Biology, importance and management of the redheaded pasture cockchafer Adoryphorus couloni (Burmeister). A review of current knowledge prepared for GippsDairy Board Incorporated Gordon Berg July 2008.
Contents 1. Introduction...4 2. Description, Lifecycle and Damage to Pastures...5 2.1 Description...5 2.2 Lifecycle...5 2.3 Damage to pastures...6 3. Factors influencing the impact of redheaded pasture cockchafer on pastures...7 3.1 Soil Type...7 3.2 Pasture species...8 3.2 Rainfall...9 3.3 Altitude...9 3.4 Dynamics of redheaded pasture cockchafer outbreaks...9 4. Control Options...10 4.1 Synthetic pesticides...10 4.2 Biological pesticides...10 4.2.1 Entomopathogenic nematodes...11 4.2.2 Fungal pathogens...12 4.2.3 Fungal endophytes...12 4.2.4 Bacterial pathogens...13 4.2.5 Viral pathogens...14 4.3 Cultural options...14 4.3.1 Hardy or resistant pasture species...14 4.3.2 Grazing Management...15 4.3.3 Physical disturbance...15 4.3.4 Monitoring cockchafer populations...15 2
5. Management Strategies...16 6. Acknowledgements...19 7. References...20 3
1. INTRODUCTION The redheaded pasture cockchafer, Adoryphorus couloni (Burmeister)(Coleoptera: Scarabaeidae) is an Australian native insect that has become an important pest of semi-improved and improved pastures in the higher rainfall areas of south-eastern Australia (Parvri and Young 2007). The insect is a member of the beetle family and the damaging stage is the larva which is a typical scarab curl grub which feeds underground on the roots of pasture species. Apart from direct feeding damage the cockchafer renders the pasture susceptible to further damage from grazing stock and birds seeking the larvae. The severed root systems of the pasture are easily torn up by foraging animals or birds. Redheaded pasture cockchafer is also a pest of turf in golf courses, lawns and turf farms (Berg et al. 1993). The species occurs commonly in parts of Tasmania, Victoria, South Australia and New South Wales. It has also been found in Queensland, and since 1963, in localised areas of New Zealand s south island. In Tasmania it is found in the Southern Midlands, Derwent Valley, Hobart, South Arm and Flinders and King Islands (Hardy and Tandy 1971, Hardy 1981, Hamlet et al. 2005). In South Australia the cockchafer occurs in the lower south east (Heap 1998). In New South Wales the cockchafer has been an important pest in the southern tablelands area. In Victoria the cockchafer is an important pest in areas of the Western, Central and Gippsland districts (Douglas 1972, Blackburn 1983). In New Zealand it is found in several localised areas on the Bank s Peninsula area of the south island (Gorton et al. 1998). 4
2. DESCRIPTION, LIFECYCLE AND DAMAGE TO PASTURES 2.1 DESCRIPTION There are four main life stages of the redheaded pasture cockchafer: Egg (Figure 1) larvae (of which there are 3 instars) (Figure 1) pupa adult beetle (Figure 1) The adults are stout, shiny, black to dark reddish-brown beetles from 10 to 15 mm long (Carne 1957). Eggs are white, spherical or slightly oval in shape and about 2mm in diameter. The larvae are soft, whitish grubs. Their body is slightly transparent in appearance with the posterior quarter being a little swollen and more greyish in colour. The larvae have three pairs of yellowish legs just behind the head which has a hard, reddish brown appearance (hence the name redheaded pasture cockchafer). When at rest the body is curved in the shape of a letter C, and is sometimes referred to as a curl grub. Newly hatched larvae are only 5 mm long and grow through three instars to about 30 mm in length. The larvae become more creamy in colour just before they reach the pupal stage. There a many hundreds of different species of cockchafer species in Australia with soil feeding larvae. Several of these can be found in pastures and are easily confused with redheaded pasture cockchafers. Goodyer (1977) provides a description and identification key for the larvae of some common species of pasture cockchafers. Goodyer and Nicholas (2007) describe a number of other common pasture scarab species. The pupa is yellow-brown in colour about 20mm long and forms in a pupal cell in the soil. 2.2 LIFECYCLE In southern Australia the redheaded pasture has a two year lifecycle (Hardy 1981). Except for the adult beetle the entire life cycle is spent below the soil surface. 5
