Made available in DSpace on 2014-06-11T19:25:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05-25Bitstream added on 2014-06-13T18:53:12Z : No. of bitstreams: 1 peres_fsc_me_jabo.pdf: 331825 bytes, checksum: 18b3c8bc6500ae52044825067eb8d2af (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Foi avaliada a atratividade de Tagetes patula (cravo-de-defunto) sobre tripes (Thysanoptera) e micro-hymenoptera em cultivo protegido de melão. Foram estudadas a abundância, dominância, freqüência e constância de espécies de insetos utilizando-se a análise faunística, análise de agrupamento (AA) e análise de componentes principais (ACP). Nas extremidades das estufas com cultivo de melão foram plantadas duas faixas transversais de cravo-de-defunto. As amostras foram tomadas nas plantas de melão, batendo-se três ponteiros e nas plantas de T. patula 1m2 sobre bandeja branca. Os pontos de amostragem consistiram em: T. patula, melão consorciado com T. patula e melão à distancia de 6m, 12m, 18m e 24m de T. patula. Onze espécies de tripes e 21 espécies de himenópteros parasitóides foram observados. As espécies dominantes de tripes e superdominantes e constantes de himenópteros foram analisadas para avaliar a distribuição na estufa. Os resultados permitiram verificar que houve três grupos diferentes em relação a abundância de espécies de tripes: (1) T. patula, (2) melão consorciado com T. patula e (3) melão a distancia de 6m, 12m, 18m e 24m do cravo-de-defunto. Também foi possível observar que as espécies de tripes foram mais abundantes em T. patula e que a bordadura com essa planta apresenta maior população de himenópteros parasitóides. Com isso, bordaduras de T. patula podem ser utilizadas para implementar o controle biológico bem como para servir de cultura atrativa. / The attractiveness of Tagetes patula (marigold) on thrips (Thysanoptera) and parasitic wasps (Hymenoptera) was ingestigated in protected melon crop. Insect abundance, dominance, frequency, and constancy were evaluated using faunistic analysis, cluster and principal component analyses. Transversal strips of T. patula were grow at both ends of the protected melon greenhouse. Samplings were taken by shaking three melon vine tips and all T. patula plants from 1 m2 on white trays. Samplings sites were T. patula, melon along with T. patula and melon plants at 6m, 12m, 18m, and 24m from T. patula. Eleven thrips species and 21 parasitic wasps were observed. The dominant species of thrips as well as superdominant and dominant and constant species of parasitic wasps were analysed to evaluated species distribution on the crop. The results showed that there were three different groups according to thrips species abundance: (1) T. patula, (2) melon along with T. patula, and (3) melon alone at 6m, 12m, 18m, and 24m from T. patula. It was also possible to note that thrips species were more attracted to T. patula, and that the border presented a higler population of parasitic wasps. Thus, T. patula border can be used to improve biological control as well as serve as trap crop.

