Degree Of Defoliation Research Articles

Levels and times of artificial defoliation on performance of second cycle cassava

The information on behavior of crop linked to defoliation is essential to determine the management of herbivore pests. The aim of this study was to evaluate the performance of cassava as a function of the time and level of defoliation applied in the second cycle of cultivation, that is, after the first year of cultivation in which the crop was naturally submitted to the physiological rest period, caused by low temperatures and pluviometric precipitation typical of the southern Brazilian region. We used a randomized block design in factorial 5 x 5.in which 5 levels of defoliation (0, 25, 50, 75 or 100% of defoliation) were applied at 5 different times of 45, 90, 135, 180, or 225 days after sprouting (DAS) of the stems. The following variables were measured: plant height, stem diameter, number of roots per plant, root mass and amount of starch in the roots. The means were submitted to the F test at 5% of probability and analyzed by the regression test using the Sisvar software. Plant height and diameter were inversely proportional to the degree of defoliation when subjected to treatments, especially when subjected to 100% defoliation at 90 DAS. For the root mass, the more drastic defoliation treatments (100 %), when applied at 132 DAS, led to a low production, whereas only the defoliation levels induced a meaningful reduction in the deposition of starch in roots, showing a linear effect and decreasing according to the increase in defoliation. It can be concluded that defoliation between 90 and 135 DAS at the more drastic levels resulted in a greater root mass loss, regardless of the time of defoliation, caused the greatest losses in the amount of starch, therefore, it is recommended to the producer to control this pest before the 90 days of sprouting of the stems at the beginning of the defoliation.

A new method of equiangular sectorial voxelization of single-scan terrestrial laser scanning data and its applications in forest defoliation estimation

Voxelization is an efficient and frequently used data process that is applied to terrestrial laser scanning (TLS) data to facilitate data management and reduce storage size. In this study, an innovative method of equiangular sectorial voxelization is presented based on the distinctive point distribution characteristic of single-scan TLS. It has the function of containing the same number of laser beams going through each voxel, which results in metrics that can be applied to delineate forest conditions. To verify the effectiveness of the new voxelization method and to illustrate its application, 48 plots and 1098 individual trees with different degrees of defoliation were scanned using single-scan TLS. Their defoliation could be linearly regressed by using only point density metrics derived from this new shape of voxels. A 0.89 R2 value and a 12 RMSE (% of defoliation) were obtained for individual-tree-scale estimation, and a 0.83 R2 value and a 12 RMSE (% of defoliation) were obtained for plot-scale estimation. We conclude that the new voxelization method was effective, and the point density that was thus calculated was an efficient feature that revealed forest attributes.

Assessment of functional and structural changes of soil fungal and oomycete communities in holm oak declined dehesas through metabarcoding analysis

Forest decline is nowadays a major challenge for ecosystem sustainability. Dehesas, which consists of savannah-like mediterranean ecosystems, are threatened by the holm oak decline in the south-west of Iberian Peninsula. Phytophthora cinnamomi is considered the main agent of holm oak root rot, but little is known about the relationship between diversity of soilborne microbial community and the decline syndrome of holm oak. It would be hypothesized that the changes in the structure and functionality of the soil microbiome might influence tree health status through changes in richness and diversity of beneficial organisms such as mycorrhizal species, or fungal plant pathogens such as Fusarium spp. or Alternaria spp. Total DNA of soil samples from declined oak dehesas was extracted and analyzed through metabarcoding techniques, to evaluate the specific composition and diversity of the fungal and oomycete communities and their relationship with the disease symptoms. The fungal community included a wide range of pathogens and abundance of ectomycorrhizal key taxa related with low defoliation degree. Phytophthora cinnamomi and Pythium spiculum did not appear among the most abundant oomycetes, nor were they related directly to defoliation levels. Moreover, a particular taxon belonging to the genus Trichoderma was strongly correlated with the scarcity of pathogenic Phytophthora spp. The diversity and composition of fungal and oomycete communities were related to the severity of the decline symptoms. The metabarcoding study of microbiome represents a powerful tool to develop biocontrol strategies for the management of the holm oak root rot.

