Host stage preference, efficacy and fecundity of parasitoids attacking Drosophila suzukii in newly invaded areas

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) causes severe damage to certain fruit crops in both North America and Europe. This may be due, in part, to the absence of specialized natural enemies that suppress population outbreaks. We performed a series of experiments under controlled laboratory conditions in tandem with a field study to evaluate the presence and efficacy of natural enemies associated with this pest in Italian and western United States fruit production regions. Our study involved one larval parasitoid, Leptopilina heterotoma (Thomson) (Hymenoptera: Figitidae), and two pupal parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae). Three indices were used to describe host-parasitoid interactions: degree of infestation (DI), success rate of parasitism (SP) and total encapsulation rate (TER). Results confirmed that each of these parasitoid species can develop on certain populations of the pest. In addition, host stage preferences of the tested parasitoid populations, developmental parameters and lifetime fecundity of North American P. vindemiae are provided. Results are discussed with respect to differences in potential utilization of D. suzukii among the tested parasitoid species and regional populations.Keywords: Leptopilina heterotoma (Hymenoptera: Figitidae), Parasitoid, Trichopria drosophilae (Hymenoptera: Diapriidae), Biological control, Drosophila suzukii (Diptera: Drosophilidae), Pachycrepoideus vindemiae (Hymenoptera: Pteromalidae

Seasonal occurrence of resident parasitoids associated with Drosophila suzukii in two small fruit production regions of Italy and the USA

For the first time we report the results of a survey to determine the presence, seasonal phenology and biological control status of indigenous parasitoid populations utilizing Drosophila suzukii (Matsumura) and Drosophila melanogaster Meigen (Diptera Drosophilidae) as hosts in Trento Province, Northern Italy, and the Willamette Valley, Oregon, USA. Larval and pupal parasitoids were sampled using sentinel traps baited with larvae of D. suzukii or D. melanogaster, or traps baited with fruit or yeast-based host substrates. Two generalist parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera Pteromalidae) and Leptopilina heterotoma (Thomson) (Hymenoptera Figitidae) emerged from the sentinel traps in both regions, and a third generalist parasitoid, Trichopria drosophilae Perkins (Hymenoptera Diapriidae), was found in Italy. L. heterotoma was present during the early portion of the season in Italy while P. vindemiae was found throughout the growing season in both production regions. Low numbers of parasitoids relative to initial larval load in baits suggest a limited effect of indigenous parasitoids on D. suzukii in these two important fruit production regions. These findings highlight the need for improved biological control of D. suzukii through introduction or augmentation of specialist parasitoids from the native range of D. suzukii. This report provides baseline data on the current status of biological control of D. suzukii in Italy and Oregon.Keywords: Leptopilina heterotoma, biological control, Trichopria drosophilae, invasive pest, Pachycrepoideus vindemiae, parasitis

Drosophila suzukii population response to environment and management strategies

19openInternationalInternational coauthor/editorDrosophila suzukii causes economic damage to berry and stone fruit worldwide. Laboratory-generated datasets were standardized and combined on the basis of degree days (DD), using Gompertz and Cauchy curves for survival and reproduction. Eggs transitioned to larvae at 20.3 DD; larvae to pupae at 118.1 DD; and pupae to adults at 200 DD. All adults are expected to have died at 610 DD. Oviposition initiates at 210 DD and gradually increases to a maximum of 15 eggs per DD at 410 DD and subsequently decreases to zero at 610 DD. These data were used as the basis for a DD cohort-level population model. Laboratory survival under extreme temperatures when DD did not accumulate was described by a Gompertz curve based on calendar days. We determined that the initiation of the reproductive period of late dormant field-collected female D. suzukii ranged from 50 to 800 DD from January 1. This suggests that D. suzukii females can reproduce early in the season and are probably limited by availability of early host plants. Finally, we used the DD population model to examine hypothetical stage-specific mortality effects of IPM practices from insecticides and parasitoids at the field level. We found that adulticides applied during the early season will result in the largest comparative population decrease. It is clear from model outputs that parasitism levels comparable to those found in field studies may have a limited effect on population growth. Novel parasitoid guilds could therefore be improved and would be valuable for IPM of D. suzukii.openWiman, N.G.; Dalton, D.T.; Anfora, G.; Biondi, A.; Chiu, J.; Daane, K.M.; Gerdeman, B.; Gottardello, A.; Hamby, K.; Isaacs, R.; Grassi, A.; Ioriatti, C.; Lee, J.C.; Miller, B.; Rossi Stacconi, V.; Shearer, P.W.; Tanigoshi, L.; Wang, X.; Walton, V.M.Wiman, N.G.; Dalton, D.T.; Anfora, G.; Biondi, A.; Chiu, J.; Daane, K.M.; Gerdeman, B.; Gottardello, A.; Hamby, K.; Isaacs, R.; Grassi, A.; Ioriatti, C.; Lee, J.C.; Miller, B.; Rossi Stacconi, M.V.; Shearer, P.W.; Tanigoshi, L.; Wang, X.; Walton, V.M

