The forums are being held at two locations on Thursday the 28th of July:

The  Dalby RSL:  9am – 11.30am

and

The Brookstead Hall:  1.30pm – 4.00pm

 Topics and presenters

 Cotton Bunchy top     

(Murray Sharman – DEEDI Virologist,  Lewis Wilson – CSIRO Entomologist, Jeff Werth – DEEDI weed scientist)

After the prevalence of cotton aphids and cotton bunchytop in some parts of the Downs, now is the time to start thinking about how to reduce aphid populations and remove sources of bunchytop that may otherwise invade your cotton crops next season. 

Seedling pests of cereals 

 (Hugh Brier – DEEDI Entomologist)

 Winter and spring crops are susceptible to a host of establishment pests, and cool and wet conditions can exacerbate the damage they cause. Learn what might be a problem this season, and how to identify the pest and its damage, and what you can do to control or manage the problem. Hugh will run through the common, and not-so-common, establishment pests.

Pest suppressive landscapes

  (Nancy Schellhorn - CSIRO Entomologist  and Jamie Hopkinson – DEEDI Entomologist)

Ever wondered whether the trees and shrubs along the creek, or in that nearby reserve were harbouring beneficial insects that might be benefitting your crops? Well, this is the focus of research being undertaken on the Downs, in NSW and WA. Nancy Schellhorn is leading a project that is examining the relationship between remnant vegetation and pest and beneficial abundance to answer questions about the role of this vegetation in the agricultural landscape.

Minimising the risk of a Solenopsis Mealybug outbreak 

 (Melina Miles,  DEEDI Entomologist)

You may have heard about the mealybug outbreak in Emerald cotton two seasons ago. You may be wondering if this new pest is coming your way. Melina has been involved in preliminary work on this pest, and will discuss some key management and monitoring strategies to minimise the likelihood of an outbreak in your crops.

For more information contact Melina Miles at the Toowoomba DEEDI office on 4688 1369, or 0407113306.  

Morning and afternoon tea will be provided. For catering purposes please RSVP to melina.miles@deedi.qld.gov.au

 Scarab damage in barley crop at Jandowae.  The severely damaged crop area on the right was under pasture prior to planting. The area on the left was previously cropped and cultivated.   

The insect responsible for the damage is the juvenile (larval) stage of a scarab beetle. Larvae collected from one of the affected fields have been identified as most likely black soil scarab (Othnonius batesii). Larvae are currently being reared to adulthood to confirm the identity.  The adults (yet to emerge) are very distinctive

Third (and final) instar black soil scarab larva (30 mm) found under damaged barley plants at Jandowae.  Note the pale head capsule of this species. 

 Damage to crops was significant because the larvae were large from crop establishment onwards. Black soil scarabs have a 2 year larval stage. The eggs would have been laid in the pasture in spring/summer of 2009/10, and the small larvae developed whilst feeding on the roots of the pasture grasses. By autumn/winter 2010, the larvae were large (up to 30 mm), and feeding voraciously. When the pasture was removed and the winter cereal planted, the scarab larvae started feeding on the emerging cereal plants.  Larvae in the field are currently estimated as 10-12 months old and at the early 3^rd instar stage. They are likely to pupate in mid to late summer and emerge as adults in the spring of 2011.

The scarab larvae feed on the below-ground parts of the cereal seedlings, limiting root growth or severing roots completely. As a result, seedling cereals are moisture stressed and unthrifty.

Because scarab larvae live entirely below ground, once the crop is planted and the damage evident, there is no control option available to prevent further damage to the crop. It is simply impossible to contact the larvae with insecticide and large larve would be difficult to control even if they could be reached.

Black soil scarab adult (17 mm).  Note the two-tone colour scheme – dark head and thorak, and light brown wing covers.  Image by CSIRO.

Scarab damage to winter cereals is uncommon, but these cases highlight the importance of checking for soil insects prior to sowing, particularly in high risk situations such as when coming out of a pasture into a crop.  Seasonal conditions (the onset of wetter than average seasons) may also have contributed to an increase in black scarab numbers.

