Currently the size and frequency of wildfires are increasing at a global scale, including arid ecosystems that exhibit great sensitivity to disturbance. Fire effects on plant pollination and reproductive success in deserts are largely unknown. Plant dependence on animal pollinators for reproduction can increase the risk of reproductive failure if pollination services are hindered or lost. Species that depend on few taxonomically related pollinator species are expected to be most negatively affected by disturbances that disrupt pollination interactions. To assess fire and isolation effects on reproductive success in desert plant communities, and how wildfire influences the pollination success of generalist and specialist pollinated plants, the number of flowers, fruits, and viable seeds produced by plants surviving in burned and unburned desert landscapes were compared. Fire increased flower production for wind and generalist pollinated plants, and did not affect specialist plant flower production. Increases may be associated with positive physiological responses exhibited by plants surviving in burned areas. Fire did not affect pollination services. Wildfire effects on fruit production were neutral or positive, and overall seed:ovule ratios varied by 3% or less in burned and unburned areas for each pollination strategy. Increasing isolation within burned areas did not affect fruit production for generalist or specialist pollinated plants, suggesting that pollination services are functional across expansive burned desert landscapes. Annual reproductive output varied between years in burned and unburned areas, and shifts likely resulted from variation in annual precipitation patterns. Reductions in landscape reproductive output may be partially compensated by increased per plant fruit and seed production and maintaining pollinator services across burned landscapes, providing native shrub communities the possibility to naturally recover from fire disturbances. Habitat disturbances can influence plant interactions with herbivores, in addition to pollinators. To understand how fire and ungulate herbivory affect reproductive success of specialist pollinated desert plants, reproductive effort, floral herbivory, and pollinator visitation and success, were compared for Yucca baccata, and Yucca brevifolia in burned and unburned areas of the Mojave Desert. Fire increased Y. baccata flowering from 12% to 22% of plants in burned areas, but had no effect on the number of flowers or fruits produced per plant. Fruit set and pollinator collection failed at all sampled Y. baccata individuals, while fire and herbivory had no effect on Y. brevifolia flower, fruit, and pollinator collection. Herbivores consumed 50% and 67% of floral stalks produced by Y. baccata in unburned and burned areas. Herbivores pose a clear threat to successful sexual reproduction for Y. baccata. Removal of ungulate herbivores during important flowering periods may still result in failed fruit and seed production if local pollinator reserves have been drastically reduced or lost.

京都大学 / 新制・論文博士 / 博士(農学) / 乙第13529号 / 論農博第2910号 / 新制||農||1096(附属図書館) / 学位論文||R5||N5425(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 中﨑 鉄也, 教授 土井 元章, 教授 樋口 浩和 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Made available in DSpace on 2017-07-25T19:29:53Z (GMT). No. of bitstreams: 1 Alexandre Pavanello.pdf: 2830870 bytes, checksum: 6cfe2c059418ba0841f20c1f7b9ba383 (MD5) Previous issue date: 2012-05-10 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / Fruit thinning is one of the main practice to produce good quality fruit today. It promotes a balance between vegetative growth and production, increases fruit size and avoids alternation of production. Thinning can be done during flowering, but its often done later after fruit set, which can be defined best fruiting. Manual thinning of large number of plants is not practical or economical. An alternative is chemical thinning, which involves the application of chemicals on flowering or right after flowering and leads to fruit abscission, reducing or eliminating manual thinning. The objectives of this trial was to evaluate the effect of different concentrations of ethephon (2-chloroethylphosphonic) in chemical thinning of plum cvs. Irati, Reubennel during the harvest of 2010/2011 and 2011/2012 and its economic feasibility in Arapoti-PR. East central region of Paraná. The following characteristics were evaluated, number of fruits per branch, per plant, production, medium weight, firmness, soluble solids, pH, acidity and color. In the season 2010/2011, it was observed that increased concentration of ethephon linearly decreased the number of fruit caliber I, II, III, since the gauge IV had a higher number of fruits on the estimated concentration of 0.093 mL L ethephon and necessary to drive studies at lower concentrations, which were made in 2011/2012 harvest. In this harvest, the estimated concentration of 0.07 mL L ethephon, cv. Irati produced 23 kg/plant and the cv. Reubennel 73 kg/plant having satisfactory quantity of fruit size III and IV. The use of ethephon decreased the firmness of the fruits for cv. Irati and did not influenced