Heteronychus Arator Research Articles

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

AbstractPerennial ryegrass (Lolium perenne) is often infected with the fungal‐endophyte Neotyphodium lolii. In addition to the ‘wild‐type’ strain (EWT), several ‘selected’ strains of N. lolii are now being marketed as AR1 (EAR1) and AR37 (EAR37). 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 EWT or EAR1 or EAR37 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 EWT, 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 EAR1 and EAR37 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 EWT and EAR1. The attractiveness of EAR37 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.

Effect of Bt-Maize Expressing Cry1Ab Toxin on Non-Target Coleoptera and Lepidoptera Pests of maize in South Africa

While many studies have been conducted on possible effects of Bt-maize on beneficial arthropods, information on its effects on non-target pests of maize is scarce. Bt-maize has been planted in South Africa since 1998 for control of the maize stem borers, Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae). No information is available on the possible effects that feeding on Bt-maize may have on other pests exposed to Cry1Ab protein when they attack seedlings or ears of Bt-maize. Important pests attacking maize seedlings are Heteronychus arator (Coleoptera: Scarabaeidae) and Somaticus angulatus (Coleoptera: Tenebrionidae), while Helicoverpa armigera (Lepidoptera: Noctuidae) is a sporadic pest of maize ears. The objectives of this study were to determine the effects of Bt-maize, expressing Cry1Ab protein, on these non-target pests. Laboratory studies in which larvae or adults of these species were fed with Bt and non-Bt-maize leaves or ears were conducted and mortality, growth, fecundity and fertility determined. Feeding on Bt-maize did not have a significant effect on any of these life-history parameters of H. arator or S. angulatus. In greenhouse and laboratory studies with H. armigera no larvae survived to the pupal stage on Bt-maize. This study showed that Cry1Ab-producing maize may protect the crop against H. armigera feeding damage. However, the likelihood of H. armigera becoming resistant to Cry1Ab protein over time, and it becoming an important secondary pest, is high.

Impact of novel endophytes in perennial ryegrass on herbage production and insect pests from pastures under dairy cow grazing in northern New Zealand

AbstractPerennial ryegrass (Lolium perenne L.) infected with a novel endophyte (AR37 or AR1), Wild‐type endophyte or no endophyte (Nil) was sown with white clover (Trifolium repens L.) in autumn 2005. The pastures were rotationally grazed by dairy cows from 2005–2009. Annual dry matter (DM) yield did not differ but AR37 pastures had a higher ryegrass tiller density, especially after the 2008 summer drought (+130%), and less white clover than did AR1 pastures. Concentrations of alkaloids produced by the Wild‐type association (lolitrem B, ergovaline) followed the same seasonal trends as did the AR37 alkaloids (epoxy‐janthitrems) but summer drought reduced concentrations of lolitrem B and epoxy‐janthitrems to less than half the mid‐summer (February) peak concentrations in the other years. Insect pests were monitored annually between 2006 and 2009. Tiller damage by Argentine stem weevil (Listronotus bonariensis (Kuschel)) was significantly reduced by all endophyte treatments. African black beetle (Heteronychus arator (F.)) populations in soil samples increased during the experiment with Nil > AR1 > Wild‐type = AR37. Root aphid (Aploneura lentisci (Pass.)) infestations followed the pattern AR1 > Nil > Wild‐type = AR37. A lower pest pressure from all insect pests in AR37 pastures is likely to have contributed to this treatment having the highest ryegrass tiller densities.

Influence of pasture renewal, soil factors and climate on black beetle abundance in Waikato and Bay of Plenty

An outbreak of the sporadic pest black beetle caused major damage on farms throughout Waikato and Bay of Plenty regions from 2007 to 2010. Two projects were initiated in these regions to gain an understanding of the interaction of black beetle with endophyte/ cultivar combinations and pasture renewal strategies. Monitoring of black beetle populations on the project farms showed that overall, abundance steadily declined from 2009 to 2013, possibly due to cool temperatures, and in the case of Bay of Plenty, high rainfall in 2010. In Waikato, pasture renewal in 2012 had no significant effect on beetle abundance in the following year compared to the unrenewed paddocks. Greater population levels in the Waikato sites were associated with lower soil pH. El Niño and La Niña weather events appear to be associated with changes in black beetle population levels, which may assist prediction of future outbreaks and damage risk. Keywords: Heteronychus arator, pasture, La Niña

Evaluation of spring and autumn applied insecticides for the control of black beetle

