Effects Of Defoliation Research Articles

Late Leaf Spot Defoliation, Microclimate Modification, and Southern Stem Rot Development in Peanut (Arachis hypogaea L.) in South Carolina

ABSTRACT Southern stem rot (SSR) of peanut, caused by Athelia rolfsii, is commonly influenced by environmental conditions. Defoliation from late leaf spot (LLS), caused by Nothopassalora personata, alters canopy structure and has the potential to affect microclimates. A better understanding of the potential interaction between SSR and LLS through potential microclimate modification might contribute to improved disease management. Eight field experiments were conducted from 2016 to 2019 to investigate the effect of LLS defoliation on peanut canopy and soil microclimates and SSR development. To encourage different levels of LLS defoliation, 3 spray programs (3, 4 and 6 chlorothalonil applications) were applied across four cultivars varying in susceptibility to LLS and SSR via a split-plot design. Defoliation was rated every 2 weeks from 75 days after planting (DAP) to harvest. Canopy and soil temperature and soil moisture were recorded from 75 to 140 DAP. Interaction of LLS spray program and peanut cultivar significantly affected LLS defoliation in nearly all trial years except in 2019 where low disease pressure occurred due to dry weather. Significant relationships were observed between LLS defoliation and daily maximum canopy temperatures and between area under LLS defoliation curve (AUDC) and slope of daily canopy temperature change. The influence of LLS defoliation on the microclimate was generally erratic. The relationship between AUDC and SSR was not significant. Results from this study suggest that the influence of LLS on microclimate was insufficient to substantially affect SSR development.

Effects of Runner Removal and Partial Defoliation on the Growth and Yield Performance of ‘Favori’ Everbearing Strawberry Plants

It is not known to what degree growth and fruit yield are source-limited in everbearing strawberry plants. The growth and yield performance effect of bi-weekly removal of all runners and/or one or two leaves during the cropping season of tunnel-grown ‘Favori’ everbearing strawberry plants was determined. Plants were grown on a table-top system in an open plastic tunnel under natural light conditions in Norway from May to October. Removal of runners and leaves was bi-weekly from 5 June until 25 September. Fruits were harvested from 5 July to 7 October. Bi-weekly runner removal increased total and marketable yield and number and size of fruits, while increasing leaf thinning had the opposite effects. However, none of the treatments affected the fruit number and yield of the first fruiting flush. The treatments did not affect realization of the yield potential of the plants at planting, whereas the continued floral initiation and fruit growth were enhanced by runner removal. Increasing leaf thinning had the opposite effects. Both floral initiation and fruit growth in heavily flowering and fruiting everbearing strawberry are source-limited owing to the high fruit/leaf ratio of such plants.

Impacts of a regional multiyear insect defoliation event on growing‐season runoff ratios and instantaneous streamflow characteristics

AbstractRepeated moderate severity forest disturbances can cause short‐ and long‐term shifts in ecosystem processes. Prior work has found that stand‐replacing disturbances (e.g., clear‐cutting) increase streamflow in temperate forests, but streamflow responses to repeated moderate severity disturbances are more equivocal. This study examined a moderate disturbance caused by an unexpected population irruption of the invasive insect Lymantria dispar (common name: gypsy moth) in 2015–2017. This irruption resulted in defoliation that was locally severe in some areas but spatially heterogeneous at a regional scale. L. dispar larvae consume leaves during the summer growing season, which effectively reduces tree leaf area and associated evapotranspiration. Our regional approach in Southern New England, USA, used data from 83 US Geological Survey (USGS) stream gages to assess whether changes in growing‐season watershed runoff ratios and instantaneous streamflow characteristics during the 2015–2017 L. dispar irruption were associated with satellite‐derived metrics of changes in forest condition (i.e., defoliation), compared to a 20‐year baseline streamflow period. We found a small, linear increase in growing‐season runoff ratio anomalies that was associated with defoliation intensity. The association between defoliation intensity and runoff ratio anomalies was magnified in less anthropogenically impacted reference watersheds. We also found that defoliation intensity was associated with larger volumes of high and medium instantaneous streamflows compared to baseline mean flow conditions. This study provided important insights into the impacts of moderate disturbance on ecohydrology in mesic temperate forests with a unique methodological approach that assessed the impacts of spatially heterogeneous and repeated moderate disturbance at a regional scale.