Orientador: Odair Aparecido Fernandes / Banca: Sérgio de Freitas / Banca: Sandra Regina Magro / Resumo: Foi avaliada a atratividade de Tagetes patula (cravo-de-defunto) sobre tripes (Thysanoptera) e micro-hymenoptera em cultivo protegido de melão. Foram estudadas a abundância, dominância, freqüência e constância de espécies de insetos utilizando-se a análise faunística, análise de agrupamento (AA) e análise de componentes principais (ACP). Nas extremidades das estufas com cultivo de melão foram plantadas duas faixas transversais de cravo-de-defunto. As amostras foram tomadas nas plantas de melão, batendo-se três ponteiros e nas plantas de T. patula 1m2 sobre bandeja branca. Os pontos de amostragem consistiram em: T. patula, melão consorciado com T. patula e melão à distancia de 6m, 12m, 18m e 24m de T. patula. Onze espécies de tripes e 21 espécies de himenópteros parasitóides foram observados. As espécies dominantes de tripes e superdominantes e constantes de himenópteros foram analisadas para avaliar a distribuição na estufa. Os resultados permitiram verificar que houve três grupos diferentes em relação a abundância de espécies de tripes: (1) T. patula, (2) melão consorciado com T. patula e (3) melão a distancia de 6m, 12m, 18m e 24m do cravo-de-defunto. Também foi possível observar que as espécies de tripes foram mais abundantes em T. patula e que a bordadura com essa planta apresenta maior população de himenópteros parasitóides. Com isso, bordaduras de T. patula podem ser utilizadas para implementar o controle biológico bem como para servir de cultura atrativa. / Abstract: The attractiveness of Tagetes patula (marigold) on thrips (Thysanoptera) and parasitic wasps (Hymenoptera) was ingestigated in protected melon crop. Insect abundance, dominance, frequency, and constancy were evaluated using faunistic analysis, cluster and principal component analyses. Transversal strips of T. patula were grow at both ends of the protected melon greenhouse. Samplings were taken by shaking three melon vine tips and all T. patula plants from 1 m2 on white trays. Samplings sites were T. patula, melon along with T. patula and melon plants at 6m, 12m, 18m, and 24m from T. patula. Eleven thrips species and 21 parasitic wasps were observed. The dominant species of thrips as well as superdominant and dominant and constant species of parasitic wasps were analysed to evaluated species distribution on the crop. The results showed that there were three different groups according to thrips species abundance: (1) T. patula, (2) melon along with T. patula, and (3) melon alone at 6m, 12m, 18m, and 24m from T. patula. It was also possible to note that thrips species were more attracted to T. patula, and that the border presented a higler population of parasitic wasps. Thus, T. patula border can be used to improve biological control as well as serve as trap crop. / Mestre

Stinkbugs (Pentatomidae) and other agricultural pests such as bark beetles and flea beetles are known to synthesize terpenoids as aggregation pheromones. Knowledge of the genes and enzymes involved in pheromone biosynthesis may allow engineering of pheromone biosynthetic pathways in plants to develop new forms of trap crops and agricultural practices for pest management. The harlequin bug, Murgantia histrionica, a specialist pest on crucifer crops, produces the sesquiterpene, murgantiol, as a male-specific aggregation pheromone. Similarly, the southern green stink bug, Nezara viridula, a generalist pest worldwide on soybean and other crops, releases sesquiterpene cis-/trans-(Z)-α-bisabolene epoxides as male-specific aggregation pheromone. In both species, enzymes called terpene synthases (TPSs) synthesize precursors of the aggregation pheromones, which are sesquipiperitol and (Z)-α-bisabolene as the precursor of murgantiol and cis-/trans-(Z)-α-bisabolene epoxide, respectively. We hypothesized that enzymes in the family of cytochrome P450 monooxygenases are involved in the conversion of these precursors to the final epoxide products. This study investigated the tissue specificity and sequence of these conversions by performing crude enzyme assays with protein extracts from male tissues. Furthermore, candidate P450 genes were selected by RNA-sequencing and co-expression analysis and the corresponding recombinant proteins tested for enzyme activity. To engineer the pheromone biosynthetic enzymes in plants, transient expression of the TPSs of both stink bugs was performed in Nicotiana benthamiana leaves. Both sesquipiperitol and (Z)-α-bisabolene were found to be produced and emitted from inoculated N. benthamiana leaves. Future work will implement stable transformation to engineer murgantiol biosynthesis in crucifer trap crops and develop similar approaches for pheromone engineering of other agricultural pests. / Master of Science / Stinkbugs including the harlequin bug, Murgantia histrionica and southern green stinkbug, Nezara viridula, are major agricultural pests in the US and worldwide. To control these pests with alternative pest management strategies, we have proposed to develop trap crops that emit pheromones to lure the insects away from crop fields. To establish pheromone biosynthesis in plants, we investigated the corresponding enzymatic steps in both stink bugs. We show that terpene synthase enzyme from both stink bugs can be transformed into plants for the engineering of pheromones in trap crops. With identification of P450 genes in pheromone biosynthesis enhanced trap crops can be made.