The adult beetles emerge from the soil at dusk from later winter to early spring (the end of August until mid-october), fly for a brief period, mate and lay their eggs singly in the soil under pastures. They tend to prefer to lay eggs in areas with denser pasture cover. The eggs hatch in the late spring 6-8 weeks after being laid. Larvae grow through three stages or instars and reach the pupal stage in January. Larvae feed on organic matter and pasture roots. The larvae do not come to the surface to feed. Most damage to pastures is done by the third instar larvae. Their feeding severs the roots of a number of pasture species. The larvae dig deeper into the soil to pupate. The pupal stage lasts 6-8 weeks before the adult beetle emerges from the pupal skin in February to March. However the beetle remains in the pupal cell as a sexually immature adult for about another six months when it then digs its way to the surface. The adult beetle does not feed. The life-cycle in Victoria is illustrated in Figure 3 (Blackburn 1983). 2.3 DAMAGE TO PASTURES Redheaded pasture cockchafer can severely reduce the amount of pasture available for livestock during autumn, winter and sometimes during spring because the soil-dwelling larvae either prune or completely cut off the roots of pasture plants; damaged plants either have reduced growth or die (Heap 1998). Damage usually first appears in late March and may be severe by May or early June. Low soil temperatures in winter cause larval activity to diminish before more active feeding resumes in late August. Feeding continues until early summer when larvae reach full maturity. Grasses with weak, fibrous roots such as ryegrass are especially vulnerable to damage. In a mixed pasture sward the ryegrass component is often uprooted completely by foraging stock. Birds such as ravens or ibis feed on the cockchafer larva. They will uproot the pasture in doing so. Infestations are often first noticed by the presence of flocks of birds feeding in a pasture (Figure 2). Cockchafer numbers in heavy infestations can reach from 50 to 750 or even 1100 per square metre (Hardy 1981, Parvri and Young 2007, Heap 1998)). Numbers as low as 70 per square metre can caused damage in an unpublished plot trial in Victoria in 2007 (G O Brien pers. comm.).numbers of over 300 per square will result in substantial pasture damage (Heap 1998). Heavily infested pastures can sometimes be rolled up like a carpet because of the damaged root systems. In these situations pasture productivity is reduced dramatically and the plants are 6
particularly susceptible to lack of water with their damaged root systems. Damage can range from isolated patches to larger areas of 50 ha (Hardy 1981). Persistence of sown perennial grasses is reduced and weeds invade more aggressively in severely affected pastures resulting in continuing losses in production following an outbreak (Heap 1998). If the affected areas are wet the pasture can become badly pugged by stock (Blackburn 1983). Because of the two year life-cycle heavy damage is sometimes noticed every second year for a period of years. However there may also be overlapping cockchafer generations present which can result in damage in successive years (Parvri and Young 2007, Blackburn 1983). Resowing of infested pastures may be affected by the presence of cockchafer larvae. There is little information published on the economic costs of redheaded pasture cockchafer to either dairying or other grazing industries. In Tasmania an attempt was made to quantify losses of three major pasture pests, common corbie (Oncopera intricate), blackheaded pasture cockchafer (Acrossidius(Aphodius) tasmaniae) and redheaded pasture cockchafer (Adoryphorus couloni). Losses (1993 figures) in an average year were estimated as over $1 million for redheaded pasture cockchafer (Pauley and Miller 1993). In Victoria estimates in 1993 for redheaded pasture cockchafer damage ranged from $100/ha for lamb production, $500/ha for dairying and $9000/ha for turf production in 1993 (Berg et al. 1993) 3. FACTORS INFLUENCING THE IMPACT OF REDHEADED PASTURE COCKCHAFER ON PASTURES 3.1 SOIL TYPE In Victoria outbreaks have been noted as occurring on acidic sand and sandy-loam soils over clay and were most severe where the top soil was deeper than 6 inches (Douglas 1972). In Tasmania the cockchafer was only known as a minor pest until 1967. In 1969 to 1971 it caused more serious damage and was most common in improved pastures which were three or more years old. It occurred on most types of soil but more commonly on free-draining selfmulching clays and in loams over gravel, clay or both. In other areas in Tasmania sandy loam and loam soils were most affected (Hardy and Tandy 1971). 7
