Eriborus Terebrans Research Articles

Differences in susceptibility to chlorantraniliprole between Chilo suppressalis (Lepidoptera: Crambidae) and two dominant parasitic wasps collected from Sichuan Province, China

Chilo suppressalis Walker (Lepidoptera: Crambidae) is one of the most destructive pests occurring in the rice-growing regions of Asia. Parasitoids, mainly egg parasitoids, have been of interest for several years even with practical used cases. Therefore, the potential impact of insecticides on natural enemies needs great attention. In this study, chlorantraniliprole was evaluated for its impact on C. suppressalis and two dominant parasitic wasps. Bioassays showed that chlorantraniliprole had negligible toxicity to Eriborus terebrans but was significantly toxic to Chelonus munakatae; the mortality exceeded 50% when the concentration reached 46.83 ng/cm2. Enzyme assays suggested that the significantly different carboxylesterase activity may be involved in the high-level detoxification metabolism of E. terebrans. According to the results of enzyme gene correlation analysis, P450s may be the dominant factor in the detoxification metabolism of C. munakatae. In addition, the ryanodine receptor C-terminus of C. suppressalis (CsRyR), C. munakatae (CmRyR) and E. terebrans (EtRyR) were successfully cloned. Different amino acids at resistance mutation I4758 M between susceptible C. suppressalis (I) and parasitic wasps (M) may be related to susceptibility differences. Simulated docking showed that CsRyR and CmRyR can interact with chlorantraniliprole but not EtRyR. More interaction forces were formed between CsRyR and chlorantraniliprole than CmRyR. Furthermore, a Pi-Pi T-shape formed between 73PHE in CsRyR and the benzene ring in chlorantraniliprole. These results indicated that both detoxification metabolism and the target site could mediate the susceptibility difference between C. suppressalis and its parasitic wasps.

European corn borer and its parasites overwintering abundance and damages on different corn FAO maturity groups

European corn borer (ECB) is one of the most significant maize pests in the world and also in Croatia. ECB causes yield reduction from 2 to 25%, even more in years favorable for its development. According to estimations, these losses are around 7%. About 90% of the hybrids had some resistance to whorl-leaf feeding (first-generation ECB) and 75% had some resistance to sheath and sheath-collar feeding (second-generation ECB). Along with resistance, modern maize hybrids possess certain level of tolerance. The main aim of this paper was to determine moth eclosion of the overwintering generation and presence of the parasites of ECB larvae during the overwintering as well as to estimate population density of ECB on maize growing area in Croatia. Also, we aimed to establish the differences among different maize FAO maturity groups in damage caused by ECB larvae. Estimated overwintering population was over 8,000 moths/ha i.e. more than 4 million larvae of first generation. During the overwintering four different parasites attacked the larvae. Two species belong to the order Hymenoptera (Cotesia marginiventris Cresson and Eriborus terebrans Gravenhorst) and two species belong to the order Diptera (Ramonda spathulata Fallen and Lydella thompsoni Herting). One caterpillar predator species Paragymnomerus spiricornis Spinola (Hymenopetra) overwinters in maize stalks as well. The highest attack of the first ECB generation was recorded on FAO maturity group 500. The damage from second ECB generation was the highest on FAO groups 400 and 500. The maize of the higher FAO groups has high and robust stems with large number of big leaves. That intensive vegetative growth is a biological characteristic that attracts first generation of ECB to intensifying egg lying. High population level of the first generation also leads to high level of second ECB generation which ultimately caused yield reduced on the hybrids of longer vegetation period (medium-late FAO maturity groups).

Parasitism Rates in European Corn Borer (Lepidoptera: Crambidae) Larvae Collected from Six Maize Hybrids

