Timing Of Defoliation Research Articles

Severe insect defoliation at different timing affects cell wall formation of tracheids in secondary xylem of Larix kaempferi

Severe insect defoliation induced non-lignified tracheids and thin-walled latewood tracheids in the defoliation year in Larix kaempferi. These anomalous tracheids had heterogenous lignin deposition of S2 layer. Severe insect defoliation induces the formation of light ring consisted of thin-walled latewood tracheids in larch trees, which would affect wood quality. However, the identity of the secondary wall layers affected by insect defoliation remains unclear. The aim of this study is to clarify the effects of insect defoliation on the formation of secondary cell walls of tracheids in Larix kaempferi with focus on the defoliation timing. We observed by light microscopy and transmission electron microscopy (TEM) the secondary cell walls of tracheids produced in a defoliation year in L. kaempferi trees on which needles were attacked in July (gypsy moth, GM samples) or August (larch sawfly, LS samples). Light microscopy observations revealed that GM samples produced non-lignified tracheids in the transition zone between earlywood and latewood, as well as thin-walled latewood tracheids, and non-lignified tracheids were observed near the cambial zone in LS samples following defoliation for two consecutive years. TEM observations revealed that the tracheids in both samples had anomalous layers in secondary walls such as thin S2 layers with heterogeneous lignin deposition. The production of non-lignified tracheids corresponded to defoliation date in both samples, unlike changes in the layer composition of anomalous tracheids. Our study suggests that changes in wood structure depend on the date of insect defoliation and that insect defoliation affects the formation of secondary cell walls of tracheids, presumably in response to inadequate photosynthate supply as a result of defoliation.

Comparing dryland cotton upland fibre quality from on-board spindle and stripper harvesting systems

On-board spindle and brush type stripper round module harvest systems were evaluated on commercial field scale for dryland Upland cotton in Australia over two harvest seasons. Observations on harvester performance, including harvesting efficiency, harvest loss, seed cotton yield and lint turn out were conducted at three locations, during the 2017 and 2018 cotton growing seasons, with a single variety. Fibre quality was measured by High Volume Instrumentation (HVI™) and Advanced Fiber Information System (AFIS) and analysed to determine if there were any significant differences between the two harvesting systems. The stripper harvesters had higher productivity (i.e. hectares per hour), harvested more material with lower harvest loss than the spindle harvesters. The seed cotton harvested by the stripper systems contained plant material which resulted in a lower lint turn out than the spindle harvester although the yield in bales ha−1 was still higher. There were no significant differences in fibre quality as measured by the HVI except for colour and trash. The significant differences in colour and trash did not affect the economic return to the grower as the visual colour and trash grades were below, i.e. better than, the Australian base grade. There were also no significant differences in the fibre quality as measured by AFIS. It is hypothesised that the reasons for this was due to the appropriate timing and application of defoliation, harvesting when moisture content ≤ 12%, reduced leaf allowing for gentler ginning and mature fibre.

Establishment of plantain into existing pastures

In recent years plantain (Plantago lanceolata) has emerged as a potential forage for reducing nitrogen losses from dairy farm systems. However, achieving sufficient proportions of plantain in pastures to help meet target reductions in nitrate leaching presents on-farm challenges. To investigate sowing methods for establishing plantain into existing pasture to achieve high plantain populations, direct drilling was compared with broadcasting before and after grazing. Additionally, pre-graze mowing versus grazing only, and early versus late first defoliation after sowing were investigated to assess their effect on reducing competition from existing pasture. Botanical composition was determined in a small-plot study at Lincoln following summer sowing under irrigation, and from commercial dairy farms in Canterbury (irrigated) and Waikato (not irrigated). Generally, direct drilling was more effective than broadcast sowing for establishing plantain. The method of defoliation after sowing (pre-graze mowing or grazing) was not as important as timing of early defoliation in the resulting plantain populations. Early grazing, while seedlings were small enough to avoid defoliation, improved plantain establishment likely by reducing competition from the pre-existing pasture.