How vibrational signals can guide mating behaviour in Scaphoideus titanus

The development of sustainable control methods of insects requires detailed knowledge about the biology of the pest and how it communicates with conspecifics. For example, when developing a mating disruption strategy to control vibrational communicating pest species, it is important to understand the mechanisms of its mating behaviour. We have studied the leafhopper Scaphoideus titanus, which is a vector of the severe phytoplasma grapevine disease Flavescense doreé. In laboratory experiments, males and females were positioned on different parts of the same grapevine cutting and male searching behaviour was recorded with video camera and laser vibrometry. The communication started with an identification phase in which there was an increased male pulse period and random walking after female reply. Thereafter followed a location phase, in which male calls became shorter, with more regular pulse period and correct directional decisions towards the female leaf. When a searching male reached the leaf with the female the perceived intensity of female reply increased significantly and a courtship phase was shown until copulation. With these experiments we have shown for the first time that intensity is an important parameter in vibrational communication of plant-dwelling insects. Different phases of mating behaviour are associated with different levels of perceived signal intensity and accordingly, males adjust the emission of vibrational signals and searching behaviour. Consequently, external interferences may result in loss of information necessary either for identification or location and thus preventing mating. It is possible that mating disruption with vibrations can target successfully the more susceptible behavioural phases of S. titanus

Preliminary data on Stegobium paniceum (L.) larval head sensilla

Sensory structures of Stegobium paniceum (L.) head have been investigated under Scanning and Transmission Electron Microscopes and described. Their possible function is hypothesized

A horticultural cuticle supplement can impact quality characters and Drosophila suzukii damage of several small and stone fruit

Surface wax and other cellular building blocks play an important role in preserving fruit integrity from biotic and abiotic adversities. Huge energy expenses are made by plants to place these protective compounds onto the epidermal cuticle. Sprayable plant and fruit coatings have been developed to protect plant tissues from environmental stresses, pathogens, and arthropods. The aim of this study was to determine if an experimental cuticle supplement containing waxes can affect fruit quality parameters such as firmness and size of various crops. Cherry, blueberry, and winegrape plants treated with the cuticle supplement showed significant increases in berry firmness ranging from 4.6 to 11.6%. No quality benefits were however observed on blackberry. Cuticle supplement applications did not significantly affect berry size. Laboratory trials resulted in a 54% mean reduction in a model pest insect i.e., Drosophila suzukii egg laying on blueberry. Short-duration field trials over 72 ± 2 to 96 ± 2 h on commercial-standard blueberry bushes resulted in 50-93.4% reductions of D. suzukii damage. Longer-term field trials on cherry and blueberry challenged with egg-laying D. suzukii showed reductions of damage ranging from 45 to 95%, up to 30 d after initial cuticle supplement applications. These results indicate that the cuticle supplement significantly alters berry firmness and reduces D. suzukii damage under commercial production conditions. One factor that may contribute to this reduction includes improved fruit quality parameters. The current work serves to expand integrated pest management options to control D. suzukii populations in commercial field setting

Methods for rearing the parasitoid Ganaspis brasiliensis, a promising biological control agent for the invasive Drosophila suzukii

Native to East Asia, the spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), has established widely in the Americas, Europe, and parts of Africa over the last decade, becoming a devastating pest of various soft-skinned fruits in its invaded regions. Biological control, especially by means of self-perpetuating and specialized parasitoids, is expected to be a viable option for sustainable area-wide management of this highly mobile and polyphagous pest. Ganaspis brasiliensis Ihering (Hymenoptera: Figitidae) is a larval parasitoid that is widely distributed in East Asia, and has been found to be one of the most effective parasitoids of D. suzukii. Following rigorous pre-introduction evaluations of its efficacy and potential non-target risks, one of the more host-specific genetic groups of this species (G1 G. brasiliensis) has been approved recently for introduction and field release in the United States and Italy. Another genetic group (G3 G. brasiliensis), which was also commonly found to attack D. suzukii in East Asia, may be considered for introduction in the near future. There is currently enormous interest in rearing G. brasiliensis for research or in mass-production for field release against D. suzukii. This protocol and associated video article describe effective rearing methods for this parasitoid, both on a small scale for research and a large scale for mass-production and field release. These methods may benefit further long-term research and use of this Asian-native parasitoid as a promising biological control agent for this global invasive pest

First Nations In Dialogue: Cherokee and Mapuche Perspectives

This video presents the conversation between Cherokee fiction writer and journalist Annette Saunooke Clapsaddle and Mapuche-Argentinian poet Liliana Ancalao, which happened on March 21, 2018. This was the second in a series of lectures on First Nations at Furman University. Through a comparative perspective, they share important aspects of their cultures through three topics: their respective culture’s relationship to the natural world, gender representations in their writing, and current social and political issues of the Cherokee and Mapuche First Nations.https://scholarexchange.furman.edu/first-nations/1001/thumbnail.jp