Neotropical Entomology 34(6): 991-998 (2005) Resistência de PALAVRAS-CHAVE: Ácaro rajado, manejo da resistência, controle químico ABSTRACT -Studies on artificial laboratory selections with abamectin, cross-resistance relationships, and stability of resistance were carried out with Tetranychus urticae Koch to provide basic information for an abamectin resistance management program. Selections for resistance and susceptibility to abamectin were performed in a population of T. urticae, collected from a commercial strawberry field in the State of São Paulo, Brazil. After five selections for resistance and five selections for susceptibility, susceptible (S) and resistant (R) strains of T. urticae to abamectin were obtained. The resistance ratio (R/S) at the LC 50 reached 342-fold values. The toxicity of eight acaricides was evaluated in the R and S strains, observing significant differences (at LC 50 ) between R and S strains for milbemectin, fenpropathrin and chlorfenapyr. Significant correlation was detected between the LC 50 s of abamectin and milbemectin, indicating cross-resistance between these acaricides. No crossresistance was detected for the acaricides fenpyroximate, cyhexatin, propargite and dimethoate. The stability of abamectin resistance was also studied under laboratory conditions. Abamectin resistance was unstable in the absence of selection pressure. For all studied populations (with 75, 50 and 25% of initial frequency of resistant mites), the percentage of resistant mites decreased to levels equal or lower than 15% in six months. The results indicate that milbemectin should be avoided for managing abamectin resistance in T. urticae.

The two-spotted spider mite, Tetranychus urticae Koch (green-form) (Acari: Tetranychidae), is a worldwide pest of many plant species, including several agricultural crops (Flechtmann, 1985; Tomczyk and Kropczyńska, 1985). This tetranychid mite is one of the most important pests of strawberry (Chiavegato and Mischan, 1981) and causes significant damage to various other crops, such as apple, peach, papaya, kidney bean, cotton and ornamental plants in Brazil (Flechtmann, 1985). The ability of T. urticae to develop resistance to several acaricides has caused problems in many countries involved in agricultural production during the past 40 years (

This work aimed to evaluate the differential toxicity of pesticides to populations of the mite species Neoseiulus californicus (McGregor) and Tetranychus urticae Koch collected from commercial crops of strawberry (Fragaria sp.) in Atibaia county, State of São Paulo, Brazil. In the test of acute toxicity of pesticides, adult females of N. californicus received the pesticide treatment under Potter spray tower. The predaceous mite N. californicus showed the same or higher tolerance than T. urticae to various pesticides in laboratory. The highest difference was observed to the acaricide propargite, for which the predaceous mite was 25.1 times more tolerant than the two-spotted spider mite. This phytoseiid was also 4.7, 2.9 and 2.5 times more tolerant than T. urticae to chlorfenapyr, fenpyroximate, and cyhexatin, respectively. In the test of residual toxicity of pesticides, the chemicals were sprayed on plants of strawberry in the field. Leaves were collected after different periods from the treatment and artificially infested with adult females of N. californicus. The mortality was assessed 48h or 72h after treatment. Fenpyroximate, fenpropathrin, dimethoate, propargite, sulphur, and benomyl were innocuous to N. californicus. Chlorfenapyr, cyhexatin, and abamectin were significantly harmful to the predaceous mite causing initial mortality rates between 37.5% and 57.5%. The use of predaceous mites like of this population of N. californicus, which presents low susceptibility to various pesticides can be very useful for programs of management of T. urticae on strawberry in Brazil.

The purpose of this study was to evaluate the performance of Neoseiulus californicus (McGregor) for the control of Tetranychus urticae Koch in commercial strawberry fields, under greenhouse conditions, in association or not with the use of acaricides. The N. californicus strain used in this study was tolerant or resistant to several pesticides. Three experiments were carried out in the State of São Paulo, Brazil. For the first experiment, the initial infestation of T. urticae was 87.1 active stages per leaflet. Two applications of propargite were made on the first and the 14th day of the experiment. Approximately 2 h after each propargite application, N. californicus was released at a rate of 3.0 and 1.9 adult mites per plant, respectively, for each application. The population of T. urticae decreased from 87.1 to 2.8 mites per leaflet in the first three weeks. After this period, the population of T. urticae was maintained at low levels (

