Active phloem sap collection by Trigona spinipes (Fabricius) (Hymenoptera, Apidae)in Artemisia annuaLinn (Asteraceae)

Trigona spinipes Fabricius (Apidae: Meliponini), is a common stingless bee widely seen in urban and rural areas in Brazil, popularly known as irapuá, arapuá or bee-dog. Although these bees are considered pollinators of some cultivated plants, they are better known for the damage they cause in different crops. During experimental agroecological cultivation of Artemisia (Artemisia annuaLinn, Asteraceae), in Jaguariúna (SP, Brazil), stingless bees Trigona spinipes (Fabricius) were observed sucking phloem sap directly from the plant, a phenomenon not yet described in scientific literature. This study aimed to register and describe the phloem sap-sucking behavior performed by T. spinipesfor the first time, as well as to assess the potential impact of this behavior on A. annuacultivation. The behavior and the material collected by bees and the severity of attack were also analyzed. The aging and premature death of observed A. annuaspecimens occurred because of extensive lesions caused by T. spinipes, confirming the negative consequence of sap-sucking attacks of T. spinipesbees on the plants. Factors that could induce this unusual behavior were presented, pointing out the need for future studies on the development of strategies to protect plants, without causing damage to the T. spinipesbee populations, which are elements of Brazilian bee fauna and, therefore, protected by law.

Diurnal variation of methane emission from a paddy field in Brazilian Southeast / Variação diurna da emissão de metano em arroz irrigado no Sudeste do Brasil

ABSTRACT: This study aimed to investigate the diurnal variation of methane (CH4) emission in a flooded-irrigated rice field at different stages of the plant development under tropical climate in three growing seasons, in order to determine the most appropriate time for gas sampling in the Brazilian Southeast region. It aimed also to verify correlations between CH4 flux and air, water and soil temperatures, and solar radiation. The CH4 emissions were measured every 3-hour interval on specific days in different development stages of the flooded rice in the Experiment Station of the Agência Paulista de Tecnologia dos Agronegócios (APTA), Pólo Regional Vale do Paraíba, at Pindamonhangaba, State of São Paulo (22°55' S, 45°30' W), Brazil. Different CH4 emission rates were observed among the plant growth stages and also among the growing seasons. The CH4 emission showed high correlation with the soil temperature at 2cm depth. At this depth, the CH4 emission activation energy in response to soil temperature was higher in the stage R2. Emission peaks were observed at afternoon, while lower fluxes were recorded at the early morning. The most appropriate local time for gas sampling was estimated at 12:11:15a.m.±01:14:16 and 09:05:49p.m.±01:29:04.

RESUMO: Este estudo teve como objetivo investigar a variação diurna de emissões de metano (CH4) em uma lavoura de arroz irrigado por inundação em diferentes estágios de desenvolvimento de plantas de arroz irrigado, sob clima tropical, em três estações de crescimento, para determinar o período de tempo mais apropriado à amostragem de gás na região Sudeste do Brasil. O trabalho objetivou também verificar correlações entre o fluxo de CH4 e as temperaturas do ar, da água e do solo e a radiação solar. As emissões diurnas de CH4 foram medidas a cada intervalo de três (3) horas em dias específicos em diferentes estágios de desenvolvimento da planta de arroz inundado na Estação Experimental da Agência Paulista de Tecnologia dos Agronegócios (APTA), Pólo Regional Vale do Paraíba, em Pindamonhangaba, Estado de São Paulo (22°55' S, 45°30' W), Brasil. Diferentes taxas de emissão foram observadas entre os estágios de desenvolvimento da planta avaliados e também entre as estações de cultivo. A emissão de CH4 mostrou alta correlação com a temperatura do solo a 2cm de profundidade. Nesta profundidade, a energia de ativação da emissão de CH4 em resposta à temperatura do solo foi maior no estágio R2. Os picos de emissão foram observados no período da tarde, enquanto que menores fluxos foram registrados no início da manhã. O horário mais apropriado para amostragem de gás foi estimado em 12:11:15a.m.±01:14:16 and 09:05:49p.m.±01:29:04.

Microbial activities in soil cultivated with corn and amended with sewage sludge.

BACKGROUND: One of the main concerns related to the increasing use of sewage sludge in the soil is the possible presence of excess nutrients, which could cause environmental problems and detrimental effects on the soil microorganisms, considered essential to soil nutrient cycling. Thus, the objective of this work was to evaluate the microbial biomass and activity and some chemical characteristics of one specific tropical soil, classified as Dark Red Distroferric Latosol, of a loamy/clayey texture, in a long-term field experiment using anaerobically digested household sludge amendment. The sludge doses applied were the recommended dose and 2, 4 and 8 times the recommended dose. The authors hypothesized that the frequent application of this compound to the soil, even when using the recommended dose, could affect the available phosphorus (Pav) and heavy metal contents of the soil, resulting in concentrations above the needs of the culture as well as negatively affecting the activity of the soil microorganisms. RESULTS: The results demonstrated that successive applications of sludge, calculated considering the recommended dose of N for corn, did not increase the soil Pav contents in relation to the treatment in which the fertilizer was applied considering the nutrient needs of the culture, contrary to what happened with the highest sludge doses. The Cr, Ni and Cu contents increased with increase in sludge dose, but did not surpass the limits considered inadequate. There were no accentuated differences between the treatments with respect to microbial biomass C. Basal respiration and the FDA hydrolysis were considered to be the parameters that most differentiated the effect of increasing sludge doses on the microbial activity. CONCLUSION: The application of a sludge dose to a tropical soil, based on the recommended dose, did not affect the Pav or heavy metal contents of the soil even after years of application. Since there were no differences between the treatments with respect to the Cmic values, to the contrary of what happened with the other microbiological parameters evaluated, the possibility of changes in the composition of the microbial community with the higher sludge doses was considered.

Residual and cumulative effects of soil application of sewage sludge on corn productivity.

The objective of this study was to evaluate the effect of frequent and periodic applications of sewage sludge to the soil, on corn productivity. The experiment was carried out as part of an experiment that has been underway since 1999, using two types of sludge. One came from the Barueri Sewage Treatment Station (BS, which receives both household and industrial sludge) and the other came from the Franca Sewage Treatment Station (FS, which receives only household sludge). The Barueri sludge was applied from 1999 up to the agricultural year of 2003/2004. With the exception of the agricultural years of 2004/2005 and 2005/2006, the Franca sludge was applied up to 2008/2009. All the applications were made in November, with the exception of the first one which was made in April 1999. After harvesting the corn, the soil remained fallow until the next cultivation. The experiment was set up as a completely randomized block design with three replications and the following treatments: control without chemical fertilization or sludge application, mineral fertilization, and dose 1 and dose 2 of sludge (Franca and Barueri). The sludges were applied individually. Dose 1 was calculated by considering the recommended N application for corn. Dose 2 was twice dose 1. It was evident from this work that the successive application of sludge to the soil in doses sufficient to reach the productivity desired with the use of nitrogen fertilizers could cause environmental problems due to N losses to the environment and that the residual and cumulative effects should be considered when calculating the application of sludge to soil.