a b s t r a c tAlthough bees are important pollinators in many ecosystems worldwide, studies on bee diversity and their contribution to pollination of commercial plants in the Brazilian Cerrado (savannah-like biome) are scarce. The Cerrado biome covers approximately 23% of Brazil and is one of the world's most important agricultural frontiers. Here, we conducted field experiments in the Brazilian Cerrado to evaluate the diversity of bees, their foraging behaviors and flower visiting periods, and their potential contribution to the performance of six melon (Cucumis melo L.) cultivars. Five bee species (Apis mellifera, Halictus sp., Plebeia sp., Trigona pallens, and T. spinipes) were recorded visiting both male and hermaphrodite flower types of all C. melo cultivars. Whereas A. mellifera showed two peaks of flower visitation (an intense first one between 8:00 a.m. and 11:00 a.m. and a second less intense one after 4:00 p.m.), all other bee species visited the C. melo flowers only in the morning, with intensities and visitation peaks similar to those of A. mellifera. All of these bees collected nectar and pollen. Our results also indicated a moderate correlation between the intensity of bee visitation and fruit weight, demonstrating that all of these bees had the potential to pollinate C. melo and to influence its productivity. Except for the cultivar 'Hibrix', all the other cultivars showed economic feasibility and produced fruits of marketable sizes, with an estimated yield (over 25 tons/ha) in the range registered in other Brazilian regions.

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One of the most promising plant species for biofuel production in Brazil is the physic nut Jatropha curcas. Major phytosanitary problems include the attack of two pest mite species, the broad mite Polyphagotarsonemus latus and the spider mite Tetranychus bastosi. Owing to pesticide-related problems, there is an increasing demand for sustainable environmental-friendly control methods such as biological control. In this study we evaluated the suitability of the predatory mite species Iphiseiodes zuluagai and Euseius concordis in controlling P. latus and T. bastosi on J. curcas. The number of T. bastosi killed by I. zuluagai was lower than the number of P. latus consumed.Euseius concordis preyed upon both T. bastosi and P. latus but the number of prey killed was always lower in comparison with I. zuluagai. However, P. latus and T. bastosi are suitable for the development of I. zuluagai and E. concordis as oviposition of both predators did not differ in relation to prey species. The preference of I. zuluagai for leaves of plants infested by either P. latus or T. bastosi, combined with the higher values for predation obtained by this predatory mite when fed on P. latus, compared to those values obtained by E. concordis, suggests that I. zuluagai can be more efficient than E. concordis in reducing populations of P. latus and T. bastosi under field conditions. Furthermore, we report here on the first record of predatory mites associated with P. latus and T. bastosi on native J. curcas plants in Brazil. In conclusion, we emphasize the crucial importance of predatory mites as agents of natural biological control of mite pests on J. curcas in small farms.

Resumo -Este trabalho objetivou analisar o teor e a composição do óleo essencial do Cymbopogon nardus, em cinco épocas de colheita no Estado do Tocantins. As colheitas foram realizadas em cinco épocas em intervalos regulares de 28 dias, sendo a primeira aos 56 dias e a última aos 168 dias após transplante. A extração do óleo essencial foi realizada por hidrodestilação e a identificação dos componentes por CG e CG/EM. Os maiores teores de óleo essencial foram obtidos na segunda época de colheita (1,10%) e na última época de colheita (1,07%). Foram identificados vinte e três compostos químicos no óleo essencial. Os monoterpenos identificados foram: limoneno, linalol, isopulegol, citronelal, citronelol, neral, geraniol, acetato de citronelol e acetato de geraniol. Os sesquiterpenos identificados foram: beta-elemeno, germacreno, alfa-muroleno, gama-cadineno, delta-cadineno, elemol, germacreno D-4-OL, óxido de cariofileno, tau-cadinol, beta-eudesmol e alfa-eudesmol. Os compostos majoritários do óleo essencial foram o citronelol, o geraniol e o elemol. Palavras-chave -Plantas medicinais. Capim citronela. Óleos essenciais. Época de colheita.Abstract -This study aimed to analyze the content and the composition of the essential oil of Cymbopogon nardus in five harvest times in Tocantins State. Five harvesting were carried out in regular space of 28 days, the first in 56 days and the last in 168 days after transplanting. The essential oil was obtained by hydro distillation and the identification of the oil components by GC and GC/MS. The highest contents of the essential oil were obtained in the second harvest time (1.15%) and in the last harvest time (1.07%). Twenty three chemical compounds were identified in the essential oil. The monoterpenes identified were: limonene, linalool, isopulegol, citronellal, citronellol, neral, geraniol, citronellol acetate and geraniol acetate. The sesquiterpenes identified were: beta-elemene, germacrene, alpha-muurolene, gamma-cadinene, delta-cadinene, elemol, germacrene D-4-OL, caryophyllene oxide, tau-cadinol, beta-eudesmol, alpha-eudesmol. The main constituents of the essential oil were the citronellol, geraniol and elemol.

