Revista Raízes e Amidos Tropicais

7

Authors: Manuel Alberto Gutiérrez Cuenca, José Henrique de Albuquerque Rangel, Edivilson Silva Castro Filho

The objective of this study was to analyze the historical evolution of the area harvested with cassava in Pará state and evaluate the impact of this evolution over the cassava PGV Percentage of Variation Tax (TXV% of PGV) in different biennium, over the whole period, and in three sub-periods, between 1977 and 2009. Data encompassing the 1977 – 1998 period were collected from the Basic Statistic (IBGE, 1997), and data relative to the period from 1990 to 2009, collected from SIDRA (IBGE, 2011).The “Shift-share” model was used for decomposition of VBP variation Taxes in function of the effects of area, productivity, and price factors. Data were updated to December 2010 by the Prices General Index of Getulio Vargas Foundation (FGV, 2011). Cassava TXV% of PGV and the effect of area were calculated from the annual behavior of area. The TXV% of PGV was calculated for each sub-period to check out the oscillations of cassava PGV and TXV% of PGV growing sources inside those sub-periods. The productivity, the harvested area, and the production of cassava in Para State increased respectively 46%, 187%, and 320%. A decreasing of 37% in prices was not enough to null the positive variation of area and productivity that support an increasing of 164% in the Cassava PGV during the analyzed period. Means of area and PGV of cassava in Pará between 1077 and 2009 were respectively 223,672 ha and R$ 721.5 million. The largest harvested area of 324,672 ha occurred in 2007 and the maximum PGV value (R$ 1,564.2 million) in 1996, while the smallest area of 100,989 ha was registered in 1977 and the minimum PGV (R$ 282.8 million) in 1996. In some biennium there were observed differences between the percentage and directions of area and PGV variation. Such behavior is attributed to variations in productivity or in prices or even in both, annulling or compensating the variation registered in area and its possible impact over the PGV.

8

Authors: Amauri Siviero, José de Sá Pessoa, Lauro Saraiva Lessa

The cassava is the main crop grown in Acre, Amazon in terms of income, food and practiced by small farmers’ families. This study aimed to evaluate genotypes of cassava in the Extractive Reserve Cazumbá-Iracema, located in Sena Madureira city, Acre state, Amazon. Three experiments were installed in locations Cazumbá, Cuidado and Alto Caeté. Completely randomized design with four replications was used. Number of roots per plant, percentage of starch, dry mass of roots, productivity and yield of cassava flour were evaluated. It were evaluated eight genotypes in Cazumbá and Cuidado and six genotypes in Alto Caeté. Four genotypes from Panati, Araçá, Colonial and Pirarucu, which were planted in three locations, were analyzed too. Data were subjected to analysis of variance and to significant effects were applied the Tukey test and Scott-Knott at 5% probability. Cultivar Pirarucu, which is the most planted in the reserve, was the genotype that showed the best performance for yield and flour yield.

10

Authors: Marcus Henrique Dias Lima, Elisângela de Souza Loureiro, Samir Oliveira Kassab, Antônio de Souza Silva

The aim of this study was to evaluate the pathogenicity of entomopathogenic fungi in controlling the cassava whitefly. The tests were carried out at a commercial area of cassava "spit" variety at Barra Bonita farm, Dourados-MS. We used a randomized block design with 7 treatments and 4 replications. The treatments were: control, Metiê® (Metarhizium anisopliae) with 1, 2 and 3 applications, Bioveria® (Beauveria bassiana) with 1, 2 and 3 applications. Evaluations were performed 21 and 28 days after spraying and in each plot were observed and recorded the average number of live and dead nymphs. The data were transformed into (x + 0.5)½ and subjected to analysis of variance. Means were compared by the Scot-Knott test with significance level of 0.05 and efficiency was calculated by the Abbott formula. In the first evaluation, all the treatments outperformed the control, but did not differ one from the other. In the second evaluation the Bb1 treatment (Bioveria® with 1 application) provided the lowest number of nymphs showing a reduction of 44.7% compared to the living population of nymphs on the control treatment. Treatments based on the fungus Beauveria bassiana were those which provided a greater number of nymphs killed in the first and second evaluation. The Bioveria® insecticide with one application was most effective when compared to the other, which killed the nymphs in 61.4 and 64.9% at 21 and 28 days after application, respectively.

12

Authors: Manuel Alberto Gutiérrez Cuenca, José Henrique Albuquerque Rangel, Ana Alexandrina Gama da Silva, Edivilson Silva Castro Filho

The objective of this study was to determine the cassava productivity impact in Ceará between 1977 and 2009 over the PGV Percentage Variation Tax (TXV%) of Production Gross Value (PGV) in different biennium, for the total period, and in three specific sub-periods: from 1977 to 1987, 1987 to 1997, and 1997 to 2009. Data encompassing the 1977 – 1998 period were collected from the Basic Statistic (IBGE, 1997), and data relative to the period from 1990 to 2009, collected from SIDRA (IBGE, 2011). The shift-share model was used for decomposition of (PGV) variation Taxes in function of the effects of area, productivity, and price factors. It was observed that the productivity, harvested area, production, and prices obtained by cassava growers were reduced in respectively 34%, 40%, 51%, and 67%. The combination of all those reductions reflected in the PGV behavior that presented reductions up to 87% in the analyzed period. Means of cassava productivity and PGV between 1977 and 2009 were respectively 7.99 t ha-1 and R$ 203.5 million. The highest productivity (10 t ha-1) and PGV (R$ 806.8 millions) were both observed in 1977 when annual averaged rainfall in the region was 1,159.3 mm. On the other hand the lowest productivity (2.36 t ha-1) was observed in 1993. In this year the averaged annual rainfall of the region was 436.6 mm. In some of the biennium the effects of productivity and the TX% of PGV had not the magnitude of variation and/or the same direction, conducting to the conclusion that productivity between 1977 and 2009 was neither the unique nor the mean factor responsible by the negative variation of 6.13% in the Ceará cassava PGV in that period.