Pheromone lures and trap crops are appealing pest management tools that use insect and/or plant volatiles to reduce pest populations on crops of interest. Generating pheromone-emitting trap plants may allow for a continuing and highly-specific attraction of insect pests without repeated and costly application of synthetic pheromones. These trap plants may also be used to develop area-wide pest management strategies. As a proof-of-principle study we tested the possibility of producing the pheromone of the crucifer flea beetle Phyllotreta cruciferae in transgenic plants. P. cruciferae is an important pest of Brassica crops. In the presence of a host plant, males emit an aggregation pheromone, which attracts both males and females. Himachaladiene, a sesquiterpene, has been identified as a key component of the aggregation pheromone of P. cruciferae. In a close relative, Phyllotreta striolata, the compound is synthesized by a two-step pathway with an isoprenyl diphosphate synthase (PsIDS3) making (Z,E)-farnesyl diphosphate (FPP), which is converted by a terpene synthase (PsTPS1) to himachaladiene. Transient transformation of N. benthamiana with PsIDS3-TPS1 co-localized to the plastid resulted in the emission of himachaladiene and other known PsTPS1 products. Daily emissions of himachaladiene were approximately 1 µg per plant, which is six-fold higher than emissions from individual male flea beetles. Stable transformation of Arabidopsis thaliana with the same vector construct resulted in transgenic plants that expressed PsTPS1 and PsIDS3 transcripts, but no himachaladiene or other PsTPS1 products were present in volatile collections or leaf extracts of these plants. Moreover, no PsTPS1 enzyme activity was observed, indicating that post-transcriptional/translational effects prevent proper expression or targeting of functional PsIDS3 and/or PsTPS1 proteins in A. thaliana. Overall, this study demonstrates that the key component of the P. cruciferae aggregation pheromone, himachaladiene, can be transiently produced and emitted in a plant system at rates that are biologically relevant for insect attraction. However, further work is required for the stable production of the pheromone in plants. In addition, preliminary results are presented for the development of simple two-choice arenas that may allow for assessment of the movement of beetles toward host plant leaf tissue. This work can inform future efforts in developing methods for the economic production of himachaladiene in a plant system or the establishment of transgenic plants for the production and deployment of himachaladiene in a field setting. / Master of Science / The crucifer flea beetle is an important pest of vegetable and oilseed Brassica crops such as broccoli, cabbage and canola. Feeding by beetles has its greatest impact on crop health and yield in the early spring, when adult beetles emerge from overwintering sites and feed on newly- emerging Brassica seedlings. Currently these insects are controlled using broad spectrum insecticides. A general awareness of the negative aspects of insecticides drives the search for alternative pest management strategies that could diversify our management strategies and reduce reliance on insecticides. Previous work has found that the crucifer flea beetle navigates to its host plants, in part, through plant-emitted volatiles. After locating the plant host, males emit a volatile aggregation pheromone that when blended with host plant volatiles increases attraction. Here work towards the development of a specialized trap crop is presented. Plants were engineered to emit a key component of the crucifer flea beetle aggregation pheromone. In an engineered non-host plant, Nicotiana benthamiana, transient production of the aggregation pheromone was established. However, in an engineered Brassica plant, Arabidopsis thaliana, no aggregation pheromone was detected despite evidence of the presence and expression of the required biosynthetic genes for its production. A discussion on alternative engineering strategies for A. thaliana is presented. In addition, preliminary results are presented for the development of a simple behavior assay to assess the attraction of beetles toward different smells. This work can inform future efforts aimed at developing methods for the economic production of the aggregation pheromone in a plant system or the establishment of plants for the production and deployment of the aggregation pheromone in a field setting.