the cv. Reubennel. None of the concentrations of ethephon affected the physical and chemical quality of fruits in relation to total soluble solids, pH and acidity for both crops and cvs. Economical evaluation of both cvs., showed that productivity and net income of treatment with etehephon gave better results than other treatments. Manual thinning showed a higher percentage gave better results than other treatments. Manual thinning showed a higher percentage of fruit size III and IV but at higher cost, which is difficult to sustain in time, due to high cost and availability of skilled labor force in the region, which indicates that chemical thinning will be a good economical alternative. / O raleio de frutos é uma das práticas mais importantes para se produzir frutos de qualidade. Promove equilíbrio entre o crescimento vegetativo e produtivo, aumento no tamanho dos frutos e evita alternância da produção. O raleio pode ser realizado durante a floração, mas é frequentemente feito mais tarde, após a fixação dos frutos, onde pode se definir melhor a frutificação. O raleio manual de um grande número de plantas não é prático nem econômico. A alternativa é o raleio químico, o qual consiste na aplicação de produtos químicos na floração ou logo após, provocando a abscisão de frutos, diminuindo ou eliminando, a atividade do raleio manual. Nesse contexto, os objetivos deste trabalho foram avaliar o efeito de diferentes concentrações de ethephon (ácido 2-cloroetilfosfônico), para o raleio químico das ameixeiras cvs. Irati e Reubennel, nas safras 2010/2011 e 2011/2012 e sua viabilidade econômica, no município de Arapoti – PR, região centro leste do Paraná. As seguintes características foram avaliadas: número de frutos por ramo, por planta, produção, massa médio, firmeza, sólidos solúveis, pH, acidez e coloração. Na safra 2010/2011, concluiu-se que o aumento na concentração de ethephon diminuiu linearmente o número de frutos de calibre I, II e III, já o calibre IV apresentou maior número de frutos na concentração estimada de 0,093 mL Lˉˡ de ethephon, sendo necessário realizar estudos com menores concentrações, as quais foram feitas na safra 2011/2012. Nesta safra, a concentração estimada de 0,07 mL Lˉˡ de ethephon, a cv. Irati produziu 23 kg/planta e a cv. Reubennel 73 kg/planta, apresentando quantidade satisfatória de frutos calibre III e IV. A utilização de ethephon diminui a firmeza dos frutos para cv. Irati e não influenciou a cv. Reubennel. Nenhuma das concentrações de ethephon afetou a qualidade física e química dos frutos, em relação ao teor de sólidos solúveis, pH e acidez, para ambas cvs e safras. Na análise econômica, em ambas cvs., a produtividade e a receita líquida para o tratamento com ethephon, foi superior aos demais. O tratamento com raleio manual apresentou maior porcentagem de frutos calibre III e IV, porém o alto custo, a dificuldade e disponibilidade de mão-de-obra para o raleio manual, fazem com que o raleio químico venha a ser usado cada vez mais.

Made available in DSpace on 2014-06-11T19:33:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-11-27Bitstream added on 2014-06-13T18:45:21Z : No. of bitstreams: 1 nicodemo_d_dr_jabo.pdf: 529924 bytes, checksum: 436115f2f4f07ab45288d9c5ed7c0e35 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O cultivo em estufas propicia a obtenção de produtos de excelente qualidade, porém, os agentes polinizadores que contribuem na maximização da produção não são adaptados a ambientes fechados. Utilizando três cultivares tipo Japonês e duas tipo Aodai de pepino (Cucumis sativus L.) foram realizados dois experimentos em três estufas localizadas na USP/Ribeirão Preto. Os objetivos foram estudar a biologia floral das cultivares no que se refere ao número de flores produzidas por planta, período de antese, porcentagem de açúcares do néctar, produção e viabilidade dos grãos de pólen, receptividade do estigma e atratividade de flores e, a importância das abelhas Jataí (Tetragonisca angustula), Iraí (Nannotrigona testaceicornis) e Africanizadas (Apis mellifera) quanto a freqüência das abelhas nas flores, tempo e tipo de coleta e produção de frutos quanto ao peso, comprimento e diâmetro. O manejo das abelhas africanizadas foi estudado e um modelo de núcleo com dois alvados desenvolvido. As flores das cultivares avaliadas têm antese de, aproximadamente, 10 horas. A viabilidade dos grãos de pólen e a receptividade do estigma não são limitantes na polinização de pepino Japonês e Aodai. Os índices de frutificação de pepino Japonês por partenocarpia são altos (78 %), porém há aumento de 19% quando ocorre polinização por abelhas. A cultivar Aodai depende dos insetos para produção de frutos, sendo que flores visitadas até às 10h30 originaram frutos mais pesados. As abelhas Africanizadas se adaptaram a colméia com dois alvados, visitando flores em parte do dia dentro da estufa, promovendo a polinização, e o restante fora, ambiente com maior oferta de recursos. / The cultivation in greenhouses allows obtaining products of excellent quality, however, the pollinators that contribute maximizing the production are not adapted to the indoor environment. Using three Japanese and two Aodai cultivars