Volatiles in perennial ryegrass infected with strains of endophytic fungus: impact on African black beetle host selection

Perennial ryegrass (Lolium perenne) is often infected with the fungal‐endophyte Neotyphodium lolii. In addition to the ‘wild‐type’ strain (E^WT), several ‘selected’ strains of N. lolii are now being marketed as AR1 (E^AR1) and AR37 (E^AR37). Each of these strains impact positively on L. perenne's resistance against many insects, including the African black beetles (Heteronychus arator). The impact of volatile oils produced specifically by each strain in the endophyte–grass association in enhancing the grass's resistance to insects is still largely unknown. Keeping these in view, we determined the volatile oil profiles produced by L. perenne infected with either E^WT or E^AR1 or E^AR37 and determined the impacts of these volatiles on the host‐selection behaviour of H. arator adults. In the absence of endophyte infection (E^–), L. perenne produced 18 different volatile oils. In L. perenne E^WT, quantities of 2‐ethyl‐1‐hexanol acetate (Rt = 14.5 min), (Z)‐2‐octen‐1‐ol (Rt = 22.2 min), and butylated hydroxyl toluene (Rt = 23.2 min) were 24, 16 and 26%, respectively, greater than L. perenne E^–. The strains E^AR1 and E^AR37 affected differently the quantities of the volatile compounds but not their identity. In the four‐choice bioassay, males and females of H. arator were equally attracted to each strain. In Y‐tube olfactometer, compared against E^–, H. arator adults were less attracted to L. perenne E^WT and E^AR1. The attractiveness of E^AR37 was similar in effect to E^– to H. arator. The results indicate that each strain of N. lolii alters the profile of volatile oils in L. perenne differently and that alteration can influence H. arator adult‐host selection.     

Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

Insect pests of Tasmanian blue gum,Eucalyptus globulus globulus,in south‐western Australia: History,current perspectives and future prospects

Trends in, and potential causes of, insect pest problems of the Tasmanian blue gum, Eucalyptus globulus globulus, in south‐western Australia are reviewed. Historical evidence suggests that insect pest problems of E. g. globulus in south‐western Australia have greatly increased in the last 10 years, which corresponds to a time of rapid expansion of the blue gum industry in the region. Current major establishment pests include the African black beetle, Heteronychus arator, spring beetles, Liparetrus spp. and Heteronyx spp., and the wingless grasshopper, Phaulacridium vittatum. Current major pests of established trees are the Eucalyptus weevil, Gonipterus scutellatus, and chrysomelid beetles, Chrysophtharta spp. and Cadmus excrementarius. The occurrence of these insects on an introduced eucalypt is not unexpected because insect‐rich native eucalypt forests dominate the landscape where E. g. globulus plantations are grown. Insect damage may also be exacerbated because E. g. globulus is grown as a monoculture.     

The influence of amino acids and inorganic salts on feeding by larvae of Heteronychus arator (Coleoptera: Scarabaeidae)

Abstract

Twenty amino acids were offered at 2 concentrations to Heteronychus arator F. larvae in an agar/cellulose powder medium. In comparison with the plain medium, only 0.1M l-alanine, 0.01M l-aspartic acid, and 0.01M l-glutamic acid significantly stimulated feeding. A mixture of inorganic salts did not induce feeding when presented in the medium alone, nor did it affect the vigorous feeding response of larvae to 0.1M maltose.     

Characterization of growth and Oryctes rhinoceros nudivirus production in attached cultures of the DSIR-HA-1179 coleopteran insect cell line

The DSIR-HA-1179 coleopteran cell line is a susceptible and permissive host to the Oryctesrhinoceros nudivirus (OrNV), which has been used as a biocontrol agent against the coconut rhinoceros beetle (Oryctes rhinoceros); a pest of palms in the Asia-Pacific region. However, little is known about growth and metabolism of this cell line, knowledge of which is necessary to develop an in vitro large-scale OrNV production process. The strong anchorage-dependent characteristics of the cell line, its particular fragility and its tendency to form dense clumps when manipulated, are the most likely reasons that have precluded further development of the cell line. In order to characterize DSIR-HA-1179 cells, there was first a need for a reliable technique to count the cells. A homogenous cell suspension suitable for enumeration could be produced by treatment with TrypLE Express™ with optimum mean time for cell release calculated as 30 min. The cell line was adapted to grow in four serum-supplemented culture media namely TC-100, IPL-41, Sf-900 II and Sf-900 III and cell growth, glucose consumption, lactate and ammonia production were assessed from static-batch cultures. The maximum viable cell density was reached in Sf-900 II (17.9 × 10⁵ cells/ml), with the maximum specific growth rate observed in this culture medium as well (0.0074 h⁻¹). Higher production of OrNV was observed in IPL-41 and TC-100 (4.1 × 10⁷ TCID₅₀/ml) than in cultures infected in Sf-900 III (2.0 × 10⁷ TCID₅₀/ml) and Sf-900 II (1.4 × 10⁷ TCID₅₀/ml). At the end of the growth period, glucose was completely consumed in cultures grown in TC-100, while remained in excess in the other three culture media. The cell line produced lactate and ammonia to very low levels in the TC-100 culture medium which is a promising aspect for its cultivation at large-scale.     