Harlequin bug (HB), Murgantia histrionica (Hahn), is a pest of cole crops. Alternative control strategies were investigated for control of HB, including trap cropping and systemic neonicotinoid insecticide applications. Potential trap crops, mustard (Brassica juncea "Southern Giant Curled" ), rapeseed (B. napus "Athena"), rapini (B. rapa) and arugula (Eruca sativa) were preferred over collard (B. oleracea "Champion"), and a non-brassica control, bean (Phaseolus vulgaris "Bronco") in field-cage choice tests. Harlequin bug could not complete development on bean, developed poorly on arugula but was found to complete development on mustard, collard, rapeseed and rapini. In the field, mustard was found to be an effective trap crop for reducing HB feeding injury on collard at three experimental sites in 2010 and 2011. Augmentation of the mustard trap crop with a systemic, neonicotinoid insecticide did not increase the level of control of harlequin bug for the duration of the ten week growing period. In olfactometer choice tests, male HB responded to plant volatiles of bean, collard and mustard, but preferred Brassica volatiles over those from bean. Female response to plant volatiles alone was weak and inconsistent. Both males and females preferred volatiles from other males feeding on Brassica host plant over plant volatiles alone, and were deterred by volatiles from males feeding on bean versus the plant alone. Laboratory toxicity assays revealed that the neonicotinoid insecticides imidacloprid, thiamethoxam, dinotefuran, and clothianidin were toxic to HB nymphs; LC50 = 0.57, 0.52, 0.39, and 0.39 mg ai/liter, respectively. Field experiments were conducted to evaluate the efficacy of these insecticides over time when applied as a one-time drench, and all were found to provide significantly higher mortality of HB for at least 14 days after application. / Ph. D.

Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, are economically important pests of potato (Solanum tuberosum) crops in potato growing regions worldwide. Integrated management is under threat, with effective nematicides increasingly being withdrawn on environmental and health grounds. Alternative strategies are urgently needed and trap cropping could be one of them. The non-tuber-bearing Solanum sisymbriifolium is regarded as an effective trap crop for PCN with strong hatching ability and immunity to PCN infection and has been used in the UK and The Netherlands. However, its mode of action is unknown. In order to shed light on the mode of action so that a novel control strategy could be identified, the interactions between G. pallida and S. sisymbriifolium were investigated using in vitro bioassays. In choice assays, G. pallida J2s were equally attracted to the roots of S. sisymbriifolium and to those of S. tuberosum. However, potato root diffusate (PRD), which is routinely used to induce PCN hatch, failed to attract G. pallida J2s in chemotaxis bioassays, indicating hatching factors (HFs) and soluble compounds present in PRD are not involved in attraction of G. pallida J2s to potato roots. The J2s invaded the roots of S. sisymbriifolium in large numbers but failed to develop further. To facilitate continuous observation of nematode development, a novel in vitro method was devised with the use of Pluronic F-127, which requires no sterilisation, and the life cycle of G. pallida was successfully observed in S. tuberosum roots. Quantitative real-time polymerase chain reaction analyses of defence related genes of S. tuberosum and S. sisymbriifolium infected with G. pallida revealed up-regulation of the chitinase gene (ChtC 2.1) at 3 days post inoculation in S. sisymbriifolium but not in S. tuberosum. Electrospray ionisation-mass spectrometry analyses of root exudate extracts of the two Solanum species and subsequent bioassay-guided fractionation showed that the HF of S. sisymbriifolium differs from that of S. tuberosum. Previously, attention had been solely paid to the hatching ability of the root exudate of S. sisymbriifolium, but this study revealed for the first time that the aerial part extract possesses a significant hatching ability.