The Effects of Different Degrees of Defoliation on ‘Seolhyang’ Strawberry’s Fruit Characteristics, Plant Growth and Changes in Nonstructural Carbohydrates

The Effects of Different Degrees of Defoliation on ‘Seolhyang’ Strawberry’s Fruit Characteristics, Plant Growth and Changes in Nonstructural Carbohydrates

Analysis of Infestation of Nematode Meloidogyne exigua in a Rubber Tree Plantation in the Triângulo Mineiro Region

ABSTRACT This study analyzed the use of the water balance, precipitation, temperature and NDVI (Normalized Difference Vegetation Index) to determine the optimum moment for evaluating infestation by the nematode Meloidogyne exigua in a rubber tree plantation by remote sensing. Nineteen sampling points were defined, divided into three areas, with high and low defoliation degrees, on a property in the Triângulo Mineiro region, where soil and root samples were collected for nematological analysis. Monthly digital images (OLI - Landsat 8 sensor) were obtained from August 2015 to August 2016. Rainfall, temperature and water balance were analyzed. The latter had no correlation with the indices; in contrast, temperature and precipitation correlated directly with NDVI. The best months for nematode soil infestation analysis were December, January and February, while for root infection it was August.

Impact of Abrostola asclepiadis combined with other stressors on invasive swallow-worts (Vincetoxicum species)

The moth Abrostola asclepiadis (Lepidoptera: Noctuidae) is being investigated for biological control of pale and black swallow-wort (Vincetoxicum rossicum and V. nigrum, respectively; Apocynaceae), European vines introduced into North America. Limited information existed on its potential impact on swallow-worts, and the combination of defoliation damage by A. asclepiadis and other stresses to the plants had not been studied. We conducted greenhouse studies of the impact of different frequencies (once or twice) and degrees of defoliation (50 or 100%-seedlings; one or two larvae per stem-mature plants) by larvae on seedlings and mature (flowering) plants of black and pale swallow-wort. Defoliation was combined with varying light levels (shaded or not) or competition with quackgrass (Elymus repens). Significant reductions in aboveground dry mass and seeds generally only occurred when plants were completely defoliated twice. Grass competition and, to a greater extent, shading reduced growth and reproduction of swallow-wort plants. However, no interactions between defoliation and the other stressors occurred, suggesting they would have an additive effect. Because A. asclepiadis is likely to be univoltine if released in North America, its impact appears to be limited even if severe defoliation is achieved. Therefore, A. asclepiadis should be given a lower priority for release.

Calibrating the Severity of Forest Defoliation by Pine Processionary Moth with Landsat and UAV Imagery.

The pine processionary moth (Thaumetopoea pityocampa Dennis and Schiff.), one of the major defoliating insects in Mediterranean forests, has become an increasing threat to the forest health of the region over the past two decades. After a recent outbreak of T. pityocampa in Catalonia, Spain, we attempted to estimate the damage severity by capturing the maximum defoliation period over winter between pre-outbreak and post-outbreak images. The difference in vegetation index (dVI) derived from Landsat 8 was used as the change detection indicator and was further calibrated with Unmanned Aerial Vehicle (UAV) imagery. Regression models between predicted dVIs and observed defoliation degrees by UAV were compared among five selected dVIs for the coefficient of determination. Our results found the highest R-squared value (0.815) using Moisture Stress Index (MSI), with an overall accuracy of 72%, as a promising approach for estimating the severity of defoliation in affected areas where ground-truth data is limited. We concluded with the high potential of using UAVs as an alternative method to obtain ground-truth data for cost-effectively monitoring forest health. In future studies, combining UAV images with satellite data may be considered to validate model predictions of the forest condition for developing ecosystem service tools.

Interactive effects of forest die-off and drying-rewetting cycles on C and N mineralization

Mediterranean forests will experience more frequent and intense drought periods and extreme rainfall events in the coming decades. Concomitantly, drought-induced forest die-off is likely to increase. Changes in rainfall patterns and forest die-off directly influence soil microbial communities and activity and, consequently, carbon (C) and nitrogen (N) turnover, but their interactive effects have not yet been explored. We investigated the short-, and the long-term interactive effects of forest die-off and drying-rewetting cycles on soil C and N mineralization rates of a Mediterranean woodland. Soil samples collected under and out of the influence of holm oak (Quercus ilex) trees with different defoliation degrees (six healthy, six affected and six dead) were incubated under two contrasting water regimes (i.e. drying-rewetting cycles vs. constant soil moisture). Potential soil C and N mineralization responded differently to water regimes, with an overall 55% increase in C mineralization and a 22% decrease in N mineralization in the drying-rewetting cycle treatment compared to the constant moisture treatment. Holm oak decline decreased the response of C mineralization while increased the response of N mineralization to the drying-rewetting cycles at both the short- and the long-term. Moreover, N turnover showed a higher sensitivity to these environmental changes than that of C during most of the year. Our study provides solid evidence that an intensification of the drying-rewetting regimes can result in a decoupling of soil C and N cycles in Mediterranean forests and that forest die-off might enhance this decoupling at both the short- and the long-term, with important implications for the ecosystem functioning.

