The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys

Környezetvédelmi célú P vizsgálatok összehasonlító elemzése szabadföldi tartamkísérletek talajain = Comparison and evaluation of environmental P test methods in soils of long-term fertilization field trials

Tenyészedény és inkubációs kísérleteket folytattunk szabadföldi tartamkísérletek talajaival, melyekben a 10 éves intenzív P trágyázás három ellátottsági szintet eredményezett. Vizsgáltuk a frissen adott P kezelések hatására a növényi P tartalom és felvétel változását, a talaj-tulajdonságok szerepét, ill. a növényi és a vizsgált kivonószerekkel mérhető talaj P tartalom kapcsolatát. Inkubációs kísérleteink fő célja a P utóhatás, valamint a frissen adott P hatásának értékelése volt. Kimutattuk, hogy a kedvező talajnedvesség alacsony hőmérsékleten elősegíti a kivonható P mennyiségek mobilizácóját, míg a magasabb hőmérséklet az immobilizációt fokozta. Esőszimulátoros kísérleteinkben megállapítottuk a homoktalajok eróziós P-veszteségeit, különböző esőztetési intenzitás mellett. Eredményeink szerint a P tartalom és a fajlagos talajvesztés kapcsolata közel lineáris. Az agronómiai és a környezetvédelmi céllal mért talaj P tartalmak (AL-, Olsen-, Bray1-, CaCl2-, H2O-, ill. FeO) és a P szorpciós kapacitás telítettsége, valamint a tavaszi árpa bokrosodáskori tömege és P tartalma közötti összefüggések alapján meghatározott agronómiai optimumok az eltérő pufferkapacitású két talajon jóval kisebbnek bizonyultak, mint a környezeti szempontból kritikus talaj P tartalmak, melyeket az Olsen-P és a CaCl2-P összefüggése alapján határoztuk meg. A talaj P telítettségének (DPS%) mérése szintén alkalmas lehet a potenciális P veszteség/eutrofizációs veszély becslésére. | Pot experiments and laboratory incubations were conducted with soil samples of long-term trials showing three P supply levels resulting from 10 years of intensive P fertilization. Influences of soil characteristics in plant P uptake and P contents were studied in freshly applied treatments. Relationships between plant parameters and soil P test results in different extracts were characterized. Laboratory incubations were carried out for evaluating the role of residual and freshly added P. From the results it was evident that constant soil moisture favoured the mobilization of extractable soil P at the lower temperature while high temperature favoured the immobilization. In our rainfall simulation experiments, erosion P losses of a sandy soil were determined with different irrigation intensities. Results showed that the relationship between P content and soil loss was nearly linear. Based on the correlations between agronomic and environmental soil P test values (AL-, Olsen-, Bray1-, CaCl2-, H2O-, or FeO) and the degree of P saturation, as well as young barley shoot weight and P %, the agronomic optimum and the environmentally critical soil P values were significantly different in both soils having different P buffer capacity. Environmentally critical soil P threshold values were determined from the correlation between the Olsen-P and CaCl2-P values. The soil P saturation method can also be suitable for estimating in the increase in potential P losses/eutrophization

The Discovery of Trissolcus japonicus (Hymenoptera: Scelionidae) in Michigan

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), is a pest of growing economic importance in the United States, the control of which currently relies on pesticide applications. Biological control could provide sustainable and long-term control but classical biological control agents have not yet been approved. Adventive populations of a potential biological control agents, the Samurai wasp, Trissolcus japonicus (Ashmead), have been found in the United States, first in Maryland in 2014, expanding its range west to Ohio by 2017. Trissolcus japonicus is a highly effective parasitoid of H. halys eggs, but its redistribution and augmentative releases are restricted to states where it has been detected in the wild. To assess the presence of T. japonicus in Michigan and attack rates of H. halys by native natural enemies we deployed 189 H. halys egg masses at ten sites in lower Michigan between May and October in 2018. In addition, we deployed 51 native stink bug egg masses at the same sites to evaluate potential non-target effects of T. japonicus in the field, which were shown to occur in laboratory studies. We found T. japonicus in a single H. halys egg mass, which constitutes the first record of this Asian parasitoid in Michigan. Native predators and parasitoids caused minimal mortality of H. halys eggs and we did not find evidence of non-target effects of T. japonicus on native stink bug species. These findings open the door to initiation of a classical biological control program using an efficient, coevolved parasitoid from the native range of H. halys

Data from: The effects of agent hybridization on the efficacy of biological control of tansy ragwort at high elevations

The success rate of weed biological control programs is difficult to evaluate and the factors affecting it remain poorly understood. One aspect which is still unclear is whether releases of multiple, genetically distinct populations of a biological control agent increase the likelihood of success, either by independent colonization of different environmental niches or by hybridization that may increase the agent’s fitness and adaptive ability. Since hybridization is often invoked to explain the success of unintentionally introduced exotic species, hybridization among biocontrol agents may be similarly important in shaping the effectiveness of biological control programs. In this study, we first evaluated intraspecific hybridization among populations of a weed biological control agent, the ragwort flea beetle, Longitarsus jacobaeae. These insects were introduced as part of a classical biological control program from Italy and Switzerland. We genotyped 204 individuals from 15 field sites collected in northwest Montana, and an additional 52 individuals that served as references for Italian and Swiss populations. Bayesian analysis of population structure assigned seven populations as pure Swiss and one population as pure Italian while intra-specific hybrid individuals were detected in seven populations at frequencies of 5–69%. Subsequently we conducted a two-year exclusion experiment using six sites with Swiss beetles and three with hybrid beetles to evaluate the impact of biological control. We found that biological control by Swiss beetles and by hybrid beetles is effective, increasing mortality of the target plant, Jacobaea vulgaris, by 42 and 45%, and reducing fecundity of surviving plants by 44 and 72%, respectively. Beetle densities were higher and mortality of larger plants was higher at sites with hybrids present. These results suggest that hybridization of ragwort flea beetles at high elevation sites may improve biological control of tansy ragwort, and that intraspecific hybridization of agents could benefit biological control programs

The power of evolutionary rescue is constrained by genetic load

International audienceThe risk of extinction faced by small isolated populations in changing environments can be reduced by rapid adaptation and subsequent growth to larger, less vulnerable sizes. Whether this process, called evolutionary rescue, is able to reduce extinction risk and sustain population growth over multiple generations is largely unknown. To understand the consequences of adaptive evolution as well as maladaptive processes in small isolated populations, we subjected experimental Tribolium castaneum populations founded with 10 or 40 individuals to novel environments, one more favorable, and one resource poor, and either allowed evolution, or constrained it by replacing individuals one-for-one each generation with those from a large population maintained in the natal environment. Replacement individuals spent one generation in the target novel environment before use to standardize effects due to the parental environment. After eight generations we mixed a subset of surviving populations to facilitate admixture, allowing us to estimate drift load by comparing performance of mixed to unmixed groups. Evolving populations had reduced extinction rates, and increased population sizes in the first four to five generations compared to populations where evolution was constrained. Performance of evolving populations subsequently declined. Admixture restored their performance, indicating high drift load that may have overwhelmed the beneficial effects of adaptation in evolving populations. Our results indicate that evolution may quickly reduce extinction risk and increase population sizes, but suggest that relying solely on adaptation from standing genetic variation may not provide long-term benefits to small isolated populations of diploid sexual species, and that active management facilitating gene flow may be necessary for longer term persistence