Issue Number: 03 Date: 30/May/2014 PestFax PestFax is a weekly informative and interactive reporting service, providing risk alerts, current information and advice on pests and diseases threatening crops and pastures throughout the grain belt of Western Australia (WA). PestFax is supported by the National Invertebrate Pest Initiative (NIPI) a GRDC project that promotes national pest management information and Integrated Pest Management (IPM) principals. Newsletter of the Department of Agriculture and Food, Western Australia Contents Mites and lucerne flea Canola downy mildew Barley net blotch Weevils Rhizoctonia root rot Aphid activity Grain weevils at seeding Our PestFax newsletters (including earlier editions) and the PestFax Map are available online. If you have recently observed or heard news of insect or disease pests in crops and pastures email us or make an on- line report . Mites and lucerne fleas Matt Willis (Elders) reports finding infestations of redlegged earth mites, bryobia mite and weevils in emerging canola crops near Trayning, Koorda and Dowerin this week. He observed that the bryobia mites are a fully grown mature size, whilst the redlegged earth mites have generally been immature and a smaller size. Spray applications of chlorpyrifos and bifenthrin is occurring to control these pests. Ty Henning (TekAg) reports that lucerne flea and weevils have caused plant damage and contributed to reducing levels of cotyledon canola in a
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Issue Number: 03Date: 30/May/2014
PestFaxPestFax is a weekly informative and interactive reporting service, providing risk alerts, current information and advice on pests and diseases threatening crops and pastures throughout the grain belt of Western Australia (WA).
PestFax is supported by the National Invertebrate Pest Initiative (NIPI) a GRDC project that promotes national pest management information and Integrated Pest Management (IPM) principals.
Newsletter of the Department of Agriculture and Food, Western Australia
ContentsMites and lucerne fleaCanola downy mildewBarley net blotchWeevils Rhizoctonia root rotAphid activity Grain weevils at seeding
Our PestFax newsletters (including earlier editions) and the PestFax Map are available online. If you have recently observed or heard news of insect or disease pests in crops and pastures email us or make an on-line report.
Mites and lucerne fleasMatt Willis (Elders) reports finding infestations of redlegged earth mites, bryobia mite and weevils in emerging canola crops near Trayning, Koorda and Dowerin this week. He observed that the bryobia mites are a fully grown mature size, whilst the redlegged earth mites have generally been immature and a smaller size. Spray applications of chlorpyrifos and bifenthrin is occurring to control these pests.
Ty Henning (TekAg) reports that lucerne flea and weevils have caused plant damage and contributed to reducing levels of cotyledon canola in a paddock South of Cadoux. The crop was sown into a non-wetting sandy/duplex soil which resulted in a poor germination and disappointingly low plant density. The crop is being sprayed now to prevent further seedling loss. Ty has been surprised to see higher than expected levels of lucerne flea on some sandplain and sandy gravel soil types east of Wongan Hills. Lupins and wheat crops that were sown into some of these paddocks with long term cereal rotations also have levels of lucerne fleas that were not anticipated. These lucerne flea are currently posing a moderate risk to seedlings but are likely to be controlled when post emergent herbicides are applied.
Loamy and clay soils are well known to support higher levels of lucerne flea than soils with low clay/silt content. This is because the female lucerne flea requires these fine particles for its
reproduction and egg survival. Paddocks with pasture rotations, especially with a high component of broad-leafed plants such as capeweed and clover are known to be favoured by lucerne flea. Cereals and grasses will also support populations of lucerne flea and it now appears that last spring was a good season for lucerne flea population increase and carry-over into 2014.
Courtney Piesse (Elders) reports that high levels of redlegged earth mites, blue oat mites and/or lucerne flea have been found attacking emerging canola crops in some paddocks within the Great Southern region. Courtney found that a canola paddock West of Kojonup has extensive damage from a combination of lucerne fleas and slugs. In areas of the paddock where both pests are present, damage has been severe resulting in no crop. These patches are small and may be re-seeded. Areas where the canola seedlings are being damaged by lucerne flea alone have the appearance of being ‘shot’ with windowpane holes and distorted leaves. The paddock was initially dry sown and received an application bifenthrin and chlorpyrifos post seeding. Since then poison baits have been applied to control the slugs and chlorpyrifos is likely to be re-applied to control the lucerne flea and allow the struggling and late germinating plants to survive.
