Relationship of Black Vine Weevil Egg Density and Damage to Two Cranberry Cultivars

Black vine weevil (BVW), Otiorhynchus sulcatus (Coleoptera: Curculionidae, Fabricius), is a serious pest of cranberry, Vaccinium macrocarpon Ait. Larvae feed undetected within the soil and cause damage to roots and underground vines. We correlated damage caused by feeding larvae from known BVW egg densities. Two cultivars of potted cranberry vines, ‘Stevens’ and ‘McFarlin’, were inoculated with 0, 5, 10, 20, 40, and 80 eggs per pot. Root damage and canopy health were assessed. ‘Stevens’ exceeded ‘McFarlin’ in dry shoot weight, total shoot length, total leaf area, and dry root weight before egg treatments. Damage to underground vines increased with increasing egg density and more damage was found in ‘Stevens’ than ‘McFarlin’ at the highest egg densities. In August, plant water use and total shoot length in ‘McFarlin’ were significantly greater in plants treated with 0–5 eggs per pot compared with plants treated with 40–80 eggs per pot. The effect on total shoot length was more pronounced in October. ‘Stevens’ showed no response to increasing BVW density for up to 24 weeks. Destructive measurements showed decreased root weight in ‘McFarlin’ but not ‘Stevens’. Both cultivars showed a similar decrease in dry shoot weight, total shoot length, and percent green leaf area with increasing BVW egg density. Root damage increased as BVW egg density increased and this damage resulted in reduced plant water use for ‘McFarlin’. Reduced shoot growth and leaf area was recorded for both cultivars, although these effects were more apparent in ‘McFarlin’ and at an earlier stage than in ‘Stevens’.This is a scanned version of a published article. The original can be found at: http://hortsci.ashspublications.org/.Keywords: Pacific Northwest, Vaccinium macrocarpon, ‘McFarlin’, Root damage, ‘Stevens’, Leaf area, Otiorhynchus sulcatu

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

Integrating Temperature-Dependent Life Table Data into a Matrix Projection Model for Drosophila suzukii Population Estimation

Temperature-dependent fecundity and survival data was integrated into a matrix population model to describe relative Drosophila suzukii Matsumura (Diptera: Drosophilidae) population increase and age structure based on environmental conditions. This novel modification of the classic Leslie matrix population model is presented as a way to examine how insect populations interact with the environment, and has application as a predictor of population density. For D. suzukii, we examined model implications for pest pressure on crops. As case studies, we examined model predictions in three small fruit production regions in the United States (US) and one in Italy. These production regions have distinctly different climates. In general, patterns of adult D. suzukii trap activity broadly mimicked seasonal population levels predicted by the model using only temperature data. Age structure of estimated populations suggest that trap and fruit infestation data are of limited value and are insufficient for model validation. Thus, we suggest alternative experiments for validation. The model is advantageous in that it provides stage-specific population estimation, which can potentially guide management strategies and provide unique opportunities to simulate stage-specific management effects such as insecticide applications or the effect of biological control on a specific life-stage. The two factors that drive initiation of the model are suitable temperatures (biofix) and availability of a suitable host medium (fruit). Although there are many factors affecting population dynamics of D. suzukii in the field, temperature-dependent survival and reproduction are believed to be the main drivers for D. suzukii populations

Population genomics of Drosophila suzukii reveal longitudinal population structure and signals of migrations in and out of the continental United States

Drosophila suzukii, or spotted-wing drosophila, is now an established pest in many parts of the world, causing significant damage to numerous fruit crop industries. Native to East Asia, D. suzukii infestations started in the United States (U.S.) a decade ago, occupying a wide range of climates. To better understand invasion ecology of this pest, knowledge of past migration events, population structure, and genetic diversity is needed. In this study, we sequenced whole genomes of 237 individual flies collected across the continental U.S., as well as several sites in Europe, Brazil, and Asia, to identify and analyze hundreds of thousands of genetic markers. We observed strong population structure between Western and Eastern U.S. populations, but no evidence of any population structure between different latitudes within the continental U.S., suggesting there is no broad-scale adaptations occurring in response to differences in winter climates. We detect admixture from Hawaii to the Western U.S. and from the Eastern U.S. to Europe, in agreement with previously identified introduction routes inferred from microsatellite analysis. We also detect potential signals of admixture from the Western U.S. back to Asia, which could have important implications for shipping and quarantine policies for exported agriculture. We anticipate this large genomic dataset will spur future research into the genomic adaptations underlying D. suzukii pest activity and development of novel control methods for this agricultural pes

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

Log of estimated <i>Drosophila suzukii</i> populations for each of Parlier (California), Wilmington (North Carolina) and Salem (Oregon), US during 2013.

<p>Log of estimated <i>Drosophila suzukii</i> populations for each of Parlier (California), Wilmington (North Carolina) and Salem (Oregon), US during 2013.</p