Abundância e sazonalidade de cigarrinhas (Hemiptera, Cicadellidae, Cicadellinae) em vegetação herbácea de pomar de laranja doce, no município de Montenegro, Estado do Rio Grande do Sul, Brasil.

O presente estudo teve por objetivo conhecer a flutuação populacional e a constância de cicadelíneos presentes na vegetação herbácea de um pomar de laranja doce (Citrus sinensis (L.) Osbeck), variedade Valência, em Montenegro, RS. O levantamento foi realizado com a metodologia da rede-de-varredura, tendo início em fevereiro de 2001 e finalizando-se em janeiro de 2002. Mensalmente foram coletadas dez amostras, sendo cada uma destas composta por 50 golpes de rede em movimento de avanço sobre a vegetação herbácea e cultura intercalar nas entrelinhas do pomar (n = 500 golpes/ocasião de coleta). No total foram coletados 928 cicadelíneos,pertencentes a nove espécies: Bucephalogonia xanthophis (Berg, 1879), Diedrocephala variegata(Fabricius, 1775), Hortensia similis(Walker, 1851), Macugonalia leucomelas (Walker, 1851), Parathona gratiosa (Blanchard, 1840), Plesiommata corniculata Young,1977, Sibovia sagata (Signoret, 1854), Sonesimia grossa (Signoret, 1854) e Tapajosa rubromarginata (Signoret, 1855). O período de maior abundância da comunidade de cicadelíneos foi durante a primavera e o verão. Hortensia similis e M. leucomelas foram as únicas espécies consideradas constantes durante o levantamento. A menor abundância dos cicadelíneos em abril e dezembro provavelmente devese a efeitos causados por fatores abióticos (pluviosidade) e aqueles relativos à estrutura da vegetação (altura das plantas) sobre a comunidade

Population Genomic Analysis of a Bacterial Plant Pathogen: Novel Insight into the Origin of Pierce's Disease of Grapevine in the U.S.

Invasive diseases present an increasing problem worldwide; however, genomic techniques are now available to investigate the timing and geographical origin of such introductions. We employed genomic techniques to demonstrate that the bacterial pathogen causing Pierce's disease of grapevine (PD) is not native to the US as previously assumed, but descended from a single genotype introduced from Central America. PD has posed a serious threat to the US wine industry ever since its first outbreak in Anaheim, California in the 1880s and continues to inhibit grape cultivation in a large area of the country. It is caused by infection of xylem vessels by the bacterium Xylella fastidiosa subsp. fastidiosa, a genetically distinct subspecies at least 15,000 years old. We present five independent kinds of evidence that strongly support our invasion hypothesis: 1) a genome-wide lack of genetic variability in X. fastidiosa subsp. fastidiosa found in the US, consistent with a recent common ancestor; 2) evidence for historical allopatry of the North American subspecies X. fastidiosa subsp. multiplex and X. fastidiosa subsp. fastidiosa; 3) evidence that X. fastidiosa subsp. fastidiosa evolved in a more tropical climate than X. fastidiosa subsp. multiplex; 4) much greater genetic variability in the proposed source population in Central America, variation within which the US genotypes are phylogenetically nested; and 5) the circumstantial evidence of importation of known hosts (coffee plants) from Central America directly into southern California just prior to the first known outbreak of the disease. The lack of genetic variation in X. fastidiosa subsp. fastidiosa in the US suggests that preventing additional introductions is important since new genetic variation may undermine PD control measures, or may lead to infection of other crop plants through the creation of novel genotypes via inter-subspecific recombination. In general, geographically mixing of previously isolated subspecies should be avoided

Sampling Hymenoptera along a precipitation gradient in tropical forests: the effectiveness of different coloured pan traps

Measuring species richness of tropical insects is an important but considerable challenge. Several techniques have been developed to quantitatively sample the non-formicid Hymenoptera (bees and wasps). One of themost common is the use of colored pan traps. Although it is known that Hymenoptera are attracted differently by different colors, it is not yet known if these preferences shift in different habitats and hence affect comparisons of Hymenoptera diversity.We studied the effectiveness of differently-colored pan traps along a latitudinal, climatic, and forest structure gradient from tropical to subtropical forests.Overall, we found a strong increase in individual numbers fromnorth to south. Yellow traps sampled significantly more individuals than blue ones, mainly due to the responses of the families Ichneumonidae, Nyssonidae, Pompilidae, and Crabronidae, but trap catch was also related to canopy cover. Notably, traps located at forest edges had yellow⁄ blue ratios similar to those of forests with comparable canopy cover. This suggests that, in contrast to the overall number of individuals caught, the relative effectiveness of yellow vs. blue traps was driven by canopy cover and hence light conditions or visibility of the traps. Thus comparisons of pan trap results between forests having different structures should only bemade with great care

Control of the Silverleaf Whitefly (SW) on Poinsettia Under Greenhouse Conditions, Fall 1993

Abstract Poin settias obtained as rooted cuttings were potted in 15 cm pots. Plants were allowed 4 wk growth (25-30 cm tall) before use in trials. Leaves were counted from the top (leaf of &amp;gt;2 cm2) down. Twenty SW adults were clip-caged (2.5 cm diam) on the adaxial surface of leaf no. 5 for 24 h to obtain a moderate no. of eggs/leaf. Ten days later the no. of nymphs were counted as a pre-treatment count (0 DAT). Plants were assigned to treatments to obtain an equal no. of immatures/treatment. Five plants/treatment were arranged in a randomized block design on a greenhouse bench. Ten treatments and a water treated control were applied by hand sprayer at 45 psi. Post-treatment counts were made at 7 DAT and 14 DAT.</jats:p

Control of Adult Whitefly on Poinsettia Under Greenhouse Conditions, Winter 1992

Abstract Poinsettias obtained as rooted cuttings were potted in 15 cm pots and allowed 8 wk growth (10-12" tall) before use. Twenty-seven plants were treated by soil application and arranged in a randomized block design on a greenhouse bench. Forty DAT, a 2.5 cm diam clip-cage containing 20 adult SWF was placed on the abaxial side of a fully expanded leaf of each plant. Eight h later the adults were removed and clip-caged to a separate set of untreated plants. Live and dead adults were counted at transfer, 24, and 48 h after transfer.</jats:p

A new species of Ceraticelus Simon from southern California and a redescription of Ceraticelus phylax Ivie &amp;amp; Barrows, its probable sister species (Araneae: Linyphiidae)

A new species of Ceraticelus Simon, 1884 from southern California is described, Ceraticelus artemisiae sp. nov. Its probable sister species, Ceraticelus phylax Ivie &amp; Barrows, 1935, a potential adventive species with which it now often co-occurs in southern California, is redescribed for the first time. We provide detailed descriptions of both species because an adequate definition of the genus is lacking and the conformation of the male Ceraticelus palpal bulb has been only superficially treated. We also provide a definition of Ceraticelus based on examination of specimens of the type species, Ceraticelus fissiceps (O. P.-Cambridge). Problems associated with both the conformation of the male bulb and the paracymbium morphology are discussed. Despite the lack of a phylogenetic analysis of Ceraticelus, we propose that Ceraticelus phylax and Ceraticelus artemisiae sp. nov. are sister species based on shared characters that distinguish them from all other congeners. We suggest that the presence of Ceraticelus phylax in California is the result of incidental introduction rather than natural dispersal. Habitat, distribution, and phenology data are presented in the text. Illustrations and a distribution map are also furnished for both species.</jats:p