Clorose Variegada dos Citros (CVC), causada pela bactéria Xylella fastidiosa Wells et al., tem causado grandes perdas na citricultura do estado de São Paulo, afetando cerca de 40% das plantas de laranja doce. A bactéria é transmitida por 12 espécies de cigarrinhas sugadoras de xilema (Hemiptera: Cicadellidae) da subfamília Cicadellinae. O manejo da CVC é baseado no plantio de mudas sadias, poda ou eliminação de árvores infectadas no campo, assim como o controle químico dos vetores. No entanto, as cigarrinhas vetoras possuem hábitats e hospedeiros alternativos que servem como refúgio, particularmente na vegetação adjacente aos pomares cítricos. Esta característica ecológica explica a rápida reinfestação dos pomares de laranja pelas cigarrinhas após a aplicação de inseticidas. O uso de plantas hospedeiras atrativas às cigarrinhas em uma estratégia de plantio-isca poderia reduzir a imigração de vetores da vegetação adjacente. O objetivo deste trabalho foi selecionar plantas hospedeiras adequadas para serem usadas neste tipo de estratégia, assim como testar a eficácia do plantio-isca em reduzir a população de cigarrinhas em um pomar de laranja. Experimentos de livre escolha foram conduzidos sob condições de casa-de-vegetação para avaliar a preferência de dois importantes vetores, Bucephalogonia xanthophis (Berg.) e Oncometopia facialis (Signoret) por plantas hospedeiras alternativas em relação à Citrus sinensis (L.) Osbeck (laranja doce). As espécies vegetais preferidas por B. xanthophis foram Baccharis dracunculifolia DC., Duranta repens L., Eupatorium maximiliani Shrad., E. laevigatum Lam. e Vernonia condensata Baker, enquanto que O. facialis apresentou preferência por D. repens e Lantana camara L. Um segundo estudo em casa-de-vegetação foi conduzido para avaliar o efeito da fertilização com níveis variados de nitrogênio sobre a preferência de B. xanthophis por uma das plantas hospedeiras selecionadas, V. condensata. Maiores porcentagens de adultos de B. xanthophis selecionaram plantas que haviam sido tratadas com doses mais elevadas de nitrogênio, até um limiar máximo. Em condições de campo (Fazenda Oxford, Gavião Peixoto, SP), 14 espécies de hospedeiros alternativos de cigarrinhas, incluindo plantas preferidas nos testes de livre escolha, foram avaliadas com respeito ao desenvolvimento vegetativo e incidência natural de cigarrinhas. Essas espécies foram plantadas em cinco linhas de 50 m (com espaçamento de 1 m entre linhas e 1 m entre plantas) entre um pomar de laranja doce e uma área de brejo (fonte de vetores) de maneira a formar um plantio-isca. Para avaliar o efeito do plantio-isca na migração de cigarrinhas de cigarrinhas da área de brejo, a população de vetores foi monitorada por armadilhas adesivas amarelas no interior de dois subtalhões no mesmo pomar de laranja, um separado do brejo pelo plantio-isca e outro sem esta barreira. Este monitoramento foi conduzido por vários meses antes e depois que o plantio-isca foi tratado com inseticidas sistêmicos. A população de vetores foi significantemente reduzida no subtalhão adjacente ao plantio-isca, após as plantas hospedeiras serem tratadas com inseticidas. Durante o período de amostragem antes do tratamento com inseticidas, observou-se uma queda na população de cigarrinhas da borda para o interior do subtalhão vizinho ao plantio-isca. Aloysia virgata (Ruiz & Pav.) Juss., Croton urucurana Baill., L. camara, e V. condensata foram consideradas as espécies mais adequadas para uso em plantio-isca porque são plantas atrativas às cigarrinhas e possuem rápido desenvolvimento e emissão de brotos após plantio ou poda. / Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa Wells et al. has caused great losses in the citriculture of São Paulo State, affecting over 40% of the citrus plants. The bacterium is transmitted by 12 species of xylem-feeding leafhoppers (Hemiptera: Cicadellidae) in the subfamily Cicadellinae, commonly known as sharpshooters. CVC management is based on planting of healthy nursery trees, pruning or roguing of infected trees in the field as well as vector control. However, the sharpshooter vectors have alternative hosts and habitats that serve as refuge, particularly woody vegetation adjacent to the citrus groves. This ecological characteristic explains the rapid reinfestation of citrus groves by vectors after insecticide applications. The use of attractive alternative hosts plants of sharpshooters in a dead-end trap cropping strategy could reduce immigration of vectors from adjacent vegetation. The goal of this research was to select adequate host plants to be used in such strategy, as well as to test the efficacy of trap cropping for reducing sharpshooter