit weight as well as pulp fresh weight and dry weight of seed compared to non-infested trees. Overall our study highlights that the direct impact of herbivores at leaf level has lagged effects on productivity in terms of fruit and seed quality in the year following the leaf damage.

No carbon limitation after lower crown loss in Pinus radiata.

Background and AimsBiotic and abiotic stressors can cause different defoliation patterns within trees. Foliar pathogens of conifers commonly prefer older needles and infection with defoliation that progresses from the bottom crown to the top. The functional role of the lower crown of trees is a key question to address the impact of defoliation caused by foliar pathogens.MethodsA 2 year artificial defoliation experiment was performed using two genotypes of grafted Pinus radiata to investigate the effects of lower-crown defoliation on carbon (C) assimilation and allocation. Grafts received one of the following treatments in consecutive years: control–control, control–defoliated, defoliated–control and defoliated–defoliated.ResultsNo upregulation of photosynthesis either biochemically or through stomatal control was observed in response to defoliation. The root:shoot ratio and leaf mass were not affected by any treatment, suggesting prioritization of crown regrowth following defoliation. In genotype B, defoliation appeared to impose C shortage and caused reduced above-ground growth and sugar storage in roots, while in genotype A, neither growth nor storage was altered. Root C storage in genotype B decreased only transiently and recovered over the second growing season.ConclusionsIn genotype A, the contribution of the lower crown to the whole-tree C uptake appears to be negligible, presumably conferring resilience to foliar pathogens affecting the lower crown. Our results suggest that there is no C limitation after lower-crown defoliation in P. radiata grafts. Further, our findings imply genotype-specific defoliation tolerance in P. radiata.

The influence of management and environmental factors on insect attack on cork oak canopy

The decline of oak (Quercus spp.) forests is a current trend in Northern Hemisphere and is characterized by a loss in tree vigour and increased mortality. The canopy insects are suspected to have role in this decline, but there is poor knowledge about their incidence in evergreen-oak stands. The main aim of this study is to characterize the incidence of main insect groups affecting branches and leaves of an evergreen-oak species (the cork oak Quercus suber) and evaluate which management practices and environmental traits of agroforestry systems affect it. In the spring/summer of 2018, we measured the incidence of attacks on branches and leaves by gall-makers (Diptera, Cecidomyiidae), blade-miners (Lepidoptera and Coleoptera), midrib-miners (Lepidoptera, Heliozelidae), chewer caterpillars (Lepidoptera), chewer sawflies (Hymenoptera, Tenthredinidae), weevils (Coleoptera, Curculionidae) and branch-borers (Coleoptera, Buprestidae). We analysed the frequency of pest signs according to different indicators: management practices, tree maturity, forest diversity, forest fragmentation, and latitude and longitude. The most frequent signs of insect pests on tree leaves corresponded to blade-miners, midrib-miners, chewer caterpillars and chewer sawflies. With exception of midrib-miners and branch-borers, all insect pests were found on cork oak stands experiencing decline and benefited from management intensification. Our study suggests that a diverse-aged stand may reduce the frequency of midrib-miners and chewer caterpillars, as well the attack of branch-borers. Moreover, a high plant diversity in forests can contribute to reduce the impact of defoliators on cork oaks (e.g., chewer sawflies) and understory reduction decreased the exposure of trees to gall-makers. Moreover, we found that forest fragmentation may increase the frequency of blade-miners and chewer caterpillars. We conclude that insect pests have a high incidence in cork oak stands and thus, may have and important role in its decline. Considering that a high frequency of pests is often associated with increased management intensity, a change to a more sustainable use of these systems is urgently needed.

Understanding Yeast Impact on 1,1,6-Trimethyl-1,2-dihydronaphthalene Formation in Riesling Wine through a Formation-Pathway-Informed Hydrolytic Assay.

The occurrence in Riesling wine of the potent odorant 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) is dependent upon vineyard and winemaking conditions, and TDN can have a prominent impact on the attributes of a wine after years in a bottle. As such, immediately assessing the impact of vineyard or winery treatments on future TDN formation requires forced creation of the aroma compound under non-wine-like conditions from other precursors. Here, we use a Box-Behnken approach and known TDN end points in commercial wines to optimize the conditions (pH, temperature, and time) of a "total TDN" hydrolytic assay for Riesling wine, which was intended to not interfere with yeast-derived formation pathways. The new assay (75 °C, pH 1.7, and 60 min) was used to determine the role of industry-relevant commercial yeasts as well as novel hybrid yeast strains on total TDN concentrations in young Riesling wines. While significant differences were observed between some yeasts, the impact of defoliation as a viticultural intervention outweighed yeast effects, suggesting that elevated TDN concentrations in wine are likely due to grape growing conditions and cannot be readily reduced or compensated for in the winery.