The influence of the bakery on the quality of the environment

Plants are extremely sensitive to the environment, because they assimilate substances simultaneously from two environments: from soil and air. In connection with the fact that plants lead an attached way of life, the state of their organism reflects the state of a particular local habitat. Since vegetation is directly affected by unfavorable factors, it allows the researcher to evaluate the entire complex of negative impacts exerted by the enterprise on whose territory they grow. This paper is devoted to the analysis of fluctuating asymmetry of sheet plates as an indicator of the quality of the environment. The coefficient of fluctuating asymmetry is often used to estimate the level of contamination of a particular area, taking into account the species-specific reaction of plants to unfavorable factors. A conclusion about the stability of the development of vegetation growing on the territory under investigation is made on the basis of the obtained value of the coefficient of fluctuating asymmetry. An important indicator of the state of the air environment is the condition of coniferous trees, in addition to the asymmetry of the leaves of tree plantations: the degree of defoliation of the crowns, the yellowing of the needles, the number of cones and the growth of shoots. The assessment of the life condition of coniferous trees was carried out on the basis of the analysis of the data relating to all of the above parameters established for the trees.

Bidirectional interactions between beet armyworm and its host in response to different fertilization conditions.

Fertilizer with different ratios of nitrogen (N) to phosphorus (P) can influence crop plant performance and defense against herbivores. Spodoptera exigua is an important agricultural pest that has caused serious economic loss, especially in recent decades. In the present study, we explored effects of different intensities and durations of S. exigua herbivory on host plant biomass and on S. exigua enzyme activities in response to five fertilizer treatments with different N: P ratios of 1: 5, 1: 3, 1: 1, 3: 1 and 5: 1. The results showed that fertilizer type can significantly influence interactions between caterpillars and its hosts. Compensatory growth of leaf biomass was detected under fertilizer with N: P = 3: 1. Fertilizer with a higher proportion of N appears to maintain stem biomass in defoliated seedlings similar to controls that are not exposed to herbivory. There was no significant difference in root biomass under most conditions. High proportion of N also enhanced the activity of two antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD) in low density of beet armyworm. However, with increased herbivorous intensity, a higher proportion of P played a more important role in increasing the activities of CAT and SOD. Higher P likely enhanced acetylcholine esterase (AChE) activity at lower degrees of defoliation, but a higher N proportion resulted in higher AChE activity at higher degrees of defoliation. Higher N proportion contributed to reduced carboxylesterase (CarE) activity at high intensity, short-term defoliation. However, when defoliation intensity increased, the difference in CarE activity between fertilizer categories was little. The study explored the interaction between the damage of S. exigua and the biomass accumulation of its host plant Brassica rapa, and the influence of the N/P ratio in plant fertilizer on this interaction. Systematic analysis was provided on the biomass of B. rapa and the activity of metabolic enzymes of S. exigua under different treatments.

傾斜放牧草地の地形と草地管理 : 2. 糞の分布の偏りが土壌養分や牧草の生産量およびその利用率に及ぼす影響

傾斜放牧草地の地形と草地管理 : 2. 糞の分布の偏りが土壌養分や牧草の生産量およびその利用率に及ぼす影響

The Effect of Partial Defoliation, Leaf Position and Developmental Stage of the Vine on the Photosynthetic Activity of Vitis vinifera L. cv Cabernet Sauvignon

The effect of partial defoliation, :eaf position and developmental stage of the vine on the photosynthesis, stomatal resistance and transpiration of Vitis vinifera L. cv Cabernet Sauvignon was investigated. Partially defoliated vines displayed a higher rate of photosynthesis, generally increasing with degree of defoliation. The highest photosynthetic rates were found for the apical leaves, while those of the leaves opposite and below the bunches were restricted. Generally, rate of photosynthesis declined as the season progressed. The course of transpiration rate and stomata! resistance correlated with that of the rate of photosynthesis. However, transpiration and photosynthesis correlated poorly in the case of the apical leaves. In general, photon flux density and relative humidity at the leaf surface increased with an increase in defoliation percentage for all leaf positions. Leaf temperature was not significantly affected by partial defoliation. The results of the investigation suggested that excess vegetative growth is detrimental to interior-canopy microclimate as well as the photosynthetic rate of the entire vine. Partial defoliation seemed to provide a means to reduce some of the deleterious effects of vigorous growth.

