Zorica Duric (00:00): I'm your next presenter and I will speak about
aphids in pulse crops and cereal crops.
Zorica Duric (00:10): Okay. We are monitoring aphids in pulse crops,
mainly for the last few years. We are doing that work under the Grains Agronomy and Pathology
Bilateral Programme, which is actually founded jointly by investment of GRDC and New South
Wales DPI.
Zorica Duric (00:34): Why we are doing that? Well, because monitoring
and early detection of aphids in different crops is key to effective management. Aphids
can be very destructive crop pests, and they can damage plants directly through feeding
damages, or they can cause indirect damages by secretion of honeydew and also cause damages
through the transmission of plant viruses.
Zorica Duric (01:06): In order to support profitable cropping, there
is a need to actually monitor different aphids and find the best way to understand their
behavioural movement. We are conducting this kind of work using different trapping methodologies
as you can see from this picture.
Zorica Duric (01:31): Monitoring aphids is actually constant work.
Environmental conditions can influence, which in 2017, was shown as being very unfavourable
year for aphid and aphid multiplication. We can see from this slide that aphid movement
was very low in 2017.
Zorica Duric (02:02): In 2018, movement was even lower and which
was reflecting environmental condition during the season. In generally very low aphid moment
was noticed even with the mild autumn condition, so we could see that the aphid population
was really low. So in some traps even lower than 158 aphids per square metre per day.
Zorica Duric (02:38): But even though we had such a low aphid movement,
we noticed the very high population in our faba bean crop. So we found cowpea aphid built
quickly in observed crops and these dense colonies actually caused the damages, so the
direct damages together with the production of honeydew.
Zorica Duric (03:07): We noticed that in 2019, compared to 2017
and '18, it was still a higher peak of aphids coating our traps, especially one peak was
noticed from July to September. After that periods, aphid numbered declined as crop matured
earlier due the extreme drought.
Zorica Duric (03:33): At that same time, the population of beneficials
increased, which you can see from next slide where we actually find different beneficials
in our crops, including lady beetles like on this picture, but also at [inaudible 00:03:51]
hoverflies, parasitic wasps, and either predatory species.
Zorica Duric (04:00): In 2020, we noticed that aphid numbers in
our crops, actually we monitored the aphids in Lucerne crop, we noticed that the aphid
population actually at this moment is dropping down. So there were two main peaks observed
depending on the environmental condition and different aphid species were recorded. Among
others, the main aphid species were cowpea aphid, spotted alfalfa aphid, cotton aphid,
green peach aphid and oat aphid.
Zorica Duric (04:46): In this season, aphid infestation was reported
in [inaudible 00:04:51] district. During the inspection, actually high activity of beneficials
was noticed together with the cowpea aphid. Even though the New South Wales thresholds
for aphids in faba been emphasised that there is need to treat very low aphid numbers in
order to stop virus transmission, we considered not to use chemical control, as most insecticide
would destroy beneficial insects along with the pest.
Zorica Duric (05:26): Also we expected the cooler temperatures will
have significant impact on reducing aphid population, which actually they had. So we
decided actually not to spray this crop.
Zorica Duric (05:49): One more fact that actually helped us to decide
for such a thing because after testing faba bean plants, there were no positives for presence
of any viruses.
Zorica Duric (06:01): Now, just to conclude the story on aphids
in pulse crop, generally aphid population dynamics are affected by environmental conditions,
crop development, but also aphid biology and population of natural enemies. So please just
consider that your decision on aphid control has to have integrated the approach of all
mentioned factors.
Zorica Duric (06:35): One more thing I would like to point out,
this is picture of Megoura crassicauda, faba bean aphid, which has been found in parts
of New South Wales, actually in Sydney, Tamworth and Breeza in faba bean crop in 2017. It is
large aphid with a bright green body and dark head and legs. It has very intensive red eyes,
as you can see from these pictures, which are very recognisable and easy actually to
identify maybe this aphid.
Zorica Duric (07:19): But do not bother with identification. If
you find something similar, something suspicion-looking like this aphid, please just contact New South
Wales DPI or QDAF entomologist, and we will help you with the identification. So far in
2018 and '19, we didn't find this aphid. But we had two drought here, so it's possible
that this year, this spring, this aphid could again be in our faba bean crop.
Zorica Duric (07:57): Regarding aphids in cereal crops, different
aphids could be observed. Oat aphid usually form colonies in lower leaves on base of plant.
On the other hand, corn aphids and Rose grain aphids colonise the top of plant, particularly
corn aphid colonise the whorls. Cereal aphids are known as vectors of barley yellow dwarf
virus, and these aphids are found each year in crops in northern region.
