Pests of Field Crops and Pastures: Identification and Control

By CSIRO PUBLISHING

This comprehensive handbook on economic entomology for Australian field crops and pastures is the first of its kind. It encompasses pests and beneficial insects as well as allied forms of importance in Australian agriculture.

Organised by commodities – such as cereals, sugar and tropical pasture legumes – it examines all the pest species for a particular commodity across Australia. Identification, distribution, damage, host range, biology, risk period and monitoring techniques are described for each entry, accompanied by useful illustrations. The book also describes introduced biological control agents that effectively control crop pests.

Pests of Field Crops and Pastures will be a useful tool in crop management for progressive farmers, agronomists, agricultural consultants and academics alike.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Oct 8, 2007
• ISBN: 9780643099425

Book preview

1

INTRODUCTION

This book aims to provide a comprehensive presentation of the main pest and beneficial species of insects and allied forms in the main field crops and pastures presently grown in Australia. ‘Allied forms’ are other arthropods and molluscs: invertebrates that are normally managed by similar methods as those of insects. ‘Beneficial species’ included are those predators and parasitoids which are known, or thought, to provide a level of control of pest species in crops and pastures. Also included are insects introduced to Australia for the biological control of weeds, and dung beetles introduced for the dual purposes of reducing bovine dung and the bush flies that breed in it.

Each of the main crops and pasture regions in Australia is presented as a separate chapter in which the identification, biology and management of pest and beneficial species are detailed. ‘Field crops’ are those grown under extensive cultivation, as distinct from horticultural crops that require more intensive cultivation methods. To keep this book to a reasonable size, it has been necessary to arbitrarily exclude crops such as potatoes, tomatoes and other vegetable crops which, although often grown in extensive field plantings, are usually regarded as horticultural crops.

Included are pests from areas where production of some crops has recently ceased. These crops include tropical rice and tobacco, and summer cotton grown in the Ord irrigation area of WA. Inclusion is justified on the basis that the considerable pest management information developed for these crops may be useful if these crops are again produced in tropical areas.

This book aims to present the best available knowledge on the identification, biology and management of crop and pasture pest and beneficial species. The authors are field biologists with experience in particular field crops and pastures. Some of the information presented in this book has been published in mainstream scientific books and journals, but most can be found in industry or regional publications such as ute guides, fact sheets and newsletters, or in the filing cabinets of government entomologists. As such, the basis of the information presented ranges from well-founded laboratory experiments and field trials to field observations and informed guesses by experienced field biologists. In practice, there may be little basis for preferring one over the other, especially in estimating ‘action levels’, choice of monitoring techniques or pest management techniques. The criterion for inclusion is what works best in the field.

Crop, pasture and rainfall regions

The main cropping and pastoral areas of Australia are shown in Figure 1.1 and the main rainfall divisions referred to in this book are shown in Figure 1.2.

Indicative crop areas quoted in this book are 5-year averages to 2002/2003 (Australian Bureau of Agricultural and Resource Economics 2005).

Layout of the book

In the chapters on insects of annual crops, the order of presentation of the insects is firstly related to the phenological stage of the crop in which they are first likely to cause damage (or in the case of beneficials, to exert control). Secondly, within each growth stage, insects are presented by taxonomic groups (all aphid species, for example, are presented together) in the order that they are presented in The Insects of Australia (CSIRO 1991). In the chapters on stored products insects and pasture insects, order of presentation is by taxonomic group alone.

For major pests and those with a widespread distribution, sufficient biological background is provided to enable rational decisions on their management. For insects that occur in a number of crops, a full biological background is given under the crop in which the insect causes most economic impact, while crop-specific information is provided in other crops in which it occurs. The format for a full entry is:

Fig. 1.1. Summer and winter rainfall areas of Australia. (Australian Bureau of Statistics)

Names of insects are generally consistent with those of the CSIRO Australian Insect Common Names website.

Distribution: Origin, present world distribution (by continent) and distribution in Australia.

Pest (or beneficial) status: (1) Major/moderate/minor; (2) widespread/restricted; or (3) regular/irregular.

Major: Failure to manage likely to result in significant economic loss.

Moderate: Failure to manage likely to result in some economic loss.

Minor: Damage may result in some economic loss.

Widespread: Occurs as a pest (or beneficial) over most of the range where crop is grown.

Restricted: Pest (or beneficial) in only part of the area where crop is grown.

Regular: Likely to be a pest (or beneficial) in most years.

Irregular: Not likely to be a pest (or beneficial) every year.

Identification: Size of insect. Distinctive colouration.

May be confused with: Any other organism or damage symptom with which the subject may be confused on the particular commodity.

Host range: Plants or insects (in the case of beneficials) eaten.

Fig. 1.2. Major Australian rainfall divisions. (Bureau of Meteorology, redrawn)

Life cycle on commodity: Number of generations each year, and number spent on the commodity.

Risk period: Stage of the crop and/or month(s) when the insect causes damage. (Beneficials: when they are effective.)

Damage: Symptoms and economic impact. (Beneficials: impact on pest.)

Monitoring: An indicative guide on techniques to detect significant populations of the species.

Action level: An estimate of the numbers, density, etc., at which it is cost-effective to apply control. Precision of estimates is likely to vary considerably between pest species and crops. The action level also depends on costs and the economic benefits of treatment. Action levels are provided as a guide only.

Chemical control*: Availability (including registration status) of chemicals is indicated, and whether application is cost-effective at the action level indicated.

‘Cost-effectiveness’ is an estimate based on:

• value of the crop

• cost of the chemical, including application cost

• effectiveness of the treatment

• ability of the crop to tolerate pest damage and still yield well

• prevalence and effectiveness of natural enemies.

No specific chemicals or chemical groups are mentioned other than to indicate chemicals to which resistance is recorded.

Cultural control: Includes cultural techniques, resistant varieties, and other techniques to avoid damage. May be omitted if no cultural control methods are in general use.

Conservation of natural enemies: An attempt has been made to include only those natural enemies that are effective in control on the particular commodity and whose conservation is likely to be of economic benefit. Since there is often a paucity of information to aid this judgement, natural enemies have generally been included where possible. This category may be omitted if little is known of the natural enemies of a particular pest.

*A note on registration and usage of agricultural chemicals in Australia

Registration of agricultural chemicals in Australia is the responsibility of the Commonwealth Government, presently through the agency of the Australian Pesticides and Veterinary Medicines Authority (APVMA). To be registered, an agricultural chemical must satisfy public health, food safety, occupational health and safety, environmental, trade and efficacy criteria.

Regulation of usage of agricultural chemicals is the responsibility of State and Territory Governments who, through various acts, regulate the use, storage, disposal and compliance with label instructions, including withholding periods. Pesticides acts between various states and territories are generally similar in objectives and content, but there are some differences. States may place additional restrictions on pesticide usage that further limit their registered use.