Anyone with suspected scarab activity can contact the entomology team via this blog.

Further information on scarabs, and soil insect monitoring strategies can be found at: http://www2.dpi.qld.gov.au/fieldcrops/3689.html

Acknowledgements: Dr Peter Allsop from BSES for the identification of the scarab larvae. Steve Henning for photographs of the scarab larva and the damaged barley crop.

Article by Hugh Brier and Melina Miles

Rod Collins and Hugh Brier did some investigative work back in 1998. They reared a couple of larvae through to the adult moths and had them identified by ANIC.

Rod Collins made the following observations: “The damage was usually confined to a single tiller per plant at a relatively low incidence through fields. Infected tillers seemed to have flowered normally, but soon after flowering the stem upwards from the last node (and including the head) died and was white in colour with no grain in the head. From a distance, these symptoms appeared to be the same as those of crown rot. However, infected tillers were green and apparently healthy from the last node (including the flag leaf) down. On closer examination, a small entry hole about the size of a pinhead was evident usually at or just below the first node up from the base of the plant. In some cases an exit hole was noted just above the last node.”

“When the stem was split open, you could follow where the larva had been up until the last node, where it was often found feeding on the tip of the stem just above the last node. In some cases, the larva had chewed through the tip and continued to move upwards towards the head. It appeared that once the stem began to dry out, the larva would bore a hole in the stem and exit. Only one larva was found per stem in all the plants that I saw.”

It seems not much is known about this species. It is believed to be a native species, one of three in this genus found in Australia. Ephysteris promptella is recorded as a pest of sugarcane in Australia. Ephysteris silignitis occurs widely in Australia south to about 35 degrees south and is thought to be confined to Australia. It is in the wettest parts e.g. Brisbane and Mt Bellenden Ker and the driest. It is common at Alice Springs. It was suggested that it may feed on grasses but there was no evidence.

Being aware of their presence is one thing; whether to intervene is another.

In some late crops starting to turn, the presence of up to 12 small armyworm larvae per square metre need not necessarily sound alarm bells. This situation requires careful and regular monitoring, but there is every chance the crop will make it to harvest without the need to control armyworm.

If however, the crop lingers and the armyworm develop into medium and large larvae, there is a risk, particularly with barley, that head cutting will result in high yield losses. In this situation, quick action may be required to control armyworm and prevent losses.

The key points are
1) to be aware that armyworm are present and
2) to inspect regularly as the crop approaches maturity so that appropriate action can be taken if head cutting occurs.

For more information on armyworm, see the posting made on 20 October 2008.
Photo: Watch for the early signs of head cutting.

Reminder: Last date for Steward® EC use on chickpeas is 15 October

Winter pulses have had their expected share of helicoverpa infestations over recent weeks and most crops have been sprayed to control grubs. Strategies to minimise the risk of insecticide resistance are available. The following points should be observed.

Under the Insecticide Resistance Management Strategy (IRMS), the last use of Steward® EC for Central and Southern regions is 15 October, while the last use date for Northern (Central Queensland) regions (15 September) has long passed.

Grower and consultants are also reminded that for all pulse crops, not more than one application of Steward® EC per field is allowed for the crops entire growth cycle.

Access the full IRMS for 2009-10 on the Cotton CRC website:
http://www.cottoncrc.org.au/content/Industry/Publications/Pests_and_Beneficials/Insect_Resistance_Management.aspx

In this article, I will not go over aphid basics i.e. identification and sampling. You can follow the links to previous articles to read about these

In this posting, I want to discuss what is known, from overseas research, and what we might draw on from this work to help us make decisions about aphid management and control. This review may provide some useful information, in the absence of any locally generated data on aphid impacts. Surprisingly, there has been very little work done on cereal aphids in Australia.