Same Season and Carry-Over Effects of Source-Sink Adjustments on Grapevine Yields and Non-structural Carbohydrates

The grapevine (Vitis vinifera L.) is managed to balance the ratio of leaf area (source) to fruit mass (sink). Over cropping in the grapevine may reveal itself as spontaneous fruit abortion, delayed ripening, or as alternate bearing. The aim of this work was to study the same season and carry-over effects of manipulating source to sink ratios on grapevine phenology, leaf gas exchange, yield components, berry soluble solids accumulation, and reserve carbohydrate and soluble sugar concentration in roots. Cabernet Sauvignon grapevines were subjected to defoliation (33, 66, and 100% of the leaves retained) and fruit removal treatments (33, 66, and 100% of clusters retained) arranged in a factorial design. Results from two seasons of source-sink manipulations were substantially different. In both seasons defoliation treatments affected season-long net carbon assimilation (AN) and stomatal conductance (gs) where the less leaves were retained, the greater the AN and gs, and fruit removal had no impact on leaf gas exchange. In the first season, leaf area to fruit mass was hardly related to berry soluble solids and in the second season they were strongly correlated, suggesting a degree of acclimation. Defoliation treatments had great impacts on berry size, berries per cluster, and total soluble solids in both years. Fruit removal treatments only had effects on berry mass and berries per cluster in the first season, and only on berry soluble solids in the second. The predominant effect of defoliation (carbon starvation) cascaded onto reducing root starch content, root mass and delaying of veraison and leaf senescence, as well as harvest which was delayed up to 9 weeks with 33% of the leaves retained. In a third season, where grapevines grew without treatments, defoliation treatments had resultant carryover effects, including reduced leaf area, number of berries per cluster, clusters per vine, and yield, but not on leaf gas exchange dependent on previous seasons' severity of defoliation. Balancing source-to-sink ratio is crucial to obtain an adequate speed of ripening. However, this was the culmination of a more complex whole-plant regulation where the number of leaves (source strength) outweighed the effects of fruits (sink strength).

Disentangling the effects of climate and defoliation on forest growth: The case of an outbreak of a Thaumetopoea pityocampa population with a shifted phenology in a Pinus pinaster monoculture

Forests are widely affected by disturbances, both abiotic, climate related, and biotic, like insect outbreaks. However, the impact of the interaction of these disturbances on tree growth is still not well understood. On the present work the impact of climatic and long-term defoliation by Thaumetopoea pityocampa (Dennis and Schiff.) during summer on Pinus pinaster growth was evaluated. At the National Pine Forest of Leiria, in Portugal, we sampled defoliated and non-defoliated forest plots covered by monocultures of young P. pinaster trees. Growth was assessed using dendrochronological techniques, and its relationship with climatic variability, including severe droughts, and defoliation, was analysed using hierarchical partitioning models. Results suggest that long term defoliation result in trees not being able to take advantage of favourable climatic conditions, leading to a reduced radial and height growth. Droughts were the major climatic disturbance, causing growth reduction as well, although the impacts of both disturbances did not act synergistically. Additionally, models showed that previous year climatic conditions have a significant effect on annual growth, namely, previous year annual precipitation and temperature. Yet, the best model obtained include a positive effect of the previous year annual precipitation and a negative effect of the interaction between this climatic parameter and defoliation. This work illustrates the potential of defoliation and climate to reduce forest productivity and the importance of water availability for tree development in Mediterranean climates. In addition, our results also emphasise the need to simultaneously evaluate the effects of different disturbances, particularly in a time of global change when an increase in forests disturbances is expected. This approach will certainly contribute to a more informed management of production forests.

Effect of Defoliation on the Defense Reactions of Silver Birch (Betula pendula) Infected with Phytophthora plurivora

In natural environments, plants develop adaptive mechanisms at the cellular and molecular levels to cope with many external factors, e.g., insects and soil pathogens. We studied physiological stress induced by different levels of foliage removal (defoliation 30% and 60%) and by infection of root rot pathogen Phytophthora plurivora on the common Polish tree species, Betula pendula, grown in an open greenhouse. This study showed that P. plurivora damaged the root system which negatively impacted all morphological parameters. However the loss of 30% of the leaves had a positive effect on defense responses. Chlorophyll-a fluorescence parameters indicated a decrease in photosynthetic efficiency in defoliated plants, but plants inoculated with the pathogen had a higher performance index showing increased vigor of the infected plant than birches. The study demonstrated the intense immunity response of birch to P. plurivora through the expression of Hsp90 and Hsp83 genes. The trees weakened by P. plurivora became more susceptible to infection by Erysiphe ornata var. ornata.