Pesticide usage may be further regulated by non-statutory means, such as area-wide resistance management agreements between farmers. Residue requirements more restrictive than those allowed for registration may be required by national and international commodity buyers. Farmers producing for organic and integrated pest management (IPM) markets may have restrictive contractual requirements for pesticide usage.

Sources of information used throughout this book

Australian Bureau of Agricultural and Resource Economics (2005). Crop Report No. 133, February 2005.

Australian Bureau of Statistics (1996). Australian Agriculture and the Environment. Catalogue no. 4606.0. Figure 2.31. p. 40

CSIRO. Australian Insect Common Names. <http://www.ento.csiro.au/aicn>.

CSIRO (1991). The Insects of Australia. Melbourne University Press, Melbourne

2

CEREALS

CEREALS—PESTS AND BENEFICIALS IN THE FIELD

D.C. Hopkins and G. McDonald

   Barley, Hordeum vulgare Poaceae. Origin: Asia, Europe

   Oats, Avena sativa Poaceae. Origin: Europe

   Rye, Secale cereale Poaceae. Origin: Europe

   Triticale, Triticosecale rimpaui Poaceae. Hybrid

   Wheat, Triticum

aestivum, and durum wheat, T. durum Poaceae. Origin: West Asia

(a) Tillering

(b) Wheat

(c) Barley

(d) Stubble

Phenology of a cereal crop in the south-eastern and southwestern grain belt. Time of sowing depends on opening rains.

Introduction

Cereals are grown mostly as dryland crops in the rainfall belt of 250 to 600 mm in NSW, southern Qld, SA, Tas., Vic. and WA. Wheat is the predominant cereal crop (approximately 12 M ha in 2004) then barley (3.5 M ha in 2004), oats (0.85 M ha in 2004) and triticale (0.34 M ha in 2004). Approximately 70% of the wheat and barley and 25% of the oats grown are exported, while triticale and rye are used domestically. Many of the pests of cereals are introduced exotic species (e.g. mites, snails and aphids) but some are native species (e.g. soil dwelling scarab, elaterid and tenebrionid beetles) that existed in woodland and grassland habitats prior to European settlement but now still occur in these same areas that have been cleared largely for grain and pasture production. In the Australian grain belt, cereals may be rotated with oilseeds, pulses and, less commonly, pastures.

PESTS OF ESTABLISHING CEREALS

Common white or vineyard snail

Cernuella virgata (Da Costa) Eupulmonata: Hygromiidae

Distribution: European–Mediterranean Basin in origin, now in Australia (Baker 1986), where it occurs in NSW, SA, Tas., Vic. and WA but is most prevalent in SA (Hopkins et al. 2003).

Pest status: Major, restricted, regular.

Identification: The diameter of the shell of a mature snail ranges from 10 to 15 mm. The coiled white shell has a brown band around the spiral in some individuals while others completely lack this banding. The umbilicus is open and circular (Fig. 2.1) (Hopkins and Miles 1998). Under magnification, regular straight scratches are visible across the shell.

May be confused with: The white Italian snail, Theba pisana. They can be separated by the differences in the umbilicus (Figs 2.1 and 2.3) and the scratchings/etches on the shell.

Host range: Includes field crops such as wheat, barley, oats, field peas, faba beans, canola and also pastures. It feeds mainly on organic matter on the soil surface but may damage young plants. It is an important pest because it contaminates grain crops at harvest and clogs and damages harvest machinery.

Life cycle on cereals: This species aestivates over summer by climbing on to crop stubble and residues, various weeds and fence posts to avoid high summer temperatures at the soil surface (Fig. 2.2). Autumn rains trigger activity down onto the ground, mating and egg-laying. Most eggs are laid in late autumn or early winter but some egg-laying continues through to early spring. Eggs hatch in about 2 weeks and immature snails grow steadily throughout the winter and spring before they aestivate through the next summer. It can have an annual or biennial life cycle.

Fig. 2.1. The shell of the common white snail (shell diameter 15 mm). Note the completely round hole (umbilicus) in the shell on the right. (SARDI: G.J. Baker)

Risk period: Cereals, particularly barley, and pulses and canola are susceptible to direct feeding damage shortly after crop emergence in the autumn. The risk of machinery clogging and grain contamination occurs at harvest.

Damage: Moderate to high densities of snails can cause serious defoliation of emerging barley, pulse and canola crops to the point where re-sowing of the worst-affected areas is necessary. At harvest, snails can clog and damage harvest machinery and cause frustrating delays in the harvest period. They can also contaminate harvested grain samples and lead to the downgrading of grain classification, or total rejection of the contaminated load at the point of delivery.

Monitoring: Successful management depends on regular monitoring of snail numbers across the whole farm. Square sampling quadrats (30 × 30 cm) can be placed on the ground, and snails counted and usually converted to numbers of snails per square metre. It is important to count only live snails; the shells of dead snails persist for many years and should be excluded from the count. As snails often move from adjacent roadside verges, it is important to also monitor these areas to assess the risk of snail movement in adjacent paddocks.

Fig. 2.2. Common white snail aestivating on a fence post. (SARDI)

Action level: In cereals, 20 per square metre or more at the time of crop-sowing.

Chemical control: A number of baits are registered for snail control. Controls should be applied prior to or immediately after seeding of cereals. The objective is to control adult snails prior to major egg-laying for the season and prevent major increases in numbers that pose a risk at harvest time later in the season. Use the label rate of bait for moderate snail numbers, but if snail densities exceed 80 per square metre this rate should be increased.

Cultural control: Stubble management (slashing, rolling or cabling) in January and February is an important control tactic for snails. Snails dislodged from stubble and crop residues onto the soil surface on hot summer days (maximum temperature greater than 35°C) may desiccate and die; snail numbers can be reduced by 50 to 70% using stubble management techniques. Burning stubble residues provides excellent snail control but should only be practiced where the risk of soil erosion is low and when burning is allowed. Burning may reduce snail numbers by up to 99%. Both of these cultural control tactics should be followed with baiting if snail numbers still exceed the established threshold levels.

Fig. 2.3. The shell of the white Italian snail (shell diameter 17 mm). Note the hole (umbilicus) in the shell on the right is half closed off. (SARDI: G.J. Baker)

Host-plant resistance: No host-plant resistance is recorded for cereals or other host plants.

Natural enemies: Apart from some predation by birds and lizards, there are no known natural enemies of the common white snail across southern Australia.