Entomologist Svet Micic commented that insecticide sprays being applied now will in many cases be controlling first generation lucerne flea and mites before they reach their adult size and commence laying their winter eggs. Later application of sprays used in coming weeks will not kill winter eggs laid by adult lucerne flea and mites. In some high pest pressure situations a follow-up second spray may be needed to kill off second generation pests.
Once canola seedlings reach the 2–4 true leaf growth stage they are usually able to out-compete most seedling pest pressure and application of sprays on low pest densities is not recommended. Unnecessary spray applications will not eradicate pests but rather could have the reverse result of selecting for survivors who have genetic resistance against some insecticides. This has been the case with redlegged earth mites where more than 26 properties have been identified has having mites that are resistance to high rates of synthetic pyrethroid (SP) chemicals such as bifenthrin and alphacypermethrin.
Resistance testingGrowers and agronomists who observe surviving redlegged earth mites following applications of insecticides should take advantage of a free testing service this year to determine the resistance status of their mites. The testing service is funded by GRDC in 2014/15 and is conducted by Department of Agriculture and Food, Western Australia (DAFWA) researchers in collaboration with CSIRO, University of Western Australia (UWA) and cesar Victoria.
For further information see the following links – Diagnosing redlegged earth mites and Prevent redlegged earth mite resistance
Canola downy mildewFurther reports this week have confirmed the widespread incidence of downy mildew infections on canola seedlings.
Courtney Piesse (Elders) reports finding mild to severe downy mildew symptoms on canola plants over a widespread area from Williams to Kendenup. The infection is mainly being seen on the canola cotyledons with the true leaves that have emerged being relatively unaffected. In some cases canola that was sown into last season’s pasture paddocks has higher infection levels than comparable paddocks sown into stubbles.
Tim Scott (AgVivo) reports seeing downy mildew infection on cotyledon to 2–3 leaf canola crops near Wagin. Consultant Wade Longmuir has also found the disease in other young canola seedlings in the same district.
Matt Willis (Elders) reports that downy mildew infection is being found in low levels on cotyledon to 4 leaf canola crops in the Dowerin and Koorda areas.
Ty Henning (TekAg) reports reports that he was encouraged to see a canola crop at Kondut (Nth Wongan) that is out-growing the effects of downy mildew infection. The crop is now around the 4 leaf growth stage with upper leaves looking healthy and unaffected by the disease whilst some of the remaining senescing cotyledons are still showing the fluffy grey-white fungal growth. Ty says that the canola seedlings have had excellent growth with good soil moisture and now have their root systems drawing on the banded fertilizer that was applied at sowing.
Senior Plant Pathologist Ravjit Khangura says that wet conditions have favoured extensive sporulation by the downy mildew fungus and some strong wind events could have facilitated its long distance spread.
SymptomsThe symptoms of downy mildew appear mostly as yellowed cotyledons and lower leaves. Examination of the underside of these leaves often shows a corresponding patch of grey/white fluffy growth, although this can become less apparent with age. The disease mainly affects the cotyledons and the upper leaves (third and fourth leaves) are usually healthy looking. This seasons weather conditions (frequent rainfall, warm temperatures, high humidity and cloudy days) have been perfect for the early onset of downy mildew.
Ravjit commented that downy mildew is either soil/seed borne or requires a green bridge for carry over. Disease spread is generally favoured by cool moist winter conditions (including heavy dew) in the early stages of canola growth. Although some early seedling mortality may occur, canola plants usually overcome the disease once they reach the 5–6 leaf stage and new growth appears healthy.
Last week’s PestFax mentioned copper based products and that products containing metalaxyl are registered for foliar application against downy mildew in brassica vegetables in Australia. PestFax has now been advised that a copper fungicide (350 grams per litre (g/L) cupric hydroxide) is registered for foliar application against downy mildew in canola, available as Cung Fu 350 SC Fungicide® (registration till June 2014).
For more information on downy mildew see last week’s PestFax No.2 23 May 14 and for diagnosing symptoms and management options refer to Diagnosing downy mildew in canola webpage.
Barley net blotchCourtney Piesse (Elders) reports that some paddocks with self-sown cereals in in the Kojonup area are showing a low level of spot type net blotch (STNB) leaf infection.
Kirsty Smith (Landmark) reports seeing extremely high levels of net blotch in some seedling barley crops in the Hyden area. Crops with the highest infection levels are in paddocks with barley-on-barley crop rotations, with the worst affected crops having all of the currently emerged leaves showing net blotch symptoms. Kirsty commented that there have been a number of significant rainfall events in the area which have promoted spread of net blotch spores from stubbles by rain splash onto seedling leaves. She also noted that all varieties to date seem to be equally damaged by the disease.