Seedling defoliation of cereal crops increases peanut growth and yield in an intercropping system

Intercropping cereals and legumes is practiced widely in the world for improving yields and economic benefits. Shorter legume crops in intercropping are shaded by taller cereals, substantially reducing legume growth and yield. Reducing shade in intercropping by shortening the plant height of cereals by seedling defoliation has been proposed as a practical approach to increase crop yields and land productivity. A two-year field experiment was conducted to investigate the effect of defoliation of cereal crops at seedling stage on the growth and yield of peanut (Arachis hypogaea L.) intercropped with corn (Zea mays L.) or millet (Setaria italica L.). In comparison with non-defoliation controls, defoliation reduced final plant height by 29 cm on average for corn and 18 cm for millet. Photosynthetically active radiation on peanut in intercropping systems with corn or millet intercropping was respectively 27.0% and 22.8% higher than those in controls, significantly improving the light environment of intercropped peanut. Net photosynthetic rates of peanut were on average 25.5% higher in corn and peanut intercropping and 19.6% higher in millet and peanut intercropping than those in non-defoliation controls. Total biomass of intercropped peanut increased owing to increased root growth. Across two years, yield of peanut intercropped with corn was 27.7% and with millet 32.8% higher than those of controls. Defoliation of cereal crops did not affect corn yield but significantly decreased millet yield by 24.5%. Our results suggest that applying seedling defoliation in intercropped corn could increase peanut yield without compromising corn yield in an intercropping system.

Impact of Plant Density and Leaves Defoliation of Sunflower Intercropped with Sugar Beet on The Productivity of Both Crops and Competitive Relationships تأثير الکثافة النباتية وتوريق دوار الشمس المحمل على بنجر السکر على إنتاجية کلا المحصولين والعلاقات التنافسية

At Sakha Agricultural Research Station, two field experiments were conducted during 2018/2019 and 2019/2020 seasons to study the effect of sunflower densities (12.5, 25.0 and 37.5 % from the recommended) and defoliation (25.0, 37.5 and 50.0 % leaves) of sunflower intercropped with sugar beet on productivity and quality of both crops and economic evaluation. The productivity of sugar beet root yield t/fed. reached 83.69 and 83.07% compared to pure stand in both seasons, respectively. Simultaneously, increase defoliation of sunflower leaves increased all studied characters of sugar beet in both seasons. Sugar beet yields i.e. root, top and sugar yield t/fed were significantly affected by the interaction between plant density and leaves defoliation ratio in both seasons. Plant height, seed yield kg/fed. and oil yield kg/fed. of sunflower were increased by increasing sunflower plant densities from (12.5 to 37.5) in both seasons. All studied characters of sunflower were not significantly affected by increasing defoliation except, 100-seed weight and seed yield/plant in both seasons. Stem and head diameter, seed yield/plant and seed oil % were significantly affected by the interaction between plant density and defoliation ratio in both seasons. The treatment of intercropping sunflower with the highest density and 50% defoliation gave the highest values for land equivalent ratio (LER), total and return incomes in both seasons. It could be concluded that sunflower intercropped with sugar beet at (37.5%) and 50% sunflower leaves defoliation gave the highest LER, total income and economic return for sugar beet and sunflower were obtained when .

CYTOKININ, GIBBERELLIC ACID AND DEFOLIATION ON DENSITY AND MORPHOLOGY OF TRICHOME OF Pelargonium graveolens L’Hér FOR ESSENTIAL OIL BIOSYNTHESIS