White Italian snail

Theba pisana (Müller) Eupulmonata: Helicidae

Distribution: An introduced species of European–Mediterranean Basin origin. Recorded from South Africa and Australia (Baker 1986), where it occurs in coastal areas of NSW, SA, Tas., Vic. and WA.

Pest status: Minor, restricted, regular.

Identification: The diameter of the shell of a mature snail ranges from 10 to 20 mm. The coiled white shell has a broken brown band around the spiral in some individuals, while others completely lack this banding. The umbilicus is semi-circular or partly closed (Fig. 2.3) (Hopkins and Miles 1998). Under magnification cross-hatched scratches/etchings can be seen on the shell.

May be confused with: The common white or vineyard snail, Cernuella virgata. It can be separated from this species by the different umbilicus (Fig. 2.1) and the scratchings on the shell, and sometimes by the nature of the banding around the spiral of the shell.

Host range: The white Italian snail occurs in a broad range of agricultural field crops and pastures including wheat, barley, oats, field peas, faba beans and canola. This species feeds on green plant material and organic matter and can cause significant damage to emerging crops and pastures. Like the common white snail, this species also contaminates grain crops at harvest and clogs and damages harvest machinery.

Life cycle, risk period, damage, monitoring, action level and control: The same as for the common white snail.

Natural enemies: Apart from some predation by birds and lizards, there are no known natural enemies of the white Italian snail across southern Australia.

Pointed snail

Cochlicella acuta (Müller) Eupulmonata: Hygromiidae

Distribution: An introduced species of European origin. Recorded from Australia (Baker 1986), where it occurs in NSW, SA, Vic. and WA, but is most prevalent on Yorke Peninsula in SA.

Pest status: Major, restricted, regular.

Identification: Fawn, grey or brown in colour with some white markings. The shell is conical in shape (Fig. 2.4). The length of the shell of a mature snail is up to 18 mm (Hopkins and Miles 1998). The ratio of the shell length to its diameter at the base is always greater than two.

May be confused with: Immature snails of this species may be confused with the small pointed snail, Cochlicella barbara. They can be separated using the ratio of the shell length to diameter.

Host range: This snail feeds on organic matter but has not been reported to damage crops. It is an important contaminant of grain, particularly barley on southern Yorke Peninsula in SA.

Fig. 2.4. Shell of the pointed snail (shell length 16 mm). (SARDI: G.J. Baker)

Life cycle on cereals: This species aestivates over summer by climbing onto crop stubble and residues, various weeds and fence posts to avoid high summer temperatures at the soil surface. Autumn rains trigger activity down onto the ground, mating and egg-laying. Most eggs are laid in late autumn or early winter but some egg-laying continues through to early spring. Eggs hatch in about 2 weeks and immature snails grow steadily throughout the winter and spring before they aestivate through the next summer. It can have an annual or biennial life cycle.

Risk period: This species causes major contamination of cereal crops, particularly barley, at harvest but should be controlled during January to April, before the crop is sown.

Damage: Unlike the common white and white Italian snails, this species does not damage emerging cereal crops and does not cause major clogging of harvesters. However, it passes through harvesting machines and contaminates harvested grain (Hopkins et al. 2003). If limits for snail contamination are exceeded, the load can be downgraded to a lower classification or totally rejected by the grain marketer.

Monitoring: Monitor using a square quadrat as for the common white snail.

Action level: No thresholds have been established for the pointed snail.

Chemical control: Use baits as for the common white snail. Baits are less effective against this snail as compared to the common white or white Italian snails.

Cultural control and host-plant resistance: The same as for common white snail.

Natural enemies: A parasitic fly, Sarcophaga penicillata, has been released as a biocontrol agent against this species (Fig. 2.5). Its establishment was confirmed in 2003 but its impact on the target species is yet to be assessed (Leyson et al. 2003).

Small pointed snail

Prietocella barbara (Linnaeus) Eupulmonata: Hygromiidae

Fig. 2.5. Sarcophaga penicillata (sarcophagid parasite) on the shell of C. acuta. (SARDI: N. Luke)

Distribution: An introduced species of European–Mediterranean Basin origin. Recorded from Australia (Baker 1986), where it occurs in NSW, SA, Tas., Vic. and WA.

Pest status: Minor, restricted, regular.

Identification: Shell is fawn, grey or brown in colour (Fig. 2.6). The length of the shell of a mature snail is up to 10 mm. The ratio of the shell length to its diameter at the base is always two or less (Hopkins and Miles 1998).

May be confused with: Immature pointed snails. They can be separated using the ratio of the shell length to diameter.

Host range: Organic matter and green plant material. It has mostly been recorded as a pasture pest in districts with greater than 500 mm annual rainfall. It may feed on cereals, pulses and canola but its pest status is as a contaminant of cereals and canola in higher rainfall districts in SA.

Life cycle on cereals: Annual or biennial life cycle. This species aestivates over summer by seeking refuge in clumps of grass or in soil cracks or climbing onto crop stubble and residues to avoid high summer temperatures at the soil surface. Autumn rains trigger activity, mating and egg-laying. Most eggs are laid in late autumn or early winter but some egg-laying continues through to early spring. Eggs hatch in about 2 weeks and immature snails grow steadily throughout the winter and spring before they aestivate through the next summer.

Fig. 2.6. Shell of the small pointed snail (shell length 8 mm). (SARDI: G.J. Baker)

Risk period: Germination and harvest. Control during January to April, before the crop is sown, avoids contamination of cereal and canola grain at harvest.

Damage: May defoliate cereals shortly after crop emergence. Snails pass through harvesting machines and contaminate harvested grain. If limits for snail contamination in grain samples are exceeded, the load can be downgraded to a lower classification or totally rejected by the grain marketers.

Monitoring: Monitor using a square quadrat as for the common white snail.

Action level: No thresholds have been established for the small pointed snail.

Chemical control: Bait as for the common white snail. Baits are less effective against this snail as compared to the common white or white Italian snails.

Cultural control: Stubble management and burning as for the common white snail.

Host-plant resistance: No host-plant resistance has been recorded for cereals.

Natural enemies: The parasitic fly released against the pointed snail also attacks this species.

Slugs

Eupulmonata: Limacidae

Black-keeled slug, Milax gagates Draparnaud and reticulated slug, Deroceras reticulatum (Müller)

   (Main entry in Chapter 5 Oilseeds.)

Pest status: Minor, restricted, irregular. Mainly pests in the high rainfall (> 500 mm p.a.) areas of the cereal zone, particularly on farms where stubble retention is practised.

Host range: Includes most crop and pasture plants. Can be significant pests of emerging pastures, pulses and canola and sometimes damages young wheat, oats and barley, particularly those direct-drilled into existing stubble.

Risk period: Cereals are most susceptible at or soon after crop emergence. Damage is more pronounced when seedling growth is slow due to cool wet weather.

