Sandra Maria Morais Rodrigues

Resposta à temperatura de Aphidius colemani Viereck (Hymenoptera, Braconidae, Aphidiinae) originário de três regiões climáticas de Minas Gerais, Brasil

The parasitoid Aphidius colemani Viereck, 1912 presents higher mortality at constant temperatures above 25°C, and probably it is the cause of the failure on the biological control of Aphis gossypii Glover, 1877 when this parasitoid is used at higher temperatures in greenhouses. The aim of this work was to evaluate the influence of different temperatures on individuals of A. colemani from different climatic regions of Minas Gerais state, Brazil. Individuals of A. colemani were collected in the localities of Juramento, Lavras and Sao Gotardo, and reared in laboratory (22±2°C, 70±10% RH and 12h photophase) for three generations in the host A. gossypii, on cucumber plants. One mated female of A. colemani, 24-48 h old, was released for one hour, in a Petri dish (15cm) with 20 nymphs of 2nd instar of A. gossypii on a leaf disk of cucumber (4 cm of diameter) laid on a layer of agar-water (1%). The parasitized aphids were kept at 16, 19, 22, 25 and 28±1°C, 70±10% RH and 12h photophase. The emergence rates of individuals from Juramento (65.9 and 35.4%) and Sao Gotardo (71.4 and 47.6%) were lower compared to those from Lavras (87.1 and 80.9%) at 16 and 28°C. The more suitable temperature for the development of A. colemani from Lavras was higher than those for individuals from Juramento and Sao Gotardo. The individuals from Lavras showed highest emergence at 28°C, and this demonstrated the existence of individuals of A. colemani with tolerance to higher temperatures. These results open news perspectives on the use of different strains of A. colemani on biological control of A. gossypii in protected cultivation.

Desenvolvimento e parasitismo de Lysiphlebus testaceipes (Cresson) e Aphidius colemani Viereck (Hymenoptera: Braconidae) em Aphis gossypii Glover (Hemiptera: Aphididae) em duas cultivares de crisântemo

The parasitoids Lysiphlebus testaceipes (Cresson) and Aphidius colemani Viereck play an important role on the regulation of aphid populations on chrysanthemum grown in greenhouses. This study evaluated the interaction of biological control and plant resistance by the development and the parasitism of L. testaceipes and A. colemani on Aphis gossypii Glover. The aphid host was kept on commercial cultivars of chrysanthemum susceptible Yellow Snowdon (YS) and resistant White Reagan (WR). The experiment was carried out in climatic chamber at 22 +/- 1 masculineC, 70 +/- 10% RH, and photophase 12h. Nymphs of 2nd and 3rd instars of A. gossypii attacked only once by the parasitoids were used in the experiment. The development time was 15.0 and 12.9 days for L. testaceipes and 17.0 and 16.3 days for A. colemani kept on A gossypii on cvs. YS and WR, respectively. The parasitoid L. testaceipes showed greater parasitism rate (68.4%) on A. gossypii on cv. YS than on WR (50%), and for A. colemani was not found significative difference on parasitism (46.8 and 35% to YS and WR, respectively). The emergence rates of L. testaceipes and A. colemani were 91.6% and 85.3% on A gossypii reared on YS, and 78.1% and 100% on WR, respectively. The longevity of A colemani and the parasitism rate of L. testaceipes were affected in a negative way by the cv. WR. The results indicated a positive interaction of biological control with parasitoids and the resistant cv. WR on A. gossypii control in protected cultivation.

Desenvolvimento de Aphidius colemani Viereck (Hymenoptera: Braconidae, Aphidiinae) e alterações causadas pelo parasitismo no hospedeiro Aphis gossypii Glover (Hemiptera: Aphididae) em diferentes temperaturas

Aphidius colemani Viereck is among the main natural enemies used for biological control of Aphis gossypii Glover. The objective of the present study was to evaluate the development of A. colemani and the alterations caused by the parasitism in the host A. gossypii in different temperatures and to estimate the thermal requirements of the parasitoid. The experiments were carried out in controlled environmental chambers at 16, 19, 22, 25, 28 and 31 +/- 1 degrees C, 70 +/- 10% RH, and 12h photophase. Second-instar nymphs of A. gossypii were parasitized once and kept individually in glass tubes (2.5 cm x 8.5 cm), containing leaf disc of cucumber (2 cm) and 1% water/agar solution. The development time of A. colemani, from oviposition to mummies (11.9, 9.8, 7.7, 6.4 and 6.4 days) and from oviposition to adult (19.4, 16.2, 12.6, 10.5 and 10.7 days) decreased with the increase of the temperature from 16 degrees C to 25 degrees C. The rates of mummies and the emergence of the parasitoid, and its longevity also decreased with the increase of the temperature. Mummies were not produced at 31 degrees C. The lower temperature threshold of A. colemani was 5.94 degrees C and its thermal constant was 200 degrees-day. The alterations caused by the parasitoid in the A. gossypii host were minimized at 31 degrees C, where 98% of the host did not show symptoms of parasitism and produced nymphs. The temperature of 22 degrees C was optimal for the development time of A. colemani.

Selection of bee species for environmental risk assessment of GM cotton in the Brazilian Cerrado

The objective of this work was to list potential candidate bee species for environmental risk assessment (ERA) of genetically modified (GM) cotton and to identify the most suited bee species for this task, according to their abundance and geographical distribution. Field inventories of bee on cotton flowers were performed in the states of Bahia and Mato Grosso, and in Distrito Federal, Brazil. During a 344 hour sampling, 3,470 bees from 74 species were recovered, at eight sites. Apis mellifera dominated the bee assemblages at all sites. Sampling at two sites that received no insecticide application was sufficient to identify the three most common and geographically widespread wild species: Paratrigona lineata, Melissoptila cnecomola, and Trigona spinipes, which could be useful indicators of pollination services in the ERA. Indirect ordination of common wild species revealed that insecticides reduced the number of native bee species and that interannual variation in bee assemblages may be low. Accumulation curves of rare bee species did not saturate, as expected in tropical and megadiverse regions. Species-based approaches are limited to analyze negative impacts of GM cotton on pollinator biological diversity. The accumulation rate of rare bee species, however, may be useful for evaluating possible negative effects of GM cotton on bee diversity.

Minimal effective dose of phosphine to control the cashew root borer, Marshallius bondari Rosado-Neto (Coleoptera: Curculionidae)

Objetivou-se determinar, em condicoes de campo, a dose minima de fosfina para o controle da broca da raiz do cajueiro. Foram instalados 3 experimentos em epocas distintas, sendo o primeiro em agosto, o segundo em outubro e o terceiro em novembro de 1994 para o controle de Marshallius bondari Rosado-Neto (Coleoptera: Curculionidae) em cajueiro, Anacardium occidentale L. no municipio de Pio IX, Estado do Piaui. Foram testadas 1; 2; 3 e 6 pastilhas de fosfina na forma de fosfeto de aluminio, de 3 gramas cada, por planta. No ensaio conduzido em agosto nenhum tratamento foi eficiente para o controle de brocas adultas no solo. No ensaio instalado em outubro, a fosfina foi eficiente a partir de duas pastilhas por planta e no ensaio de novembro a partir de uma pastilha por planta para o controle de adultos no solo. A eficiencia foi tanto maior quanto maior foi o tempo decorrido apos a ultima chuva, estando, portanto, o solo mais seco.