The density and morphology of glandular trichomes in rose geranium (Pelargonium graveolens L’Her.) are often correlated to the essential oil biosynthesis. However, whether the different organs in the same rose geranium plant are affected by hail damage, or if they recover similarly following hail damage is still unknown concerning the essential oil biosynthesis. The objective of this study was to evaluate the effects of split-applying cytokinin (CK), gibberellic acid (GA) and defoliation on rose geranium trichome morphology and density, and essential oil biosynthesis. The experiment was carried out in a hail-net covered tunnel structure during 2017-2018 growing season. The experimental design was a complete randomized blocks with a 3x3 factorial arrangement of treatments: three defoliation levels (0, 50, and 100%), two levels of split-application of CK and GA (0.32 mg L-1 CK + 150 mg L-1 GA; and 0.64 mg L-1 CK + 300 mg L-1 GA), and a control. The attenuate, peltate, and capitate trichome groups were identified in the leaf. Morphologically, the attenuate trichome group was less dense on both recovered and new plant leaves, despite split-applied CK and GA treatment. With the peltate group, brevicollate trichome density declined in all plant leaves treated with 0.64 mg L-1 CK + 300 mg L-1 GA on both leaf surfaces. Application of 0.64 mg L-1 CK + 300 mg L-1 GA led to high density of the elongated-capitate type on leaves recovered from 50 and 100% defoliation. The essential oil yield was not affected by density and morphological changes of the trichomes. However, the application of 0.32 mg L-1 CK + 150 mg L-1 GA increased the citronellol content where plants endured 100% defoliation. Results demonstrated that the effects of hail damage stress and subsequent split-applied CK and GA could transform the morphology of trichomes, subsequently increasing the density.

Effects of Defoliation at Fruit Set on Vine Physiology and Berry Composition in Cabernet Sauvignon Grapevines.

Grapevine canopy defoliation is a fundamentally important technique for the productivity and quality of grapes. Leaf removal is a pivotal operation on high-density vines which aims to improve air circulation, light exposure, and leaf gas exchange. The effects of leaf removal (LR) on vine physiology and berry composition in Cabernet Sauvignon grapevines were studied during the 2018–2019 growing season in the Bolgheri area, Tuscany, Italy. The basal leaves were removed at fruit set at two severity levels (removal of four basal leaves of each shoot (LR4) and removal of eight basal leaves (LR8)). The two treatments were compared with the not defoliated control (CTRL). The following physiological parameters of vines were measured: leaf gas exchange, leaf water potential, chlorophyll fluorescence and indirect chlorophyll content. The results showed that defoliation increased single leaf photosynthesis. In addition, qualitative grape parameters (phenolic and technological analyses) and daytime and night-time berry temperature were studied. The results showed that leaf removal had an impact on total soluble solids (°Brix), titratable acidity, and pH. The LR8-treated grapes had higher titratable acidity, while those in the LR4 treatment had higher °Brix and extractable anthocyanin and polyphenol content. Berry weight was not significantly influenced by the timing and severity of basal defoliation. Therefore, this research aims to investigate the effects of defoliation at the fruit set on vines performance.

Buried but unsafe – Defoliation depletes the underground storage organ (USO) of the mesic grassland geophyte, Hypoxis hemerocallidea

Mesic grasslands in South Africa (> 650 mm a − 1 MAP) are rich in herbaceous forbs, which outnumber grass species by more than 5 to 1. Many of these forbs are geophytes with underground storage units (USOs), such as thickened rootstocks, rhizomes, bulbs, or corms, that provide resources (non-structural carbohydrates, minerals, and water) enabling them to resprout after dry, frosty winters, and fire. However, despite their extensive biomass and reserves ostensibly protected underground, mesic grassland geophytes can be severely depleted or extirpated by chronic trampling and grazing of their aerial parts by livestock. This study examined a possible explanation for the demise of grassland geophytes in overgrazed grassland by investigating, in a pot trial, whether the growth of a geophyte and the size of its USOs are negatively affected by simulated green leaf loss. In a 2 × 2 factorial (clipped vs. unclipped x spring regrowth in the dark vs. light), five replicate plants of Hypoxis hemerocallidea, a common mesic grassland geophyte that resprouts from a corm, were subject to six severe (clipped to 80 mm) defoliations during the growing season and regrown in spring under full or restricted light to measure stored reserve contribution to regrowth. Defoliated plants were resilient to defoliation during the growing season, matching the total biomass production of unclipped plants, though cutting reduced the number of leaves by ¬60% and flowers by almost 85%. Spring regrowth on stored reserves equalled that from reserves plus concurrent photosynthesis, indicating the value of USOs for regrowth. However, there was a marked carry-over effect of previous season defoliation, resulting in a one-third reduction in shoot growth and 40% fewer inflorescence in spring. Crucially, corm mass was more than halved by clipping, which resulted in lower spring biomass and inflorescence production. It was concluded that buried stored reserves are not protected from recurrent defoliation and mechanical damage to aerial plant parts and that continued diminishment of USOs under chronic disturbance by overgrazing or frequent mowing would weaken and likely eventually kill plants, reducing overall forb species richness. Lenient management by infrequent summer mowing or grazing at moderate stocking rates combined with periodic rotational full season resting and dormant-season burning is recommend to maintain the USOs and vigour of grassland geophytes in mesic grassland.