Bees are key pollinators whose population numbers are declining, in part, owing to the effects of different stressors such as insecticides and fungicides. We have analysed the susceptibility of the Africanized honeybee, Apis mellifera, and the stingless bee, Partamona helleri, to commercial formulations of the insecticides deltamethrin and imidacloprid. The toxicity of fungicides based on thiophanate-methyl and chlorothalonil were investigated individually and in combination, and with the insecticides. Results showed that stingless bees were more susceptible to insecticides than honeybees. The commercial fungicides thiophanate-methyl or chlorothalonil caused low mortality, regardless of concentration; however, their combination was as toxic as imidacloprid to both species, and over 400-fold more toxic than deltamethrin for A. mellifera. There were highly synergistic effects on mortality caused by interactions in the mixture of imidacloprid and the fungicides thiophanate-methyl, chlorothalonil and the combined fungicide formulation in A. mellifera, and also to a lesser extent in P. helleri. By contrast, mixtures of the deltamethrin and the combined fungicide formulation induced high synergy in P. helleri, but had little effect on the mortality of A. mellifera. Differences in physiology and modes of action of agrochemicals are discussed as key factors underlying the differences in susceptibility to agrochemicals.

Resumo -O objetivo deste trabalho foi avaliar a influência da adubação orgânica sobre o teor e a composição do óleo essencial de capim citronela (Cymbopogon nardus), bem como a fungitoxicidade desse óleo ao crescimento micelial dos fungos Didymella bryoniae, Colletotrichum gloeosporioides e Amphobotrys ricini. A extração do óleo essencial foi realizada por hidrodestilação, a partir de plantas cultivadas em quatro doses de adubação orgânica (0, 3, 6 e 9 kg de esterco bovino curtido por cova), e a identificação dos constituintes químicos foi conduzida por cromatografia gasosa/espectrometria de massas. Para avaliar a inibição do crescimento micelial, o experimento foi instalado no delineamento inteiramente casualizado, em arranjo fatorial. Foram testadas sete alíquotas do óleo essencial (0, 5, 10, 15, 20, 25 e 30 µL), em cinco épocas de avaliação, com quatro repetições. O teor de óleo essencial do capim citronela não foi afetado pela adubação orgânica, e o óleo essencial do capim citronela apresentou 24 compostos químicos, entre estes monoterpenos e sesquiterpenos, com maior concentração dos compostos citronelal, β-citronelol, geraniol e elemol. O óleo essencial do capim citronela apresenta maior efeito de inibição a Amphobotrys ricini, em comparação aos fungos Didymella bryoniae e Colletotrichum gloeosporioides.Termos para indexação: Cymbopogon nardus, bioatividade, óleo essencial, plantas medicinais. Composition and fungitoxicity of essential oil of citronella grass as affected by organic fertilizationAbstract -The objective of this work was to evaluate the influence of organic fertilization on the content and composition of the essential oil of citronella grass (Cymbopogon nardus), as well as to assess the fungitoxicity of this oil to the mycelial growth of the fungi Didymella bryoniae, Colletotrichum gloeosporioides, and Amphobotrys ricini. The extraction of the essential oil was done by hydrodistillation in plants cultivated with four doses of organic fertilizer (0, 3, 6, and 9 kg matured cattle manure per hole), and the identification of the chemical compounds was done by gas chromatography/mass spectroscopy. To evaluate the inhibition of mycelial growth, the experiment was installed in a completely randomized design in a factorial arrangement. Seven aliquots of essential oil were tested (0, 5, 10, 15, 20, 25, and 30 µL) in five evaluating times, with four replicates. The contents of the essencial oil in citronella grass were note affected by organic fertilization, and the oil includes 24 chemical compounds, among these monoterpenes and sesquiterpenes, with higher concentrations of the compounds citronellal, β-citronellol, geraniol, and elemol. The essential oil of citronella grass has higher inhibition effect on Amphobotrys ricini, when compared to the fungi Didymella bryoniae e Colletotrichum gloeosporioides.