populations in a citrus grove. Choice experiments were carried out under greenhouse conditions to evaluate the preference of two important vectors, Bucephalogonia xanthophis (Berg.) and Oncometopia facialis (Signoret), for alternative host plants in relation to Citrus sinensis (L.) Osbeck (sweet orange). Preferred plant species by B. xanthophis were Baccharis dracunculifolia DC., Duranta repens L., Eupatorium maximiliani Shrad., E. laevigatum Lam. and Vernonia condensata Baker, whereas O. facialis showed strong preference for D. repens e Lantana camara L. A second greenhouse study was conducted to evaluate the effect of fertilization with variable nitrogen levels on the preference of B. xanthophis for one of the selected host plants, V. condensata. Higher percentages of B. xanthophis adults selected plants that had been treated with higher doses of nitrogen, up to a threshold. Under field conditions (Fazenda Oxford, Gavião Peixoto, SP), 14 alternative hosts of the sharpshooters, including preferred host plants in the choice experiments, were evaluated with respect to vegetative growth and natural incidence of sharpshooters. These species were planted in five rows of 50 m (spaced 1 m in a row and 1 m between plants) between a sweet orange grove and a swamp (source of vectors), in order to form a trap crop. In order to assess the effect of the trap crop against immigration of sharpshooters from the swamp area, vector population was monitored by yellow sticky cards inside two adjacent plots in the same citrus grove, one separated from the swamp by the trap crop and the other without this barrier. Populations in the two citrus plots were monitored for several months before and after the trap crop was treated with a insecticide. Vector population was significantly reduced in the citrus plot adjacent the trap crop, after the alternative host plants were treated with insecticide. During the period of sampling before the insecticide treatments, a pattern of lower vector populations in rows of citrus trees closer to the trap crop was observed. Aloysia virgata (Ruiz & Pav.) Juss., Croton urucurana Baill., L. camara, and V. condensata were considered the most adequate species for trap cropping because of their attractiveness to the sharpshooters and rapid flushing and growth after planting or pruning.

Clorose Variegada dos Citros (CVC), causada pela bactéria Xylella fastidiosa Wells et al., tem causado grandes perdas na citricultura do estado de São Paulo, afetando cerca de 40% das plantas de laranja doce. A bactéria é transmitida por 12 espécies de cigarrinhas sugadoras de xilema (Hemiptera: Cicadellidae) da subfamília Cicadellinae. O manejo da CVC é baseado no plantio de mudas sadias, poda ou eliminação de árvores infectadas no campo, assim como o controle químico dos vetores. No entanto, as cigarrinhas vetoras possuem hábitats e hospedeiros alternativos que servem como refúgio, particularmente na vegetação adjacente aos pomares cítricos. Esta característica ecológica explica a rápida reinfestação dos pomares de laranja pelas cigarrinhas após a aplicação de inseticidas. O uso de plantas hospedeiras atrativas às cigarrinhas em uma estratégia de plantio-isca poderia reduzir a imigração de vetores da vegetação adjacente. O objetivo deste trabalho foi selecionar plantas hospedeiras adequadas para serem usadas neste tipo de estratégia, assim como testar a eficácia do plantio-isca em reduzir a população de cigarrinhas em um pomar de laranja. Experimentos de livre escolha foram conduzidos sob condições de casa-de-vegetação para avaliar a preferência de dois importantes vetores, Bucephalogonia xanthophis (Berg.) e Oncometopia facialis (Signoret) por plantas hospedeiras alternativas em relação à Citrus sinensis (L.) Osbeck (laranja doce). As espécies vegetais preferidas por B. xanthophis foram Baccharis dracunculifolia DC., Duranta repens L., Eupatorium maximiliani Shrad., E. laevigatum Lam. e Vernonia condensata Baker, enquanto que O. facialis apresentou preferência por D. repens e Lantana camara L. Um segundo estudo em casa-de-vegetação foi conduzido para avaliar o efeito da fertilização com níveis variados de nitrogênio sobre a preferência de B. xanthophis por uma das plantas hospedeiras selecionadas, V. condensata. Maiores porcentagens de adultos de B. xanthophis selecionaram plantas que haviam sido tratadas com doses mais elevadas de nitrogênio, até um limiar máximo. Em condições de campo (Fazenda Oxford, Gavião Peixoto, SP), 14 espécies de hospedeiros alternativos de cigarrinhas, incluindo plantas preferidas nos testes de livre escolha, foram avaliadas com respeito ao desenvolvimento vegetativo e incidência natural de cigarrinhas. Essas