Black beetle (Heteronychus arator) is a sporadic but serious pest of North Island pastures Field trials were established to test the efficacy of insecticides currently registered for use against scarab pests in pasture Three life stages were targeted newly emerged black beetle adults in autumn egglaying adults in spring and newly hatched larvae in early summer Although the insecticides used caused significant beetle mortalities in spring no treatment reduced the subsequent larval populations in summer Similarly while the autumn application caused significant beetle mortality; the number of surviving black beetle adults remaining in the plots was not affected Soil factors and the high mobility of adult beetles are likely to have contributed to treatment failure

Black beetle: lessons from the past and options for the future

An outbreak of the pasture insect pest black beetle began in the Waikato and Bay of Plenty in 2007/8 and has persisted. The extent and severity of damage caused by black beetle during the current outbreak has focused farmer and researcher attention on methods to maintain persistent pasture now and in future outbreaks. This paper reviews previous research in combination with data from the current outbreak and relates these to current pasture management practice. The possibility of being able to predict the distribution, occurrence and duration of black beetle outbreaks is explored while actual and potential means of controlling black beetle are outlined. We conclude that there are methods available to successfully renew pastures in the presence of black beetle but that outbreak situations increase risks and may limit subsequent pasture persistence. There are fewer readily available options to maintain an existing pasture and more research is urgently needed to provide these options. Keywords: Heteronychus arator, paspalum, pasture, pasture renewal, pest resistance, pest tolerance, ryegrass

Response of black beetle and redheaded pasture cockchafer larvae to loline alkaloids in meadow fescue roots

Meadow fescue (Festuca pratensis) infected with Neotyphodium uncinatum endophyte was used to investigate the response of redheaded pasture cockchafer (Adoryphorus coulonii) and black beetle (Heteronychus arator) larvae to loline alkaloids Root material of meadow fescue genotypes varying in loline alkaloid concentration were fed to individual larvae in a nochoice bioassay Total root loline concentrations ranged from 500 to 3000 g/g DM Growth of second instar cockchafer larvae was significantly reduced under treatments with highest loline concentrations (P

The role of endophyte in determining the persistence and productivity of ryegrass, tall fescue and meadow fescue in Northland

Evidence from small plot and farm trials demonstrate that fungal endophyte infection plays a pivotal role in enhancing the persistence and yields of perennial, hybrid and Italian ryegrasses, tall and meadow fescues in Northland. In most situations these effects were evident within 2-3 years of sowing and were largely attributed to protection from insect attack that is conferred by endophyte infection. Keywords: fungal endophyte, Neotyphodium, perennial ryegrass, Lolium perenne, tall fescue, Festuca arundinacea, meadow fescue, Festuca pratensis, African black beetle, Heteronychus arator

Agronomic response of Italian ryegrasses infected with different Neotyphodium strains

Italian (Lolium multiflorum) and short-term hybrid ryegrasses (L. boucheanum) are utilised by farmers for their reliable establishment and yield potential for winter feeding, but lack summer production and persistence. To improve the performance of these ryegrasses, endophyte (Neotyphodium lolii) strains from perennial ryegrass were inoculated into several cultivars and evaluated for agronomic performance in the Northland region of New Zealand. 'Moata' tetraploid Italian ryegrass families usually showed a reduction in yield when infected with the AR5 strain compared with endophyte-free Moata. Infection of the Italian ryegrass cultivars 'Corvette' and 'Status' with the N. lolii endophytes strains, AR1 and more particularly AR37, usually increased plant production and persistence. Natural infection with the N. occultans endophyte also improved plant performance. Improved plant performance was most closely associated with reduced damage from African black beetle. Interactions between plant line/cultivar and endophyte strain offer the potential for plant breeders to provide enhanced endophyte-infected cultivars of Italian ryegrasses to farmers. Keywords: endophyte, Neotyphodium lolii, Neotyphodium occultans, Italian ryegrass, Lolium multiflorum, dry matter yields, plant persistence, insect damage

