A caracterização fisiológica da cultura de soja auxilia na compreensão do comportamento da planta em resposta ao ambiente, permitindo estabelecer estratégias de manejo mais eficientes. Sendo assim, o presente trabalho teve por objetivo: (i) analisar a taxa fotossintética e transpiratória por unidade foliar, caracterizando a participação de cada estrato foliar, (ii) avaliar a fotossíntese líquida e respiração em estratos foliares após a aplicação de fungicidas e (iii) verificar a influência da senescência foliar natural, induzida por doença e controlada pela aplicação de fungicidas em folhas do estrato inferior com diferentes níveis de desfolha. O experimento I foi conduzido em câmara de crescimento na área experimental do Campus da ESALQ/USP no Departamento de Ciências Biológicas, em Piracicaba-SP, em 2007, onde foram realizadas avaliações de trocas gasosas. O experimento II foi instalado na estação experimental da Basf em Santo Antônio da Posse-SP, em 2011, neste experimento foram realizadas avaliações de fotossíntese líquida e respiração no estrato superior e inferior de plantas com aplicação de estrobilurina e triazol. O experimento III foi conduzido no Campus II do UNIPAM em Patos de Minas-MG, em 2011, onde se avaliou a influência das folhas senescentes do estrato inferior ao nível de 0, 25, 50, 75 e 100% de desfolha e aplicação de fungicidas. De acordo com os resultados encontrados no experimento I é possível inferir que a participação de cada unidade foliar da planta de soja na fotossíntese líquida total e na transpiração total se dá em função do seu estádio de desenvolvimento. A aplicação de estrobilurina Piraclostrobina + Epoxiconazol direcionada em folha do estrato inferior apresentam incrementos na fotossíntese líquida e decréscimos na atividade respiratória. A retirada de folhas do estrato inferior de plantas de soja ocasiona decréscimos na formação e enchimento de vagens e consequentemente diminuição da produtividade que variam de 1140, 1740 e 1680 kg ha-1, em plantas com 100% de desfolha, para os tratamentos 1 (testemunha), 2 (Piraclostrobina + Epoxiconazol) e 3 (Epoxiconazol), respectivamente. / The physiological characterization of the soybean crop helps in understanding the behavior of the plant in response to the environment, allowing establishing more effective management strategies. Therefore, this study aimed to: (i) analyze the photosynthetic and transpiration rates per leaf area unit, featuring the participation of each stratum leaf, (ii) evaluate the net photosynthesis and respiration in lower layer leaves after application of foliar fungicides and (iii) verify the influence of natural leaf senescence induced by disease and controlled by applying fungicides on the lower layer leaves with different levels of defoliation. The experiment was carried out in growth chamber at the Biology Department in Piracicaba, São Paulo State, in 2007, where assessments of gas exchange were made. The experiment II was installed at the Basf experimental station in Santo Antonio da Posse, São Paulo State, in 2011, where net photosynthesis and respiration were evaluated in the upper and lower layer leaves of the plants with strobilurin and triazol application. The experiment III was carried out in the Campus II of UNIPAM, in Patos de Minas, Minas Gerais State, in 2011, where the influence of lower layer senescent leaves were evaluated at 0, 25, 50, 75 and 100% of defoliation and fungicides application. According to the results of experiment I, the participation of each foliar unit of soybean plant on the total net photosynthesis and transpiration was inferred as function of its phenological stage of development. The application of Pyraclostrobin (strobilurin) + Epoxiconazol in the lower layer leaves present increments on net photosynthesis and decreases the respiratory activity. The removal of the lower layer leaves of soybean plants caused a decreasing of pod formation and filling and, consequently, decreases productivity ranging from 1140, 1740 and 1680 kg ha-1 in plants with 100% defoliation, for the treatments 1 (untreated), 2 (Pyraclostrobin + Epoxiconazole) and 3 (Epoxiconazole), respectively.