In South Australia the cockchafer occurs in the lower south east particularly on pastures grown on meadow podsolic and terra rosa soils and it has been noted that its emergence as a pest is probably caused by the increased levels of soil organic matter associated with pasture improvement and the use of shallow-rooting species (Heap 1998). In April 2007 an unpublished replicated plot trial was conducted at Willow Grove in Gippsland investigating the effect of applications of burnt lime (0, 1, 2 and 4 tonnes lime per hectare broadcast and raked in) on redheaded pasture cockchafer infestations (G. O Brien pers. comm.). No significant effect on larvae numbers was recorded in the season of application by the lime treatments. 3.2 PASTURE SPECIES Redheaded pasture cockchafer can damage a range of annual and perennial grasses and subterranean clover. Some perennial grasses may have more tolerance to damage (Parvri and Young 2007). However ryegrass is severely damaged. Analysis of gut content of the larvae has shown that they feed preferentially on organic matter in soil under perennial rye grass (Lolium perenne) pastures in Tasmania (McQuillan and Webb 1994). Wheat can also be severely stunted by the cockchafer (Douglas 1972). Pasture species such as phalaris, lucerne and cocksfoot have been noted as being less susceptible to damage (Anon. 1970, Heap 1998). Victoca perennial ryegrass is a selection of certified Victorian perennial ryegrass. It was selected in Tasmania by the Department of Primary Industries and Water in response to problems of pasture persistence, frequently due to Cockchafer attacks. Selections were made over two generations, each of four years from a bulk population of surviving plants which had been exposed to a dry environment and repeated infestations of red headed pasture cockchafer (Anon 1988). Victoca is available commercially and features claimed for the variety include that it is deep rooted, tolerance to waterlogging and close grazing and that it shows quick recovery after summer (Anon 1988, Tas Global Seeds 2008). 8
3.2 RAINFALL In Victoria it has been noted that the cockchafer is usually found in areas where there is more than 500mm annual rainfall (Douglas 1972, Blackburn 1983). Flooding however can cause high mortality to larvae in some situations where they appear to sometimes come to the soil surface and drown (Berg et al. 1984). 3.3 ALTITUDE In Tasmania it has been noted that the cockchafer has not been recorded at altitudes above 200 meters (Hardy 1981, Hamlet et al. 2005). 3.4 DYNAMICS OF REDHEADED PASTURE COCKCHAFER OUTBREAKS Redheaded pasture cockchafer is native to south-eastern Australia. Normally the insect occurs in relatively low numbers in various types of pastures causing little apparent damage. Its emergence as a pest is thought to be associated with increased levels of soil organic matter in improved pastures and the use of shallow-rooting species (Hamlet et al. 2005, Heap 1998). Damage has been reported to mainly occur in pastures that are three or more years old and which contain subterranean clovers, annual volunteer grasses and, sometimes, a low level of perennial grasses (Heap 1998, Parvri and Young 2007). The extent and severity of damage can vary greatly from year to year and from property to property. Because of the two year life-cycle heavy damage is sometimes noticed every second year, however overlapping cockchafer generations can cause damage in successive years. Severe damage is reported to often occur in years with a dry autumn following heavy spring rains. The spring rains provide good pasture cover during spring and summer which favours egglaying and survival of the young cockchafer larvae. The dry autumn stresses the plants which have suffered root damage resulting in poor pasture production. The damage may be worsened by stock pulling up the damaged plants or by birds foraging for the larvae. Ongoing effects following outbreaks can be associated with the subsequent invasion of weeds in damaged pastures (Heap 1998). Pastures lightly grazed during the previous spring and summer may be more favourable for egg laying by the adult cockchafer beetles. Observations in adjacent pastures, where one is 9