The parasitoid complex and level of parasitism of European corn borer, Ostrinia nubilalis (Hübner), larvae in six maize, Zea mays L., hybrids was determined in Nebraska during 1995 and 1996. Three parasitoids, Eriborus terebrans (Gravenhorst), Macrocentrus grandii Goidanich, and Lixophaga sp., were reared from field-collected European corn borer larvae. Larvae collected from Hoegemeyer 2626 exhibited the highest percentage parasitism for the 1995 first generation in Lancaster (37.2%) and Dixon (28.6%) counties. No significant differences were identified for the 1995 second generation at both sites because of reduced sample size and high larval mortality caused by naturally-occurring entomopathogens. During 1996, there were several significant differences in percentage parasitism of larvae collected from the hybrids. Larvae collected from Northrup King N7070 exhibited the highest first-generation parasitism (23.8%), while larvae collected from Hoegemeyer 1125W exhibited the highest second-generation parasitism (46.0%) in Dixon Co. In Lancaster Co., parasitism of first-generation larvae collected from Hoegemeyer 1125W (10.3%) was only significantly greater than parasitism of larvae collected from Hoegemeyer 2626 (1.1%). Results indicate that European corn borer larval parasitism is significantly affected by the maize hybrid planted in the field; however, differences may vary among years and generations as environmental factors affect the maize phenology.

Notes on the biology and ecology of the parasitoids of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lep., Sesiidae) in Bulgaria. II. Eriborus terebrans (Gravenhorst, 1826) (Hym., Ichneumonidae)

The biology and ecology of Eriborus terebrans (Grav.), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.), were studied during the period 1987–98. One‐year‐old poplar (Populus spp.) shoots infested with P. tabaniformis larvae were collected from poplar seedlings at 11 localities in Bulgaria and examined in both field and laboratory conditions. Eriborus terebrans was recorded in seven localities as a solitary internal larval parasitoid of P. tabaniformis which developed two generations in early and mid‐stage host larvae. Eriborus terebrans overwintered as a larva in P. tabaniformis overwintering larvae. In the field adult parasitoids of the overwintering generation appeared between late April/early May, and June or July. The peak activity of E. terebrans adults only coincided with the beginning of host emergence, which resulted in low levels of parasitism, being no more than 6.2%. Parasitoid adults of the summer generation appeared in late June–mid August. In this period enough larvae of the host were suitable for attacking and parasitism reached 24.4–39% in some cases. The average mortality of P. tabaniformis overwintering larvae caused by this parasitoid in Bulgaria during the period of the study was 4.7%. A significant part of the parasitized P. tabaniformis larvae constructed tunnel structures of frass and silk threads over the external openings of the galleries. It is possible that these structures protect the parasitoid cocoons from natural enemies – hyperparasitoids and predators.

Occurrence and bionomics of Eriborus terebrans (Gravenhorst) (Hymenoptera: Ichneumonidae), a parasitoid of the European corn borer, Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), in Central Europe

Eriborus terebrans (Gravenhorst), the parasitoid of the European corn borer, Ostrinia nubilalis Hbn., was studied at four locations in central Europe during 1993–1995. Regular parasitism of O. nubilalis was found only at Blatnice in Moravia (eastern part of Czech Republic). At this location, the parasitism was 2.22% in 1993, 0.47% in 1994 and 0.06% in 1995. In 1994 and 1995, low parasitism (0.56 and 0.12% ,respectively) was found at Kráľovský Chlmec (eastern Slovakia). The records are the first from Czech Republic and Slovakia. The parasitoid was not found at Nitra (south-western Slovakia) and Wroclaw (south-western Poland). The first cocoons of E. terebrans developed in the first half of June. Parasitoid adults emerged from mid June to mid July. Results showed complete coincidence between bionomics of E. terebrans and bionomics of its host O. nubilalis.

Diurnal Behavior of Eriborus terebrans (Hymenoptera: Ichneumonidae)

Unmated pairs of Eriborus terebrans (Gravenhorst), a parasitoid of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae), were confined in flight cages provisioned with food, water, and corn plants infested with O. nubilalis . Individuals were observed hourly from before sunrise until after sunset for 3 d to assess diurnal patterns of behavior. Observed behaviors were assigned to 13 categories including resting, preening, walking, flying, feeding and drinking, mating, host searching, and ovipositing. Resting and preening accounted for the majority of observations. Drinking and feeding occupied only a small proportion of the total as did host searching and ovipositing. E. terebrans followed consistent daily patterns of activity. Before sunrise, wasps were quiescent and exhibited a characteristic body and antenna posture (inactive rest). For both males and females, walking and flying peaked between 0900 and 1100 hours eastern standard time. Host search by females peaked at 0900 hours. During the afternoon, both male and female activity declined. Inactive rest reached a high at 1300 hours, decreased somewhat until 1500 or 1600 hours, then increased as all wasps returned to inactive rest by sunset. Wasps were significantly more active on hotter than on cooler afternoons.

