Aphids – to spray or not to spray?
Plant virologist Dr Benjamin Congdon (DPIRD) reports that there are higher levels of green peach aphids (GPA) in canola around Northam and Ben’s surveillance project had its first detection of turnips yellow virus (TuYV) in winged aphids in Northam.
Ben advises that any late canola crops in the Northam area that are still in the rosette phase are at risk of TuYV infection. However, most crops are flowering and not at risk.
Green peach aphid management
GPA are found on the underside of leaves.
GPA are resistant to many insecticides, and will develop resistance very quickly, so consider spraying only if these aphids are retarding crop growth and causing crop death.
Trials conducted by DPIRD have shown that GPA colonising canola in spring do not cause yield loss. If GPA colonise canola at the seedling stage and are not controlled leading to more than 600 aphids on leaves by 10% flowering canola then only those plants will incur a yield loss. For more information refer to DPIRD’s Canola yield loss to green peach aphid, Geraldton 2016 trial report and GRDC’s Yield loss to canola from green peach aphid page.
For more information refer to DPIRD’s Aphid management in canola crops page and GRDC’s Resistance Management Strategy for the Green Peach Aphid in Australia Grains.
Growers are reminded to contact Dr Paul Umina (cesar) on +61 (0)3 9349 4723 if you see GPA survive a Transform™ application.
Cabbage and turnip aphid management
The PestFax team has recently received reports of cabbage and turnip aphid activity in canola or on canola volunteers at;
The department has undertaken extensive trials over several years to determine the optimal thresholds for cabbage or turnip aphid treatment. These trials have been funded by the Council of Grain Grower Organisations and GRDC.
Field and glasshouse trials have shown that it is the length of the cabbage or turnip aphid colony present on the flowering spike that causes yield loss. Cabbage aphid colony lengths of 2.5 centimetres or longer cause yield loss on the flowering spike that is infested. A small scale field trial has shown that if over 95% of the flowering spikes in a crop are infested, for every centimetre of colony length there is a 10% yield loss.
Trials have confirmed that the best bet threshold for cabbage and turnip aphid feeding damage is when 20% of plants are infested with aphids and aphid numbers are expected to continue to increase.
If spraying is required, a border spray may suffice for cabbage aphids, which are most commonly found within 20 to 30 metres of the crop edge.
Also consider insecticide options that are soft on predators if spraying. Predators such as parasitic wasps, hover flies and ladybirds will also increase with warming weather. If on close inspection the aphids look shiny and bloated, it means they have been parasitised by wasps. These predators can keep aphid populations below threshold levels.
For more information refer to DPIRD’s Aphid management in canola crops page.
For a list of insecticides registered for use on aphids see the department’s 2020 Winter Spring Insecticide Guide.
Growers and consultants can use the PestFax Reporter app to request or confirm identification of aphids found in crops.
For previous canola activity this season refer to DPIRD’s 2020 PestFax Issue 9 Green peach aphid and turnip yellows virus update article and PestFax Issue 5 article Aphid activity update.
For more information on identifying and managing canola aphids see DPIRD’s;
- Aphid management in canola crops page
- Diagnosing canola aphids page
- 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children
- Aphids in your crops YouTube video.
For more information on TuYV contact Dr Benjamin Congdon, Research scientist, South Perth on +61 (0)8 9368 3499.
For more information on aphids contact Svetlana Micic, Research scientist, Albany on +61 (0)8 9892 8591 or Alan Lord, Technical officer, South Perth on +61 (0)8 9368 3758.
Article authors: Svetlana Micic (DPIRD Albany) and Cindy Webster (DPIRD Narrogin).
Garren Knell (ConsultAg) reports finding up to 6 relatively large armyworm caterpillars on ryegrass plants within a lupin crop near Narrogin. This indicates that the moths have been in the area for many weeks. The caterpillar characteristics visible in photos submitted indicate that they are more likely to be a common armyworm species (Mythimna sp.) and not the new fall armyworm (Spodoptera frugiperda).
Growers are encouraged to monitor cereal crops for armyworm as they can defoliate plants during vegetative stages and damage heads (especially barley) later in the season during grain fill stages.
Armyworm caterpillars are fat and smooth and may be distinguished by the three parallel white stripes on the collar just behind the head. The first visible sign of armyworm caterpillars is often their green to straw-coloured droppings, about the size of a match head, found on the ground between the cereal rows.
Armyworm caterpillars are most damaging in barley crops close to harvest. When barley crops are maturing in spring, large armyworm caterpillars climb plants and can chew through the stems causing the heads to fall to the ground. Damage to wheat and oat crops occurs less frequently and is usually minor compared to damage in barley because the stems are thicker and leaf defoliation does not usually result in yield loss. Armyworms are seldom a serious problem in pastures.