undergrazed compared to the other, have shown heavier infestations in the undergrazed pasture (Douglas 1972). It has been noted in New Zealand where the cockchafer is an introduced pest that it appears to spread at the rate of 1.14km per year (Gorton et al. 1998). 4. CONTROL OPTIONS 4.1 SYNTHETIC PESTICIDES No synthetic insecticides have given effective economical control of redheaded cockchafers. Their subterranean feeding habits result in difficulties of synthetic pesticides reaching the larvae. This contrasts to blackheaded cockchafers where the larvae come to the surface to feed and are accessible to synthetic insecticides. A range of synthetic pesticides trialed in Victoria gave no significant levels of control (Berg and Williams 1986). In New Zealand a range of pesticides gave some level of control of first and second instar larvae, which feed closer to the soil surface, but no significant control of the damaging third instar larvae (Stufkens and Farrell 1980). Drilling in insecticides with superphosphate was also shown to be ineffective for controlling redheaded pasture cockchafer (Hardy and Tandy 1971). Since these trials were conducted in the 1970 s and 1980 s there appears to have been little investigation of newly developed synthetic pesticides for control of redheaded pasture cockchafer. A number of new synthetic chemicals have been developed for control of soil pests during this period and may be worth trialling against redheaded pasture cockchafer. 4.2 BIOLOGICAL PESTICIDES Several pathogens of redheaded pasture cockchafer have been found to occur naturally in infested pastures. Examples include the nematode Neoaplectana spp., the fungus Metarrhizium anisopliae and bacterial and viral pathogens (Hardy 1981). Some pathogens have been investigated as potential biological pesticides for control of redheaded pasture cockchafer and other pasture pests in Australia and New Zealand. 10
4.2.1 ENTOMOPATHOGENIC NEMATODES Nematodes are microscopic worm-like organisms. There are many species which feed on both plants and animals. One group, entomopathogenic nematodes, feeds on insects. Bedding (2006) has recently reviewed the use of nematodes as biopesticides. Entomopathogenic nematodes will parasitize soil insects and kill them with a symbiotic bacteria which the nematode carries in its gut. The bacteria render the insect s body contents into a suitable nutrient state that the nematode can then use to complete its life-cycle. A single infested cockchafer larva can result in many thousands of nematodes then leaving the host and seeking new larvae. The potential use of entomopathogenic nematodes for control of redheaded pasture cockchafer was investigated in trials conducted Victoria during the 1980 s (Berg et al., 1984, 1987, 1993). In the trials a suspension of the nematode Steinernema glaseri (strain NC 513) selected for its pathenogenicity for the cockchafer was applied to redheaded pasture cockchafer infested pastures. The nematode was applied in a suspension of water either by watering can in small plot trials or by injection via a modified coil-tyne coulter drill in larger scale trials. The drill allowed much lower volumes of water to be used in the application of the nematode and decreased losses of nematodes due to drying out before they could enter the soil. Whilst results were promising with a 37% reduction in cockchafer numbers in treated plots this was insufficient to prevent pasture damage in heavy cockchafer infestations. The nematode strain also was inactive during the colder winter months. Since the 1980 s other strains have been found that may be more effective (Grewel et al. 2005). Currently a strain of the nematode Heterorhabditis zealandica is available commercially in Australia for the control of a number of turf and pasture pests. The product Weevilnem produced by Ecogrow Australia Pty Ltd (see website - www.ecogrow.com.au) is listed as being useful for the control of redheaded pasture cockchafers in nursery situations (the product is also used in turf for the control of a number of similar soil borne pests). There are similar products used for other cockchafer pests overseas (eg. Nemasis G for European chafer (Rhizotrogus majalis) control - see website - www.beckerunderwood.com). 11
