Lucia Maria Lopes de Almeida Guedes Diefenbach

Ocorrência de Parasitismo em Ovos de Spartocera dentiventris (Berg) (Hemiptera: Coreidae) em Cultura de Fumo

The paucity of information about egg parasitoids of Spartocera dentiventris (Berg) motivated the present work. This study aimed to determine the parasitoid species involved as well as to quantify the mortality caused by these natural enemies in field conditions. The investigation was carried out in a tobacco crop (cultivar Virginia, var. K-326) in Porto Alegre, RS. From December/97 to February/98, 20 egg masses of known age were left exposed to all causes of mortality for a period of 13 days. Two species of parasitoids were found on eggs of S. dentiventris: Gryon gallardoi (Brethes) (Hym.: Scelionidae) and Neorileya ashmeadi Crawford (Hym.: Eurytomidae). From a total of 321 observed eggs, only 34.3% (110 eggs) originated nymphs of S. dentiventris. Parasitism was the main mortality factor, killing 148 eggs (46.1%) from the total observed.

Parâmetros reprodutivos de Corecoris dentiventris Berg (Hemiptera: Coreidae) em cultura de fumo (Nicotiana tabacum)

Information about Corecoris dentiventris Berg, is mostly restricted to adult morphology, host plants and injuries. The objective of the present investigation was to study some reproductive parameters of this species. The experiment was carried out in a tobacco culture (Virginia type, var. K 326), in the experimental area of the Departamento de Fitossanidade of the Universidade Federal do Rio Grande do Sul, in Porto Alegre, RS. The reproductive parameters were estimated from ten couples isolated in plants, protected by cages, and observed until their death. The following average values were found: eggs/female = 355.9; pre-oviposition period = 11.8 days; oviposition period = 48.61 days; adult longevity = 62.6 and 66.1 days, respectively, for males and females. The reproductive potencial was estimated as 2.0 X 104 descendents per female in tobacco crop.

Spatial distribution of parasitism on Phyllocnistis citrella Stainton, 1856 (Lepidoptera: Gracillariidae) in citrus orchards

Many species of microhymenopterous parasitoids have been registered on Phyllocnistis citrella, the citrus leafminer. The present study aimed to identify the spatial distribution pattern of the native and introduced parasitoids of P. citrella in two citrus orchards in Montenegro, RS. The new shoots from 24 randomly selected trees in each orchard were inspected at the bottom (0-1.5 m) and top (1.5-2.5 m) stratum and had their position relative to the quadrants (North, South, East and West) registered at every 15 days from July/2002 to June/2003. The leaves with pupae were collected and kept isolated until the emergence of parasitoids or of the leaf miner; so, the sampling was biased towards parasitoids that emerge in the host pupal phase. The horizontal spatial distribution was evaluated testing the fitness of data to the Poisson and negative binomial distributions. In Montenegrina, there was no significant difference in the number of parasitoids and in the mean number of pupae found in the top and bottom strata (chi2 = 0.66; df = 1; P > 0.05) (chi2 = 0.27; df =1; P > 0.05), respectively. In relation to the quadrants, the highest average numbers of the leafminer pupae and of parasitoids were registered at the East quadrant (chi2 = 11.81; df = 3; P < 0.05), (chi2 = 10.36; df = 3; P < 0.05). In the Murcott orchard, a higher number of parasitoids was found at the top stratum (63.5%) (chi2 = 7.24; df =1 P < 0.05), the same occurring with the average number of P. citrella pupae (62.9%) (chi2 = 6.66; df = 1; P < 0.05). The highest number of parasitoids and of miners was registered at the North quadrant (chi2 = 19. 29; df = 3; P < 0.05), (chi2 = 4.39; df = 3; P < 0.05). In both orchards, there was no difference between the numbers of shoots either relative to the strata as well as to the quadrants. As the number of shoots did not varied much relative to the quadrants, it is possible that the higher number of miners and parasitoids in the East and West quadrants would be influenced by the higher solar exposure of these quadrants. The data of the horizontal spatial distribution of the parasitism fit to the negative binomial distribution in all sampling occasions, indicating an aggregated pattern.

Biology of Corecoris dentiventris Berg, 1884 (Hemiptera, Coreidae) in tobacco culture (Nicotiana tabacum)

Corecoris dentiventris Berg, 1884 (HEM., Coreidae) represents a pest in the tobacco culture in Southern Brazil. Nymphs and adults cause the wilting and twisting of the tobacco leaves due to their sucking habit. There are very few works about this species and these are restricted to concise description of the adult morphology, records of host plants and enumeration of injuries. The present investigation aims to study the life cycle of this bug. The experiment was carried out in a tobacco culture (Virginia type, var. K 326) implanted in the experimental area of the Departamento de Fitossanidade of the Universidade Federal do Rio Grande do Sul, in Porto Alegre, RS. The life cycle was studied in field conditions, in nylon cages, from egg clusters oviposited by females of the colonizing generation. The preferred oviposition site was the main vein in the abaxial side of the leaf. The average incubation period was 13.7 +/- 0.04 days and the egg viability, 99.63%. The average periods of the different instars of the bug, in days, were: 5.4 +/- 0.08, 9.7 +/- 0.19, 4.5 +/- 0.08, 5.3 +/- 0.08, 9.0 +/- 0.13 respectively for the first, second, third, fourth and fifth instars. The first instar presented the highest mortality (13.86%). The accumulated mortality of the nymphal phase was 35.29%. The sex ratio was 0.97 males: 1 female.

Internal reproductive organs of Cosmoclopius nigroannulatus (Hemiptera: Reduviidae).