Damage: Defoliation of seedling cereals.

Monitoring: The presence or absence of slugs can be monitored by providing a series of refuges for slugs, such as carpet, ceramic ties or damp hessian bags randomly placed across a paddock.

Action level: None established.

Chemical control: Use molluscicide baits in autumn to kill mature slugs before they commence the breeding cycle for the growing season and to protect seedling crops. Where slug densities are high, baiting may not prevent some damage.

Cultural control: No cultural techniques have been developed, although European experience suggests that heavy grazing of previous-crop stubbles during summer can reduce oversummering populations. The presence of stubble provides protected habitat, so windrowing of stubbles or cultivation may assist.

Host-plant resistance: No resistant cereal varieties are available.

Natural enemies: Predatory ground beetles (Family Carabidae) prey on slugs.

Blue oat mites

Acarina: Penthaleidae

Penthaleus major (Dugès), P. falcatus (Qin and Halliday) and P. tectus Halliday

Distribution: Cosmopolitan distribution, unknown origin. Presently found in Europe, the Americas, Asia, South Africa, New Zealand and Australia. In Australia, P. major has a wider distribution than the redlegged earth mite, occurring across many areas of southern Australia including southern NSW and Qld, SA, Vic., Tas. and WA. The range of P. falcatus appears to overlap with that of P. major, but P. tectus appears to have a discontinuous and restricted distribution in parts of NSW and Vic. (Robinson and Hoffmann 2001).

Pest status on cereals: Major, widespread, except for P. tectus, which has a restricted distribution, irregular.

Identification: Adult mites are about 1 mm long with a blue–black body, red legs and a red mark on the back (Fig. 15.35). The three species are difficult to distinguish in the field but may be distinguished under a microscope by the length and position of the hairs on their back. P. major has comparatively long hairs running in four or five longitudinal rows down the mite’s back. P. falcatus has short hairs covering the back of its body. P. tectus has short hairs on the anterior of its body and longer hairs running in longitudinal rows on the posterior of its body.

May be confused with: Blue oat mites appear similar in size and colour to the redlegged earth mite, but blue oat mites may be distinguished by a red dot on their backs (Fig. 15.35). Blue oat mites are generally seen feeding singularly or in small groups, whereas redlegged earth mites generally feed in larger groups. Blue oat mites prefer grasses and cereals, whereas redlegged earth mites prefer the legume and capeweed content of pastures (Robinson and Hoffmann 2001; Umina et al. 2004).

Hosts: Mainly a pest of cereals and grass pastures, but will also feed on pasture legumes and many weeds, including capeweed.

Life cycle on winter rainfall cereals and grassy pastures: Blue oat mites are active in the cool wet months from May to November. The first generation develops from oversummering eggs after the onset of favourable conditions of moisture and temperature, usually around April–May. They hatch into six-legged larvae that develop through two nymphal stages into adults. Both nymphs and adults have eight legs. During the winter, the mites pass through two generations on average, each lasting about 11–12 weeks. When conditions are favourable their populations can increase rapidly, with peaks in autumn and/or spring. Females of both generations lay winter eggs, usually on leaves, stems or roots of food plants. Unlike the redlegged earth mite, both generations of blue oat mite are able to produce diapause (oversummering) eggs, beginning soon after emergence in autumn. However, most of the diapause eggs are produced in spring. The eggs are not retained inside the body of the mite as with redlegged earth mite but are laid on food plants. In late spring, when temperatures increase and the pasture begins to senesce, the mites die. The oversummering eggs remain on the vegetation throughout the summer months (Narayan 1962).

Risk period: Autumn, particularly shortly after crop emergence.

Damage: Silvering of leaves is symptomatic of damage.

Monitoring: At crop emergence look for the presence of mites, being careful to distinguish the blue oat mite from the redlegged earth mite. Accurate identification is important for the selection of appropriate control strategies (Umina and Hoffmann 2004).

Action level: No action thresholds have been established for cereals but any evidence of mite activity indicates potential damage.

Control: Foliar applications of insecticides may be cost-effective, particularly if applied within 2–3 weeks of emergence in the autumn. Penthaleus spp., particularly P. falcatus, are often more tolerant of insecticides than redlegged earth mite (Robinson and Hoffmann 2001). In addition, the use of control tactics solely in spring will not prevent the carry-over of all eggs into the following autumn, unlike with the redlegged earth mites.

Redlegged earth mite

Halotydeus destructor (Tucker) Acarina: Penthalaeidae

   (Main entry in Chapter 15 Pastures—winter rainfall.)

Pest status: Major, widespread and irregular pests of cereals. Pest status is greater if cereals are grown in rotation with legume pastures.

Damage: The damage of this species and blue oat mite species is similar. Separate these two mite genera by using the presence (blue oat mites) or absence (redlegged earth mites) of a small red marking in the middle of the back (Fig. 15.35).

Host range: Will damage all cereals but cannot survive or reproduce on them (McDonald et al. 1995).

Risk period: Autumn to spring, but especially at crop emergence.

Monitoring: Close monitoring after crop emergence is required to achieve well-timed treatments. Estimate the numbers of mites in 10 cm × 10 cm squares around the base of plants. Repeat at five to 10 sites across the paddock. Avoid sampling in sunny conditions; sample on cloudy days, early morning or late afternoon. Mite damage is typically greater around the edge of paddocks.

Action level: For cereals, treatment is usually warranted at the seedling stage if there are 50 or more mites per 100 cm² (10 × 10 cm).

Chemical control: Bare earth treatments for this pest in autumn are not warranted for cereals. Foliar sprays are cost-effective. In pasture-crop rotations, control in the spring in the pasture phase may remove the need for control in the following cereal crop. The TIMERITE® model is designed to determine the best time for spring treatments.

Cultural control: Pest pressure in autumn may be reduced using crop rotations that include lentils or lupins prior to cereals (McDonald et al. 1995), or alternatively heavy spring grazing, cultivation, clean fallowing and destruction of weeds prior to cereals.

Natural enemies: See Chapter 15.

Lucerne flea

Sminthurus viridis (Linnaeus) Collembolla: Sminthuridae

   (Main entry in Chapter 15 Pastures—winter rainfall.)

Pest status on cereals: Major, widespread and irregular.

Host range: Includes all cereals.

Life cycle on cereals: Similar to that on winter rainfall pastures (Chapter 15).

Risk period: Autumn to spring, but especially at crop emergence. Pest risk is greatest if cereals are grown in rotation with legume pastures. Bare earth pyrethroid treatments for redlegged earth mite in the preceding canola or pulse crop may increase the pressure of this pest in the current cereal crop.

