Herbivore Impact Versus Host Size Preference: Endophagous Insects on Heracleum mantegazzianum in Its Native Range

Classical biological control is a practice to control alien invasive weeds, but many introduced biological control agents exhibit only a weak negative impact on their targets. One reason is that prerelease impact studies in the natural environment are often difficult to carry out. Heracleum mantegazzianum Sommier and Levier (Apiaceae), which is native to the Caucasus, is a perennial noxious weed introduced into Europe and North America. We examined the impact and host size preference of different endophagous insect guilds in the weed's native range. Instead of the commonly used insect exclosure approach, we estimated plant vigor before and after herbivore attack under natural conditions. Endophagous herbivores were dominated by the weevil species Lixus iridis Olivier, Nastus fausti Reitter, and Otiorhynchus tatarchani Reitter (Coleoptera: Curculionidae), the fly Melanagromyza heracleana Zlobin (Diptera: Agromyzidae), and an unidentified root-boring agromyzid fly species. Most observed insect species exhibited a strong preference for either big or small plants, but none of them caused serious damage within the study period. Occurrence of root-feeding weevils was associated with weak plants, but because of their long larval development, it was not possible to assign this relationship clearly to either feeding damage or host size preference. A comparison with other studies indicated that mature H. mantegazzianum plants are quite tolerant to herbivory. Insects belonging to the feeding guilds studied here will probably not guarantee successful biological control. Further research should focus on earlier stages in the weed's life cycl

To Every Thing There Is a Season: Phenology and Photoperiodic Control of Seasonal Development in the Invasive Caucasian Population of the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae)

Studies on the phenology of local populations of invasive insects are necessary for monitoring and predicting their dispersion. We investigated the phenology of the brown marmorated stink bug, Halyomorpha halys, in the Sochi region (Krasnodar Territory, Russia) from 2018 to 2021 by regular field sampling and dissecting. The results of the sampling suggest that H. halys is at least partially bivoltine in the studied region: the main period of mass oviposition (by the overwintered females) occurs from June to July; the second, much shorter period of egg-laying (by females of the new, i.e., the first generation) occurs in August. Reproductively active individuals (i.e., females with developed ovaries and filled spermatheca and males with filled ectodermal sac) were recorded from the end of May to the beginning of September. Such a seasonal pattern correlated with day length: when the natural photoperiod decreased below the experimentally determined critical day length (15.0–15.5 h), the proportions of females with fully developed ovaries sharply dropped to zero. Both the rate of H. halys pre-adult development and the timing of the induction of winter adult diapause observed under natural conditions fully agreed with the earlier predictions that had been based on the results of laboratory experiments

Meet Me Halfway: Will Photoperiodic Responses of Interpopulation Hybrids of the Brown Marmorated Stink Bug <i>Halyomorpha halys</i> (Hemiptera: Heteroptera: Pentatomidae) Promote or Constrain Subsequent Invasions?

Biological invasions often result from multiple invasion events. In the case of several subsequent invasive episodes, ‘newcomers’ are usually poorly adapted to local environmental conditions in contrast to the representatives of the already-established invasive population of the same species. Therefore, the mode of inheritance of life-history features determining the survival and performance of interpopulation hybrids is an important component of invasiveness. We investigated the mode of inheritance of the photoperiodic response in the brown marmorated stink bug, Halyomorpha halys, by crossing between the native population of South Korea and the invasive population of the Black Sea coast of Russia. The aim of this study was to predict the overwintering potential of the progeny from possible crosses between representatives of the native and invasive populations. The pre-adult development time and the incidence of winter adult diapause in the progeny of the interpopulation crosses were close to the average of the values recorded in ‘pure’ (unmixed) crosses. Female and male genotypes were equally important in the determination of these characters. Such a mode of inheritance is most likely determined by a polygenic control and would only partially promote subsequent invasion events from the native South Asian range of H. halys into Europe

Meet Me Halfway: Will Photoperiodic Responses of Interpopulation Hybrids of the Brown Marmorated Stink Bug Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae) Promote or Constrain Subsequent Invasions?

Biological invasions often result from multiple invasion events. In the case of several subsequent invasive episodes, &lsquo;newcomers&rsquo; are usually poorly adapted to local environmental conditions in contrast to the representatives of the already-established invasive population of the same species. Therefore, the mode of inheritance of life-history features determining the survival and performance of interpopulation hybrids is an important component of invasiveness. We investigated the mode of inheritance of the photoperiodic response in the brown marmorated stink bug, Halyomorpha halys, by crossing between the native population of South Korea and the invasive population of the Black Sea coast of Russia. The aim of this study was to predict the overwintering potential of the progeny from possible crosses between representatives of the native and invasive populations. The pre-adult development time and the incidence of winter adult diapause in the progeny of the interpopulation crosses were close to the average of the values recorded in &lsquo;pure&rsquo; (unmixed) crosses. Female and male genotypes were equally important in the determination of these characters. Such a mode of inheritance is most likely determined by a polygenic control and would only partially promote subsequent invasion events from the native South Asian range of H. halys into Europe

Storage Potential of the Predatory Ladybird <i>Cheilomenes propinqua</i> in Relation to Temperature, Humidity, and Factitious Food

The ability of the females of the predatory ladybird Cheilomenes propinqua to survive and to retain reproductive potential in the absence of natural food (aphids) was estimated under various hydrothermal (temperatures of 7, 12, 17, 22, and 27 °C; air humidities of 50% and 80–90%) and trophic (starved vs. fed on the frozen eggs of the grain moth Sitotroga cerealella) conditions. The post-storage reproductive potential was estimated using the mean number of eggs laid over 20 days. The experiments showed that fed females can be stored at temperatures of 15–17 °C for 20 days with a rather low (about 20%) and for up to 80 days with an acceptable (not more than 50%) loss of the reproductive potential. The successful short-term (up to 3 days) storage or transportation of fed and starved females can occur at temperatures from 12 to 27 °C. However, storage for more than 10 days at temperatures of 7 °C and lower results in the 100% mortality of both the starved and fed beetles. These data suggest that (1) in greenhouses, C. propinqua can be used for the biological control of aphids by preventing colonization, although this would require the regular supplementation of factitious food, and (2) escaped individuals would not survive the winter even in the south of the temperate zone

Flying over Eurasia: Geographic Variation of Photoperiodic Control of Nymphal Development and Adult Diapause Induction in Native and Invasive Populations of the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae)

Facultative winter adult diapause in Halyomorpha halys is regulated by a long-day photoperiodic response. Day length also influences nymphal development, which slows down at the critical (near-threshold) day lengths. We compared the photoperiodic responses of one native (Andong, South Korea) and three invasive (Torino, Italy; Basel, Switzerland; and Sochi, Russia) populations in a laboratory common-garden experiment. Nymphs developed and emerging adults were reared at 24 &deg;C in a range of photoperiods with day lengths of 14.0, 14.5, 15.0, 15.5, and 16.0 h. The critical day lengths of the photoperiodic responses of both sexes fell between 14.5 and 15.0 h in the native Korean population and between 15.0 and 15.5 h in three invasive European populations. The differences between the three invasive populations were not significant, despite their distant origins. Moreover, the difference between the Korean and European populations was much smaller than was expected. The microevolution was possibly &lsquo;too slow to keep up&rsquo; with the rapid spread of the invader across Eurasia. It is expected that soon the critical day length of the invasive H. halys populations will gradually change to adapt better to local conditions. At present, the critical day length for diapause induction of 15 h 15 min can be used to model the phenology, further spread, and response to climate change for all European populations of the pest