The internal reproductive organs of Cosmoclopius nigroannulatus males and females are described, illustrated and measured. No significant difference was registered among immature and reproductive structures of males and their aspect was also similar. However, in females noteworthy differences both in size and aspect were found.

Fertilidade e longevidade de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)em genótipos de milho

Spodoptera frugiperda (J. E. SMITH) is one of the main corn crop pest. Neverthless, studies about its biology in the sweet corn crop are scarce. This study aimed to evaluate the effect of the genotypes ELISA, BR 400 (sweet corn) and BR PAMPA (field corn) in the reproductive phase of S. frugiperda concerning: pre-oviposition, oviposition and post-reproduction periods; number of ovipositions/female and eggs/oviposition; eggs viability; incubation period; interval between ovipositions and longevity. In laboratory conditions (25 ± 1°C; 70 ±10% RH; 12 hours photophase), 60 larva/genotype were fed with leaves of three genotypes. From the pupae, 15, 20 and 24 couples were formed in ELISA, BR 400 and BR PAMPA, respectively. The number of ovipositions per female and eggs per oviposition was daily registered. Differences between the genotypes ELISA, BR 400 and BR PAMPA, respectively, were not noticed, concerning: pre-oviposition (4.78; 3.94; 3.94 days); oviposition (7.55; 6.5; 6.11 days) and post-reproductive (4.87; 4.64; 5.5 days) periods; number of ovipositions/female (6.33; 5.25; 4.88) and eggs/oviposition (216.72; 215.03; 226.02); eggs viability (59.02; 69.76; 60.81%); interval between ovipositions (0.63; 0.86; 1.0 days); longevity of male (15.22; 13.62; 13.29 days) and female (16.33; 14.06; 15.65 days) with offspring and of the male (19.17; 13.67; 13.86 days) and female (16.43; 8.25; 19.37 days) without offspring. The incubation period of the eggs generated by females whose caterpillars were kept in BR 400 genotype was numerically longer than the others.

Larval and pupal stage of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in sweet and field corn genotypes

Spodoptera frugiperda, the fall armyworm, is a very significant polyphagous pest due to the damages it causes, and control difficulties. Lack of information about its impact on sweet corn motivated a comparison of its biology, with respect to the larval and pupal stages, among the genotypes ELISA, BR 400 (sweet corns), and BR PAMPA (field corn). In laboratory conditions (25 +/- 1 masculine C; 70 +/- 10% RH; photophase 12 hours), 35 caterpillars were individualized and fed daily with 3.14 cm(2) sections of corn leaves from the referred-to genotypes, cultivated in plots in the experimental area of the Departament of Fitossanidade, UFRGS, Porto Alegre, RS from October to November 2000. The caterpillars were weighed daily; after each molt, the cephalic capsules were collected and measured (in width), to establish growth rate; pupae were weighed and sexed when 24 hours old. The duration of the larval instars, the pupal sex ratio, and the mortality of larvae and pupae were evaluated. In the first three instars there were no differences registered in capsule width. In the fourth and fifth instars, capsules of caterpillars kept in BR 400 were smaller. The weight of caterpillars and pupae, instar duration and sex ratio did not differ among the genotypes. Pupal phase duration was less in females kept in BR 400. Mortality was greater in the larval phase in ELISA and in the pupal phase in BR PAMPA.

Descrição dos estágios imaturos de Corecoris dentiventris Berg (Hemiptera: Coreidae)

The immature stages of Corecoris dentiventris Berg were studied. The external morphological characters of the five instars including the spatial pattern of the abdominal trichobothria of nymphs, and the egg are described and illustrated.

Carabid taxocenes of an urban park in subtropical Brazil: II. Specific diversity and similarity (Insecta: Coleoptera: Carabidae)∗

Epigeal carabids of a typical urban park in subtropical Brazil (Porto Alegre) were sampled by means of 48 dry pitfall traps running for 13 months and emptied at weekly intervals. Sampling was confined to areas covered by English ivy (Hedera helix) and strata were defined as follows: the centre and the margin of the patch; the percentage cover of the soil given by the ivy (dense or sparse); the type of periphery of a patch (lawns or bare/paved soil). A total of 2107 specimens in 27 species was captured. Measures of diversity and similarity of carabid taxocenes were carried out between habitat strata. Six indices were used to measure diversity and the Simpsons index c was elected the most adequate due to the strong dominance of the taxocenes of all the strata by a single species (P. (P.) cordicollis). Similarity was measured by the Renkonen Coefficient (PS) and the Sorensen Quocient of Similarity (QS). The PS was elected the best measure given the type of dominance structure of the taxocenes. Dominance-div...

SEASONAL ABUNDANCE AND MORTALITY OF Oebalus poecilus (DALLAS) (HEMIPTERA: PENTATOMIDAE) IN A HIBERNATION REFUGE

Oebalus poecilus (Dallas) is an important pest affecting irrigated rice in Rio Grande do Sul, Brazil. It hibernates during the coldest months of the year in refuges such as bamboo litter. This study examined O. poecilus hibernation to determine the causes of mortality during this period. The study was conducted in a 140 m(2) bamboo plantation located in a rice-growing area in Eldorado do Sul County (30 degrees 02 S and 51 degrees 23 W), RS. During June 2000 to April 2002, 63 samples of litter were taken in weekly or fortnightly intervals, and the number of bugs recorded in the laboratory. The arrival at the hibernation site (bamboo litter) began in the first fortnight of March, and was completed in the beginning of May. O. poecilus left this refuge from middle October to the end of December. Parasitism by tachinid flies and Beauveria bassiana (Bals.) Vuill. fungus were the most important mortality factors.