Damage: Lucerne flea damage appears as thin, transparent windows on the leaf and is sometimes confused with that of the redlegged earth mite that appears as a silvering of the leaf surface.

See more detail under Chapter 15.

Monitoring: Monitor for 3–4 weeks after crop emergence.

Action level: No thresholds have been developed for cereals.

Chemical control: Foliar insecticides are cost-effective.

Cultural control: No cultural control is available in cereal crops.

Host-plant resistance: No resistant varieties of cereals are available.

Natural enemies: See Chapter 15.

Sandgroper

Cylindracheta psammophila Orthoptera: Cylindrachetidae

Distribution: Native to WA.

Pest status: Minor, restricted mainly to the sandy coastal areas north of Perth, irregular (Woods and Michael 1987).

Identification: Sandgropers remain under the soil surface and are only seen when soil is worked or dug. The front section of the body is hard and orange–brown, whereas the remainder of the body is soft and cream-coloured (Fig. 2.7). The body is cylindrical in shape and up to 75 mm long. The front legs are flat and strong and adapted for digging. Young sandgropers are similar to the adult except they are smaller and paler.

Fig. 2.7. Sandgroper (body length 75 mm), an occasional pest of WA cereals. (DAFWA)

May be confused with: Mole crickets, from which they are distinguished by the orange–brown front part of the body.

Host range: Includes wheat, barley and sweet lupins.

Life cycle on cereals: Adults probably survive the summer deep in the soil. Eggs are probably laid in autumn as immatures are often seen during winter.

Risk period: Autumn and winter.

Damage: Sandgropers attack the underground portion of the stem, and to a lesser extent the roots, giving them a characteristic shredded appearance. Damaged plants turn yellow, wither and die, giving rise to bare or thinned patches in the crop (Fig. 2.8).

Monitoring: Look for yellow or wilting plants. Digging in soil may lead to detection of this pest.

Action level: None available.

Chemical control: No insecticidal control measures have been developed.

Cultural control: Autumn fallowing for several weeks can reduce numbers but may be insufficient to prevent damage.

Host-plant resistance: If monitoring detects a heavy infestation is present in a paddock, it may be advisable to sow oats which are less susceptible to attack.

Natural enemies: None recorded.

Corn aphid

Rhopalosiphum maidis (Fitch) Hemiptera: Aphididae

Distribution: An introduced species, probably Asiatic in origin, found in all states of Australia.

Fig. 2.8. Part of a wheat crop thinned by sandgroper feeding on underground parts of plants. (DAFWA)

Fig. 2.9. A colony of corn aphids on a maize leaf. Each aphid has two siphunculi protruding from its abdomen. Each siphunculus has a purple area at its base, characteristic of corn aphids. The largest, adult, aphid is 2 mm. White skins are moulted casts. (SARDI: G.J. Baker)

Pest status: Minor, widespread, irregular.

Identification: Colour varies from light green to dark olive green with two dark-coloured areas near the base of the cornicles at the tip of the abdomen (Fig. 2.9). Adults are approximately 2 mm long.

May be confused with: Oat aphid but can be separated using an antennal feature (Fig. 2.10). The terminal process of the sixth antennal segment of the corn aphid is about twice as long as the basal portion, whereas in the oat aphid it is about four to five times as long (Hopkins 1987).

Host range: Grasses and cereals including wheat, oats, barley, millet, corn and sorghum. Common on barley across southern Australia.

Life cycle on cereals: A parthenogenetic species that undergoes many generations through the growing season. Both alate (winged) and apterous (non-winged) forms occur.

Risk period: Most prevalent on cereals in late winter to early spring. High numbers often occur in years when an early break to the season and mild weather in autumn and early winter provide favourable conditions for colonisation and multiplication.

Damage: Aphids feed directly on stems, leaves and heads, and in high densities cause yield losses. However, this type of damage is uncommon throughout the cereal belt.

Fig. 2.10. Adult corn and oat aphids and detail of antennae. The antennal segment VI of the corn and oat aphids have different ratios of the length of the terminal process to the length of the basal portion; about 2:1 for corn aphid and 4 or 5:1 for oat aphid.

Corn aphids are vectors of barley yellow dwarf virus (BYDV), a disease of wheat, oats and barley (Fig. 2.11). Yield losses due to BYDV can be severe, particularly in oats and to a lesser degree in wheat. Losses due to BYDV are most severe in the wetter parts of the cereal belt (rainfall > 500 mm p.a.).

Monitoring: Assess the potential for direct-feeding damage in late winter. Estimate the number of aphids per tiller. In areas of high risk for BYDV, prediction models may assist in deciding whether to use insecticidal seed dressings or early season insecticide applications to reduce or prevent yield losses by BYDV.

Fig. 2.11. (a) Depressed patch in an oat crop with reddened leaves, typical of the secondary spread of BYDV (left) (UnivAd: J. Randles), and (b) the wheat plant on the right is stunted by BYDV compared with a healthy plant on the left (CSIRO: N. Grylls).

Action level: Aphids are unlikely to cause economic damage to cereal crops expected to yield less than three tonne per ha. To avoid direct-feeding damage, consider treatment if there are 10 to 20 or more aphids on 50% of the tillers. There is no threshold for aphid transfer of BYDV.

Chemical control: Apply a foliar insecticide in late winter or spring to avoid direct damage to tillers and heads. To prevent major losses from BYDV in virus-prone areas, control aphids early in the cropping year. Use a seed dressing and apply foliar treatments at 4 and 8 weeks after sowing. Foliar treatments with registered pyrethroids provide extended protection through an anti-feedant effect.

Cultural control: There are no known effective cultural control methods for this aphid.

Host-plant resistance: In virus-prone areas, use resistant plant varieties to minimise losses due to BYDV.

Natural enemies: Predation by hoverflies (Fig. 2.12c), lacewings and ladybirds and parasitism by wasps (Fig. 2.12b) can suppress aphid populations, but this does not happen in every season. Heavy rain may cause significant mortality of aphid populations.

Oat or wheat aphid

Rhopalosiphum padi (Linnaeus) Hemiptera: Aphididae

Distribution: Probably Palaearctic in origin and now cosmopolitan. An introduced species found in all states of Australia.

Pest status: Minor, widespread, irregular.

Identification: The oat aphid varies in colour from olive-green to black and has a rusty red area around the tip of the abdomen (Fig. 2.12a). Adults are approximately 2 mm long.

May be confused with: The corn aphid, from which it can be readily separated using an antennal feature (Fig. 2.10). The terminal process of the sixth antennal segment of the oat aphid is about four to five times as long as the basal portion, whereas in the corn aphid it is about twice as long.