Compensatory growth mechanisms in lettuce plants after partial defoliation

Leaf area loss is a frequent problem in crops, and it can be caused by biotic or abiotic factors. Reduced leaf area can produce alterations in plants, affecting their metabolism, growth, and yield. The leaf area in lettuce plants (Lactuca sativa L.) is often affected by herbivores such as slugs. The effects of partial defoliation on the growth of lettuce plants were evaluated under greenhouse conditions in Tunja, Colombia. Some plants had half of their leaves removed, while others were left intact as a control. The variables normally used in the basic analysis of plant growth were evaluated. There was nonsignificant difference between the two treatments; however, lettuce plants showed a remarkable ability to reduce the negative effect caused by partial defoliation, and they managed to maintain a balance in the root to shoot ratio, leaf area ratio, specific leaf area, leaf weight ratio, DM partitioning, and harvestable DM. Partial defoliation decreased the absolute growth rate by 17.8% and the relative growth rate by 13.8%. Additionally, the chlorophyll content index and the number of leaves increased by 16.0% and 15.4%, respectively, in plants subjected to partial defoliation compared with the control plants. These results indicate the regeneration capacity of the plants after partial defoliation.

Direct and Joint Effects of Genotype, Defoliation and Crop Density on the Yield of Three Inbred Maize Lines

The aim of this study was to observe direct and joint effects of three factors (genotypes, ecological environmental conditions and the applied crop density) on the level of defoliation intensity and yield. Three inbred lines (G) of maize (G1–L217RfC, G2–L335/99 and G3–L76B004) were used in the study. The trials were performed in two years (Y) (Y1 = 2016 and Y2 = 2017) and in two locations (L) (L1 and L2) under four ecological conditions of the year–location interaction (E1–E4) and in two densities (D1 and D2) (50,000 and 65,000 plants ha−1). Prior to tasselling, the following five treatments of detasseling and defoliation (T) were applied: T1—control, no leaf removal only detasseling, T2–T5—removal of tassels and top leaves (from one to four top leaves). The defoliation treatments had the most pronounced effect on the yield reduction in G1 (T1–Tn+1… T5), p < 0.05. The ecological conditions on yield variability were expressed under poor weather conditions (E3 and E4), while lower densities were less favorable for the application of defoliation treatments. The result of joint effects of factors was the lowest grain yield (896 kg/ha) in G3 in the variant E3D1 for T2 and the highest grain yield (11,389 kg/ha) in G3 in the variant E2D2 for T1. The smallest effect of the defoliation treatment was on the kernel row number (KRN).

Soil microbial structure and activity in a semiarid rangeland of Patagonia, Argentina: Plant species and defoliation effects

Natural grasslands are an important renewable resource for livestock production. Grazing in these areas alters the plant community composition, litter quality, and soil microbial structure and activity. Three cool-season species were studied in a semiarid rangeland area of Argentina: Poa ligularis and Nassella tenuis (desirable/preferred for livestock) and Amelichloa ambigua (undesirable/non preferred). The objective was to analyze the effect of moderate defoliation and plant species on the structure and activity of soil microbial communities associated with their roots. In winter 2012, soil samples (0–10 cm) were taken underneath marked plant canopies of the three species (n = 8). Immediately thereafter, half of the plants (n = 4) were defoliated (5 cm stubble height) and the other half remained undefoliated (controls). The defoliation treatment was conducted again in the spring. Soil samples were taken 30 days after each defoliation event. The study was repeated in 2013, using a different plant set. Bacterial community structure and soil microbial activity were analyzed using PCR-DGGE analysis and basal soil respiration, respectively. Moderate and early defoliations allowed compensatory growth in the defoliated plants. Variations in the soil genetic profiles of A. ambigua suggest a higher dependence on its rhizospheric bacterial communities. Defoliation treatments did not substantially affect basal soil respiration but showed strong links between desirable species and soil microbial activity. Sustainable management practices that promote the persistence of these species are important for the development of microbial communities that respond quickly to stress conditions, favoring decomposition processes that maintain soil fertility in semiarid grasslands.

