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Öğe Foraging efficiency and outcomes of interactions of two pupal parasitoids attacking the invasive spotted wing drosophila(Academic Press Inc Elsevier Science, 2016) Wang, Xin-Geng; Kaçar, Gülay; Biondi, Antonio; Daane, Kent M.Two generalist pupal drosophilid parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae Perkins (Hymenoptera: Diapriidae), are sympatric and among only a few parasitoid species attacking the invasive Drosophila suzukii Matsumura (Diptera: Drosophilidae) in many regions of the world. In this study, we evaluated their foraging efficiency when attacking D. suzukii infesting cherry fruit in a laboratory cage experiment; and we examined their potential interspecific interactions, including outcomes of intrinsic competition, host discrimination, and the impact of their interaction on pest control. We show that both parasitoids readily parasitized D. suzukii pupae located inside fruit or buried in soil. However, T. drosophilae was more efficient than P. vindemiae and that parasitism by either parasitoid species was higher in the fruit than in the soil. Generally, the parasitoid species that oviposited first in the host out-competed the later parasitoid in multiparasitized hosts, we assume, through physiological suppression. Both parasitoids discriminated against hosts parasitized previously by the other species. In an additive-series design experiment with single (D. suzukii) or two (D. suzukii and Drosophila melanogaster Meigen) host species, T. drosophilae performed similarly regardless of the presence of a competitor, while P. vindemiae achieved a higher parasitism when alone. The observed parasitism when the two parasitoid species were present together was always lower than the expected one, assuming each species acted independently. This indicates a negative effect by P. vindemiae on interspecific competition on host suppression. (C) 2016 Elsevier Inc. All rights reserved.Öğe Host stage preference, efficacy and fecundity of parasitoids attacking Drosophila suzukii in newly invaded areas(Academic Press Inc Elsevier Science, 2015) Stacconi, Marco Valerio Rossi; Buffington, Matt; Daane, Kent M.; Dalton, Daniel T.; Grassi, Alberto; Kaçar, GülayDrosophila 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. (C) 2015 Elsevier Inc. All rights reserved.Öğe Life-history and host preference of Trichopria drosophilae, a pupal parasitoid of spotted wing drosophila(Springer, 2016) Wang, Xin-Geng; Kaçar, Gülay; Biondi, Antonio; Daane, Kent M.Trichopria drosophilae is a cosmopolitan pupal parasitoid that attacks many species of Drosophilidae, including the invasive Drosophila suzukii. This study reports on the life-history traits and host preferences of a Californian population of T. drosophilae and compares its life-time fecundity with a South Korean population of T. drosophilae. Female parasitoids emerge with a high mature egg-load (47.6 +/- 2.3 eggs per female). The number of mature eggs of female T. drosophilae was affected by the female age and body size but not by the interaction between these two factors. The parasitoid did not show preference among differently aged (1-4 days old) D. suzukii pupae and host age did not affect the parasitoid's fitness, except that offspring developmental time slightly increased with host age. In a choice test, more offspring successfully developed from the larger D. suzukii than the smaller D. melanogaster, and adult females reared from D. suzukii were larger than those that were reared from D. melanogaster, apparently at no cost in parasitoid fitness. T. drosophilae females from the Californian and the South Korean populations survived 27.5 and 20.2 days, produced a total of 63.8 and 52.0 offspring, and had an intrinsic rate of increase of 0.124 and 0.113, respectively, when provided with adult food and D. suzukii pupae as host material.Öğe Linear functional response by two pupal Drosophila parasitoids foraging within single or multiple patch environments(Public Library Science, 2017) Kaçar, Gülay; Wang, Xin-Geng; Biondi, Antonio; Daane, Kent M.Functional response describes the number of prey or hosts attacked by a predator or parasitoid as a function of prey or host density. Using three different experimental designs, we found a linear functional response by two insect parasitoids (the pteromalid Pachycrepoideus vindemiae and the diapriid Trichopria drosophilae) to their hosts (the drosophilids Drosophila suzukii and D. melanogaster). A linear function response is considered unusual for insect parasitoids. The first design was a 'fixed time within patch experiment' where individual parasitoids were