Biological control of twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), using Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae) on impatiens

The effectiveness of the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), as a suppressive agent of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), was evaluated on impatiens plants at predator:prey release ratios of 1:3 (high), 1:15 (medium) and 1:30 (low). Releases at each ratio were made at low and high initial T. urticae densities to determine if initial pest population size influenced the suppressive ability of the predator. After only one week, P. persimilis was reduced both the higher and lower T. urticae populations to negligible levels and kept damage to 5% or less, but only at the 1:3 ratio. At the medium predator:prey ratio, predators prevented spider mite numbers and damage from increasing, but did not reduce either. At the lowest ratio (1:30) spider mite populations and plant damage continued to increase. Both the medium and low ratios allowed unacceptably high levels of plant damage. A regression model indicated that a release ratio of 1:10 or higher should consistently reduce the pest population and associated damage to acceptable levels. However, if spider mites establish at high levels of infestation similar to those we tested experimentally, even releasing predators at a 1:3 ratio will not provide certain control. To reliably control damage from spider mites on impatiens, predators must be released as soon as spider mites are detected in order to reduce spider mite populations to non-detectable levels within one or two weeks of predator release

Variação sazonal das condições internas de colônias de Melipona marginata obscurior Moure, no Rio Grande do Sul, Brasil Seasonal variations in the internal condictions of colonies the Melipona marginata obscurior Moure, at Rio Grande do Sul, Brazil

O conhecimento das condições internas das colônias de Melipona marginata obscurior Moure, 1971, ao longo do ano, é importante para a compreensão do comportamento das abelhas sem ferrão e seu manejo. Visa-se o estudo da biologia de M. marginata obscurior em ambiente natural, com ênfase na variação sazonal das condições internas das colônias. Quatro colônias foram estudadas no Centro de Pesquisas e Conservação da Natureza Pró-Mata, em São Francisco de Paula, RS. Avaliou-se o volume dos ninhos, a ocorrência e duração da diapausa e o número total de favos e de células de cria nos dois últimos favos. O volume do invólucro inicial das quatro colônias foi semelhante, variando de 2,26 a 2,69 litros. Ao final da avaliação observou-se que o volume do invólucro da colônia A reduziu 5%, enquanto as demais cresceram 61% (colônia B), 84% (C) e 71% (D). A partir do monitoramento mensal dos favos de cria constatou-se a ocorrência de diapausa em três colônias (B, C e D) enquanto a colônia A permaneceu com postura ininterruptamente. As colônias cessaram a construção de células de cria e postura da rainha durante o outono e reiniciaram esta atividade no final do inverno. Sugere-se que a variação do período de diapausa (8 a 23 semanas) seja determinada por fatores internos das colônias. O número máximo de favos registrado durante a primavera e o verão variou de 6 a 8, enquanto que o número estimado de células de cria dos dois últimos favos variou de 116 a 1190. Foi possível reconhecer padrões, bem como variações sazonais, relacionados ao volume do invólucro dos ninhos, à ocorrência de diapausa e ao número de favos e de células de cria nos dois últimos favos. Variações sazonais das condições internas entre as colônias mostraram-se evidentes e podem ser creditadas a características intrínsecas das colônias.<br>The knowledge of the internal conditions of Melipona marginata obscurior Moure, 1971 colonies, through the year, is important for the understanding of the behavior and handling of the stingless bees. This work aims the biological study of the M. marginata obscurior in its natural environment, whith emphasis on the seasonal variation of the internal conditions of colonies. Four colonies were studied at Centro de Pesquisas e Conservação da Natureza Pró-Mata, in São Francisco de Paula, Rio Grande do Sul. It was valuated the nest volume, the diapause occurrence and duration, and the total number of combs and brood cells in the two last combs. For the four colonies the initial involucrum volume was similar, varying from 2.26 to 2.69 liter. In the final of the valuation, it was observed that the colony A volume was reduced to 5%, while the others grow up 61% (colony B), 84% (C) e 71% (D). From the monthly monitoring of the brood combs it was shown that diapause occurred in three colonies (B, C e D), while the colony A remained ininterruptly with posture. The colonies ceased the construction of brood cells and posture of the queen during the autumn and restarted this activity on the final of the winter. It's suggested that diapause period variation (8 to 23 weeks) is determined by internal factors of the colonies. The maximal number of combs, registered during the spring and the summer, varied from 6 to 8, while the number of the brood cells of the two last combs varied from 116 to 1190 cells. It was possible to recognize patterns, as well seasonal variations related to involucrum volume of the nest covering, to diapause occurrence and to number of the combs and brood cells on the two last combs. The seasonal variations of the internal conditions among the colonies were obvious and can be credited to intrinsic characteristics of the colonies

Atividades de coleta e origem floral do pólen armazenado em colônias de Plebeia saiqui (Holmberg) (Hymenoptera, Apidae, Meliponinae) no sul do Brasil Collection activities and floral origin of the stored pollcn in colonies of Plebeia saiqui (Holmberg) (Hymenoptera, Apidae, Meliponinae) in south Brazil

<abstract language="eng">Four colonies of Plebeia saiqui (Holmberg, 1903), of São Francisco de Paula, were studied during the period from October/1998 to October/1999. The counting of the bees was proceeded monthly, differentiated workers that came back with and without pollen in the corbicula. Grains of pollen of pots previously marked were collected monthly and identified. The percentage of the pollen types of the samples was estimated: 20% of Asteraceae, 17% Myrtaceae, 15% type Meliaceae and 10% Euphorbiaceae. The remaining corresponds to other pollen types of small representation, besides those the were no identified. The climatic influence on the pollen collection was analyzed being used simple and multiple regressions. It was verified that in the spring and in the summer the temperature, the solar irradiation and relative humidity were significant for the pollen foraging. During autumn and winter the relative humidity had smaller influence in the pollen collection