Spittlebugs: Bioecology, Host Plant Resistance and Advances in IPM

Several species and genera of spittlebugs (Homoptera: Cercopidae) are economic pests of grasses in tropical America. These insects compete with grazing animals by reducing forage availability and quality. They may cause serious losses on millions of hectares of improved pastures based on cultivars of several species of Brachiaria (signal grasses). Except for the cultivar Marandu, most of the available commercial cultivars of Brachiaria are susceptible to spittlebugs. In spite of their economic importance, much research need to be done yet. Such insect-plant system encompasses a diverse group of spittlebug species, a diverse group of forage grass species, which are under different management systems, in a broad range of ecological zones. Control efforts have been directed to host plant resistance, alternative that has been recognized as being of easy adoption and of low cost to farmers. It is probably the best control measure for controlling insect pests in low value crops, like pastures, widely established over vast areas. Screening for spittlebug resistance has been conducted both at CIAT and Embrapa-Beef Cattle Center, and promising accessions have been found. It is important however, that additional biological and behavioral studies of these insects, together with evaluations of other control techniques, like biological control and cultural practices, are also performed. Promising control measures and future research needs are discussed

Genetic variation among pathogens causing "Helminthosporium" diseases of rice, maize and wheat.

Vinte amostras de espécies de fungos, agentes da helmintosporiose em cereais, foram obtidas de diferentes regiões geográficas, sendo nove constituídas de Bipolaris oryzae, isoladas de cultura do arroz (Oryza sativa), sete de B. sorokiniana coletadas de trigo (Triticum aestivum), duas de B. maydis e duas de Exserohilum turcicum provenientes de milho (Zea mays). As amostras foram analisadas através das técnicas de PCR-RFLP e RAPD. O polimorfismo de tamanho observado entre as amostras na região ITS1-ITS2 e o espaço compreendido da região 5,8S do rDNA indicou diferenças genéticas entre as amostras, enquanto o fenograma construído através do método de UPGMA após a digestão com as enzimas de restrição, indicaram polimorfismo inter e intraespecífico. Os perfis de RAPD indicaram um expressivo grau de polimorfismo entre as diferentes espécies. Entre as amostras da mesma espécie ocorreu um baixo índice de polimorfismo. O fenograma, obtido pelo método de UPGMA, permitiu diferenciar as quatro espécies analisadas e agrupou as mesmas conforme a espécie hospedeira. Os perfis de RAPD obtidos revelaram ausência de correlação entre os fatores climáticos e a origem geográfica dos isolados de B. sorokiniana e B. oryzae. Espécies teleomórficas revelaram alto nível de similaridade com seus correspondentes anamorfos

Screening \u3ci\u3eBrachiaria\u3c/i\u3e Introductions for Resistance to Spittlebugs (Homoptera: Cercopidae)

Spittlebugs are the most evident and damaging pests of Signal grasses (Brachiaria) in tropical America. Damage caused by these insects can result in the complete loss of available forage, thereby reducing the carrying capacity of infested pastures. Host plant resistance is a low-cost method of controlling insects. High level of spittlebug resistance is found in the cultivar Marandu (B. brizantha), but it requires more fertile soils. Brachiaria germplasm provided by the International Center for Tropical Agriculture (CIAT) is available at National Beef Cattle Research Center of the Brazilian Agricultural Research Corporation (Embrapa Beef Cattle) and it is being screened for spittlebug resistance. In the present study, 23 introductions of Brachiaria were evaluated for resistance to the spittlebug Deois flavopicta, based on the parameters: nymphal survival and nymphal period. The introductions CIAT 16125 and CIAT 16309, both B. brizantha, were selected as resistant in this test. Given the great number of available introductions and hybrids, tests like this have been conducted routinely at Embrapa Beef Cattle. A total of 551 introductions and hybrids have already been screened in the past few years. As a result 40 introductions and 11 hybrids were found resistant. The aim of continuing evaluations is to release new spittlebug resistant Brachiaria cultivars

Selecting New \u3ci\u3eBrachiaria\u3c/i\u3e for Brazilian Pastures

Brazilian beef production relies heavily on cultivated pastures, of which about 80% are planted mainly to two Brachiaria cultivars. The narrowness of diversity associated with reproduction by apomixis of most plants in this genus prompted an intense search for new cultivars amongst recently collected and introduced ecotypes from Africa. This paper reports results for a three-year evaluation of 21 pre-selected ecotypes in two typical Cerrado ecosystems. Plots, replicated four times, were seeded in rows and cut every 6 weeks during the rainy season followed by a cut in the middle and one at the end of the dry season. Significant differences were found between ecotypes, seasons and years for total, leaf or leaf + stem dry matter production, percentage of leaves, leaf: stem ratio and regrowth rate. Ecotypes differed in the two ecosystems for percentage of leaves, leaf: stem ratio and regrowth. Superior ecotypes (BRA004308, 003361, 002844, 003204, 003441) could be identified and were equally advantageous in both ecosystems

The Composition of the São Brás Copper Hoard in Relation to the Bell Beaker Metallurgy in the South-western Iberian Peninsula

A large ceramic vessel was discovered at São Brás (southern Portugal) containing a metallic hoard from the Chalcolithic/Early Bronze Age period. These weapons and tools were characterized by microanalytical techniques as being composed of copper with varying arsenic contents (2.2± 1.6 wt%) and minor amounts of lead, bismuth and iron. The collection shows a clear association between daggers and copper with a higher arsenic content, which can be explained by the high status of these silvery alloys. Finally, the compositional distribution of the hoard was compared with the metallurgy of the Bell Beaker and non–Bell Beaker communities inhabiting the south-western Iberian Peninsula.info:eu-repo/semantics/acceptedVersio

Diagnóstico de morte de pastagens nas regiões central e norte do Estado de Mato Grosso.

No Estado de Mato Grosso, na região compreendida pelos municípios de Rondonópolis, Cuiabá, Tangara da Serra, Diamantino, Sinop, Santa Helena, e Chapada dos Guimarães, não se observou problema significativo de morte de pastagens de Brachiaria brizantha, conforme diagnostico realizado no período de 27 de marco a 2 de abril de 2000, por pesquisadores da Embrapa Gado de Corte. Por meio de observações realizadas nas fazendas visitadas, bem como, através de informações obtidas junto a proprietários e/ou administradores, constatou-se que os raros casos de morte de pastagens na região estavam restritos a pequenas áreas dentro das pastagens. Excesso de umidade, em alguns casos (Tangara da Serra e Sinop) e estresse hídrico, em outro (Chapada dos Guimarães), foram as causas dos casos de morte de pastagens constatados nessa região.bitstream/CNPGC/9941/1/DOC098.pd