General points
The literature, largely from North America and Europe, indicates that there can be significant differences in the way different cultivars respond to the impact of aphids. For this reason, it is important to use this information as general information that may assist in understanding how your crop may be responding to an aphid infestation. In the absence of local data, it is a useful starting point.
Early aphid infestations (from seedling)
Root and shoot growth may be impaired as a result of aphids competing for N. Inadequate N for the crop may make the crop more vulnerable to the impact of an aphid infestation.There is no impact on yield after grain has filled and is maturing (soft-hard dough). http://www.grdc.com.au/director/events/grdcpublications?item_id=8D607A46EDDFD98A822CFAEC7FCC4EC2&pageNumber=1).

Aphids have a requirement for nitrogen (N) to complete development and reproduce. Honeydew is a by-product of their feeding. Essentially aphids compete with the plant for available N, which can impact on the plant in at different stages of crop development.

Prolonged infestation can reduce tillering and result in earlier leaf senescence. Controlling aphids generally results in a recovery of the rate of root and shoot development, but there can be a delay.

Late aphid infestations

Infestations that occur during booting to milky dough, particularly where aphids are colonising the flag leaf, stem and ear, result in yield loss. Generally, the distal grains in the head fail to fill. Infestations at this stage in which aphids colonise the leaves, particularly lower in the canopy, tend to result in grain with reduced N (protein) rather than a loss in yield. Aphids are intercepting the N being relocated from leaves to the filling grain.

The relative impact of timing and location of infestation makes sense if you review it along with what is known about the contribution of different parts of the crop to yield. The figure below illustrates the contribution of the upper leaves, stem and ear to the yield of wheat and barley (GRDC Winter Cereal Crop Growth Guide 2005

Ongoing research
There is currently research being conducted on cereal aphids, by QPIF and the Northern Grower Alliance (NGA).

In 2008, initial trial work by QPIF and NGA showed different results (see the GRDC Update, Goondiwindi, 2009 papers for NGA results. Briefly, NGA trial work showed an overall yield benefit of around 10% from using seed dressings containing imidacloprid. QPIF results showed no difference from seed treatment, but a yield benefit where a foliar treatment (pirimicarb) was applied at head emergence.

Article by Melina Miles

Slaters are not generally regarded as a pest of broad acre agriculture and tend to feed on decaying vegetation and dead animal matter. Overall they perform an important recycling role in the environment however on rare occasions they can also attack seedlings of broad acre crops.

Slaters are woodlice and they are crustaceans, not insects. They have a hard skeleton on the outside and many pairs of jointed legs. The native slater species doing the damage to cereal crops is Australiodillo bifrons. This species has a light brown oval shaped and flattened body with a dark brown stripe in the middle of the back. Both males and females have a characteristic split on the frontal plate. Males tend to be larger than females and can grow as large as 9 mm long and 6.5 mm wide.

This native slater is commonly found in low lying swampy regions and tends to be more active after rain periods. They need damp conditions and will die if exposed to open and dry situations.Control: There are no registered pesticides for the control of slaters in winter cereals. Non chemical approaches such as providing alternative habitats may decrease slater numbers in crops. Shelterbelts containing a complex understorey of vegetation and soil litter may be more attractive to slaters. Such environments also harbour many natural enemies of broad acre insect pests which can also keep slater populations in check.

Other winter cereal seedling pests

Cutworms
Several species of cutworms attack establishing cereal crops in Queensland and NSW. As their name suggests cutworm larvae sever (cut) the stems of young seedlings at or near ground level, causing the collapse of the plant.

Cutworm larvae are up to 50 mm long, hairless with dark heads and usually dark coloured bodies, often with longitudinal lines and/or dark spots. Larvae curl up and remain still if picked up.

Damage: Young caterpillars climb plants and skeletonise the leaves or eat small holes. The older larvae may also climb to browse or cut off leaves, but commonly cut through stems at ground level and feed on the top growth of felled plants. Caterpillars that are almost fully grown often remain underground and chew into plants at or below ground level.

Monitoring and control: Inspect crops twice weekly in seedling and early vegetative stage. The best time to monitor is late afternoons and evenings when larvae feed. Chemical control is warranted when there is a rapidly increasing area or proportion of crop damage. If distribution is patchy, spot spraying may suffice. Chlorpyrifos and various pyrethroids are mainly used to control cutworm.
Cultural control measures include weed control – at least 3-4 weeks prior to sowing.