of cucumber (Cucumis sativus L.) were conducted two experiments in three greenhouses located in USP / Ribeirão Preto. The aims were to study the cultivars floral biology with regard to the number of flowers produced per plant, anthesis period, the percentage of sugars in nectar, production and viability of pollen grains, stigma receptivity and attractiveness of flowers, and the importance of Jataí (Tetragonisca angustula), Iraí (Nannotrigona testaceicornis) and Africanized honeybees (Apis mellifera) with regard to the frequency of bees in the flowers, time and type of collection and fruit weight, length and diameter. The management of Africanized bees has been studied and a hive with two entrances was developed. The anthesis period was approximately of 10 hours. The viability of pollen grains and the receptivity of stigma did not limit the pollination of Japanese cucumber and Aodai. The parthenocarpy fruit set of Japanese cucumber was high (78%), but there is an increase of 19% in fruit set when the flowers were pollinated by bees. The cultivar Aodai depends on the insects for production of fruits. Flowers visited until 10h30 originated the heaviest ones. Africanized bees adapted itself to the hive with two entrances, visiting flowers in part of the day inside the greenhouse, promoting pollination, and the rest outside, the environment with greater supply of resources.

Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05-18Bitstream added on 2014-06-13T20:49:53Z : No. of bitstreams: 1 apazaquevedo_ae_me_rcla.pdf: 800607 bytes, checksum: 267307790610778739a78e2fefb26944 (MD5) / Os efeitos de borda incluem mudanças abióticas e bióticas nas condições ambientais, as quais afetam os padrões fenológicos das plantas. Comparamos a fenologia reprodutiva (quanto a data, duração, amplitude e sincronia) e o sucesso reprodutivo (medido pela conversão de flores em frutos fruit set) de Attalea geraensis e Syagrus petraea, entre borda e interior em um fragmento de Cerrado sensu stricto em Itirapina, estado de São Paulo, Brasil. Considerando as mudanças tanto abióticas quanto bióticas nos ambientes de borda em relação aos de interior, esperamos encontrar diferenças fenológicas entre ambientes. A caracterização do microclima local apresentou diferenças entre borda e interior na temperatura, umidade relativa, intensidade luminosa e abertura do dossel, tanto na estação úmida quanto na seca (exceto para abertura do dossel na estação seca, possivelmente pela queda de folhas no Cerrado). Attalea geraensis floresceu principalmente na estação úmida e frutificou o ano todo. Syagrus petraea floresceu e frutificou continuamente, com um pico de floração e frutificação em Outubro e Dezembro respectivamente. Ambas as espécies não apresentaram diferenças temporais significativas na fenologia reprodutiva entre borda e interior, o mesmo ocorrendo para duração, sincronia e sucesso reprodutivo. A reprodução vegetativa pode ter atenuado as diferenças entre as condições de borda e interior em Syagrus. A maior produção de inflorescências estaminadas em Attalea na borda pode estar relacionada com a elevada intensidade de luz neste ambiente. Características da borda tais como uma vegetação mais aberta, um baixo contraste em relação ao ambiente adjacente e, por outro lado, uma elevada abundância de indivíduos e longa duração das fenofases reprodutivas nestas espécies, poderia ter conduzido à resposta neutra observada. / Edge effects include both abiotic and biological changes on environmental conditions that affect plant phenological patterns. We compared the reproductive phenology (in terms of time, duration, amplitude and synchrony), and the reproductive success (fruit set) of Attalea geraensis and Syagrus petraea, between the edge and interior of a fragment of Cerrado sensu estricto (a savanna vegetation), at Itirapina, São Paulo State, Brazil. Considering both abiotic and biological changes on the edge in relation to the interior, we hope to find phenological differences between these environments. A local microclimatic characterization showed differences between edge and interior on temperature, relative humidity, light intensity and canopy openness in both wet and dry seasons (except for canopy openness in the dry season possibly due to the leaffall in the Cerrado). Attalea flowered mainly in the wet season and fruited all year round. Syagrus flowered and fruited continually, with a flower and fruit peak in October and December, respectively. Both species did not present temporal significant differences between edge and interior with regard to the reproductive phenology, duration, synchrony and fruit set. Any differences between edge and interior conditions could have been buffered by the vegetative reproduction in Syagrus. With regard to Attalea, the higher production of staminate inflorescences on the edge may be related to the greater light intensity in this environment. Edge characteristics such as the open structure of the vegetation and the low contrast with the adjacent environment, as well as the high abundance of individuals and long duration of the reproductive phenophases in these species, could have led to the neutral response observed.