Anatomy and histology of the alimentary canal of the black beetle,Heteronychus arator

Abstract

The gut anatomy of adult and third- instar larval black beetle is described, illustrated, and discussed in relation to the condition reported for other scarabs.     

Ecology of black beetle,Heteronychus arator (Coleoptera: Scarabaeidae) — influence of temperature on feeding,growth, and survival of the larvae

Abstract

The influence Of temperature on the growth and survival of first-instar larvae of black beetle feeding in soil was examined. Similarly the consumption, utilisation, growth, and survival of second- and third-instar larvae feeding on carrot were investigated using gravimetric methods. Soil temperatures in the range 20–25° c were found to be necessary for optimum growth of all instars. First-instar larval growth increased exponentially over the temperature range 10–20°c. Third-instar larvae were tolerant of higher temperatures than second-instar larvae. The temperatures for optimum levels of consumption and utilisation of carrot varied between the instars.     

Changes in the karyotype of the cell line,DSIR-HA-1179, and a comparison with that of its parent insect,Heteronychus arator (F.) (Coleoptera: Scarabaeidae)

Abstract

Eighteen months after establishment of the primary cell culture, 36 metaphase nuclei of cell line DSIR-HA-1179, derived from the black beetle, Heteronychus arator (F.), had between 32 and 43 chromosomes; one cell contained 67 chromosomes. Structural abnormalities such as double minute chromosomes, ring and di- and tri-centric chromosomes were observed. Thirty-six months after establishment the chromosomes appeared to be similar, but the number of chromosomes per cell was much more variable (range, 12–73; 42 metaphase cells). The modal chromosome number of testicular tissues from H. arator was 2n = 20 — including an Xy pair — which is characteristic of the Scarabaeidae. The karyotype of DSIR-HA-1179 cells is unstable, with the number of chromosomes becoming more variable with continued propagation.     

The biology and life history of currant clearwing,Synanthedon tipuliformis (Lepidoptera: Sesiidae), in Canterbury

Abstract

Details of the life cycle and biology of currant clearwing, Synanthedon tipuliformis (Clerck), in Canterbury, New Zealand, are discussed. The adults live for about 7 days, and are found from mid November to early January. The sex ratio approximates 1:1. Adults are active only when the air temperature exceeds 15°c, and peak flight activity is observed on cloudy days at 20-23°c. Males are attracted to females between 1400 h and 1600 h, and mating lasts for over 2 h. Fecundity averaged about 100 eggs per female, and fertility exceeded 98%. Egg incubation required an average of 19 days in the field; the thermal constant is 91 day degrees. The mean number of eggs per blackcurrant cane varied in different years from 2.68 to 13.54; there was no significant difference between blackcurrant varieties in the same year. Larvae entered the cane through openings or axillary buds and then fed on the pith until late April or May. Quiescence occurred during winter, and feeding resumed in late August or September. Larvae tunnelled 15.20 ± 0.74 cm of pith. It is suggested that there are six larval instars. Mean numbers of larvae per cane varied in the early stage from 1.91 to 7.36, and at the post-winter stage from 1.23 to 3.10. Pupation occurred in mid October, and the pupal stage lasted for up to 6 weeks; the thermal constant is 216 day degrees. Mortality factors discussed include establishment failure, parasites, pathogens, predators, larval combat, winter pruning, loss of pupae at cane breaks, and pupal eclosion failure. The first record of the fungus Cordyceps sp. attacking currant clearwing is reported.     

Ecology of black beetle,Heteronychus arator (Coleoptera: Scarabaeidae) — relative consumption of pasture plant roots by larvae

Abstract

The relative consumption by third-instar black beetle larvae of roots of paspalurn, ryegrass, and white clover was determined from the rate of passage of ingested glass beads through the gut Consumption of grasses exceeded that of white clover, indicating their greater acceptance as a food source.