Assessing the numbers of armyworm in a cereal crop can be difficult, as their movements will vary with weather conditions and feeding preference. Sometimes they are found sheltering on the ground and under leaf litter whilst on other days they will be high up on the plants or on the heads and easily picked up using sweep nets. Larger caterpillars often prefer to hide during the day and feed at night.
Growers should be mindful to distinguish armyworm caterpillars from native budworm caterpillars given the incidence of budworm in cereal crops this season and from the new fall armyworm.
The economic level for spraying armyworm in mature barley is about three large armyworm grubs per square metre of crop. The threshold for wheat or oats is much higher as only grains are consumed and heads are very rarely dropped. Spray thresholds in these crops are more likely 10 grubs per square metre of crop. For more armyworm threshold information refer to DPIRD’s Management of armyworm in cereal crops page.
A number of effective insecticides are registered for the control of armyworm if required (see DPIRD’s 2020 Winter Spring Insecticide Guide). However, their effectiveness is often dependent on good penetration into the crop. This can sometimes be difficult to achieve in high-yielding, thick canopy crops, especially when caterpillars are resting under leaf litter at the base of plants. Spraying late in the afternoon or evening is recommended as armyworms are predominately night feeders. Spray withholding periods also need to be observed.
For further information on armyworm refer to DPIRD’s Diagnosing armyworm and Management of armyworm in cereal crops pages.
For more information contact Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758 or Svetlana Micic, Research Scientist, Albany on +61 (0)8 9892 8591.
Article authors: Cindy Webster (DPIRD Narrogin) and Dustin Severtson (DPIRD Northam).
Cockchafers are causing extensive damage in cereals and pastures
A grower has experienced significant cockchafer damage in tillering barley east of Kondinin. Plants along patch edges are showing yellowing lower (not upper younger) leaves, then complete yellowing and dead leaves further into patches. Digging up one plant at a time yielded one to 4 cockchafer larvae in or just under the root zone. Cockchafers are being reared to identify the species.
Two other growers have also reported concerning amounts of cockchafer damage in the Kondinin area in cereals. The more damaged areas do not seem to be near bushland or along crop edges, most damage is inwards into the paddock. One 80 ha paddock would have 20-30% plant loss.
Foliar insecticide applications are having little or no effect on cockchafer numbers.
A barley crop east of Woodanilling has also experienced extensive damage from cockchafers. As the cockchafers did not appear to be African black beetle (ABB) larvae they were sent to taxonomist Andras Szito (DPIRD) who identified the cockchafers as Heteronyx obesus.
A local consultant reports that cockchafers are causing damage to cereals and pastures over a number of properties east of Woodanilling.
Cockchafers are native insects that occasionally reach damaging levels when conditions favour adult egg laying.
Larvae feed on underground plant parts, causing them to wither and die potentially leading to large bare areas. Crops after pasture are more likely to be damaged with damage worse near tree belts.
Cockchafers belonging to the genus Heteronyx are typically not regarded as a pest of agriculture. However, two have been seen as occasional pests, with H. obesus causing severe damage to a range of crops and pastures, and H. elongatus causing damage to pastures and eucalypt seedlings.
Cockchafer larvae found only in soil and are up to 12 millimetres long, creamy-white with a darker head and curled into a ‘C’ shape.
Identification of cockchafers belonging to the Heteronyx genus is difficult. Larvae can only be separated by the layout of hairs around the anus and the adults have few distinguishing features. This is compounded by the fact that there are thousands of species, many of which have never been identified.
The adult beetles can come to the surface at night but are usually very difficult to eradicate because they predominantly feed underground and avoid contact with surface applied insecticides. The insecticide needs to penetrate the soil surface where the larvae are.
Growers finding cockchafers damaging their crops can request a species diagnosis by contacting DPIRD’s Pest and Disease Information Service (PaDIS) by email or phone on +61 (0)8 9368 3080.
To read about previous ABB larvae cockchafer activity reported to PestFax this season refer to the 2020 PestFax Issue 4 article African black beetle larvae (cockchafers) found in emerging barley.
For more information on cockchafers refer to DPIRD’s Diagnosing cockchafers and Cockchafer damage to broadacre crops pages.
For more information contact Svetlana Micic, Research scientist, Albany on +61 (0)8 9892 8591 or Alan Lord, Technical Officer, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.
Article authors: Cindy Webster (DPIRD Narrogin) and Dustin Severtson (DPIRD Northam).