No abstract

The Eucoilinae, together with the Opiinae (Braconidae) are the most important parasitoids of the flies of the superfamily Tephritoidea. In order to provide knowledge on the Eucoilinae species in Brazil such as geographic distribution, hosts and the parasitism levels, 170 samples of parasitoids from 51 counties of the five Brazilian regions were examined. A total of 2025 parasitoids were obtained from which, six species (42.82%) have been associated to larvae of Tephritoidea. The parasitoids were associated to seven species of fly larvae which feed on the fruits of 33 species belonging to 15 families. The Eucoilinae species are generalists, as they parasite Anastrepha species (Tephritidae) and Lonchaeidae as well. Aganaspis pelleranoi (Brèthes) was the most abundant species (29.93%) with the broadest distribution in Brazil. Dicerataspis flavipes (Kieffer) was only collected in São Paulo State, associated to Anastrepha species. This parasitoid is attracted to star fruits (Averrhoa carambola L.), since 96,34% of D. flavipes were obtained in larvae inside this fruit. Lopheucoila anastrephae (Rhower) and Odontosema anastrephae Borgmeier were associated to Anastrepha pseudoparallela (Loew) and to species of Neosilba in Passifloraceae (first record). Aganaspis nordlanderi Wharton was recorded in Amazonas State associated to Anastrepha bahiensis Lima (first record). Aganaspis pelleranoi, D. flavipes and L. anastrephae were associated to Anastrepha amita Zucchi in Citharexylum myrianthum Cham. in São Paulo State (first record). Trybliographa sp. parasites mainly lonchaeid larvae, and it is being recorded for the first time in the State of São Paulo. The parasitism levels varied from 0.07 to 42.86%, depending on collection sites, fruit types and host flies.Recebido em 22/10/98. Aceito em 29/03/99.

Studies of community assembly have emphasized snapshot comparisons of spatially replicated samples from “natural” assemblages. Agro-ecosystems are characterized by relatively little habitat heterogeneity and no dispersal barriers for actively flying insects. Therefore, dynamic patterns of species segregation and aggregation are more likely to reflect the direct or indirect effects of species interactions. We studied the temporal organization of a guild of 21 congeneric species of Anastrepha that colonized fruit orchards in Monte Alegre do Sul, São Paulo, Brazil. This assemblage also included the introduced Mediterranean fruit fly Ceratitis capitata. One hundred six consecutive weekly censuses (11 Jan 2002-16 Jan 2004) of flies in guava, loquat, and peach orchards revealed a pattern of minimum abundance during the coldest months of each year (June and July) and a maximum abundance during periods of flowering and fruit ripening. Overall, phenological overlap was greater than expected by chance. However, conditioned on the pattern of seasonal abundances, temporal occurrence and abundance matrices exhibited patterns of significant species segregation and anti-nestedness. In each year, the 3 orchards contained a small number of species pairs that exhibited statistically significant temporal segregation or aggregation. Most aggregated and segregated pairs reflected seasonal shifts in species presences that were not related to variation in air temperature. Most of the significant pairwise associations involved C. capitata: 8 of the 11 segregated pairs and 2 of the 7 aggregated pairs. These results suggest that species interactions between introduced and native species can be an important determinant of species associations in agro-ecosystems.

-A total of 3,008 braconid parasitoids in 26 species of fruit fl y host plants were collected in 33 localities of São Paulo State. The majority of the braconids (96.2%) belonged to four Opiinae species, Doryctobracon areolatus (Szépligeti), Doryctobracon brasiliensis (Szépligeti), Opius bellus (Gahan) and Utetes anastrephae (Viereck), and the remaining 3.8%, a single species of Alysiinae, Asobara anastrephae (Muesebeck). Doryctobracon areolatus was collected on Anastrepha fraterculus (Wied), A. obliqua (Macquart) and A. amita Zucchi, and was found associated with the largest number of fruit fl y host plant species (26), being recorded for the fi rst time in fruits of Clausena lansium and Cryptocarya aschersoniana. This species was the most common, occurring in most of the sampled localities, totaling 77.5% of all parasitoids collected. Doryctobracon brasiliensis was associated only with A. fraterculus and recorded, for the fi rst time, in Japanese plum (Prunus salicina). It was not possible to associate the remaining braconids to the fruit fl y species. Opius bellus was also reared from larvae in C. aschersoniana. The natural parasitism percentage ranged from < 1% to 40%.KEY WORDS: Opiinae, Alysiinae, natural parasitism, distribution, Anastrepha RESUMO -Foram coletados 3.008 braconídeos em larvas/pupas de moscas-das-frutas em 26 espécies de frutos, distribuídos em 33 municípios paulistas. A maioria dos braconídeos pertencia a Opiinae (96,2%), representada por quatro espécies -Doryctobracon areolatus (Szépligeti), Doryctobracon brasiliensis (Szépligeti), Opius bellus (Gahan) e Utetes anastrephae (Viereck) -e os demais a Alysiinae (3,8%), representada apenas por Asobara anastrephae (Muesebeck). Doryctobracon areolatus foi atraída por mais frutos hospedeiros de moscas-das-frutas (26) e ocorreu na maioria dos municípios amostrados, totalizando 77,5% dos parasitóides coletados. Doryctobracon areolatus foi associada com Anastrepha fraterculus (Wied.), A. obliqua (Macquart), A. amita Zucchi e, pela primeira vez, em frutos de wampi (Clausena lansium) e em canela-batalha (Cryptocarya aschersoniana). Doryctobracon brasiliensis foi associada apenas com A. fraterculus e registrada, pela primeira vez, em larvas em ameixa-japonesa (Prunus salicina). Não foi possível associar as demais espécies de parasitóides às espécies de moscas-das-frutas. Opius bellus foi obtida de larvas em canela-batalha. A percentagem de parasitismo natural variou de <1% a 40%.