Influence of burning and defoliation on Festuca costata (Nees) in the Drakensberg

Fire occurs naturally in grasslands and savannas and it is commonly used as a management tool to influence structure and composition. The ability of a grass plant to recover from fire may be influenced by the fire frequency and intensity (influenced by seasonal weather conditions and fuel load), defoliation and competition from neighbouring plants. This study sought to investigate factors influencing the fire and herbivore dynamics of an evergreen C3 grass, Festuca costata, in a high-altitude C4 dominated grassland in the Drakensberg Mountains of South Africa. We experimentally examined the effect of fire frequency, defoliation and competition from neighbours on the growth dynamics of F. costata. Annual burning significantly decreased aboveground biomass production, number of tillers and tuft circumference of F. costata. Defoliation similarly reduced aboveground biomass production, number of tillers, tuft circumference and specific leaf area of F. costata. Competition from neighbouring plants reduced aboveground biomass production, number of tillers and tuft circumference of F. costata. Given the expected variable impacts of increasing CO2 levels and temperature on C3 and C4 grasses, these results provide insights for managing the matrix of C3 and C4 grasses in the Drakensberg grasslands in a changing climate.

Crown defoliation decreases reproduction and wood growth in a marginal European beech population.

Abiotic and biotic stresses related to climate change have been associated with increased crown defoliation, decreased growth and a higher risk of mortality in many forest tree species, but the impact of stresses on tree reproduction and forest regeneration remains understudied. At the dry, warm margin of species distributions, flowering, pollination and seed maturation are expected to be affected by drought, late frost and other stresses, eventually resulting in reproduction failure. Moreover, inter-individual variation in reproductive performance versus other performance traits (growth, survival) could have important consequences for population dynamics. This study investigated the relationships among individual crown defoliation, growth and reproduction in a drought-prone population of European beech, Fagus sylvatica. We used a spatially explicit mating model and marker-based parentage analyses to estimate effective female and male fecundities of 432 reproductive trees, which were also monitored for basal area increment and crown defoliation over 9 years. Female and male fecundities varied markedly between individuals, more than did growth. Both female fecundity and growth decreased with increasing crown defoliation and competition, and increased with size. Moreover, the negative effect of defoliation on female fecundity was size-dependent, with a slower decline in female fecundity with increasing defoliation for the large individuals. Finally, a trade-off between growth and female fecundity was observed in response to defoliation: some large trees maintained significant female fecundity at the expense of reduced growth in response to defoliation, while some other defoliated trees maintained high growth at the expense of reduced female fecundity. Our results suggest that, while decreasing their growth, some large defoliated trees still contribute to reproduction through seed production and pollination. This non-coordinated decline of growth and fecundity at individual level in response to stress may compromise the evolution of stress-resistance traits at population level, and increase forest tree vulnerability.

Quantification of One-Year Gypsy Moth Defoliation Extent in Wonju, Korea, Using Landsat Satellite Images

We quantified the extent and severity of Asian gypsy moth (Lymantria dispar) defoliation in Wonju, Korea, from May to early June in 2020. Landsat images were collected covering Wonju and the surrounding area in June from 2017 to 2020. Forest damage was evaluated based on differences between the Normalized Difference Moisture Index (NDMI) from images acquired in 8 June 2020 and the prior mean NDMI estimated from images in June from 2017 to 2019. The values of NDMI ranged from −1 to 1, where values closer to 1 meant higher canopy cover. The NDMI values for 7825 ha of forests were reduced by more than 0.05 compared to the mean NDMI values for the prior 3 years (2017 to 2019). The NDMI values of 1350 ha of forests were reduced by >0.125 to 0.2, and the NDMI values for another 656 ha were reduced by more than 0.2. A field survey showed that these forests were defoliated by gypsy moth and that forests with NDMI reductions of more than 0.2 were heavily defoliated by gypsy moth. A 311 ha area of Japanese larch (Larix kaempferi) was severely damaged by gypsy moth and the proportion of larch damaged was higher than that of other tree species. This intense damage to larch suggests that gypsy moths preferentially attack Japanese larch in Wonju. Our study shows that the use of NDMI values to detect areas defoliated by gypsy moth from satellite images is effective and can be used to measure other characteristics of gypsy moth defoliation events, such as host preferences under field conditions.