espécies foram plantadas em cinco linhas de 50 m (com espaçamento de 1 m entre linhas e 1 m entre plantas) entre um pomar de laranja doce e uma área de brejo (fonte de vetores) de maneira a formar um plantio-isca. Para avaliar o efeito do plantio-isca na migração de cigarrinhas de cigarrinhas da área de brejo, a população de vetores foi monitorada por armadilhas adesivas amarelas no interior de dois subtalhões no mesmo pomar de laranja, um separado do brejo pelo plantio-isca e outro sem esta barreira. Este monitoramento foi conduzido por vários meses antes e depois que o plantio-isca foi tratado com inseticidas sistêmicos. A população de vetores foi significantemente reduzida no subtalhão adjacente ao plantio-isca, após as plantas hospedeiras serem tratadas com inseticidas. Durante o período de amostragem antes do tratamento com inseticidas, observou-se uma queda na população de cigarrinhas da borda para o interior do subtalhão vizinho ao plantio-isca. Aloysia virgata (Ruiz & Pav.) Juss., Croton urucurana Baill., L. camara, e V. condensata foram consideradas as espécies mais adequadas para uso em plantio-isca porque são plantas atrativas às cigarrinhas e possuem rápido desenvolvimento e emissão de brotos após plantio ou poda. / Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa Wells et al. has caused great losses in the citriculture of São Paulo State, affecting over 40% of the citrus plants. The bacterium is transmitted by 12 species of xylem-feeding leafhoppers (Hemiptera: Cicadellidae) in the subfamily Cicadellinae, commonly known as sharpshooters. CVC management is based on planting of healthy nursery trees, pruning or roguing of infected trees in the field as well as vector control. However, the sharpshooter vectors have alternative hosts and habitats that serve as refuge, particularly woody vegetation adjacent to the citrus groves. This ecological characteristic explains the rapid reinfestation of citrus groves by vectors after insecticide applications. The use of attractive alternative hosts plants of sharpshooters in a dead-end trap cropping strategy could reduce immigration of vectors from adjacent vegetation. The goal of this research was to select adequate host plants to be used in such strategy, as well as to test the efficacy of trap cropping for reducing sharpshooter populations in a citrus grove. Choice experiments were carried out under greenhouse conditions to evaluate the preference of two important vectors, Bucephalogonia xanthophis (Berg.) and Oncometopia facialis (Signoret), for alternative host plants in relation to Citrus sinensis (L.) Osbeck (sweet orange). Preferred plant species by B. xanthophis were Baccharis dracunculifolia DC., Duranta repens L., Eupatorium maximiliani Shrad., E. laevigatum Lam. and Vernonia condensata Baker, whereas O. facialis showed strong preference for D. repens e Lantana camara L. A second greenhouse study was conducted to evaluate the effect of fertilization with variable nitrogen levels on the preference of B. xanthophis for one of the selected host plants, V. condensata. Higher percentages of B. xanthophis adults selected plants that had been treated with higher doses of nitrogen, up to a threshold. Under field conditions (Fazenda Oxford, Gavião Peixoto, SP), 14 alternative hosts of the sharpshooters, including preferred host plants in the choice experiments, were evaluated with respect to vegetative growth and natural incidence of sharpshooters. These species were planted in five rows of 50 m (spaced 1 m in a row and 1 m between plants) between a sweet orange grove and a swamp (source of vectors), in order to form a trap crop. In order to assess the effect of the trap crop against immigration of sharpshooters from the swamp area, vector population was monitored by yellow sticky cards inside two adjacent plots in the same citrus grove, one separated from the swamp by the trap crop and the other without this barrier. Populations in the two citrus plots were monitored for several months before and after the trap crop was treated with a insecticide. Vector population was significantly reduced in the citrus plot adjacent the trap crop, after the alternative host plants were treated with insecticide. During the period of sampling before the insecticide treatments, a pattern of lower vector populations in rows of citrus trees closer to the trap crop was observed. Aloysia virgata (Ruiz & Pav.) Juss., Croton urucurana Baill., L. camara, and V. condensata were considered the most adequate species for trap cropping because of their attractiveness to the sharpshooters and rapid flushing and growth after planting or pruning.

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