Orientador: Leonor Patricia Cerdeira Morellato / Banca: Vânia Regina Pivello / Banca: Marco Antonio de Assis / Artigo seguindo as normas da revista Journal of Tropical Ecology / Artigos em inglês e português / Resumo: Os efeitos de borda incluem mudanças abióticas e bióticas nas condições ambientais, as quais afetam os padrões fenológicos das plantas. Comparamos a fenologia reprodutiva (quanto a data, duração, amplitude e sincronia) e o sucesso reprodutivo (medido pela conversão de flores em frutos fruit set) de Attalea geraensis e Syagrus petraea, entre borda e interior em um fragmento de Cerrado sensu stricto em Itirapina, estado de São Paulo, Brasil. Considerando as mudanças tanto abióticas quanto bióticas nos ambientes de borda em relação aos de interior, esperamos encontrar diferenças fenológicas entre ambientes. A caracterização do microclima local apresentou diferenças entre borda e interior na temperatura, umidade relativa, intensidade luminosa e abertura do dossel, tanto na estação úmida quanto na seca (exceto para abertura do dossel na estação seca, possivelmente pela queda de folhas no Cerrado). Attalea geraensis floresceu principalmente na estação úmida e frutificou o ano todo. Syagrus petraea floresceu e frutificou continuamente, com um pico de floração e frutificação em Outubro e Dezembro respectivamente. Ambas as espécies não apresentaram diferenças temporais significativas na fenologia reprodutiva entre borda e interior, o mesmo ocorrendo para duração, sincronia e sucesso reprodutivo. A reprodução vegetativa pode ter atenuado as diferenças entre as condições de borda e interior em Syagrus. A maior produção de inflorescências estaminadas em Attalea na borda pode estar relacionada com a elevada intensidade de luz neste ambiente. Características da borda tais como uma vegetação mais aberta, um baixo contraste em relação ao ambiente adjacente e, por outro lado, uma elevada abundância de indivíduos e longa duração das fenofases reprodutivas nestas espécies, poderia ter conduzido à resposta neutra observada. / Abstract: Edge effects include both abiotic and biological changes on environmental conditions that affect plant phenological patterns. We compared the reproductive phenology (in terms of time, duration, amplitude and synchrony), and the reproductive success (fruit set) of Attalea geraensis and Syagrus petraea, between the edge and interior of a fragment of Cerrado sensu estricto (a savanna vegetation), at Itirapina, São Paulo State, Brazil. Considering both abiotic and biological changes on the edge in relation to the interior, we hope to find phenological differences between these environments. A local microclimatic characterization showed differences between edge and interior on temperature, relative humidity, light intensity and canopy openness in both wet and dry seasons (except for canopy openness in the dry season possibly due to the leaffall in the Cerrado). Attalea flowered mainly in the wet season and fruited all year round. Syagrus flowered and fruited continually, with a flower and fruit peak in October and December, respectively. Both species did not present temporal significant differences between edge and interior with regard to the reproductive phenology, duration, synchrony and fruit set. Any differences between edge and interior conditions could have been buffered by the vegetative reproduction in Syagrus. With regard to Attalea, the higher production of staminate inflorescences on the edge may be related to the greater light intensity in this environment. Edge characteristics such as the open structure of the vegetation and the low contrast with the adjacent environment, as well as the high abundance of individuals and long duration of the reproductive phenophases in these species, could have led to the neutral response observed. / Mestre

Resumo: O cultivo em estufas propicia a obtenção de produtos de excelente qualidade, porém, os agentes polinizadores que contribuem na maximização da produção não são adaptados a ambientes fechados. Utilizando três cultivares tipo Japonês e duas tipo Aodai de pepino (Cucumis sativus L.) foram realizados dois experimentos em três estufas localizadas na USP/Ribeirão Preto. Os objetivos foram estudar a biologia floral das cultivares no que se refere ao número de flores produzidas por planta, período de antese, porcentagem de açúcares do néctar, produção e viabilidade dos grãos de pólen, receptividade do estigma e atratividade de flores e, a importância das abelhas Jataí (Tetragonisca angustula), Iraí (Nannotrigona testaceicornis) e Africanizadas (Apis mellifera) quanto a freqüência das abelhas nas flores, tempo e tipo de coleta e produção de frutos quanto ao peso, comprimento e diâmetro. O manejo das abelhas africanizadas foi estudado