Oviposition of European Corn Borer (Lepidoptera: Pyralidae) and Impact of Natural Enemy Populations in Transgenic Versus Isogenic Corn

In a 1994 field experiment, oviposition, predation, and parasitism of the European corn borer, Ostrinia nubilalis (Hubner), were recorded in transgenic and isogenic corn, Zea nays L. Plots of plants expressing the CrylA(b) protein of Bacillus thuringiensis Kurstaki and plots of isogenic plants both had 2nd-generation O. nubilalis egg mass densities of =1.1 per plant, indicating a lack of antixenosis by transgenic plants. Distribution and size of egg masses on plants also was unaffected by corn type. Size of plants was the same in both treatments. Levels of egg mass predation were 24.75 and 19.35%, respectively, but not significantly different between the transgenic and isogenic plots. Parasitism of egg masses was not significantly different between transgenic and isogenic plots, and was low at 6.31 and 4.41%, respectively. Percentage of eggs within masses which hatched was 10.2% lower in transgenic than in isogenic plots. However, neither predation, parasitism, or sloughing of eggs from plants were significantly different between the 2 treatments. Densities of O. nubilalis predators were not different between the 2 treatments throughout the O. nubilalis oviposition period. Parasitism of O. nubilalis larvae by Eriborus terebrans (Gravenhorst) and Macrocentrus grandii Goidanich was not significantly different between plots and ranged from 2.4 to 7.0%. Although most differences between transgenic and isogenic plants were nonsignificant, all observed differences in natural enemy population parameters under our conditions were in the direction opposite to that expected if transgenic plants had an adverse impact.

Influence of Noncrop Habitats on the Distribution of Eriborus terebrans (Hymenoptera: Ichneumonidae) in Cornfields

Eriborus terebrans (Gravenhorst) is the most abundant parasitoid of the European cornborer, Ostrinia nubilalis (Hubner), in Michigan. The within-field distribution of adult E. terebrans was sampled in 1991 and 1992 by placing malaise traps near a wooded edge, near an herbaceous edge, and in the field interior in each of 4 fields of corn, Zea mays L. During the 1st generation of 1991, significantly more females were captured in wooded-edge traps than in herbaceous-edge or interior traps. In the 1st generation of 1992, more females were again captured in wooded-edge traps in 2 fields, whereas in the other 2 fields, more were captured in both herbaceous-edge and wooded-edge traps than interior traps. In the 2nd generation of both years, there was no consistent pattern of distribution of adult females among sites. The distribution pattern of adult females among fields was not consistently correlated with the distribution of O. nubilalis larvae or percentage parasitism. Overall, fewer males were captured than females, and in the 1st generation of both years, more males were captured near wooded edges of cornfields in which the previous crop had been corn, than any other sites. Both male and female E. terebrans were captured in malaise traps at the interface of a woodlot canopy and a cornfield with capture zones from 1 to 4.3 m high. We propose that E. terebrans distribution in cornfields is influenced by resources such as sugar and a moderate microclimate present in adjacent woodlots but unavailable in early-season cornfields. Perennial noncrop habitats may play an important role in conservation of natural enemies for biological control.

Effects of Habitat, Temperature, and Sugar Availability on Longevity of Eriborus terebrans (Hymenoptera: Ichneumonidae)

Eriborus terebrans (Gravenhorst) is the primary parasitoid of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae), in Michigan. Previous studies demonstrated that early in the growing season, E. terebrans adults are more abundant, and parasitize a greater proportion of O. nubilalis larvae, near wooded edges of cornfields. We hypothesized that E. terebrans requires a source of sugar and a moderate microclimate available in the woodlot, but not in the cornfield. Growth chamber and greenhouse experiments demonstrated that longevity of E. terebrans that are provided sugar was greater than those provided only water, or neither; and wasp longevity was greater at 25 than 35°c. In field experiments, wasps were caged in cornfields, woodlots, wooded fencerows, and herbaceous vegetation, early and late in the season. Longevity of E. terebrans adults was greater in woodlots than early season cornfields. Wasps lived longer in all habitats late in the season than early in the season. In all habitats, wasp longevity was enhanced by sugar. These and previous studies indicate that E. terebrans needs habitats adjacent to cornfields for sources of sugar and a moderate microclimate unavailable in early season corn. In annual agriculture, perennial habitats adjacent to crop fields may be necessary to provide the structure, stability, and resources needed for the successful conservation of natural enemies and effective biological control.

