Adaptability and Comparative Biology of Fall Armyworm on Maize and Perennial Forage Species and Relation with Chemical-Bromatological Composition.

This study compared the development of fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), on forage species of different genera (Arachis, Axonopus, and Cynodon) in relation to maize (preferred host) as well as its adaptability on these forage species, which are the main cultivated forages in southern Brazil. The biological performance of S. frugiperda fed on host plants studied showed the highest adaptation index (AI) in maize (26.89), followed by bermudagrass (22.02), suggesting that bermudagrass is the most suitable alternative host for the development of S. frugiperda. In contrast, the giant missionary grass (18.80) and Pinto peanut (13.81) showed lower adequacy, with a relative adaptation index (RAI) 69.93 and 51.35%, respectively, using maize as standard. The cluster analysis based on similarity of the chemical-bromatological parameters showed that maize has a richer composition than the other plant species studied. The multivariate correlation analysis between AI and chemical-bromatological composition showed a positive correlation between AI and contents of ashes, ethereal extract, potassium, phosphorus, and magnesium and, to a lesser extent, with contents of nitrogen, crude protein, and copper. In this context, complexity of host composition and balance between components could explain the biological fitness of S. frugiperda on host plant species. Pasture diversification with giant missionary grass, or especially with Pinto peanut, may be an interesting strategy for integrated pest management of fall armyworm in pasturelands in a regional context.

Consumo de forragem por ovinos ingerindo grama missioneira gigante com ou sem acesso a amendoim forrageiro / Herbage intake by lambs grazing missioneira gigante grass with or without access to peanut pastures

A grama missioneira gigante (Axonopus catharinensis Valls) é uma espécie forrageira que merece ser melhor investigada tanto pura como recebendo a inclusão de leguminosas. Objetivou-se avaliar o consumo de MS por ovinos pastejando grama missioneira gigante com ou sem acesso a pastos de amendoim forrageiro (Arachis pintoi cv. Amarillo). Para isso, foi conduzido um experimento prévio com cordeiros alojados em gaiolas metabólicas, gerando-se uma equação para a estimativa do consumo tomando como base a excreção fecal de proteína bruta (PBf), que apresentou R2= 0,91. Em um segundo experimento, foi avaliado o consumo de forragem por ovinos em pastos de grama missioneira gigante com duas alturas de entrada (25 ou 35cm), com ou sem acesso a áreas de amendoim forrageiro por duas horas diárias. A altura de entrada na grama missioneira gigante não alterou o consumo total de MS, mas o acesso aos piquetes da leguminosa aumentou o consumo em aproximadamente 20%. Em conclusão, a grama missioneira gigante pode ser manejada com alturas de entrada entre 25 e 35cm, enquanto o acesso a áreas de amendoim forrageiro por duas horas diárias aumenta o consumo de MO por cordeiros pastejando a missioneira.(AU)

The missioneira gigante grass (Axonopus catharinensis Valls) is a grass that deserves to be better investigated both pure and receiving the inclusion of legumes. The objective of this work was to evaluate the herbage intake by sheep grazing missioneira gigante grass with or without access to peanut grass (Arachis pintoi cv. Amarillo). A previous experiment was conducted using lambs housed in metabolic cages, generating an equation for estimation of herbage intake as a function of faecal crude protein excretion (CPf). The equation presented a value of R 2 = 0.91. In the grazing experiment, the herbage intake was evaluated using missioneira gigante pastures with two pre-grazing sward heights (25 or 35cm), with or without access to peanut areas during two hours per day. The pre-grazing sward height of missioneira gigante did not change the total OM herbage intake, but the access to peanut pastures increased the herbage intake by approximately 20%. In conclusion, missioneira gigante grass has shown flexibility to be used with pre-grazing sward heights between 25 and 35cm, while the access to forage peanut pastures during two hours daily increases herbage OM intake by lambs grazing grass.(AU)