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.