Distribution and Abundance of Larval Parasitoids of European Corn Borer (Lepidoptera: Pyralidae) in the East Central United States

Overwintering Ostrinia nubilalis (Hubner) fifth instars were systematically collected at 621 sample sites on a grid interval of 40 km encompassing New York, Pennsylvania, Ohio, Delaware, Maryland, Virginia, West Virginia, and North Carolina and were evaluated for parasitoids. The study was focused on the extent of dispersal of Lydella thompsoni Herting from its presumed reestablishment in Delaware during the mid-1970s and the level of parasitism of overwintering O. nubilalis larvae. The bulk of the study was conducted in 1986 and 1987 with some additional samples taken in 1988 and 1989 from outlier locations. L. thompsoni, Macrocentrus grandii Goidanich, and Eriborus terebrans Gravenhorst were the only exotic species recovered. All three of these parasitoids were found in all states surveyed. Parasitism by these three species combined was 5.4% in 1986 and 7.5% in 1987 for the entire areas surveyed. The areas of most abundance for each species were in North Carolina for L. thompsoni , a band from northeastern Pennsylvania to eastern Virginia for M. grandii , and in Ohio for E. terebrans. All three exotic parasitoids species were retrieved at less than 3% of the sample sites. Data suggest that the dispersal rate of L. thompsoni from Delaware was about 50 km per year. An uncommon native Lixophaga sp. was found in Western Ohio and Western North Carolina. The three exotic parasitoid species appear to be well established in their respective foci of abundance.

Influence of weed communities in corn plantings on parasitism of Ostrinia nubilalis (Lepidoptera: Pyralidae) by Eriborus terebrans (Hymenoptera: Ichneumonidae)

Abstract Parasitism of second generation European corn borer, Ostrinia nubilalis (Hubner), larvae by parasitoids was examined in corn (Zea mays) plantings having different weed communities. Treatments were corn without weeds, corn principally with broadleaf weeds, corn principally with grassy weeds, and corn with a mixture of broadleaves and grasses. O. nubilalis larvae were collected and maintained on artificial diet under constant environmental conditions in the laboratory to determine levels of parasitization. The ichneumonid, Eriborus terebrans (Gravenhorst), was the only parasitoid species reared, with the exception of a single tachinid, tentatively identified as Lydella thompsoni. Neither broadleaf nor grassy weeds had significant influences on parasitization of larvae during the study. Parasitism was positively correlated with host density (number of larvae per plant) in the corn-broadleaf weed community in 1988. Parasitism was greater in all treatments in 1989 than in 1988, ranging from 2.1 to 5.6% in 1988 and from 20.0 to 29.1% in 1989. The results were inconclusive as to whether weeds within corn plantings augment parasitism of O. nubilalis larvae by E. terebrans or by other parasitoids.

Influence of Landscape Structure on Abundance and Within-Field Distribution of European Corn Borer (Lepidoptera: Pyralidae) Larval Parasitoids in Michigan

Studies were conducted at eight locations in Ingham County, Michigan, during 1989–1990 to determine the within-field distribution of European corn borer, Ostrinia nubilalis (H¨bner), larval parasitism. O. nubilalis larval sampling was conducted at multiple locations on three transects across large 1st-yr corn fields during the F1 and F2 generations. Plants were destructively sampled to determine O. nubilalis abundance and larvae were returned to the lab to determine parasitism. Eriborus terebrans (Gravenhorst) (Hymenoptera: Ichneumonidae) was the dominant parasitoid of O. nubilalis in the sampled fields, accounting for 92.5% of the F1 and 99.2% of the F2 parasitism during 1989; and for 92.2% of the F1 and 99.1% of the F2 during 1990. Average parasitism by E. terebrans ( n = 4 fields) was 4.9 and 18.7% of F1, 10.2 and 9.1% of F2 larvae during 1989 and 1990 respectively. The maximum E. terebrans parasitism observed (37.4%) of the O. nubilalis larvae in one field (F1 1990), is the highest level reported for this species in the Midwest. Parasitism by E. terebrans during the F1 generation was greater along field margins than in field interiors in most fields during both years. During 1990, O. nubilalis larvae near wooded edges had significantly higher E. terebrans parasitism than those near nonwooded edges or field interiors. In the F2 generation, parasitism did not vary significantly from field margins to field interiors in either year. There was no consistent relationship between O. nubilalis larval density per infested plant and E. terebrans parasitism. These data suggest that local landscape structure, including proximity of particular noncrop habitats, plays an important role in the effectiveness of this natural enemy.