4.2.2 FUNGAL PATHOGENS A number of potential fungal pathogens have been trialed in the laboratory and field against redheaded pasture cockchafer in Australia. These include Metarhizium anisopliae, Metarhizium flavoviride and Beauveria bassiana (Milner 2000, Rath et al. 1995a, 1995b, 1995c, 1995d, 1995e). Of these the Australian native species of fungus pathogenic to insects, Metarhizium anisopliae, has been commercialised as a biological control agent in two products ( Biogreen Granules Biological Insecticide and Chafer Guard Granules Biological Insecticide ) both of which are currently registered in Australia and produced by Becker Underwood Australia (APVMA website). Unfortunately production of these products was suspended, hopefully temporarily, in 1997 (Becker Underwood statement). The products are formulated as granules that are mixed with seed (but not fertilizer) when sowing pasture. Chafer Guard contains 2500 million spores of Metarhizium anisopliae per gram and is applied at the rate of 10kg per ha. The product label instructions indicate that it is not likely to control cockchafers in the first year of application, but will exert a level of control for about the following 5 years. Good control has been reported following field application of the granules to pastures, which can be direct-drilled into existing pastures, or sown with new pastures (Heap 1998). Rath et al. (1990a, 1990b) report control levels of upto from 60 to over 80% of third instar larvae over the period from application in mid-winter to the following late summer and autumn. Rath (1992) also reported autumn applications of Metarhizium anisopliae reduced cockchafer populations by 94% whereas applications after autumn resulted in a 50% reduction. Rath and Rowe (1993) report that perennial ryegrass density was 43% greater than in untreated plots in late autumn and 36% greater in early spring in redheaded pasture cockchafer infested pastures following treatment with Metarhizium anisopliae. Whilst total herbage production was not changed the difference was due to weed ingress. 4.2.3 FUNGAL ENDOPHYTES Fungi such as Neotyphodium (prev. Acremonium) lolii have an endophytic relationship with pasture species including ryegrass and fescues. They can confer a level of resistance to some pasture pests such as Argentine stem weevil and African black beetle (Prestidge and Gallagher 1998, Ball and Prestidge 1992) by the production of various alkaloids. These alkaloids can also 12
affect grazing animals (Easton et al. 2002). Ryegrass staggers is a disease of sheep caused by the alkaloid Lolitrem B produced in endophyte infected ryegrass (Rattray 2003). Research in New Zealand has identified endophytes (such as AR-1) which confer resistance to some pasture pests without causing toxic effects to grazing animals (Rattray 2003). Further research is investigating the effects of these for the control of a range of pasture pests. In Australia endophytes, including the wild type and strain AR37, were trialed against redheaded pasture cockchafer and blackheaded pasture cockchafer in pot trials. No significant effects of endophyte were found (Watson 2006). Further research is being undertaken by CropMark Seeds NZ and a recent press release (2007) suggests some promise against pests such as grass grub and African black beetle with the endophyte strain U2. This strained is currently being tested in Australia for activity against redheaded pasture cockchafer (Nigel Johnston, Cropmark Seeds Ltd. pers. comm.). 4.2.4 BACTERIAL PATHOGENS In New Zealand a disease known as Amber disease infects a similar scarab pest, the grass grub (Costelytra zealandica White). It is caused by strains of the bacteria Serratia entomophila or S. proteamaculans, (Jackson et al. 1993, 2004). Following ingestion of pathogenic bacterial cells, larvae cease feeding after 2-5 days and become amber colored due to gut clearance. Death occurs 1 to 3 months after initial infection. Serratia entomophila has been developed into commercial products Bioshield and Invade by AgResearch, NZ. They have developed a way of putting it into polymer coated granules that can be drilled into mature pastures when grubs are small and actively feeding (Feb to May). Inoculation of the soil generally suppresses grub growth for about five years. AgResearch has formed a company called Encoate with Ballance AgriNutrients to commercialise the product. Bioshield is generally applied at a rate of 30kg/ha, and this costs about $100 per ha plus application costs. It is claimed it should be effective for five years unless there is a drought, which is likely to kill off Serratia and can lead to a grub population explosion (Jackson 2005). The commercialized strains of Serratia have been tested against redheaded pasture cockchafer but they were not active against it (Jackson 2003). 13
