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Copyright of Revista Ciência Agronômica is the property of Revista Ciencia Agronomica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arquivo Brasileiro de Medicina Veterinaria e Zootecnia is the property of Universidade Federal de Minas Gerais, Escola de Veterinaria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In Hawaii, infestations of yellow sugarcane aphid (YSA), Sipha flava (Forbes) (Homoptera: Aphididae) reduced growth of the forage grass, kikuyu (Pennisetum clandestinum Hochst. ex Chiov). To determine the effects of nitrogen (N) and potassium (K) on tolerance of kikuyu grass to YSA, cuttings of eight and five cultivars were grown in the greenhouse using nutrient solutions in two separate trials, respectively. The first trial was conducted during the summer of 1991 and the second during the winter of 1993. In both trials, kikuyu was grown at three N levels (0.05, 0.5 and 3.0mM) and four K levels (0.05, 0.5 1.0 and 3.0mM), with one cultivar comprising a block. Prior to exposure to aphids, representative plants were harvested, and shoots were analyzed for foliar nutrients. Then, plants were confined with aphids and rated visually for YSA injury. Dry matter yields and foliar N concentration increased significantly with increasing N fertilization in both trials. In the first trial, there was a significant interaction between N and K levels, in which the greatest increases of shoot and root dry matter with increasing N levels were found at the highest K level. In the second trial, K fertilization had no effect on dry weight of shoots. In both trials, foliar K concentration increased significantly with increasing K levels. Damage due to YSA tended to increase with increasing N levels, although it was unaffected by K fertilization in both trials. Thus, fertilization with increasing N resulted in greater kikuyu dry matter production, but it also tended to increase the damage caused by YSA feeding. [Copyright &y& Elsevier]

Abstract: Kikuyu grass, Pennisetum clandestinum Hochst. ex Chiov., is an important pasture species in many subtropical areas. Infestations of yellow sugarcane aphid (YSA), Sipha flava (Forbes) (Homoptera: Aphididae), have reduced kikuyu forage production in Hawaii. A novel method was developed to screen cultivars of kikuyu, and species of other forage and turf grasses for resistance to YSA. Kikuyu germplasm differed significantly in response to YSA with certain kikuyu hybrids more resistant to YSA than the common cultivar. However, even the kikuyu cultivars with the lowest damage ratings were considered only to be moderately resistant to YSA. Other forage grass species differed significantly in YSA damage, with Pacific fountain [Pennisetum macrostachys (Brongn.) Trin.], dallis (Paspalum dilatatum Poir.), torpedo (Panicum repens L.), tall fescue (Festuca arundinacea Schreb.), signal [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, formerly known as Brachiaria decumbens], bahia (Paspalum notatum Flugge), small buffalo (Panicum coloratum L.), velvet (Holcus lanatus L.), and switch (Panicum virgatum L.) grasses considered to be resistant to YSA. Turf grass species also differed significantly in YSA injury, with seashore paspalum (Paspalum vaginatum Sw.), St. Augustine [Stenotaphrum secundatum (Walter) Kuntze], and Japanese lawn (Zoysia japonica Steud.) grasses evaluated as resistant. Reduction of pasture forage by YSA could be ameliorated either by utilization of moderately tolerant kikuyu hybrids or resistant forage grass species. [Copyright &y& Elsevier]