e um modelo de núcleo com dois alvados desenvolvido. As flores das cultivares avaliadas têm antese de, aproximadamente, 10 horas. A viabilidade dos grãos de pólen e a receptividade do estigma não são limitantes na polinização de pepino Japonês e Aodai. Os índices de frutificação de pepino Japonês por partenocarpia são altos (78 %), porém há aumento de 19% quando ocorre polinização por abelhas. A cultivar Aodai depende dos insetos para produção de frutos, sendo que flores visitadas até às 10h30 originaram frutos mais pesados. As abelhas Africanizadas se adaptaram a colméia com dois alvados, visitando flores em parte do dia dentro da estufa, promovendo a polinização, e o restante fora, ambiente com maior oferta de recursos. / Abstract: The cultivation in greenhouses allows obtaining products of excellent quality, however, the pollinators that contribute maximizing the production are not adapted to the indoor environment. Using three Japanese and two Aodai cultivars of cucumber (Cucumis sativus L.) were conducted two experiments in three greenhouses located in USP / Ribeirão Preto. The aims were to study the cultivars floral biology with regard to the number of flowers produced per plant, anthesis period, the percentage of sugars in nectar, production and viability of pollen grains, stigma receptivity and attractiveness of flowers, and the importance of Jataí (Tetragonisca angustula), Iraí (Nannotrigona testaceicornis) and Africanized honeybees (Apis mellifera) with regard to the frequency of bees in the flowers, time and type of collection and fruit weight, length and diameter. The management of Africanized bees has been studied and a hive with two entrances was developed. The anthesis period was approximately of 10 hours. The viability of pollen grains and the receptivity of stigma did not limit the pollination of Japanese cucumber and Aodai. The parthenocarpy fruit set of Japanese cucumber was high (78%), but there is an increase of 19% in fruit set when the flowers were pollinated by bees. The cultivar Aodai depends on the insects for production of fruits. Flowers visited until 10h30 originated the heaviest ones. Africanized bees adapted itself to the hive with two entrances, visiting flowers in part of the day inside the greenhouse, promoting pollination, and the rest outside, the environment with greater supply of resources. / Orientador: Euclides Braga Malheiros / Coorientador: David de Jong / Banca: Leomam Almeida Couto / Banca: Luis Carlos Marchini / Banca: Roque Takahashi / Banca: Jeffrey Frederico Lui / Doutor

La transition fleur-fruit, appelée nouaison, est déclenchée par la pollinisation des fleurs et ce processus est essentiel pour cycle reproducteur des plantes, la formation des semences et le rendement de production. Les mécanismes moléculaires contrôlant cette importante transition développementale ont été peu explorés. Les marques histones et la méthylation de l'ADN sont les deux principaux modes de régulation épigénétique, mais à ce jour, leurs contributions respectives à la reprogrammation transcriptionnelle qui est associée au programme d’initiation des fruits charnus n’ont pas fait l’objet d’aucune étude sur aucune espèce de plante. Afin d’explorer l’importance dans la transition fleur-fruit de ces deux types de régulation épigénétique, des approches de transcriptomique "genome-wide", de ChIP-seq se et de séquençage bisulfite d'ADN ont été mises en place chez la tomate, une espèce économique majeure et un modèle d’étude pour les fruits charnus. Les résultats révèlent une corrélation étroite entre le repositionnement des marques histones et les changements observés de l'expression génique globale. L’étude montre aussi que les marques H3K9ac et H3K4me3 agissent en synergie pour activer la transcription génique, alors que la marque H3K27me3 a un effet répressif. A l’inverse, il n’y a pas de corrélation entre les variations de la méthylation de la cytosine et l’évolution des profils transcriptomiques. Il ressort donc que ce sont les changements au niveau des marques histones plutôt que de la méthylation de l'ADN qui constituent le moteur principal de la reprogrammation génétique associée au processus de transition fleur-fruit chez la tomate. En concordance avec cette idée, le niveau d'expression des gènes associés à l’initiation du fruit, tels que ceux liés au métabolisme hormonal, à la division cellulaire ou au développement embryonnaire, est corrélé avec les modifications des marques H3K9ac ou H3K4me3, mais pas avec la méthylation de l'ADN. En outre, l'étude comparative des profils transcriptomiques associés à la formation du fruit dépendant et indépendant de la pollinisation révèle l'intervention complexe de multiples voies de signalisation hormonales. Au total, notre étude présente