Cold temperatures have slowed native budworm moth flights
- Usual automated and manual trapping locations
Budworm moth numbers reported by volunteer farmers, agronomists and DPIRD staff have remained relatively low for most of WA’s wheatbelt over the past week. The higher numbers reported this week include Mukinbudin (61 moths), Grass Patch West (35), Maya South East (30), Beacon (18), Maya East (10) and Wyalkatchem (8).
The moth flights have probably been reduced somewhat as a result of the cold fronts that passed through the S.W in the past week. Also eggs and very small larvae can be dislodged and will die after heavy rain or wind.
A mapped view of the native budworm trap captures is available at cesar’s MothTrapVisWA page. For recent native budworm field reports refer to DPIRD’s PestFax map.
These numbers give an indication of the movement of native budworm moth flights and can be used to alert growers to regional changes and the necessity to check crops using a sweep net.
Native budworm moth flights are often variable and unpredictable but moths generally prefer to land in flowering crops in preference to nearby crops that are yet to flower. Field pea, faba bean, lentil and chickpea crops are very susceptible to budworm as their pods are attractive to all sizes of caterpillars. Lupin and canola pods are less attractive to native budworm caterpillars which do not commence to feed on these pods until closer to leaf drop and pod maturity. Serradella, lucerne, clover and annual medic seed crops will also be at risk of attack.
The economic spray threshold levels will vary with crop type, grain price and control cost; these can be calculated for each grower’s particular situation using a simple formula outlined in DPIRD’s Management and economic thresholds for Native Budworm page.
More information on native budworm can be found at DPIRD’s 2020 PestFax Issue 7 article Native budworm and other moths are active and PestFax Issue 10 article Native budworm update. Caterpillars are being found in cereals.
For more information contact Alan Lord, Technical Officer, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.
Article author: Alan Lord (DPIRD South Perth).
2020 winter spring insecticide spray guide is now available
DPIRD’s 2020 winter/spring insecticide guide is now available and can be downloaded for free at the department’s Insecticide spray guides for crops in Western Australia page.
This spray guide lists the latest registered chemicals and rates that can be applied to canola, lupin and cereal crops for controlling mature crop insect pests.
The department updates its autumn/winter and winter/spring insecticide spray guides annually to help growers and consultants manage insect pests in crops and pasture.
The spray guides are only a guide and growers still need to read chemical labels before use.
Not all insecticide trade names may be listed so growers should also check with their retailers for any other registered insecticide options.
To download these spray guides and other useful insecticide information visit the department’s Insecticide spray guides for crops in Western Australia page.
For more insecticide information contact Alan Lord, Technical officer, South Perth on +61 (0)8 9368 3758 or Svetlana Micic, Research scientist, Albany on +61 (0)8 9892 8591.
Article author: Cindy Webster (DPIRD Narrogin).
PestFax identification webinar recordings are now live
The PestFax team recently delivered some insect identification training webinars to help improve or refresh the insect identification skills of members of the WA grains industry.
On Tuesday the 21 July 2020 entomologist Dr Dustin Severtson (DPIRD) presented about how to identify insects (pests and beneficials) in canola crops in spring. PestFax newsletter editor Cindy Webster (DPIRD) discussed how growers and consultants can request insect identifications from the PestFax service. The recording is now available for viewing on the DPIRD YouTube channel and to view the presentation PowerPoints slides click here.
On Tuesday the 28 July 2020 entomologist Svetlana Micic (DPIRD) presented about how to identify insects (pests and beneficials) in pulse crops in spring. The recording is now available for viewing on the DPIRD YouTube channel and to view the presentation PowerPoints slides click here.
For more information on webinar topics presented contact research scientists Dustin Severtson, Northam on +61 (0)427 196 656 or Svetlana Micic, Albany on +61 (0)427 772 051 or Cindy Webster, Narrogin on +61 (0)404 819 534.
Article author: Cindy Webster (DPIRD Narrogin).
Nodorum blotch in wheat
Agworld users have reported finding nodorum blotch ranging from low to medium severity in wheat crops (variety unknown) near Moora, Yathroo and Gillingarra.
Symptoms of nodorum blotch are tan-brown oval or irregular shaped leaf blotches with narrow yellow margins. Tiny brown fruiting bodies can occasionally be seen in lesions. Blotches become grey as they enlarge. Lower leaves are affected on young plants.
Nodorum blotch occurs commonly throughout the Western Australian wheatbelt particularly in high rainfall areas and can reduce grain yield and grain quality.
It frequently occurs together with yellow spot and these two diseases are very hard to distinguish with the naked eye due to almost identical symptoms. Nodorum blotch has the capacity to reduce yield by up to 50% when disease development is continuous due to favourable conditions throughout the season. When disease development is only favourable for part of the season, either before or after flag leaf emergence, losses around 20-30% can occur.
