José Roberto Salvadori

Occurrence of Aceria tosichella in Brazil.

The objective of this work was to evaluate the occurrence of Aceria tosichella Keifer (Prostigmata: Eriophyidae), the wheat curl mite, in Rio Grande do Sul, Brazil. Samples to detect A. tosichella specimens were collected in wheat, corn, oat crops and potential host grasses in 46 localities, in October 2006, August and October 2007. Samples of wheat were also collected in experimental greenhouses at Embrapa Trigo, Passo Fundo, RS, Brazil. A. tosichella specimens were found in wheat samples from Passo Fundo, Palmeira das Missoes, Sao Luis Gonzaga, and Santo Antonio das Missoes, RS, Brazil. Symptoms due to A. tosichella infestations were observed only in greenhouse conditions. This is the first report of A. tosichella in Brazil and the second in South America.

Danos de Rhopalosiphum padi (L.) (Hemiptera: Aphididae) no trigo em função da duração e da densidade de infestação

Aphids are considered relevant pests on wheat either by direct damage through sap sucking or by indirect damage vectoring BYDV (Barley yellow dwarf virus). Rhopalosiphum padi L. has been observed infesting wheat fields with an increasing frequency. The knowledge and the available technology, besides being more related to other aphids species already recognized as pests, they are insufficient to control the specific problem of R. padi. Thus, this work evaluated the effects of feeding duration and infestation densities of R. padi on seedlings of wheat cv. Embrapa 16. Grain yield, yield components and the extent of symptoms were recorded. The experiment was carried out in the field under a completely randomized split-plot experimental design with four replications. The main plot was feeding duration (two and seven days) and the sub-plots were infestation densities (zero, two and 10 aphids per plant). Independent on feeding duration, 10 aphids per plant resulted in significant yield losses, reduction of number of heads and tillers per plant. Canopy dry matter was also reduced. Infestations of two and 10 aphids per plant resulted in continuous yellowing of wheat plants from tillering to the end of flowering stage. When aphids fed for seven days on wheat, more yellowing symptoms were observed at the flower stage in comparison with two days feeding.

Resposta de cultivares de trigo à infestação do pulgão Rhopalosiphum padi

The objective of this work was to evaluate the response of eight commercial wheat cultivars (BRS 194, BRS 208, BRS Camboata, BRS Guabiju, BRS Guamirim, BRS Louro, BRS Timbauva e BRS Umbu) to the infestation of Rhopalosiphum padi (Hemiptera: Aphididae). The experiment was carried out at Embrapa Trigo, in greenhouse conditions. It was used the randomized block design, in a split-plot array, with eight treatments and six replicates. The plots received treatments with or without infestation with aphids, and the split-plots were composed by the cultivars. The infestation with aphids (20 wingless adults per plant) was done 12 days after plant emergency, in the beginning of tillering, and was kept for 15 days. The cultivars responded differently to the infestation with aphids. BRS Timbauva cultivar is more resistant, and BRS Umbu and BRS Guabiju cultivars are more susceptible to R. padi, concerning plant growth and plant yield.

Avaliação de danos causados pelo Barley yellow dwarf virus: PAV em cultivares de trigo no Brasil

Assessment of damage caused by the Barley yellow dwarf virus in Brazilian wheat cultivars The aim of this study was to assess the damage caused by the Barley yellow dwarf virus (BYDV-PAV) in five wheat cultivars (BRS 177, BRS 179, BRS 194, BRS Camboata and BRS Angico) grown in a greenhouse at Embrapa (Empresa Brasileira de Pesquisa Agropecuaria), Passo Fundo, state of Rio Grande do Sul, Brazil, in 2005. The damage caused by the BDV-PAV was determined by the analysis of agronomic traits (plant height and dry matter) and yield (number of tillers, ears, and grains per plant; thousand-grain weight). The data were submitted to the analysis of variance and the means were determined by Tukeys test at 5%. The virus significantly affected all of the tested variables. Among the agronomic traits, dry matter was the most affected one, with rates between 26.1% (BRS 177) and 51.4% (BRS 179). Reductions in plant height ranged between 12.5% (BRS 177) and 15.5% (BRS Camboata). Total grain yield was greatly affected by the viral infection, with significant damage in all cultivars, with a reduction between 34.2% (BRS Camboata) and 60.8% (BRS 179). There was a reduction in the mean number of tillers per plant only in BRS Angico and BRS 179 cultivars, which amounted to 20 % and 26.6% respectively. The reduction in the mean number of grains varied between 26.1% (BRS Camboata) and 54.3% (BRS 179). Finally, the reduction in thousand-grain weight corresponded to 16.9% and 38.4% in BRS Camboata and BRS 194 cultivars, respectively. Additional keywords: Luteovirus, aphids, Triticum aestivum.

Aspectos biológicos e morfométricos de Collaria scenica (Stal) (Hemiptera: Miridae) em trigo

The present work was conducted at the Laboratory of Entomology, Universidade Federal do Rio Grande do Sul, under 20,5 ± 1,5°C, 80 ± 10%UR and photophase of 12h, in order to study biological and morphometrical aspects of Collaria scenica (Stal). Eggs from laboratory rearing were individualized and both nymphs and adults were fed with wheat cultivar BR 23. The average incubation period of the egg was 14,1 days, the nymphal period lasted 20,3 days and the adult longevity was 34,5 days. The viability of the egg was 84,4% and the nymphal mortality was 49,1%. The number of instars varied between five to six with 94,8% of the nymphs having five instars. The average number of eggs deposited by the female was 196,0. The average duration of pre-oviposition, oviposition and post-oviposition periods were 6,4, 28,9 and 1,6 days, respectively. The sexual ratio was 1:1. The expected number of individuals per female per year was 5,4 x 1010.