Defoliation Effects on Growth, Development and Yield of Okra (Abelmoschus esculentus) Under an Irrigation Regime

An experiment was conducted at Research and Demonstration Farm of Agricultural Science Department, Federal College of Education, Pankshin located in the Northern Guinea Savanna Agro-ecological Zone of Nigeria to investigate defoliation effects on morphological characters and yield attributes of okra (Abelmoschus esculentus) carried out during 2015 and 2016 dry season. The experiment comprised five levels of defoliation viz: 0% (control), 30%, 60%, 90%, and 100%. The experiment was laid out in identical Randomized Complete Block Design (RCBD) with six replications. Results revealed that defoliation had significant effect on the studied crop characters and yield. Most of the parameters like plant height, stem girth; number of leaves, leaf area, and yield parameters decreases which are a function of increasing defoliation levels intensity. Defoliation at 0% and 30% were tolerable for okra plant growth and development, while at 90% and 100% was detrimental to plant growth and yield. Hence, defoliation at 30% is recommended to meet farmers’ pod and leaf requirement.

Does the type of silvicultural practice influence spruce budworm defoliation of seedlings?

AbstractSpruce budworm (Choristoneura fumiferana (Clem)) is the main defoliator in the boreal forest of North America, and its outbreaks have major ecological and economic consequences and represent a challenge for forest management. Numerous studies have addressed the effects of this defoliator on mature trees, whereas the effects of spruce budworm on regeneration remain elusive. Furthermore, intensive exploitation practices during the last decades have left a large area of the Canadian boreal forest in an early development stage. In this context, it becomes vital to understand those factors affecting the severity of spruce budworm‐related defoliation on regeneration. Here, we determine the defoliation severity of black spruce and balsam fir seedlings in both mature pure black spruce and black spruce–balsam fir stands subjected to two different silvicultural treatments (clear‐cutting and partial cutting). Defoliation intensity varied between stand types, silvicultural treatments, species, and height classes. Seedlings in black spruce–balsam fir stands experienced twice the defoliation of those in pure black spruce stands (black spruce seedlings 10% vs. 23%; balsam fir seedlings 29% vs. 47%, respectively). Harvesting methods also influenced seedling defoliation. Under clear‐cutting, black spruce seedlings (24%) were three times as defoliated as black spruce seedlings in partial cutting stands (8%), whereas balsam fir seedlings in clear‐cutting plots experienced twice the defoliation (42%) of balsam fir seedlings in partial cutting plots (20%). The level of defoliation also increased with seedling height. This study will help silvicultural strategies adapt to the effects of natural disturbance regimes. As the intensity and severity of defoliator outbreaks are expected to increase under climate change, these results will help guide forest management strategies to select harvesting methods that will limit the effects of defoliation on conifer regeneration.

The effects of first defoliation and previous management intensity on forage quality of a semi-natural species-rich grassland.

Semi-natural grasslands occupy large parts of the European landscape but little information exists about seasonal variations in their nutritive value during the growing season. This paper presents results of novel data showing the effect of 13 years of previous contrasting management intensities on herbage nutritional value in relation to different dates of first defoliation (by grazing or haymaking). The treatments were: extensive management and intensive management from previous years (1998–2011). Both treatments were cut in June followed by intensive/extensive grazing for the rest of the grazing season (July–October). To evaluate forage quality in the first defoliation date, biomass sampling was performed in the year 2012 for 23 weeks from May to mid-October, and in 2013 for seven weeks from May to mid-June. Sampling was performed from plots that were not under management during the sampling year. Previous extensive management was associated with significantly reduced forage quality for in vitro organic matter digestibility (IVOMD), crude protein, neutral detergent fibre, acid detergent fibre and reduced divalent cations (Ca, Mg) and Na during the first seven weeks of the grazing season and the forage was suitable only for beef cattle. Due to low forage IVOMD, the forage is suitable only for cattle maintenance or for low quality hay when the start of grazing was postponed from seven weeks of vegetative growth to 13 weeks, regardless of the previous intensity. Herbage harvested after 13 weeks of the grazing season was of very low quality and was unsuitable as a forage for cattle when it was the only source of feed. Agri-environmental payments are necessary to help agricultural utilisation to maintain semi-natural grasslands by compensating for deterioration of forage quality, not only for the postponement of the first defoliation (either as cutting or grazing) after mid-June, but also when extensive management is required.