Adults are 1 mm long and have 8 legs. Adults and nymphs have a purplish-blue, rounded body with red legs. They move quickly when disturbed. The presence of a small red area on the back distinguishes it from the redlegged earth mite.

Damage: Adults and nymphs pierce and suck on leaves resulting in silvering of the leaf tips in cereals. When heavy infestations occur, the leaf tip withers and the seedling can die. In canola, leaves are mottled or whitened in appearance.

Monitoring and control:

Check from planting to early vegetative stage, particularly in dry seasons. Blue oat mites are most easily seen in the late afternoon when they begin feeding on the leaves.
Where warranted, foliar application of registered insecticide may be cost-effective if applied within 2-3 weeks of emergence in autumn.

Know your seedling pests
Correct identification of pests feeding on cereal seedlings is important as this will influence selection of control options.

Article by Kate Charleston and David Murray

Fleabane alert
Following the recent rain, the first main flush of fleabane for the year will start to emerge shortly. Whilst this weed is often regarded as one of the most difficult-to-control weed, it is much easier to control when it is a small seedling. So, growers need to be alert and think about spraying soon.To assist growers and consultants, the weeds team has recently published a brochure on fleabane, and it is available from the Queensland Primary Industries & Fisheries website http://www.dpi.qld.gov.au/cps/rde/dpi/hs.xsl/26_4251_ENA_HTML.htm

The team is also developing a best practice herbicide guide, using feedback from consultants on what is being used successfully for in-crop and fallow control across the region.

If you wish to be part of this short survey, please contact Michael Widderick on Michael.widderick@dpi.qld.gov.au or Steve Walker on steve.walker@dpi.qle.gov.au

Blue oat mite
The blue oat mite is an important pest of seedling winter cereals. When infestations are severe the leaf tips wither and eventually the seedlings die. Eggs laid in the soil hibernate over winter, allowing populations to build up over a number of years, causing severe damage if crop rotation is not practised.

Slaters are an agricultural pest in South Africa where they are generally controlled by cultivation. Changing farming practices such as minimum or non tillage seem to have worsened the slater problem, especially if there is also a large amount of stubble present in fields.

Slaters are known to do damage to seedlings of wheat and oats and there is also evidence of slater activity in canola in western and southern Australia. It is not known if other crops are hosts for slaters.

Damage: Slater damage looks similar to snail and slug damage with rasping and shredded appearance to leaves. Feeding damage can also appear as irregular patches removed from the leaves resulting in distinctive ‘windows’ of transparent leaf membrane. Thousands of seedlings can be eaten in a short time by swarms of slaters.

For information on armyworm identification see previous Beatsheet postings on armyworms.
http://thebeatsheet-ipmnews.blogspot.com/2007/10/can-you-confidently-identify-armyworm.html

http://thebeatsheet-ipmnews.blogspot.com/2007/09/watch-for-armyworms-in-barley-and-oats.html

There is no reason to expect armyworm to behave differently in wheat to barley. This means you can expect to see feeding on leaves whilst the crop is still green, and then on stems as the crop dries down further.

Characteristic armyworm damage in winter cereals
During the vegetative growth phase, plants can tolerate considerable leaf feeding. Leaves may look tattered from the eaten-out leaf margins. Faecal pellets around the base of plants are another indication of armyworm infestation. Armyworm generally do not require control during the vegetative stage.

Ragged flag and other leaves on a maturing barley crop

The most serious armyworm damage in cereal crops occurs when larvae feed on the upper flag leaf and stem node as the crop matures. Larvae target the stem node as the leaves become dry and unpalatable, and the stem is often the last part of the plant to dry. Head cutting begins at this time.

 
 
Head cutting in barley caused by armyworm

Calculating an economic threshold
The following table shows the value of yield loss incurred by 1 larva/square m per day, based on approximate current values for wheat and an estimated loss of 70 kg/ha per larva.