Defoliating insect systems, defined for the purposes of this thesis as being composed of insects which defoliate forest trees and the species with which they interact, such as their host trees and their natural enemy complexes, exhibit a wide variety of population behaviors. Similarly, a number of theories and models have been proposed to explain these behaviors. These theories emphasize the importance of different ecological processes, often concentrate on the defoliator and overlook the importance of other components. Also, much of the current understanding of the dynamics of these systems has come from forest pest research and management programs, tailored towards specific pest problems and often very short term in nature. This thesis develops and begins to test a general approach for the local dynamics of defoliating insect systems. This framework outlines the system components that are necessary to predict the behavior of defoliating insect systems. It includes ways in which the equilibrium structure of defoliating insect systems, defined as the number of equilibria for each system component, the population levels at which the equilibria occur, and the processes creating the equilibria, might be found. The framework also includes methods of inducing the qualitative behavior of these sys- terns, defined as the periodicity of defoliator outbreaks, the length of outbreaks, and the dynamics of other important system components between, during, and in the decline of defoliator outbreaks. The study begins with a detailed literature review of historical theories of defoliating insect system behavior and of the documented behavior patterns of these systems. Major classes of behavior are identified, as well as the various ecological processes which have been invoked to explain these behaviors. An analysis and documentation of the equilibrium structure and behavior of three defoliating defoliating insect systems, the eastern blackheaded budworm, the eastern spruce budworm, and the jack pine sawfly, are then used to develop general rules about how equilibrium structure and behavior can be explained. This analysis, coupled with the literature review, is used to develop the framework. The framework is then tested against historical defoliator population data and general syntheses of defoliating insect system research to assess its utility and predictability. The major results of the thesis are as follows. First, it appears that the structure and behavior of a defoliating insect system can be explained with five dynamic variables: the abundances of the defoliator; the foliage; the forest; the parasitoid; and the disease; and the effects of weather acting on the defoliator. Second, there appear to be 4 classes of defoliating insect system behavior. Third, the behavior that a defoliating insect system will exhibit seems to be determined by the magnitude of weather effects on defoliator survival and recruitment, the parasitoid numerical response to changing defoliator densities, the disease numerical response to changing defoliator densities, and the vulnerability of the forest to defoliation. Fourth, there seem to be four equilibrium structures the defoliator can exhibit, and one each for the parasitoid, the foliage, the forest, and the disease. Finally, the framework suggests that defoliating insect system structure and behavior can be induced with a particular, well-defined set of information. The framework is successful when applied to particular defoliating insect systems for explaining their behavior, but less successful in explaining defoliator equilibrium structure for other systems. Opportunities for more thorough testing of the framework exist if the particular types of data outlined above are gathered for defoliating insect systems. This lack of data for testing the framework make it currently difficult to clearly define those systems in which the framework is useful and those systems in which it is not. Experiments to test the framework are described and suggestions for future types of applied research on defoliating insect systems are presented. / Science, Faculty of / Zoology, Department of / Graduate

‘Crimson Seedless’ (Vitis vinifera L.) is an attractive, late season, red, seedless cultivar, which is currently a very popular table grape cultivar. It is one of the most planted cultivars in South Africa and third in terms of total area of table grape vineyards in production. Mature ‘Crimson Seedless’ grapes are characterized by outstanding eating quality, good flavour, firm and crisp berries. One of the key factors affecting the yield of table grape cultivars is bud fruitfulness. Low fruitfulness can have a significant effect on the yield of table grape cultivars and ‘Crimson Seedless’ is characterized by a fruitfulness problem. Summer pruning, such as the removal of shoots after harvesting grapes, is a cultivation practice widely used by some table grape producers in the Orange River region of South Africa. The first hypothesis of this study stated that the removal of shoots after harvest will increase the transmitted PAR through the canopy, increase carbohydrate reserve levels in canes and improve bud fruitfulness of ‘Crimson Seedless’. A second hypothesis of this study stated that the cut back of all main shoots and shoots developing from spurs to the nearest lateral shoot and the removal of all unproductive shoots after berry set will result in fruitful shoots the following