Fig. 2.12. (a) A wingless adult oat aphid (body length 2 mm) (SARDI: G.J. Baker), (b) a parasitised aphid (mummy) to the right of which is an unparasitised aphid (VDPI), and (c) larva of a hoverfly in a colony of cereal aphids (SARDI: G.J. Baker).

Host range: Includes all major cereal and pasture grasses including wheat, oats, barley, sweetcorn and phalaris. Occurs mainly on oats and wheat in Australia.

Life cycle, risk period, damage, monitoring, action level and control: Similar to the corn aphid.

Rose-grain aphid

Metopolophium dirhodum (Walker) Hemiptera: Aphididae

Fig. 2.13. Rose-grain aphid (body length 3 mm). (SARDI: G.J. Baker)

Distribution: Recorded from NSW, Qld, SA, Tas. and Vic. It is an introduced species that was first recorded in the country in 1984 (Carver 1984). Elsewhere in the world it is found in Europe, Central and West Asia, North and South America and New Zealand.

Pest status: Minor, restricted, irregular.

Identification: A green or yellowish-green aphid. Adults are about 1.6–3.3 mm long (Fig. 2.13).

May be confused with: Unlikely to be confused with other aphid species on cereals because of its distinctive colour.

Host range: Many species of grasses and cereals including wheat, oats and barley.

Damage: The rose-grain aphid rarely damages cereals but can transmit BYDV.

Life cycle, risk period, monitoring, action level and control: Similar to the corn aphid.

Blackheaded pasture cockchafer

Acrossidius tasmaniae Hope (= Aphodius tasmaniae) Coleoptera: Scarabaeidae

Distribution: A native species found in NSW, SA, Tas. and Vic.

Pest status: Minor, restricted, irregular.

Identification: The larvae are white C-shaped grubs with a black or dark brown head capsule. Mature larvae are about 20 mm long (Fig. 15.8). The beetles are black and about 10 mm long (Fig. 15.9).

May be confused with: This is the only cockchafer species that is likely to damage cereals and whose larva has a black head capsule. It is also the only surface-feeding scarab larva found in cereals.

Host range: May damage cereals in higher rainfall cropping districts (approximately 450 mm annual rainfall or greater). More important as a pest of pastures.

Life cycle on cereals: Adult beetles are active in late January to March after rain (Allen 1986a). Oviposition occurs during this period and young larvae feed on surface organic matter at night. By the time the cereal crop is sown in autumn, second-instar larvae tunnel in the soil and will surface to defoliate young seedlings. The larvae feed right through the growing season and pupate in December. The next generation of beetles emerges early the following year (January–March). For more details on life cycle, see Chapter 15.

Risk period: Seedling stage.

Damage: Larval movement to the soil surface at night is triggered by rainfall. They defoliate the young cereal seedlings and take the severed foliage into their soil tunnels before eating.

Monitoring: Monitor for the larval stage by taking soil cores to a depth of about 10 cm. Take five to 10 soil cores to estimate the grub density.

Action level: Apply chemical control after crop emergence if grub densities exceed 30 per square metre.

Chemical control: Some pyrethroid insecticides are registered for control of blackheaded pasture cockchafer larvae. The insecticide must be applied to the foliage of cereal seedlings to be effective. Treatments prior to crop emergence are not likely to be effective.

Cultural control: Good pasture cover during summer may deter blackheaded pasture cockchafer beetles from laying their eggs.

Host-plant resistance: No resistance cultivars are known.

Natural enemies: See Chapter 15 Pastures—winter rainfall.

White curl grubs (scarab grubs)

Coleoptera: Scarabaeidae

Yellowheaded cockchafer, Sericesthis harti (Sharp)

Wheat root scarab, S. consanguinea (Blackburn)

Black soil scarab, Othnonius batesii Olliff

Cockchafer, Heteronyx obesus Burmeister

Distribution: S. harti is the main species affecting SA cereal crops (Allen 1986c), S. consanguinea and O. batesii in NSW (Goodyer 1993) and H. obesus in WA (Emery and Szito 1999).

Pest status: Minor, restricted, irregular.

Identification: The larvae have yellow head capsules and grow up to 40 mm long (Fig. 2.14). The body of the larva is whitish grey when it is feeding and changes to white before pupation.

Fig. 2.14. (a) Larva of yellowheaded cockchafer, Sericesthis harti (body length 25 mm) (SARDI: G.J. Baker), and (b) larvae of Heteronyx obesus (body length 20 mm) (DAFWA).

Fig. 2.15. (a) Beetle of yellowheaded cockchafer (body length 11 mm) (SARDI: G.S. Dearman), and (b) beetles of Heteronyx obesus (DAFWA).

Larvae curl into a C-shape when disturbed. Adults are light to dark brown, chunky beetles up to 11 mm long (Fig. 2.15).

May be confused with: Separation of pest species (both adults and larvae) is difficult. In addition, large numbers of non-pest species of curl grubs (e.g. H. elongatus may occur with H. obesus) may be found in cereals. Identifications should be confirmed by a specialist.

Host range: Larvae feed on the roots of a broad range of crop and pasture plants that include all cereals.

Life cycle on cereals: These species may have 1- or 2-year cycles. S. consanguinea has a 1-year life cycle. O. batesii and H. obesus have 2-year life cycles. Adults of H. obesus begin to emerge in November and swarm around, and feed on, eucalypt trees for about 2 hours after sunset during warm evenings between December and March. Beetles mate and lay eggs in adjoining paddocks. Eggs hatch in May and survive as small grubs, causing little damage, until the following year when they move to the soil surface to feed on roots of germinating cereals (Emery and Szito 1999). S. harti probably has a 2-year life cycle similar to that of H. obesus.

Risk conditions: Crops following several years of pasture are most susceptible. Third-instar larvae feeding during winter and early spring cause the most damage.

Damage: Larvae prune the roots of young cereal plants by actively feeding on the roots or damaging them while foraging for soil organic matter. Damaged plants initially grow normally but wither and die at tillering resulting in bare patches in the crop.

Monitoring: Monitor for larvae in the soil prior to sowing. White curl grubs are usually in the top 50 mm of moist soil, and birds following the tractor in pre-seeding cultivations are often a sign of the presence of cockchafers. Take soil samples using a soil auger or a spade to a depth of 10 cm and determine the number of larvae per m².

Action level: Treatment is warranted when there are five or more Sericesthis larvae per square metre or two or more Othnonius per square metre. Twenty H. obesus grubs per square metre can cause visible damage, while more than 50 grubs per square metre will destroy crops (Emery and Szito 1999).

Chemical control: Can only be achieved by incorporating insecticides at sowing. If the pest is not detected before seeding and treated, it may be necessary to re-sow damaged areas using an insecticide.

Cultural control: Rotations that include intensive cropping or short pasture/crop phases can be used to avoid damage. Current trends to continuous cropping have reduced the pest status of this pest group.