Effects of copper citrate as a defoliant in nursery fruit stock production

The effects of copper citrate on defoliation of one year old fruit stocks in a nursery are presented in this paper. The investigation aimed to evaluate the defoliation efficacy of copper citrate as a new formulation, compared with other compounds recommended for that purpose. Field trials were conducted in the region of Trstenik, a center of nursery production in Serbia in 2016 and 2017. Two years of investigation showed that copper citrate could be used as an efficient compound for defoliation in nursery production. A stronger defoliation effect was observed on plum stocks, compared to apple stocks. Better results were achieved with the highest concentration of copper citrate (2%), while the effectiveness decreased with lower concentrations (0.5%, 1.0% and 1.5%). Defoliation degree on nursery apple stocks after treatment with 2.0% concentration of copper citrate varied from 80.6% to 95.6%, while it reached 100% on plum stocks.

Holm oak decline triggers changes in plant succession and microbial communities, with implications for ecosystem C and N cycling

The occurrence of drought-induced forest die-off events is projected to increase in the future, but we still lack complete understanding of its impact on plant-soil interactions, soil microbial diversity and function. We investigated the effects of holm oak (Quercus ilex) decline (HOD) on soil microbial community and functioning, and how these effects relate to changes in the herbaceous community. We selected 30 holm oak trees with different defoliation degrees (healthy, affected and dead) and analyzed soil samples collected under the canopy (holm oak ecotype) and out of the influence (grassland ecotype) of each tree. HOD increased potential nitrogen (N) mineralization and decreased inorganic N concentrations. These results could be partially explained by changes in the herbaceous composition, an increased herbaceous abundance and changes in soil microbial functional diversity and structure, with HOD favoring bacteria against fungi. Moreover, herbaceous abundance and microbial functional diversity of holm oak and grassland ecotypes converged with HOD. Our results show that HOD triggers a cascade effect on plant understory and soil microbial communities, as well as a plant succession (savannization) process, where understory species colonize the gaps left by dead holm oaks, with important implications for ecosystem C and N budgets.

Impact of the defoliating moth Hypena opulenta on invasive swallow-worts (Vincetoxicum species) under different light environments

Black and pale swallow-wort (Vincetoxicum nigrum and Vincetoxicum rossicum, Apocynaceae) are twining vines from Europe that have become invasive in eastern North America. Hypena opulenta (Lepidoptera: Erebidae), a defoliating moth from the Ukraine, has recently been released in Canada and a request for release in the United States is under review. Its potential multivoltinism, and hence repeated defoliation of swallow-worts, combined with low-light levels in an understory environment may be promising for controlling forest infestations of swallow-worts. We conducted a greenhouse study of the impact of larval defoliation on seedlings and mature (flowering) plants of black and pale swallow-wort at different frequencies (once or twice) and degrees of defoliation (50 or 100%-seedlings; three or six larvae per stem-mature plants). Defoliation occurred under two forest light-regimes: low-light conditions typical of deeply-shaded forest habitats and higher light levels representative of a more open canopy or forest edge. Plants grown under higher light conditions were generally larger and produced many more seeds than heavily-shaded plants. One round of complete defoliation by H. opulenta, but not necessarily two, generally reduced biomass and seed production for both species and life stages, except for root mass of mature plants. No mature plants died and little seedling mortality occurred apart from black swallow-wort that had been completely defoliated twice under low light. Pale and black swallow-wort seedlings and mature plants appear to be tolerant of moderate defoliation damage. Complete defoliation repeated within and across years may be needed for suppression of forest infestations of swallow-wort.

조기낙엽에 따른 참다래 착과 유목의 당년 재발아와 익년 초기생장

Abstract BACKGROUND: This study was conducted to investigate the effect of the unexpected early loss of leaves on a newly-bred kiwifruit on the regrowth of axillary buds the current season and the early growth and development the following year. METHODS AND RESULTS: The vines were defoliated on Jul. 18, Aug. 16, and Sep. 17 in 2012 and on Jul. 16, Aug. 13, and Sep. 12 in 2013. The vines were defoliated 0 (control), 50, and 100% of the total number of leaves on a vine. The regrowth of axillary buds at 30 days after defoliation increased in proportion to defoliation degrees regardless of the defoliated time. Defoliation the previous season did not influence percent budbreak the next season. Percentage of floral shoots of the control vines was 27.4%, each bearing 2-3 flowers. In those vines defoliated 100% in August and September, however, percent floral shoots and number of flowers significantly reduced. CONCLUSION(S): Defoliation in July, August, and September didnot affect percent budbreak the following year regardless of degrees of defoliation. A 100% defoliation in August and September significantly reduced flowering the following year compared to the control; that in August resulted in no floral buds at all.