Based on these figures, and the relatively low cost of controlling armyworm, populations in ripening crops in excess of 1 large larva per square metre will warrant spraying.

Monitoring and management strategy
For insecticide application to be economic, check or scout the crop and assess the problem before head cutting starts. Check for larvae on the plant and in the soil litter under the plant. Late in the day, when the larvae are becoming active, use a sweep net (or swing a bucket through the crop) to make a quick assessment of whether armyworm larvae are present in the crop. Infestations are often patchy, so check a number of sites across the field.

Some judgements will need to be made about how quickly the larvae will reach damaging size and when this will occur in relation to the crop’s development.For example, if the crop is nearing full maturity/harvest, and the grubs are still small, then there is most likely no need to spray. Small larvae take 8-10 days to reach a size capable of head lopping.The other extreme would be a late crop that is still very green and at early seed fill. In this case, any small larvae present will most likely reach their most damaging size in time to significantly reduce crop yield, and so a spray is more likely to be required.

I you are unable to monitor the crop on a regular (daily) schedule during the critical period of drying down, and armyworm are present, it may be better to spray just in case. This is not the preferred option, but provides peace of mind in a year like this where armyworm are abundant.

Early recognition
It is essential to recognise the problem early and be prepared to spray when economic damage is imminent. A cereal crop can be almost destroyed by armyworm in just a few days. Whilst large larvae do the head lopping, controlling smaller larvae that are still leaf feeding may be more achievable.

Control
Many chemicals will control armyworms. However their effectiveness is often dependent on good penetration into the crop to get contact with the caterpillars. Control may be more difficult in high-yielding thick canopy crops, particularly when larvae are resting under leaf litter at the base of plants. As larvae are most active at night, spraying in the afternoon or evening may produce the best results.

If applying sprays close to harvest, be aware of relevant Withholding Periods. Always read the label.

Biological control agents may be important in some years. These include parasitic flies and wasps, predatory beetles and diseases.

The two most likely larvae (grubs) found in winter cereals are the corn earworm, Helicoverpa armigera, and the common armyworm, Leucania convecta. See previous blog postings for more information on these pests.
http://thebeatsheet-ipmnews.blogspot.com/2007/10/can-you-confidently-identify-armyworm.html

Figure 1. Large corn earworm larva on a wheat head. (Photo: R. Lloyd)

All Helicoverpa larvae found feeding in wheat, barley or triticale crops will be corn earworm. The native budworm, H. punctigera, is not normally found on monocots (grasses). This is important to know, because the corn earworm has developed resistance to pyrethroids, and unless the larvae are small, a pyrethroid spray is unlikely to control them.

If large larvae are present, identification becomes a somewhat academic issue. However, large H. armigera larvae can be identified by the white hairs behind the head (Figure 2). In contrast, the hairs on large H. punctigera larvae are black. These compare with armyworm larvae which have three pale stripes just behind the head, and smooth skin, without any hairs or bumps.

If corn earworm infestations are detected early and larvae are small, preferably less than 7 mm in length, Helicoverpa nucleopolyhedrovirus (NPV) sold as Vivus Max could be considered as it will not harm beneficials (predators and parasites) in the crop. Some caution is needed as NPV will not kill corn earworm larvae greater than 13 mm in length, and will have no effect on armyworms.

Invariably when larvae are found on cereal crops, they are medium or large (>13 mm in length) and a more robust option is needed to control them. Both corn earworm and common armyworm are usually present in winter cereals, and control measures will be influenced by the relative abundance of each.

Follow the link below for more information related to thresholds and control options.
http://thebeatsheet-ipmnews.blogspot.com/2007/10/are-corn-earworm-problem-in-winter.html

Armyworm larvae

• have three white stripes on the collar, behind the head. These stripes may or may not persist down the body so concentrate on the collar (see the image above at right).
• skin is smooth without obvious hairs and bumps.
• larger larvae tend to curl up when disturbed.

Helicoverpa larvae

• skin is lumpy with obvious hairs.
• may be considerable variation in colour.
• may or may not have a ‘saddle’.