Zorica Duric (08:43): Russian wheat aphid is something that you
haven't seen in your crops, maybe not all of you. But northern Tamworth region, you
haven't meet Russian wheat aphid yet. Hopefully, you won't. Russian wheat aphid was firstly
identified in South Australia in 2016. In 2016-1,7 infestation stretched into Victoria
and in southern New South Wales and Tasmania. In late 2018, first detections were made in
north of Dubbo then in Liverpool Plains and in Coonabarabran.
Zorica Duric (09:32): To-date, Tamworth, as I mentioned, is the
most northern site where Russian wheat aphid has been confirmed. No new detections so far
were made in 2020. So last confirmation were Bundella, Currabubula, Breeza and Tamworth.
But in 2020, we haven't even found them in sites where actually we confirmed its presence.
So you shouldn't be afraid that this aphid will affect your crop this winter season.
Zorica Duric (10:13): How to identify Russian wheat aphid. Russian
wheat aphid is pale green, spindle-shaped aphid, cornicles or siphunculus, are very
short, almost invisible. Russian wheat aphid has so-called double tail, which is actually
formation of its caudal and supercaudal process, which actually form like two tails. That definitely
will help you to identify this aphid because that is the feature that's actually make for
you easy to distinguish it from all other aphid species.
Zorica Duric (11:09): Russian wheat aphid host range is as follows.
Firstly, barley is a primary host plant, then wheat and durum wheat. Oats are resistant
to Russian wheat aphid and triticale is moderately resistant. There are no evidence of Russian
wheat aphid being a pest in sorghum or in maize.
Zorica Duric (11:32): But at Tamworth Institute, we are conducting
research on level of potential damages in sorghum and role of sorghum that might play
in maintaining Russian wheat aphid population over summer. As soon as we got results on
these issues, we will definitely publish it. So far, we found the Russian wheat aphid in
our positives, it was from volunteer winter cereals and from barley grass.
Zorica Duric (12:12): Russian wheat aphid can infest crops under
warmer condition, usually that's happening in autumn when it's a mild autumn or early
in spring. Usually Russian wheat aphids causes problems when populations start to increase
from tillering to stem elongation. Adults, so flights of adults occur in south, in South
Australia in October or during November as the winter host starts to dry off. During
summer, Russian wheat aphid has been found, as I mentioned, on different grasses, which
provide green breach for actually infestation of autumn plants materials.
Zorica Duric (13:06): Firstly, Russian wheat aphid will infest stressed
areas in paddock, which you can see from this picture. So this is a little patch where Russian
wheat aphid is actually found. Usually it formed colonies in patches and attacks younger
leaves, which have to be unrolled to be inspected. Leaves infested with Russian wheat aphid have
a long, usually white or yellowish stripes. Sometimes stripes can be purple. That's happening
when plant has been exposed to lower temperatures. These symptoms appear because of saliva of
this aphid, which is toxic to plant.
Zorica Duric (14:00): So far, Russian wheat aphid in Australia is
found to be manageable. In recent years conducted trials by SARDI reported that there is very
little or no yield losses when Russian wheat aphid was controlled before GS40. So be aware
that Russian wheat aphid is strongly regulated by environmental conditions. For example,
in higher rainfall area where, for example, we have like a heavy rainfall. That's happening
with Russian wheat aphid that that it's often washed off plant and which cause actually
50% mortality of one colony. So they prefer relative warmer, drier climates where annual
rainfall is less than 400 millimetres.
Zorica Duric (15:15): Existing economic thresholds for cereal aphids
in general are more than 15 aphids per tiller on 50% of tillers if the expected yield will
exceed three tonnes per hectare. But SARDI is conducting research on establishing thresholds
suitable for Australian system. So until they finished their work, the US threshold, especially
for Russian wheat aphid, needs to be applied, which is before GS32 if 20% of plants being
infested, you should apply some insecticide or after GS32, if 10% of tillers are being
infested.
Zorica Duric (16:08): If you need to apply any insecticide, please
select the softest option, for example, pirimicarb. Prophylactic folio treatments are discouraged
as they can affect the beneficials. Also natural enemies could limit the Russian wheat aphid
population, which actually I witnessed in Bundella sites and, of course, in Coonabarabran
were actually beneficials to kind of control the Russian wheat aphid.
Zorica Duric (16:47): If you find Russian wheat aphid in your crop,
or if you are suspicious, you should follow this strategy. Firstly, look for symptoms.
Be sure that it's not, for example, barley yellow dwarf virus or herbicide damage. Take
a look, stretch the areas. Firstly, unroll leaves so that you can see a colony inside.
If you find colony that is still looking like Russian wheat aphid, or if you are just suspicious,
just send photos of specimens or symptoms to New South Wales DPI or QDAF's entomologist.
We will inform relevant biosecurity entity.
Zorica Duric (17:41): That concludes my presentation.