Host-plant resistance: No resistant cultivars are available.

Natural enemies: There are no known natural enemies that are effective against white curl grubs.

Spinetailed weevil or cereal curculio

Desiantha caudata Pascoe Coleoptera: Curculionidae

Distribution: A native weevil recorded from NSW, SA and Vic.

Pest status: Minor, restricted, irregular. Became a pest when tillage practices changed during the 1950s from long-term spring-prepared fallows to short-term autumn-prepared fallows allowing adults to survive the shorter fallow period (Hopkins 1996). Further changes to rotations in the 1990s to continuous cropping have seen this species decline in pest status.

Identification: The soil-dwelling larvae are white legless grubs up to 8 mm long with golden head capsule (Fig. 2.16). Adults are greyish-black beetles up to 7 mm long with a definite weevil snout. The female has two spines on the tail end of the body (Fig. 2.17).

May be confused with: The larvae of the spinetailed and spotted vegetable weevils can only be distinguished by microscopic examination of the spiracles (May 1977).

Host range: Pasture grasses and all cereals and some weeds.

Life cycle on cereals: One generation per year. Sexually immature adults emerge from the soil in November, feed on early summer annual weeds and then shelter under stones or clods of soil during summer. Autumn rain stimulates the adults to resume feeding, to mate and to begin laying eggs. The adults are flightless and lay eggs close to where they emerge. The larvae hatch in 2–3 weeks and feed on germinating grass (or cereal) seed or seedlings. Larvae can also feed on soil organic matter. The larvae feed during winter and spring. Larvae pass through five instars and pupate in the soil during October or early November. Generally, this species needs 3 or more years of consecutive grass dominant pastures to build up to damaging numbers prior to a cereal crop (Allen 1973).

Fig. 2.16. Larva of spinetailed weevil (body length 8 mm). (SARDI: G.S. Dearman)

Fig. 2.17. Female (left) and male (right) beetles of the spinetailed weevil (body length 7 mm). (SARDI: G.S. Dearman)

Risk period: Following sowing.

Damage: The larvae can attack cereal plants at three different stages: they may eat out swelling seeds soon after sowing; they may bore onto the underground part of the stem of seedlings causing them to wither and die; or they may bore into tillers causing them to wither and die. Seed or plant deaths result in thinned or bare patches in the crop.

Monitoring: Monitor for larvae using soil sampling prior to seeding. Count the number of larvae by examining soil in a 30 × 30 cm quadrat to a depth of 10 cm. Repeat at five to 10 random sites throughout the paddock.

Action level: Treatment is warranted if there are 10 or more larvae per square metre.

Chemical control: Control of larvae can only be achieved with a seed dressing. As significant larval feeding can occur before the seed dressing causes larval mortality, higher than normal seeding rates may be required for high-density infestations. If there are 100 or more larvae per square metre, use a seeding rate of about 95 kg/ha to compensate for the damage caused before the larvae are killed.

Cultural control: Short pasture phases of 1–2 years in rotations with cereals or continuous cropping of cereals, pulses and oilseeds helps avoid damage.

Host-plant resistance: No resistant varieties are available.

Natural enemies: Soil dwelling pathogens such as the fungus Beauvaria may kill some larvae.

Spotted vegetable weevil or maculate weevil

Desiantha diversipes (Pascoe) Coleoptera: Curculionidae

Distribution: A native weevil recorded from NSW, SA, Tas., Vic. and WA. Also recorded in New Zealand.

Pest status: Minor, restricted, irregular. Unlike the spinetailed weevil, this species can cause damage to successive crops (Hopkins 1996).

Identification: Adults are distinctly mottled black–grey beetles up to 7 mm with a definite weevil snout (Emery et al. 2005). The female has no spines on the tail end of the body as for the spinetailed weevil (Fig. 2.18). The larvae are very similar to those of the spinetailed weevil.

May be confused with: The larvae of this species and the spinetailed weevil require microscopic examination of spiracles to separate the species.

Host range, life cycle, risk period, damage, monitoring, action level and controls: Similar to the spinetailed weevil.

Wireworms

Coleoptera: Elateridae.

Agrypnus sp.

Fig. 2.18. Beetle of spotted vegetable weevil (body length 7 mm). (VDPI)

Arachnodima bribbarensis (Calder)

A. xenikon (Calder)

A. opaca Candèze

A. ourapilla (Calder)

Distribution: Wireworm pests of Australian cereals are native species recorded damaging wheat and barley in NSW and SA (Calder 1996).

Pest status: Minor, restricted, irregular.

Identification: Wireworm larvae have soft semi-flattened, smooth creamy white or pale bodies with darker wedge-shaped heads and forked smooth or tooth-edged tails (Fig. 2.19). Arachnodima has paired tail processes, each with two spurs (Fig. 2.19). Agrypnus has a flattened tail plate with spurs around the perimeter (Fig. 2.20). When fully grown, larvae are 25 mm (Agrypnus) and 15 mm (Arachnodima) long.

Fig. 2.19. Larvae of the wireworm Arachnodima sp. (preserved and not true colour) (body length 12 mm). The body is soft and semi-flattened with a wedge-shaped head and six legs. Arrows point to paired tail processes. (SARDI: G.J. Baker)

Wireworms: true and false

Wireworms are named for the supposed wirelike appearance of their larvae. False wireworms belong to the Family Tenebrionidae, the adults of which are dark beetles and may be elongate to oval (‘pie dish’) in shape. True wireworms belong to the insect Family Elateridae. The adults are elongate beetles that jump and click when disturbed. There are numerous species (named and unnamed) of both true and false wireworms, but only a few are recorded as crop pests.

Beetles are brown or black, torpedo-shaped and 15 mm (Agrypnus) and 10 mm (Arachnodima) long. They also have enlarged pronotums with sharp posterior corners. When laid on their backs they can flex their bodies and flip onto their feet. This action is often accompanied by a clicking sound, hence the common name ‘click beetles’.

May be confused with: Wireworm larvae can be confused with false wireworm larvae.

Fig. 2.20. Tail end of Agrypnus sp. (a) viewed from above and (b) from the side, showing flattened tail plate and spurs. (SARDI: G. Caon)

Wireworm larvae have flattened heads while false wireworms have round heads in cross-section. Wireworms may also be confused with the larvae of predatory carabid beetles. However, carabid larvae have enlarged mandibles and a prominent fleshy process on the tail, whereas wireworm larvae have smaller mandibles and a flattened process with short spines, or just forked processes (e.g. Fig. 2.20).

Host range: Includes wheat, barley, triticale and oats.

Life cycle on cereals: Probably one generation per year; life cycles are not well understood. Larval stages are usually present through autumn and winter.

