ABSTRACT Cattle production is one of the main economic activities in the state of Roraima, and insect pest attacks in pastures have a negative effect on this sector in the region. Little is known about the species that cause damage to forage fields in the state. This study presents the first report of the occurrence of the chinch bug Blissus pulchellus Montandon (Hemiptera: Blissidae) in Roraima, Brazil and a description of the population dynamics of this pest in pasture areas in this state. Pasture areas were sampled in nine municipalities of Roraima to detect the insect. The population dynamics study was conducted for two years in Alto Alegre municipality, two of which have Brachiaria brizantha cv. Marandu and one of Megathrysus maximus cv. Mombaça (Poaceae) crops. Blissus pulchellus was found in all sampled areas, except in Rorainópolis and São João da Baliza. High densities of this bug were found in in Alto Alegre. This is the first report of B. pulchellus in Brazil. The factors that affect the population dynamics and the damage caused by this insect pest to pastures as well as the risk of dispersal of this pest in Brazil are discussed.

Resumo O objetivo deste trabalho foi estimar parâmetros genéticos para caracteres agronômicos e de resistência às cigarrinhas-das-pastagens em híbridos de Brachiaria decumbens e selecionar os de melhor desempenho. Trezentos e vinte e quatro híbridos foram avaliados em campo para caracteres agronômicos e em casa de vegetação para resistência às cigarrinhas-das-pastagens. Observou-se existência de variabilidade genética entre os híbridos para todos os caracteres analisados. As estimativas de herdabilidade entre médias de genótipos foram superiores a 0,52 para todos os caracteres agronômicos e de 0,98 para sobrevivência ninfal e 0,99 para duração do período ninfal. Híbridos com melhor desempenho em relação a cultivar Basilisk foram identificados para cada caráter individualmente e conjuntamente por meio de índices de seleção. A atribuição de pesos diferentes entre os caracteres nos índices de seleção não alterou significativamente o ranqueamento dos híbridos. Híbridos superiores foram selecionados para as próximas etapas do programa de melhoramento.

Abstract The objective of this work was to estimate genetic parameters for agronomic traits and resistance to spittlebugs in B. decumbens hybrids and to select the ones with best performance. For that, 324 hybrids were evaluated in field plots for agronomic traits and in the greenhouse for resistance to spittlebugs. Genetic variability amongst the hybrids was observed for all traits analyzed. The heritability estimates between genotypes means were higher than 0.52 for all agronomic traits and 0.98 and 0.99 for nymphal survival and nymphal period duration respectively. Hybrids with better performance than cultivar Basilisk for each individual trait were identified and also through a selection index combining all traits. Assigning weights to the different traits in the selection index did not significantly alter the rank for superior hybrids. Those were selected to continue on to the next phases of the breeding program.

O estudo com substâncias derivadas de plantas com potencial no controle de pragas justifica-se pela necessidade de se identificar compostos menos agressivos ao meio ambiente. Extratos do cajuzinho-do-cerrado, Anacardium humile têm mostrado potencial como inseticida sobre alguns insetos. A cigarrinha-das-raízes, Mahanarva fimbriolata é considerada praga importante na cultura da cana-de-açúcar, ocasionando danos severos e sensível redução na produção. O objetivo deste trabalho foi avaliar o efeito do extrato aquoso de Anacardium humile, nas concentrações 0,05; 0,4 e 1,0%, sobre M. fimbriolata, em cana-de-açúcar. A ação do extrato aquoso resultou em mortalidade ninfal de 53,1% na concentração 1,0%, valor significativamente superior aquele verificado na testemunha negativa. O período ninfal e longevidade de M. fimbriolata, no entanto, não foram afetados pelo extrato aquoso.

The study of plant-derived substances for the control of insect pests is desirable in the attempt to discover less toxic insecticides that are safe for the environment. Indeed, extracts from the cashew of the savannah, Anacardium humile, have shown insecticidal activities against certain insects. The sugarcane root spittlebug Mahanarva fimbriolata is considered an important pest of sugarcane, causing severe damage and significant yield reductions. The aim of this study was to evaluate the effect of the aqueous extract of A. humile (0.05, 0.4 and 1.0%) on M. fimbriolata. The application of the aqueous extract of Anacardium humile resulted in 53.1% nymphal mortality at a concentration of 1.0%, which was significantly higher than that observed in the negative control. The nymphal period and longevity of M. fimbriolata, however, were not affected by the aqueous A. humile extract.

Spittlebugs annually infest pastures and cause severe damage, representing a serious problem for the tropical American beef cattle industry. Spittlebugs are an important biotic constraint to forage production and there is a lack of cytogenetic data for this group of insects. For these reasons, we conducted this work, in which the spermatogenesis and nucleolar behavior of Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana were studied. The males possessed testes in the shape of a "bunch of grapes"; a variable number of testicular lobes per individual and polyploid nuclei composed of several heteropycnotic bodies. A heteropycnotic area was located in the periphery of the nucleus (prophase I); the chiasmata were terminal or interstitial; metaphases I were circular or linear and anaphase showed late migration of the sex chromosome. The chromosome complement had 2n = 19, except for N. entreriana (2n = 15); the spermatids were round with heteropycnotic material in the center and elongated with conspicuos chromatin. The analysis of testes after silver nitrate staining showed polyploid nuclei with three large and three smaller nucleolar bodies. Early prophase cells had an intensely stained nucleolar body located close to the chromatin and another less evident body located away from the chromatin. The nucleolar bodies disintegrated during diplotene. Silver staining occurred in two autosomes, in terminal and subterminal locations, the latter probably corresponding to the nucleolus organizer regions (NORs). The spermatids were round with a round nucleolar body and silver staining was observed in the medial and posterior region of the elongated part of the spermatid head.

The horn fly, Haematobia irritans (L.) (Diptera, Muscidae), is reported as introduced into Boa Vista, Roraima, Brasil, possibly from Northern South America (Venezuela).