A Model to Identify Smooth Brome Elongation Using Correlation of Mean Stage Count and Accumulated Growing Degree Days

The US Fish and Wildlife Service (USFWS) uses the five-leaf developmental stage as a signal to the initiation of elongation in smooth brome (Bromus inermis Leyss.). In areas where certain plant community criteria are met, conducting a prescribed burn at elongation onset has reduced smooth brome populations. However, leaf stage identification presents USFWS managers with challenges due to the variability of smooth brome development in tallgrass prairies of the Northern Great Plains. The objective of this research was to develop an alternative method to determine when smooth brome populations reach the targeted 50% elongation by linking accumulated growing degree days and population-level plant phenological stages (mean stage count). We determined smooth brome phenological stages at sites in North Dakota, South Dakota, and Minnesota and calculated the corresponding number of growing degree days (using the base temperature of 0 °C). Linear regression models, correlating phenological stage and growing degree days, determined onset of elongation in the smooth brome population, regardless of leaf stage variation. The average accumulated growing degree days (1256 AGDD) and corresponding standard deviation (±155 AGDD) can be used to predict when 95% of smooth brome populations in northern tallgrass prairies reach 50% elongation. As part of USFWS Native Prairie Adaptive Management program, results will be used to assist management decisions regarding the timing of defoliation in an effort to enhance native plant communities where smooth brome is the dominant invader.

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.

Effects of Corn Row Width and Defoliation Timing and Intensity on Canopy Light Interception

ABSTRACTYield losses due to defoliation may be reduced in corn (Zea mays L.) grown at narrow compared to wider row widths. However, the physiological mechanisms behind this response are unclear. A 2‐yr experiment was conducted with two hybrids, row widths (38 and 76 cm), and a combination of defoliation timings–intensities: undefoliated control, V7–100%, V14–50%, V14–100%, R2–50%, and R2–100%. Intercepted photosynthetically active radiation (IPAR, MJ m−2) was measured after defoliation at V8, VT, R2, and R5. Post‐defoliation reductions in IPAR were always associated with yield losses after V14–100% and R2–100% defoliations. Conversely, V7–100%, V14–50%, and R2–50% defoliations were not always associated with yield penalties, as a result of a leaf area recovery that allowed plants to reach 72 to 85% IPAR around VT/R1. Changes in grain yields were independent from changes in IPAR‐V8 following V7–100% defoliations, and IPAR at or after VT following V14–100% and R2–100% defoliations. We found no interactions between rows and IPAR‐VT, IPAR‐R2 or IPAR‐R5 for V7–100%, V14–50%, and R2–50% defoliations, implying that the change in grain yield per unit change in IPAR was the same for both rows at each IPAR stage. No evidence of two (IPAR‐VT × IPAR‐R2) and three‐way interactions (IPAR‐VT × IPAR‐R2 × IPAR‐R5) among IPAR stages was found. A simple model explaining >35% of the yield variability in defoliated corn stands, independently of row width, using IPAR between VT and R5 as predictors was fitted. Greater yields associated with narrow rows in corn‐defoliated stands may be related to better resource allocation but was not related to greater intercepted radiation in our study.

Moments and number of defoliated leaves and hybrid corn productivity

AbstractObjectives: To determine the effect of the time and the number of lower leaves defoliated, on the productivity of hybrid corn (Zea mays L.). Methodology: Randomized complete blocks design was used, with arrangement of split plot and four replications, using the hybrid cultivar DK 7088. The plots corresponded to the defoliation times: 0, 14 and 28 days after pollination (DAP) and the subplots, number of defoliated leaves (DL): zero, two,four and six. The leaves were defoliated just below the ear, from top to the bottom. The total number of treatments was 12. Scott-Knott statistical test with a level of 5 % was used for the comparison of means. The traits studied were grain weight per ear, ear weight and grain yield per hectare. Results: The interaction between defoliation time and number of lower defoliated leaves was significant (P < 0.05) for grain weight per ear, ear weight andgrain yield. The defoliation of two, four and six leaves during pollination reduced the grain weight per ear, weight per cob and grain yield, being significantly lower than the no defoliated plants. At 14 and 28 days after pollination, defoliation did not affect significantly (P > 0.05) grain yield, but grain weight per ear and ear weight decreased (P< 0.05). Conclusions: The defoliation of lower leaves made during the pollination, reduces the grain weight per ear, ear weight and grain yield, while defoliation 14 days after pollination did not affect significantly the grain yield per hectare.Keywords: Zea mays, defoliation, leaves, grain yield

Timing and Intensity of Grapevine Defoliation: An Extensive Overview on Five Cultivars in Switzerland