Impacts from leaf spot diseases vary greatly from season to season and between locations, dependent on inoculum load and seasonal rainfall. They are particularly a problem in continuous wheat crops in stubble retention farming systems as these diseases are stubble borne.
To check your wheat variety’s susceptibility to blotches and spots refer to DPIRD’s 2020 WA Sowing Guide – Wheat.
For wheat after wheat, when there is high disease pressure prior to stem elongation, DPIRD research has shown it may be economic to apply fungicide at, or prior to, early stem elongation (Z31, first node) particularly in medium to high rainfall areas where the crop is struggling with a heavy disease burden. A second spray may be required at or after flag leaf emergence.
In rotation crops in medium-high rainfall zones, application of foliar fungicide to affected susceptible crops at or after flag leaf emergence has been shown to provide an economic benefit:
- in crops having good yield potential
- where there is evidence of increasing leaf spot intensity down the canopy
- when there are good prospects of finishing rains (approximately 80mm in the two months after flag leaf emergence).
It is important to optimise control of nodorum blotch on leaves to reduce risk of infection of heads (glume blotch). For more information on fungicides refer to the DPIRD's Registered foliar fungicides for cereals in Western Australia page.
Growers are reminded to manage fungicide applications carefully to minimise the risk of fungicide resistance.
For further information on identifying and managing these diseases refer to the department’s Diagnosing septoria nodorum of wheat and Managing yellow spot and septoria nodorum blotch in wheat pages.
For more information contact Plant pathologists Kithsiri Jayasena, Albany on +61 (0)8 9892 8477, Geoff Thomas, South Perth on +61 (0)8 9368 3262 or Andrea Hills, Esperance on +61 (0)8 9083 1144 or Ciara Beard, Geraldton on +61 (0)8 9956 8504.
Original article author: Geoff Thomas (DPIRD South Perth).
Article updated by: Ciara Beard (DPIRD Geraldton), Manisha Shankar (DPIRD South Perth) and Kithsiri Jayasena (DPIRD Albany).
Sclerotinia apothecia found in lupins
Plant pathologist Ciara Beard (DPIRD) has found apothecia under a narrow-leaf lupin crop at Yandanooka (south east of Mingenew). The crop came up in early May and is at 1-2cm pods on main spike. The crop is dense and has great yield potential. As significant rain is forecast for the weekend the grower is going to apply fungicide to some parts of the paddock to assist Mingenew Irwin Group and DPIRD in gathering some trial data (sprayed vs unsprayed) on Sclerotinia disease management in lupin.
Sclerotinia management in lupin crops
Sclerotinia in lupin is a sporadic disease. It is usually only a problem in paddocks that have a history of sclerotinia in canola or lupin and depends a lot on seasonal weather conditions. Often the disease affects only a percentage of the crop where the crop is densest and stays moist longer.
DPIRD research has found that fungicides applied at or after 100% flowering stage to early podding can significantly reduce disease levels in lupin but a yield response is not guaranteed.
Of the 11 trials conducted in the Geraldton port zone from 2016-2019, sclerotinia was at moderate to high levels in only four and there was a yield response in only one (in 2016 when there was a soft finish). Of the four trials with significant disease, two were conducted in 2016 and two in 2018, both years when rainfall was average to above average, crops were bulky and had good yield potential. In all four trials, sclerotinia infection was predominantly on the main spike and pods rather than the stems and this explains why a later fungicide timing to protect pods is appropriate. All fungicide timings applied from 100% flower to early podding on the main stem reduced incidence and severity of main spike sclerotinia infection as well as pod lesions.
More research is required but the benefits from managing the disease in lupin may lie in reducing sclerote production rather than increasing crop yield - that is reduced need to grade seed for sclerote contamination and reduced future risk of sclerotinia in future canola/lupin roations.
There was a grain quality response in one trial in 2016 so there could also be grain quality benefits from fungicide application even if no yield response.
A list of registered fungicides and rates for lupin sclerotinia can be found at DPIRD’s Registered foliar fungicides for lupin in Western Australia page. It is important to follow label recommendations and observe withholding periods.
For more information on sclerotinia stem rot in lupins refer to DPIRD’s Lupin foliar diseases: diagnosis and management.
To read about previous sclerotinia apothecia activity this season refer to DPIRD’s 2020 PestFax Issue 8 article Sclerotinia apothecia are being found.
For more information on sclerotinia in lupins contact DPIRD Plant pathologists Ciara Beard, Geraldton on +61 (0)8 9956 8504 or Geoff Thomas, South Perth on +61 (0)8 9368 3262
Article author: Ciara Beard (DPIRD Geraldton).
Article input: Geoff Thomas (DPIRD South Perth).