Agronomic performance of AR37-infected ryegrass in northern New Zealand

The agronomic merits of a perennial ryegrass (Lolium perenne) cultivar infected with a new endophyte (Neotyphodium lolii), AR37, were compared with the same cultivar infected with currently available endophytes (AR1, Standard) at two sites in northern New Zealand for at least 3 years. AR37-infected ryegrass was the highest yielding treatment at both sites (11 080 kg DM/ ha/yr) producing more dry matter than either AR1 or Standard-infected ryegrass which yielded similar amounts (8870 kg DM/ha/yr). Yield advantages of AR37-infected ryegrass were greater at Kerikeri (36%) than Hamilton (17%), with differences increasing over successive years at both sites. At Hamilton, tiller populations were lowest in AR37-infected ryegrass in Year 2, and lowest in AR1- infected ryegrass 3 and 5 years after sowing. At both sites AR37-infected ryegrass had the lowest infestation scores for root aphid. At Hamilton in Year 4, more damage by African black beetle larvae occurred to AR1-infected plants than to AR37 and Standard-infected plants. These pests are likely to have contributed to the differences in agronomic performance observed. These agronomic results suggest AR37-infected ryegrass cultivars will be a useful choice for farmers in northern New Zealand. Keywords: endophyte, Neotyphodium lolii, perennial ryegrass, Lolium perenne, dry matter yields, plant persistence, root aphid, Aploneura lentisci, African black beetle, Heteronychus arator

Development of a cost-effective, pesticide-free approach to managing African black beetle ( Heteronychus arator) in Australian eucalyptus plantations

Screening trials were established to test the efficacy of a range of physical barriers in preventing damage to stems of Eucalyptus globulus seedlings growing in Australian commercial eucalypt plantations by African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae). Seedlings treated with two types of barrier covering the lower section of stem were significantly less likely to be damaged than untreated controls. In contrast, chlorpyrifos treatments conducted within the same plantations as part of operational control programs did not appreciably reduce damage incidence, although pitfall trap captures in chlorpyrifos treated areas were consistently below those for untreated controls. One barrier, a flexible plastic mesh sleeve, was further tested in large trials as part of an operational planting program. In this less controlled commercial production setting, this barrier proved both practical and effective, with severe damage and mortality reduced by over 75%. No negative treatment effects on root formation, or tree growth, were observed. There was a statistically significant correlation between pitfall trap captures in the 2 months prior to planting and the level of damage sustained in the six months following planting. However, there was considerable variation around this trend suggesting pitfall captures alone cannot be used as a reliable indicator of risk. Barrier treatment has proven highly cost-effective and is now the operational standard. It is conservatively estimated that, in just 3 years of wider use, over 5500 ha of ‘high-risk’ land has been planted to barrier treated seedlings.

The role of perennial ryegrass endophyte in Italian ryegrass

Italian ryegrass (Lolium multiflorum) and short-term hybrid ryegrass (L. boucheanum) have reliable establishment and high cool season growth, but varying persistence after the first summer. In Northland, there is increased stress on ryegrass from invertebrate insect attack. Selected strains of endophyte (Neotyphodium lolii) have been identified that protect perennial ryegrass from invertebrate attack. Two of these endophyte strains (AR1 and AR37) were inoculated into two Italian ryegrass cultivars (Status and Corvette) and compared in a small plot agronomic trial with the same cultivars free or low in the naturally-occurring endophyte N. occultans. From April 2004 to June 2005, ryegrass plots with these endophyte-cultivar combinations were measured for dry matter yields and plant survival under summer/autumn insect pressure in Northland. In autumn/winter 2005, novel endophytes resulted in greater plant survival and yield advantages (82%) than the same cultivars with no/low N. occultans endophyte. These effects were consistent across cultivars. Increased agronomic performance corresponded with lower damage from African black beetle larvae (Heteronychus arator). This result has implications for extending the persistence and potential yields of Italian/hybrid ryegrass pastures subject to pest attack.

Bioassays to compare the systemic activity of three neonicotinoids for control of Heteronychus arator Fabricius (Coleoptera: Scarabaeidae) in maize

Two neonicotinoid seed dressing insecticides (imidacloprid and thiamethoxam) are registered in South Africa for control of the black maize beetle , Heteronychus arator, in maize. The systemically translocated antifeedant and/or repellent activity of these two neonicotinoids and an unregistered neonicotinoid, acetamiprid, were compared in laboratory bioassays. In all trials treated and untreated seed were planted in a greenhouse and stems of maize seedlings were fed to adults in glass vials. Damage to seedling stems (number of damaged leaf sheaths) was determined and beetle mortalities recorded. Results on beetle mortality indicated inadequate systemically translocated insecticidal activity of neonicotinoid insecticides at a dosage rate of 1.75 g a.i. kg −1 seed. The number of damaged maize stems, extent of damage (mean number of damaged leaf sheaths) and ability of beetles to cause severe damage, served as criteria to evaluate the efficacy of the systemically translocated antifeedant and/or repellent action. Since the majority of beetles fed on the stems before they were repelled, a high number of maize stems were damaged at the onset of the trials. The extent of damage and the ability of the beetles to cause severe damage were significantly reduced. However, in the case of acetamiprid and thiamethoxam reductions were not large enough and in some trials up to 53% of the beetles were still able to cause severe damage. This observation indicates that these two compounds may not provide adequate control during growing seasons when high beetle populations are encountered, thus increasing the probability that more than one beetle may damage a single plant.