This article synthetizes observations from five experiments and reports on the effects of timing and intensity of defoliation on the white and red Vitis vinifera cultivars Pinot noir, Gamay, Merlot, Chasselas, and Doral. Intensive defoliation (removal of six basal leaves + six lateral shoots per shoot) was completed at three developmental stages of the grapevine: preflowering, flowering, and bunch closure. Preflowering defoliation had tremendous consequences on vine agronomic performance, mainly to the detriment of berry set; the yield was highly affected by preflowering defoliation (approximately -35% of that from vines with no defoliation). The intensity of defoliation allowed its impact on the yield to be modulated. The intensity of defoliation also had a positive impact against millerandage, sunburn symptoms, and Botrytis cinerea development. The berry skin thickness doubled and the polyphenol concentration increased significantly with preflowering defoliation. Due to preflowering defoliation, the red wines were often preferred for their color and mouthfeel. However, this practice had a negligible impact on white wine composition. Regardless, preflowering defoliation did not negatively impact wine parameters. In the context of this study, preflowering defoliation has potential to reduce vigor and control high production potential. Preflowering defoliation also represents a prophylactic solution to reduce both chemical applications and cluster-thinning costs.

Investigating the Optimal Day for Nitrogen Fertilization on Piatã palisadegrass and Quênia guineagrass after Defoliation

Considering that nitrogen is the main macronutrient limiting pasture productivity, the aim of this study was to investigate the most appropriate day for nitrogen fertilization of the grasses Brachiaria brizantha BRS Piatã and Panicum maximum BRS Quênia. The experiment was conducted in a greenhouse in the city of Rondonópolis, located in the state of Mato Grosso, Brazil, using a completely randomized design. The treatments consisted of five nitrogen fertilization periods: 0; 2; 4; 6 and 8 days after defoliation. The dry mass of the leaf blade (DMLB), dry mass of stem + sheath (DMSS), dry mass of residue (DMRES) and root dry mass (RDM) were evaluated. The non-structural carbohydrate of the grass roots was also quantified. The later nitrogen fertilization after defoliation reduced DMLB (P< .01) and DMSS (P< .01) of the BRS Piatã palisadegrass, and DMRES of both grasses (P< .01). Higher levels of water soluble carbohydrates were observed when nitrogen fertilization was performed on grass cutting (day 0). Nitrogen fertilization of the BRS Piatã palisadegrass close the time of defoliation is recommended. For Quênia guineagrass, nitrogen can be applied between the cutting day and the eighth day after defoliation. For the root system, there is a higher content of water soluble carbohydrates in the BRS Piatã palisadegrass and greater accumulation of starch in the BRS Quênia guineagrass.

Effect of intensity and timing of defoliation on seed yield and yield components in oilseed gourd and its implication in insect pests’ sustainable control

Dual-purpose cropping for both leaf and seed production can be highly profitable if leaf removal by pests or farmers does not cause significant loss of seed yield. The objective of this study was to access the effect of defoliation intensity and timing on 7 yield and yield components for the cucurbit Lagenaria siceraria. The study was done in 2013 and 2014. Four defoliation intensities (0, 25, 50 and 75%) were applied to the crop at three phenological stages (tendril, flowering and fruit setting stage) in a split plot design. For all the yield traits examined, no significant difference was found between the control and 25% leaf defoliation, whatever the plant phenological stage. However, intense defoliation negatively affected seed production (from 1.99±0.98 t ha-1 with the control to 1.41±1.07 t ha-1 with 75% defoliation), irrespective of the growth stage of the plant. Seed yield decreased when defoliation was applied at advanced phenological stage, varying from a mean of 1.99±0.98 t ha1 (tendril) to 1.55±0.34 t ha-1 (fruit setting). The results suggested that the intensity of defoliation when harvesting the leaves or to trigger the treatment of bottle gourd against leaves damaging pests is about 25%, whatever the timing.Key words: Defoliation, Lagenaria siceraria, phenological stage, yield

KOMBINASI WAKTU DEFOLIASI ENTRES DAN MODEL SAMBUNG PUCUK TERHADAP PERTUMBUHAN BIBIT CACAO (Theobroma cacao, L)

Abstract
 
 The aim of the study was to get the interaction between the time of entries defoliation and shoot grafting model that gave the best Cacao seedling growth. The treatment design consists of two factors, namely the defoliation time of the entries and the top graft model. The time of entries defoliation consists of 4 defoliation times, entres defoliation at the connection (W1), entres defoliation 3 days before connection (W2), entres defoliation 6 days before connection (W3), and entres defoliation 9 days before connection (W4). The connection factor model is tested by two connection models, namely, connecting gap (S1), and diagonal connection (S2). The environmental design used is a randomized block design in factorial patterns. Parameters of cacao seedling growth observed were the percentage of live seedlings (%), time of shoot buds (days), shoot length (cm), shoot diameter (cm), and a number of leaf buds (strands). The results of this research are that there is no interaction between the treatment combination of all observed parameters. The best time for defoliation is 9 days before connection. The defoliation model used shows different results that are not real.