Similar reports have come from Matt Willis (Elders) for seedling to early tillering Scope barley around Koorda and from David Cameron (Farmanco) for seedling Buloke and Hindmarsh at Moora, Miling and Watheroo.
Spot-type net blotch lesions develop as small circular or oval dark brown spots with yellow edges. Infections can occur following around six hours of leaf wetness at temperatures between 10°C and 25°C. Primary inoculum comes from airborne spores, which are produced on stubbles from previous crops.
Plant Pathologist Geoff Thomas says that recent mild temperatures coupled with rainfall events have been favourable for production and spread of spores of the fungus and for infection of seedlings emerging into or adjacent to infected stubble. Further development of the epidemic requires ongoing favourable weather conditions and crops should continue to be monitored. In crops where disease continues to progress over the next few weeks an application of a registered fungicide leading up to stem extension can help reduce epidemic development.
For further information on symptoms and management, see the Managing net type net blotch and spot type net blotch in Western Australia webpage, which is available along with other disease management information including Registered foliar fungicides for cereals in Western Australia, publications on specific diseases, variety disease ratings, disease forecasts and instructions for submitting plant samples on the DAFWA website at www.agric.wa.gov.au/cropdisease.
As part of a local and national survey of the distribution and virulence of the net blotches, Geoff would like to receive samples of leaf material infected by either spot type or net type net blotch. The leaf samples can simply be placed in a paper envelope with variety, location and your contact information included and sent through the mail to:
Geoff Thomas
Plant Pathology
Department of Agriculture and Food, Western Australia
Locked Bag 4, Bentley Delivery Centre, WA 6983
WeevilsMatt Willis (Elders) reports finding weevil damage along with mites (see above) in emerging canola crops near Trayning, Koorda and Dowerin this week.
Courtney Piesse (Elders) reports that vegetable weevils along with other pests are attacking emerging canola crops in the Great Southern region. Courtenay estimated in one paddock near Cranbrook that levels as high as 2–3 vegetable weevils per seedling were destroying parts of a canola crop. The paddock was seeded into last year’s pasture (high capeweed component) and did not receive any post seeding pre-emergent insecticide. The weevils were present over the entire paddock, although numbers were higher near fencelines.
Entomologist Svet Micic commented that the WA pest weevil species are well adapted to survive long dry summers as adults in a suspended aestivated state. Last year’s good growing conditions through late spring appear to have also provided good conditions for weevil population survival and carry-over into this season.
Unidentified weevilsDavid Hurst (Landmark) discovered unusual looking weevils causing damage to a canola crop west of Moora. The weevils have been damaging young canola seedlings mainly in a large moon shaped area adjoining a patch of remanent bushland, with the damage incidence decreasing over distance into the crop. Canola seedling density has been reduced by the weevil damage together with damage from downy mildew disease.
The weevils were slightly smaller than the common desiantha pest species which are about six millimetres (mm) long. Samples sent in by David have been confirmed by DAFWA taxonomists to be an unknown weevil species that is currently assumed to be a localised population of native weevils. The native weevils appear to be the same as those reported by Helen Lathlain in 2012 near Cataby.
David commented that the west Moora paddock had been sprayed with 200 millilitres per hectare (mL/ha) alpha-cypermethrin and 200mL/ha bifenthrin about two weeks ago, however the damage to the canola seedlings has continued indicating it has not controlled the weevils. This is a similar experience to the one reported by Helen Lethlean (PestFax June 2012) where the crop was treated using high rates of chemicals with minimal control.
It is likely that these unknown species have a higher natural tolerance to some chemicals and / or are avoiding the chemically treated plants.
For further information refer to – Diagnosing weevils in canola and Diagnosing desiantha weevil in cereals and the GRDC Back Pocket Guide - Crop Weevils,
Rhizoctonia root rotPlant pathologist Daniel Hüberli reports that a breakthrough has occurred which will assist growers in the battle against rhizooctonia root rot. Wheat and barley collaborative trials in WA and South Australia (SA) have shown that liquid banding with Unifiorm™, one of several fungicides tested, increased yields by up to 0.87 tonnes per hectare (t/ha) in a paddock with very high levels of rhizoctonia in the soil before sowing. Liquid application is an alternative to recent registrations of seed dressing products, Evergol Prime® and Vibrance®, which on average produced a 5% increase in yield.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) has approved permits for large-scale trials this season by chemical companies and is considering an application for the liquid banding registration, which, if approved, could make the products available in 2015. Growers will be able to view the large scale trials this year at local field days as well as DAFWA demonstration trials setup in Warradarge and Kojonup.