Poor efficacy of the insecticide chlorpyrifos for the control of African black beetle ( Heteronychus arator) in eucalypt plantations

African black beetle is a major agricultural and forestry pest in south-western Australia. In this study, we examine the effectiveness of various surface-applied chlorpyrifos treatments for the control of beetle damage in commercial forestry crops. Of those treatments tested, none had a strong, consistent effect on the abundance of the subterranean adult beetles through to 9 weeks after application, nor did they consistently reduce beetle damage or improve crop productivity. When incorporated into soil at rates presently employed successfully in agriculture, chlorpyrifos caused no mortality of adult African black beetles that were added to the soil post-treatment. Chlorpyrifos decays at an exponential rate in soil with 75% of the active ingredient remaining at 1 h post-treatment, 40% at 50 days and 10% remaining after 110 up to 170 days. It appears that the capacity of chlorpyrifos to cause mortality to African black beetle is through vigorous soil incorporation bringing the chemical into direct contact with the insect. Chlorpyrifos applications are not recommended for the control of African black beetle in tree crops because the restrictions on timing and use of soil incorporation techniques will generally mean that the insecticide will not be brought into direct contact with a sufficient proportion of the beetle population.

Effect of application rate and beetle age on efficacy of imidacloprid (Gaucho®) against black maize beetle, Heteronychus arator Fabricius (Coleoptera: Scarabaeidae)

Laboratory trials were conducted to study the effect of application rate and beetle age on damage inflicted by black maize beetle, Heteronychus arator, to maize seedlings treated with imidacloprid. Application rate was evaluated in two trials using young adults during autumn and older adults during spring after hibernation. Three trials evaluating the effect of beetle age were conducted at fortnightly intervals during spring when adults were in a progressively changing reproductive phase. Only females after hibernation were used in the latter trials. In all trials treated and untreated seeds were planted in a greenhouse and maize seedling stems fed to adults in glass vials. Damage to maize seedlings (number of damaged sheaths) was determined and beetle mortalities recorded. Results indicated that with older adults a rate of half the registered rate might be as effective as the registered rate. However, it would be safer to use the higher registered rate until all factors that might affect the efficacy of imidacloprid are known. Females occurring during mid-spring were less affected by the systemic activity of imidacloprid than those occurring later during the season, which might possibly be related to their ovipositional cycle. In the majority of fields in the area where H. arator pest outbreaks traditionally occur, maize seedlings are in a vulnerable growing stage during mid-spring. The systemic component of imidacloprid might therefore not be able to control H. arator effectively in growing seasons when beetle population levels are high, especially when it is used at half the registered rate.

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

AbstractTrends 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.

Black beetle damage to perennial ryegrass infected with AR1 endophyte

AR1 is a new fungal endophyte that is being released in perennial ryegrass to New Zealand farmers. This endophyte lacks the mammalian toxins, ergovaline and lolitrem B, but produces peramine which provides resistance to a major ryegrass pest, Argentine stem weevil (Listronotus bonariensis). Black beetle (Heteronychus arator) is another important pest of ryegrass in northern areas of New Zealand. Adults are selective feeders, and avoid feeding on ryegrass infected with wildtype endophyte. A limited supply of suitable food greatly reduces their reproductive capacity. Laboratory and field investigations were therefore carried out to evaluate the degree of resistance to black beetle provided by AR1. Assessments of adult black beetle feeding were made on two field trials planted in autumn 1999. In both trials, adult feeding was significantly higher on ryegrass infected with AR1 than on ryegrass with wild-type but also significantly lower on AR1 than on endophyte-free ryegrass. In a pot trial conducted in summer, black beetle adult damage to 4-week-old AR1-infected ryegrass was no different from damage to endophyte-free plants. However in 6-month-old plants, damage to AR1 plants was significantly less than to endophyte-free plants and was similar to damage levels on wild-type plants. A further pot trial showed that beetles overwintering on AR1 ryegrass had a higher reproductive capacity than those overwintering on wild-type infected ryegrass. In February 2001, two field trials planted the previous June were sampled for black beetle larvae. Black beetle presence was significantly higher on endophyte-free plots than on wild-type plots, with presence on AR1 intermediate between these treatments. Ryegrass infected with AR1, although showing a degree of resistance to black beetle compared with endophyte-free ryegrass, is more susceptible to damage than wild-type, particularly in its first year of planting. Limited data indicate that older AR1 swards may have similar resistance to that of the wild-type but further research is needed to clarify the effect of stand maturity on black beetle damage to ryegrass infected with this new endophyte. Keywords: AR1, black beetle, endophyte, Heteronychus, Listronotus, Neotyphodium, ryegrass