season. The third and final hypothesis of this study stated that the removal of shoots after harvest and berry set will improve the yield and quality of Vitis vinifera cv. ‘Crimson Seedless’. The study was conducted over three seasons (2010/11 to 2012/13) and aimed at investigating factors, including shoot removal, impacting bud fruitfulness of an 11-year-old commercial V. vinifera L. cv. ‘Crimson Seedless’ vineyard, grafted on ‘Ramsey’ (Vitis champinii) rootstocks in the Hex River Valley. The treatment design was a complete randomized design and involved five treatments, which included 33% shoot removal (S33) and 66% shoot removal (S66) after harvest, cutting of all main and lateral shoots developing from spurs to the nearest lateral shoot (LS), removal of all unproductive shoots (RSB) which was compared with the control, in which standard pruning practices were performed. The results obtained in this experiment showed that shoot removal after harvest and after berry set improves PAR transmission into the canopy, but there was no significant impact on bud fruitfulness. In addition, it was found that shoot removal reduced vegetative growth resulting in thinner canes that also led to the improvement in PAR transmission. Furthermore, bunch number per shoot in the LS treated vines was reduced when compared with S33 treated vines, illustrating that shoot removal at berry set can reduce bunch number per shoot due to defoliation after berry set. The significant decrease in bud burst in the S33 treatments compared with the control was expected due to less shoots, resulting in a reduction in cane mass during the 2010/11 season. The significant effect of LS treatments after berry set on TSS and total red pigments compared with the S66 treatments and the control, respectively, clearly indicates that shoot removal after berry set improves grape colour. The positive effect of LS treatments on colour was supported by the significant improvement in class 4 bunches, representing an improvement in quality. Although shoot removal did not have a significant effect on the bunch mass per vine of ‘Crimson Seedless’, there was a significant reduction in total bunches for export and mass of the total export bunches in the LS treatments in the 2011/12 season. A link between carbohydrate concentration in canes and bud fruitfulness was not found in this study, as S33 and S66 treatments did not have a significant effect on carbohydrate content in canes during the 2011/12 season. The question therefore arises whether the treatments applied during the growing seasons are worthwhile, because there was no significant impact on bud fruitfulness of Vitis vinifera L. cv. ‘Crimson Seedless’. This study illustrates that growers need to decide whether it is worthwhile to utilize labour for this practice and they must manage grapevines not only for the current seasons crop, but also for the next season and this can be accomplished by maintaining sufficient carbohydrates for fruitfulness and yield from season to season. / Dissertation (MInst Agrar)--University of Pretoria, 2014. / tm2015 / Plant Production and Soil Science / MInst Agrar / Unrestricted

The influence of the spatial pattern of foliage removal on regrowth was investigated in the field with a tussock grass, Agropyron desertorum. Tussocks were hand clipped in different spatial patterns that represented extremes of defoliation patterns which could be inflicted by natural herbivores. All defoliated tussocks exhibited increases in specific growth rates following clipping in mid-May. When foliage was removed from the upper portion of the canopy (younger foliage), regrowth rates and season-long aboveground biomass production were less than if the same amount of foliage was removed from low in the canopy (older foliage). The spatial pattern of defoliation also influenced tussock regrowth in a late-May clipping experiment, but differences in the effects of the clipping patterns were associated with the removal of apical meristems rather than with the age or location of foliage removed. Changes in tussock carbon dioxide and water vapor exchange that were associated with changes in growth following mid-May clipping were explored. All clipped tussocks showed increases in integrated daytime carbon dioxide uptake per unit foliage area after defoliation. Differences among treatments in the response of net daytime carbon gain during the first 24 hours after clipping corresponded well with differences in tussock regrowth over a 14-day period following clipping. Increased carbon gain of clipped tussocks was associated with increases in tussock water vapor conductance and intercellular carbon dioxide concentration, and decreases in the ratio of carbon dioxide uptake to water vapor loss. Differences among treatments in daytime carbon gain and regrowth were paralleled by the response of instantaneous rates of light-saturated net photosynthesis for entire tussocks. Defoliation increased the proportion of foliage directly illuminated within the tussock at solar noon. Changes in the fraction of sunlit foliage and the relative amounts of different-aged foliage in tussock canopies were correlated with the responses of light-saturated photosynthesis. Thus, the effects of the spatial pattern of foliage removal on canopy light microclimate and the age of remaining foliage had important implications for carbon gain and regrowth of tussocks following mid-May defoliation.

No description available.