Risk period: At seeding or shortly after crop emergence.

Damage: Wireworm larvae feed on the seed and bore into the underground stem of the cereal plants causing them to wither and die (Goodyer 1993). Damage causes thinned crops or bare patches in the crop. Damage usually occurs following long pasture phases of 4–5 years.

Monitoring: Monitor for larvae during pre-seeding cultivations or use a spade to take soil samples to a depth of 10 cm to inspect for larvae.

Action level: 40 or more larvae per square metre warrant treatment.

Chemical control: Wireworms can only be controlled if they are detected before sowing. Crops can be protected by sowing treated seed or mixing insecticide with fertiliser at seeding.

Cultural control: Wireworm numbers can be substantially reduced by clean cultivating in summer and autumn. This discourages egg-laying by the adults and kills the young larvae by desiccation and starvation. Rotations including continuous cropping or short pasture phases often reduce wireworm damage.

Host-plant resistance: No resistant cereal cultivars.

Natural enemies: Birds feeding on wireworm larvae after cultivation which brings them to the surface. The presence of birds on newly worked ground can often indicate approaching problems with false wireworms or wireworms. Soil-dwelling larval stages of predatory carabid beetles prey on false wireworms and wireworms.

False wireworms

Coleoptera: Tenebrionidae

    (Main entry in Chapter 5 Oilseeds.)

The main species of false wireworms recorded as pests in the cereal belt include: eastern false wireworm, Pterohelaeus darlingensis; pie-dish beetle, Helea tuberculata; southern false wireworm, Gonocephalum macleayi and Gonocephalum spp.; striate false wireworm, Pterohelaeus alternatus; grey false wireworm, Isopteron punctatissimus; and bronzed field beetle, Adelium brevicorne and Saragus sp.

Pest status in cereals: Minor, restricted, irregular.

Identification: See Chapter 5.

Life cycle on cereals: Larval stages present from autumn to spring and adults aestivate over summer.

Risk period: At seeding or shortly after crop emergence.

Damage: False wireworm larvae feed on the seed and bore into the underground stem of the cereal plants causing them to wither and die. They may also damage roots, causing thinned crops or bare patches in the crop. This usually occurs following long pasture phases of 4–5 years. Some false wireworms, Isopteron and Pterohelaeus, survive through continuous cropping by feeding on stubble mulch.

Monitoring: Monitor for larvae during pre-seeding cultivations or use a spade to take soil samples to a depth of 10 cm to inspect for larvae. In Qld and Vic., the use of germinating seed baits is recommended (see Glossary).

Action level: Treatment is only warranted if larvae are present in large numbers. Treat if there are 10 or more Pterohelaeus, Helea or Saragus or 50 or more Isopteron larvae per square metre. These thresholds do not apply to Gonocephalum sp. where threshold numbers are probably higher. If using germinating seed baits, treatment is recommended if there are more than 25 southern false wireworm larvae per 20 baits (Elder et al. 1992).

Chemical control: False wireworms can only be controlled if they are detected before sowing. Use insecticides mixed with fertiliser at seeding or insecticides sprayed on the soil surface and worked into the soil prior to seeding.

Cultural control: Rotations including continuous cropping or short pasture phases may reduce and often eliminate false wireworm damage of some species. Eliminating food and shelter for beetles over summer (various stubble management techniques) can reduce false wireworm problems. Use of press wheels or rolling at planting is recommended in Qld and Vic. High seeding rates can also offset the effects of moderate infestations.

Host-plant resistance: No resistant cereal cultivars.

Natural enemies: Birds feed on false wireworm larvae after cultivation brings them to the surface. The presence of birds on newly worked ground can often indicate approaching problems with soil-dwelling beetles such as false wireworms or wireworms. Soil-dwelling larval stages of predatory carabid beetles are recorded to prey on false wireworms and wireworms.

Black cutworm

Agrotis ipsilon (Hufnagel) Lepidoptera: Noctuidae

Distribution: A. ipsilon is a cosmopolitan species. The subspecies A. ipsilon aneituma (Walker) occurs in Papua New Guinea, Australia, New Zealand and some Pacific islands (Common 1993). In Australia, the subspecies is recorded from NSW, Tas., Vic. and WA.

Pest status: Minor, restricted, irregular.

Identification: Larvae are black, green–brown or grey without distinct hairs or markings and have a greasy appearance. Body is faintly striped or without stripes (Fig. 2.21). Larvae grow up to 40 mm long. The forewing of the moth is pale purplish-brown, brown or grey–black, always with a pale brown patch towards the tip and a blackish, wedge-shaped mark extending from the outer edge of the large, dark kidney-shaped spot near the centre (Goodyer 1985) (Fig. 2.22). The wingspan ranges from 30 to 50 mm.

Fig. 2.21. Black cutworm larvae (20–30 mm extended). (DPI&F Qld: J. Wessels)

May be confused with: The larvae may be confused with those of the common cutworm. The granules on the skin of black cutworm are slightly raised whereas those on common cutworm are flattened.

Host range: Cereal, pulse and pasture grasses and a number of weed species.

Life cycle on cereals: Several overlapping generations per year. Eggs are laid in cracks in the ground and also on vegetation (Williamson and Potter 1997). Eggs laid on the ground may survive tillage, and survival is increased in low or minimum-tillage culture. There is evidence of long-range migration of adults.

Risk period: Black cutworm is most damaging during spring and autumn.

Fig. 2.22. Adult black cutworm (wingspan 50 mm). (DPI&F Qld: J. Wessels)

Damage: Recorded as damaging wheat, oats and barley. The damage symptoms are similar to those of common cutworm. Also damages turf.

Monitoring: Larvae hide under clods of soil or bury themselves in soil and may be difficult to find. Examine plants, soil litter and soil surface in a 0.5 m row in at least 10 sites spread evenly through the crop.

Action level: Treatment of cereals is warranted if there are two or more larvae per 0.5 metre of row.

Chemical control: Sprays of pyrethroid insecticides are effective against this cutworm, particularly during early- to mid-instars.

Host-plant resistance: No cereal varieties are known to be resistant to cutworm damage.

Natural enemies: Parasitic braconid and ichneumonid wasps have been reared from the larval stages of this species.

Brown or pink cutworm

Agrotis munda Walker Lepidoptera: Noctuidae

Distribution: A native species, recorded from NSW, SA, Tas., Vic. and WA.

Pest status: Minor, restricted, irregular. Outbreaks are usually patchy. In SA, major outbreaks in cereals occur about 1 in 10 years, affecting tens of thousands of hectares (Hopkins 1982).

Identification: Mature larvae grow up to 40 mm long, are greyish-green to brown and often with a reddish tinge, and generally have a