Host-Seeking Behavior of Eriborus terebrans (Hymenoptera: Ichneumonidae) Toward the European Corn Borer and the Role of Chemical Stimuli

Newly designed T trap and wind tunnel bioassays demonstrated that attraction of female Eriborus terebrans (Gravenhorst) to larvae of the European corn borer, Ostrinia nubilalis (Hubner), was elicited by odors of host plant complex (HPC), frass, corn plants, host larvae, feces, and oral secretion. Female experience had a fundamental influence on behavior, and green and yellow colors were attractive to females in the wind tunnel. Antennation, intensive examination, and probing-oviposition behavior of the parasitoid were readily stimulated in contact bioassays by HPC, host larva silk, frass, oral secretion, and cuticle. Serine and certain other amino acids elicited intensive examination and occasional probing. Volatile and contact chemicals mediating behavior were extractable with hexane, acetone, chloroform, and methanol. The role of vision and the possibility of multiple chemical cues involved in both long- and close-range host-seeking behaviors are discussed.

Current Status of Imported and Native Parasites of the European Corn Borer (Lepidoptera: Pyralidae) in Connecticutt

Of the four imported insect parasites of Ostrinia nubilalis (Hubner) which were established in Connecticut in 1954, only an ichneumonid, Eriborus terebrans (Gravenhorst), and a braconid, Macrocentrus grandii Goidanich, were recovered in fall and spring surveys conducted from 1978–1981. E. terebrans was collected from one location only and occurs at a very low level. M. grandii is widespread and sufficiently abundant in some areas to possibly aid in the natural suppression of the European com borer (ECB). M. grandii emergence from ECB larvae in the spring is well synchronized with emergence of ECB adults, and this parasite appears well adapted to the seasonal occurrence of the ECB in this region. Native parasites found include two tachinid flies, Aplomya caesar (Aldrich) and Lixophaga sp. Both are widespread but account for less than 6% of total parasitism, and neither parasite appears to have a significant controlling effect on ECB populations.

Insect Parasites of the European Corn Borer Ostrinia nubilalis in Nebraska from 1948–1976 12

Five exotic parasite species of the European corn borer, Ostrinia nubilalis (Hbn.), were introduced into Nebraska in 1948–1950. Only 3 species became established: a tachinid, Lydella thompsoni Herting (= grissescens Robineau-Desvoidy of Authors); an ichneumonid, Eriborus terebrans (Gravenhorst) (= Horogenes punctorius (Roman)); and a eulophid, Sympiesis viridula (Thomson) (= Eulophus viridulus ). Population trends for L. thompsoni and E. terebrans are reported for 2 counties for the years 1957–1971. No evidence has been found of L. thompsoni since 1965 but E. terebrans was widespread and present in low numbers in 1975 and 1976.

THE ROLE OF PARASITES IN THE CONTROL OF THE EUROPEAN CORN BORER, OSTRINIA NUBILALIS (LEPIDOPTERA: PYRALIDAE), IN SOUTHWESTERN ONTARIO

AbstractSurveys, from 1948 to 1964, showed that parasites were of minor importance in controlling the European corn borer, Ostrinia nubilalis (Hübner), in extreme southwestern Ontario. Of the three species that became established, Lydella grisescens Robineau-Desvoidy was the most widespread and the most important. Eriborus terebrans (Gravenhorst) showed considerable buildup in parts of Essex County after discovery there in 1957, and Sympiesis viridula (Thomson) was found widely dispersed, but low in density, throughout the survey area. There is an indication that parasites might be of greater importance in areas where the second-generation borer is increasing.