(1) ( 1 ) U n i v e r s i d a d e F e d e r a l R u r a l d o S e m i -á r i d o , C a i x a P o s t a l 1 3 7 , C E P 5 9 6 2 5 -9 0 0 M o s s o r ó , R N . E-mail: glauber@ufersa.edu.br, sousamadeiros@yahoo.com.br, leilson@ufersa.edu.br, ruisales@ufersa.edu.br (2) Embrapa Semi-Árido, Caixa Postal 23, CEP 56302-970 Petrolina, PE. E-mail: gmabelsantos@gmail.com.brResumo -O objetivo deste trabalho foi estimar a participação dos componentes simples e complexo da interação e identificar cultivares com adaptabilidade e estabilidade fenotípica elevadas. Foram avaliados 12 híbridos de melão amarelo em quatro municípios do Estado do Rio Grande do Norte, em 2000, 2001 e 2002, num total de 12 ambientes. Os experimentos foram conduzidos em delineamento em blocos ao acaso, com três repetições. A parcela foi constituída por duas linhas de 5 m. As características avaliadas foram produtividade e teor de sólidos solúveis totais. A fim de decompor a interação híbridos x ambientes nas partes simples e complexa, foi utilizado o método proposto por Cruz e Castoldi. Na identificação de híbridos com adaptabilidade e estabilidade fenotípica, foi utilizado o método proposto por Toler. Observou-se grande variação entre ambientes, híbridos e a interação entre esses fatores. O componente complexo é a maior parte da interação quanto às características produtividade e teor de sólidos solúveis totais dos híbridos de meloeiro. Os híbridos AMR-04 e AMR-12 apresentam elevados valores médios de produtividade e sólidos solúveis totais e respondem à melhoria ambiental.Termos para indexação: Cucumis melo, interação genótipos x ambientes, avaliação de cultivares. Phenotypic stability of yellow melon hybrids evaluated in the AgriculturalPole Mossoró-AssuAbstract -The objective of this work was to estimate the participation of single and complex components of interaction as well as to identify cultivars with high phenotypic adaptability and stability. Twelve hybrids of yellow melon were evaluated in four sites of Rio Grande do Norte in 2000, 2001, 2002 coming to twelve environments. The experiments were carried out in a randomized complete block design with three replications. The experimental plot was constituted by two 5 m long rows. Yield and total soluble solids contents were evaluated. For the partition of the hybrids by environments interaction in single and complex part, the method of Cruz and Castoldi was used. In order to indentify hybrids with high phenotypic adaptability and stability, the Toler method was utilized. Great variation among environments and hybrids as well as interaction were observed between these two factors. The complex part is responsible for most of the environment hybrids interaction. Hybrids AMR-04 and AMR-12, comprising higher means to yield and total soluble solids content, are responsive to the improved environment.Index terms: Cucumis melo, genotype x environmental interaction, evaluation of cultivars. IntroduçãoO Nordeste é a principal região produtora de melão (Cucumis melo L.) do Brasil. No Rio Grande do Norte...

Spatiotemporal dynamics studies of crop pests enable the determination of the colonization pattern and dispersion of these insects in the landscape. Geostatistics is an efficient tool for these studies: to determine the spatial distribution pattern of the pest in the crops and to make maps that represent this situation. Analysis of these maps across the development of plants can be used as a tool in precision agriculture programs. Watermelon, Citrullus lanatus (Thunb.) Matsum. and Nakai (Cucurbitales: Cucurbitaceae), is the second most consumed fruit in the world, and the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most important pests of this crop. Thus, the objective of this work was to determine the spatiotemporal distribution of B. tabaci in commercial watermelon crops using geostatistics. For 2 yr, we monitored adult whitefly densities in eight watermelon crops in a tropical climate region. The location of the samples and other crops in the landscape was georeferenced. Experimental data were submitted to geostatistical analysis. The colonization of B. tabaci had two patterns. In the first, the colonization started at the outermost parts of the crop. In the second, the insects occupied the whole area of the crop since the beginning of cultivation. The maximum distance between sites of watermelon crops in which spatial dependence of B. tabaci densities was observed was 19.69 m. The adult B. tabaci densities in the eight watermelon fields were positively correlated with rainfall and relative humidity, whereas wind speed negatively affected whiteflies population.