PENAMPILAN ALFALFA (Medicago sativa) DEFOLIASI PERTAMA PADA JARAK TANAM DAN UMUR DEFOLIASI YANG BERBEDA

Forage, the main feedstuff for ruminants, includes grasses and legumes, browses, and side products of food crops. However, legumes generally have greater crude protein content relative to other species of forage plants. One of the species of legumes is alfalfa (Medicago sativa), a perennial crop that can grow from the tropics up to sub tropics. In spite of its excellent nutrient content, In Indonesia alfalfa is still not widely explored and used for feedstuff. A study was conducted to explore and evaluate of alfalfa performances in terms of the height, number of tillers, dry matter (DM) and crude protein (CP) productions under the effects of different plant densities and ages of defoliation”. The height of the location of study was 200 m above sea level with an average temperature of 270 C. The results showed that the ranges of the height of alfalfa, the numbers of tillers, DM and CP productions were 33.31-56.32 cm, 36.38-82.36 tillers/bunch, 556.9-1018.9 kg/ha/defoliation, and 149.75 – 291.79 kg/ha/defoliation, respectively. In general, the ages of plant at the time of defoliation and plant distances affected (P<0.05) the variables being studied. The older plants resulted in greater DM and CP yields, and more densely plantation resulted in greater DM and CP yields.Keywords: alfalfa, plant density, defoliation age.

Hail Damage Impacts on Corn Productivity: A Review

Hail influence on corn (Zea mays L.) yield depends on defoliation timing and severity. Complete defoliation during early vegetative stages can have minimum yield effects if plants’ growing point is not affected but can generate some delays in the planting to flowering period. Low‐severity defoliations after V10 can reduce yield up to 30%. Higher severities gradually increase yield penalties to a peak around flowering and decrease progressively during the grain‐filling period. Charts to estimate the percentage of corn yield loss due to defoliation developed in the late 1960s are still accurate in most situations but fail to describe particular situations. Defoliation around VT commonly affects time to silking, anthesis–silking interval, and plant growth rate, but not time to anthesis, and is commonly explained by lower kernel number (KN). Defoliation at R2 commonly affects kernel weight (KW), without changing KN. However, several studies showed a reduction in both KW and KN with R2 defoliations. Under low plant disease pressure, fungicides applied around VT do not help reduce any yield defoliation impact. Specific genotypes, row spacing, and hybrid maturity can influence crop yield defoliation responses. More studies are warranted to confirm the potential for narrow rows to reduce yield loss after defoliation.

Establishing Defoliation Thresholds for Insect Pest of Peanut in Mississippi

ABSTRACT Defoliation of peanut by foliage-feeding insects reduces photosynthetic capacity, and in turn, may reduce pod yield, particularly when canopy loss occurs at critical growth stages, i.e., 40 or 80 d after full plant emergence (DAE). The objective of this research was to determine the impact of peanut defoliation levels of 0, 20, 40, 60, 80, and 100%, at 40 or 80 DAE on canopy height and width, plant biomass, pod grade and yield, and economic injury level. Research was conducted in Stoneville and Starkville MS in 2015 and 2016. The experimental design was a six (defoliation level) by two (defoliation timing) factorial arranged in a randomized complete block. Up to four wk after defoliation, canopy height, canopy width, and plant biomass were negatively correlated with defoliation level regardless of defoliation timing (40 and 80 DAE). Neither defoliation level nor timing had an effect on peanut grade or maturity. Similarly, defoliation at 40 DAE did not affect pod yield but when damage occurred 80 DAE, pod yield was reduced 18.6 kg/ha for every 1% increase in defoliation. Considering average crop value and insect control costs, the economic injury for peanut defoliation at 80 DAE is 5% defoliation. These data indicate that control of canopy-feeding insects is only economically viable when defoliation exceeds 5% defoliation at 80 DAE.