4.2.5 VIRAL PATHOGENS Although a number of viruses such as Nucleopolyhedrosis virus (studied as a control of the caterpillar pest Wiseana (Hepialidae) in NZ) and Entomopox virus (studied as a control of the scarab Melolontha melolontha in Europe) can occur in cockchafer and other pasture pest populations there is little published information on their potential for control of redheaded pasture cockchafer. 4.3 CULTURAL OPTIONS 4.3.1 HARDY OR RESISTANT PASTURE SPECIES Pasture species such as phalaris, lucerne and cocksfoot which are less susceptible to damage than ryegrass may be alternatives in some situations (Heap 1998, Hamlet et al. 2005) Some selections of pasture grasses for resistance or tolerance to root feeding pests have been made in Tasmania. One example is the selection Exceltas which is a selection of coloured brome (Bromus cloratus) (Tas Global Seeds 2008). It is claimed to be as palatable as ryegrass and as resilient as cocksfoot, more drought tolerant than the former and more productive than the latter. Victoca perennial ryegrass is a selection of certified Victorian perennial ryegrass. It was developed in Tasmania by the Department of Primary Industries and Water in response to problems of pasture persistence, frequently due to cockchafer attacks. Selections were made over two generations, each of four years from a bulk population of surviving plants which had been exposed to a dry environment and repeated infestations of redheaded pasture cockchafer. It is claimed the variety shows tolerance to redheaded pasture cockchafer damage (Anon 1988). Victoca is available commercially and other features claimed include that it is deep rooted, tolerant to waterlogging and close grazing and that it shows quick recovery after summer (Tas Global Seeds 2008). With greater interest in drought tolerant species and the use of native grasses in recent times a better understanding of their susceptibility to redheaded pasture cockchafer could provide useful management information. 14
4.3.2 GRAZING MANAGEMENT In Tasmania it is recommended to remove dry pasture residue before autumn (through grazing or cutting hay) to reduce the habitat value for redheaded cockchafer beetles (Hardy 1971, Hamlet et al. 2005). In Victoria close grazing in spring to remove rank dry herbage has been proposed as a means of reducing the attractiveness of pastures for egg-laying by the adult female beetles (Douglas 1972). In South Australia it is recommended that removing dry pasture residue by grazing before the beginning of autumn can reduce larval densities during that autumn and the next winter. Similarly cutting pastures for hay in spring may also have a similar effect (Heap 1998). It has been noted however that short, open pasture is more attractive to the egg-laying beetles blackheaded pasture cockchafers than rank pasture (Hamlet et al. 2005). 4.3.3 PHYSICAL DISTURBANCE It has been noted that cockchafer larvae can be killed by physical impacts such as tillage and rolling of pastures (Hamlet et al. 2005). 4.3.4 MONITORING COCKCHAFER POPULATIONS In areas subject to infestation it has been noted that many control options and strategies do not successfully prevent or reduce damage to pastures once the damage has been observed. Better monitoring techniques may assist in preventing damage by earlier intervention. In experimental situations traditional monitoring of redheaded pasture cockchafer larvae has been by digging up small areas with a spade and counting the larvae (eg. Berg et al. 1984). This technique is not practical on a whole farm basis. Other monitoring techniques do not appear to have been investigated for redheaded pasture cockchafer to any great extent. These include pheromone and light trapping of adult beetles, and remote sensing techniques such as acoustic monitoring to detect larvae in pastures and spectral analysis which can identify affected plants. Acoustics may used to detect and analyse spatial distribution of soil invertebrates (Mankin et al. 2007). In Victoria the Department of Primary Industries at Tatura is using acoustics to measure impact of agriculture on ecosystems and with minor modifications their software and hardware 15
could be used for detection, identification and spatial analysis of soil invertebrates (D Williams pers. comm.). Imaging spectroscopy can be used for the early detection of some pests. Instruments can measure both the visible and the invisible near infrared fractions of light reflected from crop canopies. This can detect pest activity before it is visible to the human eye by detecting subtle changes in plant chemistry and physiology caused by pest activity (Datt et al. 2006). Traps baited with pheromone have been used to monitor scarabs (Nakano and Tamaki 1986) and pheromone-mediated mating disruption of oriental beetle Anomala orientalis was attempted for turfgrass but better formulations were required to make the technique a viable alternative (Koppenhofer et al. 2005). Although mating disruption had no effect on oriental beetle fecundity or egg fertility it did impact on number of eggs laid because it reduced the time available for oviposition (Wenninger and Averill 2006). Nakano and Tamaki (1986) also used pheromones to mass trap scarabs in soybeans. 