Resumo __ O objetivo deste trabalho foi avaliar a fl utuação populacional de cigarrinhas-das-pastagens em Brachiaria brizantha, Brachiaria decumbens e Pennisetum purpureum. Fluctuation of spittlebug population in brachiaria and in elephant grassAbstract __ The objective of this work was to evaluate the fl uctuation of spittlebug population in Brachiaria brizantha, Brachiaria decumbens and Pennisetum purpureum. The evaluations were conducted in fi eld conditions, between September 2005 and March 2007. Spittlebug nymphs and adults were counted on B. brizantha cultivars Marandu, Xaraés and Arapoti, subjected to alternating grazing; on B. decumbens in a silvipastoral system and on 78 genotypes of P. purpureum. The Deois schach population density was greater on the Arapoti cultivar than on the Xaraés and Marandu cultivars. On B. decumbens, the number of spittlebugs was four times greater than on B. brizantha. No signifi cant differences were observed in the number of spittlebugs infesting the different genotypes of P. purpureum.Index terms: Brachiaria brizantha, Brachiaria decumbens, Deois schach, Pennisetum purpureum, Cercopidae, pest resistance.A espécie de Brachiaria apresenta expressivo efeito sobre a infestação de cigarrinhas-das-pastagens, como foi evidenciado por Barbosa et al. (2001), que constataram que a densidade populacional de Zulia entreriana (Berg, 1879) e Deois fl avopicta (Stal, 1854) foi aproximadamente 15 vezes superior em Brachiaria decumbens Stapf e Brachiaria humidicola (Rendle) Schweick., quando comparada à encontrada em Brachiaria brizantha (Hochst. ex A. Rich.) Stapf.Além da infl uência da espécie e cultivar de braquiária na densidade populacional das cigarrinhas-das-pastagens, os fatores climáticos (Melo et al., 1984) e a carga animal (Valério & Koller, 1981) afetam diretamente a população desse inseto-praga.Diversos estudos caracterizam B. brizantha como resistente às cigarrinhas-das-pastagens (Cardona et al., 2004;Pabón et al., 2007). No entanto, estudos da ocorrência desse inseto-praga em cultivares dessa espécie de forrageira, em campo, são inexistentes.As cigarrinhas-das-pastagens podem limitar o cultivo de capim-elefante, Pennisetum purpureum Schumacher. Contudo, são raras as pesquisas que tratam diretamente da interação desses cercopídeos com essa forrageira, o que tem limitado a recomendação de controle (Auad et al., 2007).O objetivo deste trabalho foi avaliar a fl utuação populacional de cigarrinhas-das-pastagens em B. brizantha, B. decumbens e P. purpureum.
The objective of this work was to estimate the abundance, diversity and constancy of families from the order Hymenoptera, such as the seasonality of those through a survey on the insect population in a silvopastoral system. We installed a Malaise-type trap in a Brachiaria decumbens area managed by a silvopastoral system in Coronel Pacheco, MG, from August 2006 to July 2008. The trapped insects were screened, and those of the order Hymenoptera were classified into their respective family categories and quantified. We adopted the methodology of Bodenheimer to calculate the indices of constancy, while other indices were estimated PAST program. We sampled 5841 specimens in total, which included 549 morphospecies and were distributed among 11 families. Of the total specimens sampled, 80% were Formicidae, which besides being the most abundant, was also the most diverse and constant family. When entomophagous insects were analyzed, the highest values for these indices were recorded for the families Ichneumonidae, Braconidae, and Vespidae. Pollinators were less prevalent compared to the total number of sampled individuals. The population density in the Hymenoptera was not correlated between the two sampling years and climate factors.
RESUMO Objetivou-se avaliar o benefício do mel e do pólen proveniente de duas espécies de forrageiras, sobre os aspectos biológicos da fase adulta de Chrysoperla externa (Hagen, 1861). Casais do predador foram individualizados em gaiolas cilíndricas de PVC (10 x 10 cm) mantidas em câmaras climatizadas a 25 ± 1º C, 70% UR e fotofase de 12 horas. Utilizaram-se dietas à base de lêvedo de cerveja + mel (1:1) e pólen de mamona com e sem adição de mel (testemunhas) e os seguintes tratamentos: pólens de capim-elefante, braquiária, capim-elefante + mel e braquiária + mel. Quando foi fornecido apenas pólen de mamona, os crisopídeos apresentaram o menor tempo de vida e não realizaram posturas. Os períodos de pré-oviposição e oviposição não foram influenciados pelas diferentes fontes de alimento com a presença de mel, independente da fonte proteica. O número de ovos/fêmea foi maior para a dieta com lêvedo de cerveja + mel, seguida dos pólens de capim-elefante + mel, mamona + mel e braquiária + mel. Verificou-se que o pólen das plantas apresentou efeitos positivos sobre a biologia de C. externa, quando adicionado mel como fonte de carboidrato. Portanto, para maior eficiência e permanência deste inimigo natural em cultivos dessas forrageiras, recomenda-se a suplementação alimentar com flores ou outras fontes de obtenção de carboidratos.
Collaria oleosa causes leaf injuries to the main forage grasses used for cattle feeding in Brazil. The aim of this work was to determine resistance of B. ruziziensis clones against C. oleosa. Eighty B. ruziziensis clones were maintained in greenhouse, in which C. oleosa natural infestations have been occurring in previous years. After 40 days, damage score and chlorophyll content reduction were assessed for all clones. By using these parameters, genetic gain was estimated based on REML/BLUP mixed models. We observed significant differences for damage scores and chlorophyll content reduction among B. ruziziensis clones, evidencing genetic variability in this forage specie in regard to resistance against C. oleosa. Gain derived from selection of the 10 best clones was 18.2% and 5.80% when considering the damage score and chlorophyll content reduction, respectively. The clones CNPGL BR 10, CNPGL BR 64, CNPGL BR 97 and CNPGL BR 40 presented the highest genetic gain for both damage score and chlorophyll content reduction, and then they will be selected to continue the B. ruziziensis breeding program with the possibility of maximizing genetic gain for the next generations.
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