Evaluation of key meteorological determinants of wintering and flowering patterns of five rubber clones in Xishuangbanna, Yunnan, China.

All rubber tree clones (Hevea brasiliensis) exhibit regular annual wintering characterized by senescence and abscission of leaves. After 3-4weeks, this is followed by the onset of new leaves. It is likely that the timing of leaf onset affects the susceptibility of rubber trees to rubber powdery mildew disease, as this predominantly infests young leaves. However, little information is available on the phenological behavior of different rubber clones, or how meteorological factors affect such behavior. We assessed the wintering and flowering patterns of five rubber clones in Xishuangbanna, southwest China, based on observations made from 1978 to 2011, and evaluated how these patterns responded to different meteorological factors. Partial least squares regression was used to analyze the timing of defoliation, refoliation, and flowering. Our results showed that the two clones RRIM 600 and GT1 defoliated during the last week of December and refoliated in the last week of January, and clones Yunyan 277-5, Yunyan 34-4, and PR 107 defoliated during the first week of January and refoliated in the second week of February. The number of hours of sunshine during both the rainy season and the cold dry period in the dry season were important determinants of phenological changes in the rubber trees. Similarly, higher temperatures tended to delay the onset of defoliation and refoliation, and were a triggering factor for the onset of flowering. These results may help rubber cultivators to schedule appropriate disease control measures, as well as to design hybridization programs aiming at the production of clones which are resistant to foliar disease.

Intensity and timing of defoliation on white cultivar Chasselas under the temperate climate of Switzerland

Aim: The objective of this work is to investigate the effects of early defoliation on cv. Chasselas under the temperate conditions of Switzerland, with particular attention to berry anatomical traits and wine sensory parameters.Methods and results: Defoliation (removal of 6 basal leaves + 6 lateral shoots per shoot) was completed during three developmental stages of grapevine, i.e., pre-flowering, late flowering and bunch closure, and at two intensity levels. The experimentation was performed repeatedly over four years. In addition to vintage effect, pre-flowering defoliation had a consistent impact on vine agronomic behaviour. The yield was highly affected by the technique (more than 30% loss). Earlier and more intense defoliation had more impact on yield, while post-berry-set defoliation had no effect on yield. Intensive defoliation also modified berry skin thickness and had a positive impact inhibiting Botrytis development. Wine composition and sensory analysis were not affected by the practice. However, pre-floral defoliation affected bud fruitfulness and vigour, i.e., trimming and pruning weights. This result noted a carryover effect that could affect vine sustainability under restrictive conditions.Conclusion: In the context of this study, pre-flowering defoliation seems to be an interesting practice to reduce vigour and control the high production potential of the cv. Chasselas. The intensity of early defoliation allows for the modulation of the impact on the yield in order to prevent excessive yield loss.Significance and impact of the study: Pre-flowering defoliation of the white cultivar represents a prophylactic solution to reduce both chemical entrants and bunch-thinning costs.

Effects of Basal Defoliation on Wine Aromas: A Meta-Analysis.

Basal defoliation, as one of the most common viticulture management practices to modify fruit zone microclimates, has been widely applied aiming at improving wine quality. Wine aroma contributes greatly to wine quality, yet the effects of basal defoliation on wine aromas show discrepancies according to previous studies. This study is a meta-analysis performed to dissect the factors related to the influence of basal defoliation on volatile compounds in wine. Timing of basal defoliation plays an important role in the concentration of varietal aromas in wine. Pre-veraison defoliation induces an increase in β-damascenone and linalool as well as a reduction in 3-isobutyl-2-methoxypyrazine (IBMP). The effects of basal defoliation on certain volatile compounds relative to fermentation aromas in wine (1-hexanol, β-phenylethanol, 2-phenylethyl acetate, decanoic acid, and ethyl octanoate) depend on grape maturity. There are also other factors, such as cultivar and climate conditions, that might be responsible for the effect of basal defoliation on wine aromas. The concentrations of isobutanol, isoamyl alcohol, hexanoic acid, and octanoic acid as well as ethyl isobutyrate, ethyl hexanoate, ethyl isovalerate, and ethyl decanoate in wine are not markedly affected by basal defoliation. Due to limited studies included in this meta-analysis, more trials are needed to confirm the current findings.