Vitality of European Beech (Fagus sylvaticaL.) at the Limit of Its Natural Range in Poland

The European beech is a major component of central European forests, and the eastern limit of its range lies in Poland. However, the Holocene migration of the beech is not yet finished, especially in NE Poland, so the northern distribution of the beech continues to change. The main goal of this study was to determine if the beech will reach its northern limit in the future.The investigation was carried out in 18 beech stands in Poland. To study the status of the health of the trees, circular plots were established in grids of different sizes. The basal beech stand area ranged from 3.7 m2 ha-1 to 31.2 m2 ha-1. The density of trees exceeded a hundred trees per hectare in most of the plots (61%), and the average degree of defoliation was not greater than 60% in all of the investigated stands. Environmental conditions influenced defoliation of beech trees (Fisher's test, F = 4.0204; P <0.0001). The vitality of the beech trees varied between stands (Kruskal-Walis test, H = 139.7433, P <0.0001) and was rather good in 56% of the study plots. Seedlings and saplings were observed in all of the investigated stands, and they covered from 5 to 39% and 21 to 80% of the study plots, respectively. Spontaneous beech regeneration was widespread and differed from stand to stand as well as within stands in all of the study plots. The number of tall seedlings in most of the study plots (56%) was greater than 10,000 individuals per hectare. The factors limiting beech regeneration were stand density and herb cover, and the number of beech seed trees influenced the quantity of small seedlings. Beech tree density positively influenced the number of small seedlings, and the strength of the correlation was moderate and statistically significant (Pearson correlation, r = 0.349). Beech tree density influenced the vitality of tall and small saplings (Pearson's correlations, r = 0.673 and r = 0.361, respectively). The spontaneous regeneration and strong vitality of seedlings and saplings suggests that beech can create stable stands in the future and that it is an expansive tree species both within its continuous range and at the limit of its distribution. It is quite possible that beech will reach its north-eastern limit in Poland in the future.

Response of Japanese Barberry to Varying Degrees of Defoliation

Abstract Until recently, it was thought that Berberis thunbergii (Japanese Barberry), a non-native invasive plant that has become particularly widespread in certain regions of New Jersey, benefited from a lack of herbivorous defoliators. However, in 2007 extensive defoliation was documented across a wide geographical distribution in New Jersey, calling this assumption into question. We tested whether Japanese Barberry was negatively affected by partial defoliation by manually clipping 50% or 100% of leaves on current-year stems on small and large plants in the summer of 2008. We found almost no impact of defoliation on growth, carbon storage, or leaf-level physiology for either treatment. We noted some differences between large and small plants, but these were not related to defoliation treatments. Our results suggest that, even in the presence of herbivory, Japanese Barberry is capable of maintaining growth and carbon reserves, thus making it an effective competitor for resources.

Effects of defoliation on photosynthesis, dry matter production and yield in Soybean

Two pot experiments were conducted to assess the effect of various degree of defoliation on photosynthesis, dry matter production and yield in soybean. Defoliation significantly increased rate of photosynthesis and transpiration and leaf conductance of the soybean genotypes however, it decreased dry matter production and yield. DOI: http://dx.doi.org/10.3329/bjb.v43i3.21592 Bangladesh J. Bot. 43(3): 261-265, 2014 (December)

Influence of Some Soil Characteristics on Defoliation of &amp;lt;i&amp;gt;Cryptomeria japonica&amp;lt;/i&amp;gt;

The defoliation of Cryptomeria japonica is observed in shrine forests around Hikone, Japan. Here, moisture content, soil pH, exchangeable Mg, Ca and Al of soil in shrine forests of C. japonica were examined in order to assess the relationship between these factors and defoliation. There was no relationship between soil pH, exchangeable Mg and Ca in soil and the degree of defoliation in shrine forests. Exchangeable Al in the soil of shrine forests increased with decreasing soil pH below pH 5.0, but there was no relationship between exchangeable Al and degree of defoliation in shrine forests. Soil moisture content differed between severely defoliated forests and forests with no defoliation. Soil moisture is thought to play a large role in inducing defoliation of C. japonica. Based on results from previous studies, the declining forests in the basin of the Kuzuryu River in Fukui Prefecture and in the basin of the Koito River in Chiba Prefecture reported by Yambe (1973) were considered to have been caused by the construction of dams. On these rivers, dams were constructed several years before the forest decline researched by Yambe. Dam construction is thought to have caused the low moisture content in the basins.