un nouvel aperçu du contrôle de la reprogrammation génétique nécessaire à l’initiation du développement du fruit et révèle le rôle important du contrôle épigénétique dans ce processus de transition développementale. Dans le même temps, l’étude identifie un groupe de gènes impliqués dans la régulation épigénétique qui offrent des cibles potentielles pour les programmes d’amélioration de la nouaison des fruits, un processus majeur affectant le rendement de production / The flower-to-fruit transition, so-called fruit setting, is triggered by flower pollination and this process is essential for plant reproductive success, seed formation and crop yield. The underlying molecular mechanisms controlling this developmental transition remain unclear. Histone marking and DNA methylation are the main epigenetic modes for genetic reprogramming, however, their respective contribution to the fruit set-associated transcriptomic reprogramming is also unknown. To address the contribution of the two types of epigenetic regulation to fruit set, genome-wide transcriptomic profiling, ChIP-sequencing and DNA bisulfite sequencing were applied to tomato, a major economic crop and a model system for fleshy fruit. The study emphasizes the tight correlation between histone repositioning and gene expression changes revealing that H3K9ac and H3K4me3 histone marks synergistically promote gene transcription, whereas H3K27me3 marking has a repressive effect. We concluded that changes in histone marks rather than in DNA methylation are the main drivers of genetic reprogramming associated with the fruit set transition in tomato, and H3K9ac and H3K4me3 marking is the primary players in this control mechanism. Consistently, the expression level of fruit set-associated genes such as those related to hormone metabolism, cell division, and embryo development correlated with changes in H3K9ac or H3K4me3 marking, but not with DNA methylation. In addition, comparative study of transcriptomic profiling between pollination-dependent and -independent fruit set, uncovered the complex intervention of multiple hormone signaling pathways involved in the flower-to-fruit transition. Auxin appears as the central hormone triggering the extensive transcriptomic reprogramming associated with the initiation of early fruit growth. Altogether, the study provides new insight into the control of gene reprogramming underlying fruit the shift from flower to fruit and uncovers a set of genes encoding modifiers of epigenetic marks which may provide new targets for breeding programs aiming to improve fruit setting, a major process impacting crop yield.

No description available.

Identifying the resources that limit bee populations is essential both for bee conservation and pollination management in agroecosystems. Land-use change typically leads to decreased habitat availability for wild pollinators including loss of nesting habitat, which is an essential but often-overlooked resource for wild bees. Cavity-nesting bees, such as many Osmia spp. (Hymenoptera: Megachilidae), occupy holes in wood or reeds to build their nests; due to their nesting habits, they are frequently scarce in agricultural settings, although, under the right circumstances, these bees can be ideal pollinators of apple and other orchard crops. Artificial nesting structures (“bee hotels”, “trap nests”, or “nest boxes”) are used to study cavity-nesting bees and have been posited as solutions for promoting bee conservation. To evaluate the effects of additional nesting habitat on the local abundance of Osmia spp., and on bees more generally, artificial nesting structures for cavity-nesting bees were installed at 24 sites in apple orchards around Ottawa in 2021 and 2022. Each site had two treatments: one with nest boxes, and one without (control). Transect walks were conducted to measure overall bee contact (including contact by Osmia spp.) with apple blossoms and, after the end of apple bloom, with flowers in the undergrowth and/or in shrubs. Numbers of apple buds and developing fruit were also recorded. Osmia spp. and overall bee numbers were both significantly higher in the treatment with nest boxes (44% and 15% higher, respectively, in 2021, and 113% and 47% higher, respectively, in 2022); however, there was no difference in fruit set (apple count/bud count) between the two treatments. Thus, nest boxes seem to locally increase Osmia spp. numbers as well as total bee numbers, but they have no apparent effect on apple yield, likely because apple production was not pollinator limited in the years of this study. These findings suggest that bee populations in apple orchards are limited by nesting resources, which has important implications for orchard management practices and bee conservation policy.