Impacts of White Pine Needle Damage on seasonal litterfall dynamics and wood growth of eastern white pine (Pinus strobus) in northern New England

White Pine Needle Damage (WPND) is a complex of foliar fungal pathogens that have established as a chronic disease impacting eastern white pine (Pinus strobus L.) stands in the northeastern United States. With long-term ecological and economic impacts in mind, it is critical to quantify the negative effects of this disease on tree and forest health in order to make informed management decisions. We measured litterfall to determine the timing and magnitude of WPND-induced defoliation across four study sites in the northeastern US between 2014–2016. We measured N concentrations of needles cast throughout the 2014 growing season to estimate total litter N flux resulting from WPND. Additionally, to quantify growth declines we measured annual basal area increment (BAI) from six symptomatic study sites in the infected region. We found that WPND-induced defoliation in the months of June and July accounted for 47% of the total annual litterfall across the study sites, often exceeding normal needle senescence in October. Foliar %N in June and July was 0.78 and 0.84% respectively, significantly higher than October concentrations of 0.40%, suggesting incomplete resorption of N during the summer months. Untimely summer defoliations resulted in a mean estimated N loss of 0.92 g N m−2 yr−1, representing 63% of the total growing season N input from foliage. Growth of symptomatic trees at all sites was reduced following outbreaks of WPND initiating between 2007–2009. Severely infected trees reduced BAI 25–73% compared to pre-outbreak years. Our results show that WPND-induced defoliation significantly alters litterfall and N dynamics of affected stands, and suggest that subsequent N limitation in addition to reduced foliar area greatly reduces annual wood growth within infected stands.

Corn Yield Components and Yield Responses to Defoliation at Different Row Widths

Core Ideas Limited data on the effect of row width on defoliation in modern hybrids.Yield loss in 38 cm was less for all defoliation treatments vs. 76‐cm rows.Different hybrids responded differently to defoliation at different row widths.Defoliations had greater impact on kernel number than kernel weight in both hybrids.Some defoliations during effective grain‐filling period reduced kernel number. Corn (Zea mays L.) defoliation experiments have been conducted for more than 130 yr in the United States. However, there are limited data on the effect of row width on defoliation in modern hybrids. A 2‐yr experiment was conducted in Lexington, KY, with two hybrids (113 relative maturity [RM] and 120 RM), two row widths (38 and 76 cm) and a combination of defoliation timings and severities: 0% defoliation (control), V7 growth stage, and 100% defoliation (V7–100%), V14–50%, V14–100%, R2–50%, and R2–100%. No yield difference among hybrids was observed in 2012. Yields were 26% greater in 38‐cm rows than 76‐cm rows in 2012. For 2013, corn yield for 38 cm was 10% greater, but hybrid, row width, and defoliation interacted. Lowest yields were caused by V14–100% followed by R2–100% defoliations. Defoliations of V14–50% and R2–50% reduced yields in some cases. Complete defoliations at V7 did not reduce yields in most comparisons. Kernel number and kernel weight were most reduced by V14–100% and R2–100% defoliations, respectively. There is a potential for corn in 38‐cm narrow rows to reduce grain yield losses after a defoliation event, when compared with corn in 76‐cm standard rows.

Combined Effects of Early Season Leaf Removal and Climatic Conditions on Aroma Precursors in Sauvignon Blanc Grapes.

Early leaf removal around the cluster zone is a common technique applied in cool climate viticulture, to regulate yield components and improve fruit quality. Despite the increasing amount of information on early leaf removal and its impact on total soluble solids, anthocyanins, and polyphenols, less is known regarding aroma compounds. In order to verify the hypothesis that defoliation, applied before or after flowering, could impact the biosynthesis of thiol precursors, we performed a two year (2013 and 2014) experiment on Sauvignon blanc. We provided evidence that differential accumulation of thiol precursors in berries is affected by the timing of defoliation, and this impact was related to modifications in the biosynthetic pathway. Furthermore, the possible interaction between leaf removal treatment and seasonal weather conditions, and its effect on the biosynthesis of volatile precursors are discussed. Our results suggested that in Sauvignon blanc the relative proportion of 4-S-glutathionyl-4-methylpentan-2-one (G-4MSP) and 3-S-glutathionylhexan-1-ol (G-3SH) precursors can be affected by defoliation, and this could be related to the induction of two specific genes encoding glutathione-S-transferases (VvGST3 and VvGST5), while no significant effects on basic fruit chemical parameters, polyphenols, and methoxypyrazines were ascertained under our experimental conditions.