Although the fungicide work is a promising tool to assist control, Daniel is warning that when available it will need to be used as part of an integrated disease management program. That is,
used in conjunction with controlling green bridge weeds, rotation break crops, seed dressings, time and methods of sowing and nutrient management.
Further information on rhizoctonia root rot is available in the GRDC Fact Sheet: Management to minimise Rhizoctonia disease in cereals, DAFWA MyCrop Rhizoctonia information and Crop update papers: http://researchrepository.murdoch.edu.au/21390/ andhttp://researchrepository.murdoch.edu.au/13686/
Aphid activityMatt Willis (Elders) reports finding a few adult winged cowpea aphids in a lupin crop near Trayning. Matt’s observation is a good reminder to be on the look-out for early arrival of pests into crops.
Cowpea aphids are usually easily spotted by their black colour and dense clusters on a few plant growing points. On close inspection with a magnifying lens their black and white legs are also a good identification feature.
The three most common aphid species which attack lupins are the cowpea aphid, bluegreen aphid, and the green peach aphid. The variety of lupins grown is also important as they vary largely in their susceptibility to aphid feeding damage, with most narrow-leafed varieties (e.g. Jenabillup and Mandellup) being quite resistant. The spray threshold for control of aphids on lupins is for more than 30% of flowering spikes to have 30 or more aphids. Consideration should also be given to potential crop yield.
For more information see Identification of aphids in lupin crops webpage and Aphid control in WA lupin crops
Grain weevils at seedingDAFWA staff have had a number of enquiries from Kojonup to Esperance regarding on-farm seed grain that has been infested with grain pests.
Rob Emery (DAFWA Stored Grain Entomologist) says it is important to correctly identify the grain pest and where possible to do a germination test before planting.
Granary weevil larvae burrow into the grain and can cause infested grain to have poor germination or not to germinate, whereas some of the beetle species feed on the outside of the grain, causing fewer issues with germination. Even stored grain treated with insecticide seed dressing for grain pests should be inspected for damage and insects. Grain temperature and moisture can affect the efficacy of seed dressings.
Grain storage expert, Ben White (GIWA) suggests that with seeding and stock feeding in full swing, silos are being emptied, presenting a good opportunity to implement grain storage hygiene. Grain storage insects only need a very small amount of residual grain or dust in silos to survive over winter so cleaning now is an essential task as part of good seed storage management. Cleaning silos involves sweeping and washing out on a dry day before applying a structural treatment such as diatomaceous earth e.g. Dryacide™. The insecticide fenitrithion can also be used at a 1% solution sprayed to point of run-off but not in silos or bunkers that may be used for commercial canola storage in the future.
For further information visit the stored grain website or contact GIWA for further information on +61 (0)8 6262 2128.
Free resistance testIf you have applied phosphine gas to grain in a sealed silo as per label instructions and there are still live grain pests present, contact Nuccia Eyres or David Cousins at DAFWA on +61 (0)8 9368 3333) to arrange for the grain pests to be tested for resistance.
Also available:Crop insects: the ute guide This book covers crop pests, beneficial insects, biological control, grain storage pests and biosecurity pest threats specific to WA. Copies are available from some Departmental Offices for a cost of $10.00 or by mail order by phoning the DAFWA South Perth office on +61 (0)8 9368 3710.
Free insect identification Having troubles identifying mites or other pests? Send in your digital pictures (in focus) or send live specimens in a non-crushable plastic jar for free identification. Email Peter Mangano or Svetlana Micic at the postal details above.
IPM Guidelines for grains
AgTactic and AgMemo Other regional DAFWA news updates are available online.
Growing Season Outlook Seasonal climate outlooks are available online.
AGWEST Plant Labs Plant disease diagnostic service located at the DAFWA South Perth office. For information on sending samples and charges contact +61 (0)8 9368 3721 or Fax +61 (0)8 9474 2658 or visit our website or the AgWest plant laboratories webpage.
The Chief Executive Officer of the Department of Agriculture and Food and the State of Western Australia accept no liabilitywhatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.