Commercially available leaf area index (LAI) meters are tools that can be used in making insect management decisions. However, proper technique must be determined for LAI estimation, and accuracy must be validated for the meters. Full-season soybean require LAI values of at least 3.5 to 4.0 by early to mid-reproductive developmental stages to achieve maximum yield potential, but the relationship between double-crop soybean LAI and yield is unknown. This research (1) evaluated minimum plot size requirements for mechanically defoliated soybean experiments using the LAI-2000 Plant Canopy Analyzer, (2) compared LAI estimates among LAI-2000 detector types which respond to different wavelengths of light, (3) compared LAI-2000 estimates with directly determined LAI values for 0, 33, 66, and 100% mechanical defoliation levels, (4) used linear and non-linear models to describe the response of full-season and double-crop soybean yields to reductions in LAI through mechanical defoliation, and (5) evaluated the response of double-crop soybean yields to reductions in LAI through insect defoliation. The minimum plot size for obtaining accurate LAI estimates of defoliated canopies in soybean with 91 cm row centers is four rows by 2 m, with an additional 1 m at the ends of the two middle rows also defoliated. The wide-blue detector, which is found in newer LAI-2000 units and responds to wavelengths of light from 360 to 460 nm, gave higher LAI estimates than the narrow-blue detector, which responds to light from 400 to 490 nm. The unit with the narrow-blue detector gave estimates equal to directly determined LAI in two of three years for 0, 33, and 66% defoliation levels, while the units with the wide-blue detectors gave estimates higher than directly determined LAI in the two years that they were studied, except for a few accurate 33% defoliation estimates. Therefore, the LAI-2000 usually provides reasonable estimates of LAI. Yield decreased linearly with LAI when LAI values were below 3.5 to 4.0 by developmental stages R4 to R5 in both full-season and double-crop soybean. Usually, there was no relationship between yield and LAI at LAI values greater than 4.0. There was an average yield reduction of 820 ± 262 kg ha⁻¹ for each unit decrease in LAI below the critical 3.5 to 4.0 level; maximum yields ranged from 1909 to 3797 kg ha⁻¹. Insect defoliators did not defoliate double-crop soybean plots to LAI levels less than 4.0, and there was no yield difference between insect-defoliated and control plots. Therefore, double-crop soybean that maintains LAI values above the 3.5 to 4.0 critical level during mid-reproductive developmental stages is capable of tolerating defoliating pest / Ph. D.

Biennial bearing has been investigated longer and more extensively in apple than in any other fruit tree; however, it remains a serious problem in commercial apple production all over the world. Trees that have become biennial flower profusely and carry a heavy crop in the "on" year, and flower sparsely or not at all and carry little or no crop the following year, the "off" year. Fruit in the "on" year tend to be small, poorly colored, and of low quality, while the few fruit in the "off" year are usually too large, become susceptible to physiological disorders, and also are of poor quality. Without intervention, the crops in both the "on" and "off" years are undesirable and uneconomical. The most common method used by commercial apple growers to try to prevent biennial bearing is chemical fruit thinning, which is an "on" year method of removing a part of the crop before it matures on the tree. In general, growers don't do anything in the "off" year to prevent biennial bearing with the exceptions of fertilizing and pruning lightly. In this study, several experiments were conducted with the cultivars "Braeburn", "Golden Delicious", "Ramey York", and "Fuji" in the "off" year to try and suppress FBI and thus prevent a biennial bearing situation in the following year. The first set of experiments studied the effect of whole-tree and partial-tree defoliation on suppressing spur and lateral flowering and fruit set. Flowering and fruit set were suppressed with defoliation in most cases. Defoliation in early July caused the least amount of flowering the following year and in some cases it was zero. As the defoliation timing and severity was delayed, there was less suppression of flowering and fruit set. Ammonium thiosulfate and Endothal increased flowering but decreased fruit set compared to a control. Gramoxone suppressed flowering and fruit set. In another set of experiments, gibberellic acid (GA) treatments were evaluated to suppress FBI in "off" or light crop years. The GA4+7 treatments suppressed return bloom of both spur and lateral flowers more than the GA3 treatments. The effectiveness of GA declined with delayed application. Both GA treatments reduced lateral flowering the most on the basal 1/3 of the shoot. In a four year study, apple trees were thinned to one fruit per flowering cluster every year from 1997 to 2000. Other trees were thinned to zero fruit or two fruit per flowering cluster in alternate years from 1997 to 2000. Trees thinned to one fruit per flowering cluster had moderate flowering and fruit set the following year. Trees thinned to two fruit per flowering cluster had very little to no flowering the following year. Trees thinned to zero fruit per flowering cluster had a "snowball" bloom the following year. Trees that were alternately thinned to two or zero fruit per flowering cluster were in a biennial bearing situation. / Ph. D.

