Search

The egg parasitoid Gryon aetherium Talamas (Hymenoptera: Scelionidae) is a promising candidate for biocontrol of Bagrada hilaris Burmeister (Hemiptera: Pentatomidae) in the Southwestern USA. Bagrada hilaris is a worldwide invasive pest of crops in the family Brassicaceae. The present study aims to evaluate the parasitoid’s host range in a European context. These tests complement studies underway in California and provide risk information for a potential release of G. aetherium in southern continental Europe where B. hilaris is likely to spread in the future. Of the 11 non-target species tested, four pentatomids were in the physiological host range of G. aetherium: Carpocoris mediterraneus, Dolycoris baccarum, Graphosoma italicum and Ancyrosoma leucogrammes. Parasitism rates on these four species were lower in choice than in no-choice conditions. Surprisingly, the three Eurydema spp. that belong to the same tribe as B. hilaris (Strachiini) and feed on plants in the family Brassicaceae were not parasitized. No parasitism was observed on the cosmopolitan invasive pentatomids Nezara viridula and Halyomorpha halys, nor on the rhopalid Liorhyssus hyalinus. Parasitoids that developed from non-target species were larger than ones developing on B. hilaris and took more time to complete development.

The phytophagous stinkbug pest Bagrada hilaris (Hemiptera: Pentatomidae) (= bagrada) buries single eggs in the ground, an exception among pentatomids. To investigate potential biological control strategies to mitigate the pest’s damages, an evaluation of the egg parasitoid Gryon gonikopalense (Hymenoptera: Scelionidae) as a biocontrol agent is ongoing. Its ability to detect and parasitize buried bagrada eggs could be a key factor in the short and long-term regulation of bagrada populations in the U.S. However, this foraging ability would be relevant only if bagrada mainly oviposits in the soil and if G. gonikopalense mainly parasitizes buried eggs, which is currently unknown. We assessed the oviposition pattern of bagrada in presence of three host plants (broccoli, white mustard and white rocket) and at three density levels (one, five or fifteen copulae). The prevalent oviposition site of bagrada was in the soil (92% of eggs) with no effect from the host plant neither the bagrada density. Eggs oviposited on mustard were mainly present on the top third, but no distribution pattern was observed on broccoli and white rocket. Gryon gonikopalense preferred parasitizing buried eggs (87% of total parasitism). It was also able to parasitize non-buried eggs whatever their location. Artificially increasing the number of non-buried eggs in the experimental design only resulted in a slight reduction in the parasitism of buried eggs (70%). As a result, this study highlights the relevance of using G. gonikopalense against bagrada as its specific foraging behaviour responds well to the main oviposition behaviour of its host.

Many grape viruses, such as filamentous Grapevine leafroll-associated virusesin the Closteroviridae family, are spread primarily through infected propagating material. However, there is increasing evidence that leafroll disease are spread in the field by insect vectors, namely mealybugs and other scale insects. This study was carried out in the northern wine-growing regions of France where Grapevine leafroll-associated virus-1 and -3 (GLRaV-1 and -3) are the most widespread grape Ampelovirusspecies. The vineyards were inspected for presence of mealybug and scale insects and grapes infected by GLRaV-1 and -3. Mealybugs, Heliococcus bohemicus, Phenacoccus aceris(Pseudococcidae) and the soft scale insect Parthenolecanium corni(Coccidae), were capable of a transmission efficiency of 14%, 23% and 29% respectively. GLRaV-1 and -3 infections that resulted from virus transmission were confirmed with DAS-ELISA using polyclonal antibodies. This is the first report of GLRaV-1 and -3 transmission by mealybug and coccid species in France, and the first report of the ability of H. bohemicusand Phenacoccus aceristo transmit these viruses to grapevines. The relevance of these findings with regards to maintenance of virus-free grapevine stocks and to control leafroll spread in commercial vineyards is discussed.

RésuméAccouplement et morphologie de l'appareil génital femelle de Hyalesthes obsoletusSignoret (Hemiptera: Fulgoromorpha: Cixiidae).— L'étude des genitalia femelles du genre Hyalesthes (Cixiidae) à ovipositeur court, montre que tant les structures gonocoxales que gonaphysiennes ont subi un phénomène de réduction, par rapport au genre Cixiusà ovipositeur long. La paroi de la bourse copulatrice présente des ornementations circulaires, connues chez de nombreux Fulgo-romorphes. Ces différenciations cuticulaires sont vraisemblablement liées à des formations glandulaires. La dissection de spécimens in copula montre également que, durant la copulation, des différentes structures de l'appareil génital mâle sont introduites dans le vagin: l'édéage, le périandrium, ainsi que le processus latéral gauche du pygophore.

A simple molecular tool was developed and tested to identify seven mealybug species found in North American vineyards: Pseudococcus maritimus Ehrhorn, Pseudococcus viburni (Signoret), Pseudococcus longispinus (Targioni-Tozzeti), Pseudococcus calceolariae (Maskell), Planococcus ficus (Signoret), Planococcus citri (Risso), and Ferrisia gilli Gullan. The developed multiplex PCR is based on the mitochondrial cytochrome c oxidase subunit one gene. In tests, this single-step multiplex PCR correctly identified 95 of 95 mealybug samples, representing all seven species and collected from diverse geographic regions. To test the sensitivity, single specimen samples with different Pl. ficus developmental stages (egg to adult female and adult male) were processed PCR and the resulting output provided consistent positive identification. To test the utility of this protocol for adult males caught in sex baited pheromone traps, Pl. ficus adult males were placed in pheromone traps, aged at a constant temperature of 26 ± 2°C, and processed with the multiplex each day thereafter for 8 d. Results showed consistent positive identification for up to 6 d (range, 6-8 d). Results are discussed with respect to the usefulness of this molecular tool for the identification of mealybugs in pest management programs and biosecurity of invasive mealybugs.