exposed to a range of host densities for 24 h; the second two designs were a 'variable time functional response' and a 'selective functional response' experiments where individual parasitoids were presented with a range of host patches and allowed to freely select and explore only one patch (variable time) or forage for 24 h (selective). In all experimental designs, the number of hosts parasitized increased linearly until reaching an upper limit. Under the laboratory conditions used, the functional response of P. vindemiae was limited by its egg supply and time (host handling time) whereas T. drosophilae was limited by time only. The linear functional response by both parasitoids likely resulted from a constant attack rate and an incremental foraging strategy where the parasitoids left a poor (low density) host patch or remained in a higher quality host patch when there was successful oviposition and adequate host density.Öğe Overwintering survival of Drosophila suzukii (Diptera: Drosophilidae) and the effect of food on adult survival in California's San Joaquin Valley(Oxford Univ Press Inc, 2016) Kaçar, Gülay; Wang, Xin-geng; Stewart, Thomas J.; Daane, Kent M.The overwintering survival and development of Drosophila suzukii Matsumura were investigated in California's San Joaquin Valley. Drosophila suzukii were exposed to overwintering conditions in cages hung in a citrus orchard, and the pupae were buried in the soil. Eggs exposed from late November to January did not survive; a low percentage (<3%) of larvae and pupae developed into adults. Survival of pupae was significantly higher when buried in the soil than on the citrus tree. From late January to March, all life stages developed into adults and overwintered adult female D. suzukii produced eggs when provided with 10% honey-water and sliced oranges. Adult survival varied among fruit juice provision treatments and overwintering exposure periods, ranging from 3.4 +/- 0.9 d (water) to 44.1 +/- 3.0 d (10% honey-water). Fruit juices of apple, cherry, grape, orange, and pomegranate were tested as adult food sources; results showed that adult female and male D. suzukii lived only 2 d with water only, whereas adults survived from 14.2 to 34.8 d with fruit juice treatments and the 10% honey-water control. An unexpected event was the oviposition and immature development of D. suzukii with the fruit juice. In a follow-up laboratory trial, when 10% honey-water or orange juice were provided along with an artificial diet for oviposition and immature development, female D. suzukii survived for 21.6 +/- 2.4 or 21.6 +/- 1.5 d, and produced 106.8 +/- 14.1 or 98.5 +/- 13.1 offspring, respectively. We discuss factors potentially influencing overwintering survival of D. suzukii.Öğe Temporal dynamics of host use by Drosophila suzukii in California's San Joaquin Valley: Implications for area-wide pest management(Mdpi, 2019) Wang, Xingeng; Kaçar, Gülay; Daane, Kent M.A major challenge to the area-wide management of Drosophila suzukii is understanding the fly's host use and temporal dynamics, which may dictate local movement patterns. We determined D. suzukii's seasonal host use in California's San Joaquin Valley by sampling common crop and non-crop fruits in a temporal sequence of fruit ripening. We then evaluated the suitability of selected fruits as hosts. Drosophila suzukii emerged from both intact and damaged cherries during the cooler, early season period. Fly density remained low through the hot spring-summer period and re-surged as temperatures lowered in fall when the fly did not cause damage to intact peach, nectarine, plum, pear, grape, pomegranate, apple, persimmon and citrus (in order of ripening) but did emerge from the damaged fruits of these crops. The fly also emerged from two ornamental fruits (loquats and cactus) but was not found on wild plum and two endemic wild fruits (buckthorn and bitter berry). Drosophila suzukii completed development (egg to adult) on cactus, mandarin carpel, pomegranate seed, wild plum and buckthorn at survival rates similar to cherry (51.2-68.8%), whereas it had a lower survival rate on bitter cherry (33.2%), table grape (31.5%), raisin grape (26.5%), and wine grape (4.5%). The high acidity levels of grapes negatively affected the fly's fitness. Among 10 cherry cultivars, survival rate was not affected by sugar content, but it decreased with increasing egg density per gram of fruit. Results suggest that in California's San Joaquin Valley, the early season crops are most vulnerable, summer fruits ripen during a period of low pest pressure, and late season fruits, when damaged, serve to sustain D. suzukii's populations in this region.