This field study investigated the short-term effects of riparian defoliation by gypsy moth larvae on three aspects of headwater stream ecology, water quality, benthic macroinvertebrate community structure, and benthic macroinvertebrate function (expressed as secondary production). The experimental design was to compare measurements in three streams that were extensively defoliated by gypsy moth larvae (defoliated treatment), with three streams that were not affected by gypsy moth larvae (reference treatment). Although the riparian canopy became much more open after defoliation, I observed no significant differences in any water quality parameters except temperature, which was slightly elevated for a brief period after defoliation. There was a significant increase in the amount of detritus (frass and orts) falling into defoliated streams in the spring, which was followed by a significant decrease in the of amount detritus falling into defoliated streams in autumn. Many measures of community structure were analyzed, but only the Index of Biotic Similarity demonstrated a significant difference, indicating that, at most, only slight changes in community structure occurred. Secondary production of two representative aquatic insects, Peltoperlidae (shredder) and Diplectrona modesta (collectorfilterer), was not affected by defoliation. Glossosoma nigrior (scraper) achieved higher production because of a second-generation being induced by elevated temperature. I conclude that the short-term effects of riparian defoliation by gypsy moth larvae were minor. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The work was carried out to evaluate the defoliation patterns and quantify the leaf tissue flows in Alexandergrass, grazed by beef heifers in different feeding systems, in rotational grazing method. The experimental design was completely randomized with repeated measures, three levels of supplementation with whole rice bran (0; 0.5 and 1% of body weight) and two area replications. The supply of whole rice bran for heifers grazing in Alexandergrass allows can increase 13% the stocking rate. The leaf tissue flows, consumption of leaf blades and the grazing intensity are not changed by supplement. Regardless of the system feeding the heifers graze the leaf blades growing in a smaller period of time compared to other types of leaf, which allows the leaf crop top extract canopy. / Objetivou-se avaliar os padrões de desfolhação e quantificar os fluxos de tecidos foliares em papuã, pastejado por novilhas de corte, em diferentes sistemas alimentares, em método rotativo de pastejo. O delineamento experimental foi o inteiramente casualizado, com medidas repetidas no tempo, três níveis de suplementação com farelo de arroz integral (0; 0,5 e 1 % do peso corporal) e duas repetições de área. O fornecimento de farelo de arroz integral para novilhas em pastejo em papuã permite aumentar 13% a taxa de lotação. Os fluxos de tecidos foliares, o consumo de lâminas foliares e a intensidade de pastejo não são alterados pelo fornecimento de suplemento. Independente do sistema alimentar as novilhas pastejaram as lâminas foliares em expansão num menor intervalo de tempo em relação aos demais tipos de folha, o que permite a colheita de folhas do extrato superior do dossel.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study was conducted with the aim of generating information about the tillering process and contribute to the understanding of the defoliation process of Italian ryegrass (Lolium multiflorum Lam) utilized by lambs submitted to different herbage allowances: 6, 8 and 12 kg body weight DM/100 kg. The grazing method was intermittent. Pasture was utilized during 12 days and an accumulated thermal sum of 250 degree-days was the criterion to determine the grazing interval. The experimental design was completely randomized with repeated measures on time, three treatments and two area replication. It was used 35 marked tillers per paddock to determine the intensity and interval of defoliation. Tillering dynamics on the identification and counting of remaining living tiller and new appearance tillers. The intensity of defoliation is greater in 6 and 9% herbage allowances. The interval of defoliation is higher in forage herbage allowance 12%, intermediate in 9% and lower in the 6% offer. The rate appearance, survival and death of tillers, stability index of tillers number are similar for herbage allowances and differ according phenological stages of ryegrass. Different herbage allowances and phenological stages promote variable intensity and interval of defoliation. The advance of phenological stage increases tiller mortality and reduce the interval between defoliation. / Este estudo foi conduzido com o objetivo de gerar informações a respeito do processo de perfilhamento e contribuir com o entendimento do processo de desfolhação do azevém (Lolium multiflorum Lam.) utilizado por cordeiras submetidas a diferentes ofertas de forragem: 6; 8 e 12 kg de MS/100kg de peso corporal. O método de pastejo foi intermitente. O período de ocupação da pastagem foi de 12 dias e o critério para determinar o intervalo entre pastejos foi a soma térmica acumulada de 250 graus-dia. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo, três tratamentos e duas repetições de área. Utilizaram-se 35 perfilhos marcados por parcela para a determinação da intensidade e intervalo de desfolhação. A dinâmica de perfilhamento baseou-se na identificação e na contagem de perfilhos vivos remanescentes e no aparecimento de novos perfilhos. A intensidade de desfolhação foi superior nas ofertas de forragem 6 e 9%. O intervalo de desfolhação foi superior na oferta de forragem 12%, intermediário na oferta 9% e inferior na oferta 6%. As taxas de aparecimento, sobrevivência e mortalidade de perfilhos e o índice de estabilidade da população de perfilhos são similares nas ofertas de forragem e variam em função dos estádios fenológicos do azevém. As diferentes ofertas de forragem e estádios fenológicos promovem intensidade e intervalo de desfolhação variável. O avanço do estádio fenológico aumenta a mortalidade de perfilhos e reduz o intervalo entre desfolhações.