5. MANAGEMENT STRATEGIES Current management strategies for redheaded pasture cockchafer include: South Australia (Heap 1998): Pasture management Removing dry pasture residue by grazing before the beginning of autumn may effectively reduce larval densities during that autumn and the next winter - the survival of young larvae during summer and spring appears to rely on a good pasture cover during that period. Cutting pastures for hay in spring may also have a similar effect. Removing pasture residue from a whole property is not practical nor recommended. However, hard grazing could be used on those pastures that have been most susceptible in the past, especially in years of expected damage. Annual pastures that are heavily grazed during spring and early summer are susceptible to black-headed pasture cockchafer damage in the following winter. However, while this pest can 16
be controlled cheaply with insecticide before damage occurs - redheaded pasture cockchafer can not. Damage may also be reduced by sowing perennial grasses that are more tolerant to damage than annual pasture plants. Compensation for pasture loss If there are more than 300 larvae per square metre of pasture in March, substantial losses of pasture dry matter are likely to occur during autumn and winter. Numbers can reach 1,100 per square metre. Strategies to compensate for these losses include: sowing oats for forage early in the year; buying supplementary stock feed for autumn and winter; reducing livestock numbers early in the year; growing cash crops, such as cereals, peas, oilseed crops, to compensate for expected losses in income from livestock; in extreme situations, arranging for agistment of livestock. Tasmania (Hamlet et al. 2005): Remove dry pasture residue before autumn (through grazing or cutting hay) to reduce the habitat value for redheaded cockchafer beetles. When damage is noticed in mid-autumn, stock should be removed and the paddock spelled until late winter. This will help prevent all the ryegrass being uprooted by sheep and maintain maximum leaf area needed to re-establish root growth. Although supplementary feed may have to be bought to carry displaced stock over winter, the expense will usually be repaid in superior spring production from the infested paddock. Diversify feed sources away from total dependence on ryegrass pastures. Eg. Sowing some autumn forage crops, storing extra hay in anticipation of a winter feed shortage aggravated by pests, or sowing down some areas of cockchafer-tolerant pastures. Tolerant pasture species include phalaris, cocksfoot, tall fescue, lucerne and oats. 17
If conditions are not too boggy, rolling of the infested pasture can be beneficial since this helps the sward re-establish contact with the soil. Burying surface organic matter through ploughing kills newly hatched larvae. This must be done before May. 18
6. ACKNOWLEDGEMENTS This review was prepared as part of an Australian Government, Department of Agriculture, Fisheries and Forestry Advancing Agricultural Industries AgFund funded project awarded to GippsDairy, Victoria. I thank Ms Danielle Auldist from GippsDairy for arranging the review and her constructive support and advice throughout. I also thank the members of the project steering committee who offered much advice and information during the course of the review. The primary sources of information for the review was from searches of CABAB and AGRICOLA databases and other library and internet resources. I thank Dr Alan Yen, DPI Victoria for his help in undertaking this. I am also grateful for David Williams, DPI Victoria for reviewing the early drafts of the review and offering valuable advice. Finally I thank Greg O,Brien and Frank Mickan both from DPI Victoria, Dr Robin Bedding, ACT, Nigel Johnston, New Zealand, and Ms Brigid Watson, Victoria for providing additional information. 19
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Figures Figure 1 Eggs, larva and adult of redheaded pasture cockchafer (Courtesy DPI Victoria) Figure 2 Damage to pasture by foraging birds feeding on redheaded pasture cockchafer larvae (Courtesy DPI Victoria) 25
Figure 3 Life cycle of redheaded pasture cockchafer (Courtesy DPI Victoria - from Blackburn 1983) 26