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.

Seasonally contrasting activity of African black beetle, Heteronychus arator (Coleoptera: Scarabaeidae): implications for populations, pest status and management

AbstractFlight and surface activity of the African black beetle, Heteronychus arator (Fabricius), detected by pitfall, light and window traps, was seasonally reversed. High surface activity relative to flight occurred in spring when beetles were mature, while relatively higher levels of flight occurred in autumn when they were immature. Pitfall trap captures were male-dominated in spring and female-dominated in autumn, and were a poor estimator of adult density. Light trap captures were consistently female-dominated. Although autumn flight was dispersive and inferred to have some role in population regulation, it was largely localized within the usual pasture habitat of the species. Some beetles flew into irrigated potato crops in autumn, but not specifically, as beetle abundance was consistently less than in surrounding dry pasture. High surface activity indicates spring is a strategic time for surface-applied control measures to prevent increase of H. arator in the next generation, a less disruptive alternative to conventional soil-incorporated insecticide directed at the new generation's larvae in summer. Such an approach would be best aimed early in the upsurge of activity, as most of the season's cohort of eggs was laid by the time surface activity peaked in mid-spring.

Ergopeptine Alkaloids and Neotyphodium lolii-Mediated Resistance in Perennial Ryegrass Against Adult Heteronychus arator (Coleoptera: Scarabaeidae)

Heteronychus arator F. adults are deterred from feeding on perennial ryegrass, Lolium perenne L., infected with the endophytic fungus Neotyphodium lolii, which produces many alkaloids and other mycotoxins in the host grass. This article examines the effects of a number of these compounds on adult H. arator feeding. Pure mycotoxins at several concentrations were incorporated into a carrot-based artificial diet developed specifically for this study. The mycotoxins tested were either compounds commonly found in N. lolii-infected perennial ryegrass (peramine, lolitrem B, paxilline, ergovaline, and ergovalinine), or compounds structurally similar to those occurring in N. lolii/perennial ryegrass associations (ergotamine, alpha-ergosine, alpha-ergocryptine, festuclavine, lysergol, lysergic acid amide, ergonovine, dihydroergotamine, alpha-bromoergocryptine, and dihydroergocrystine). Peramine, a Listronotus bonariensis (Kuschel) feeding deterrent, did not affect adult H. arator feeding. Lolitrem B, a mycotoxin involved in livestock health problems, and its structurally related precursor, paxilline, had no effect. The ergot alkaloids festuclavine, lysergol, and lysergic acid amide also did not deter adult H. arator feeding. Ergonovine was the only nonergopeptine ergot alkaloid to deter adult H. arator, though only moderately. The greatest antifeedant effects were observed with the ergopeptine alkaloids ergotamine, ergovaline, alpha-ergosine, and alpha-ergocryptine, all of which significantly reduced feeding at 5.0 micrograms/g. The ergopeptine epimer ergovalinine, and the ergopeptine alkaloid derivatives dihydroergotamine, dihydroergocrystine, and alpha-bromoergocryptine were also active, although less so than the parent ergopeptines. Thus ergopeptine alkaloids are likely to be a major factor in the N. lolii-mediated resistance to H. arator. It was further observed that perennial ryegrass seed containing an endophyte strain that did not produce ergot alkaloids, but did produce other mycotoxins normally associated with N. lolii infection, did not deter H. arator feeding, whereas an ergot alkaloid producing N. lolii/perennial ryegrass association did. The implications of these findings in relation to the toxicity of ergot alkaloids to mammals, and in relation to the definition of a desirable endophyte, are discussed.