It's really important that growers check their crops now because as we head into spring and
temperatures start rising, as they're doing now, we have this scenario where they can
absolutely explode in populations.
So what conditions are sort of the worst cases for insect pressure, and aphids are no different,
it's basically warm temperatures and relatively dry conditions.
This is what we saw earlier in the season, and this is what we'll see as we head into
spring when the canola canopy starts drying out and certain pests, particularly aphids,
become an increasing problem.
So they are very much dependent on temperature, anywhere from 20 to 27 degrees are really
ideal for aphid reproduction and they can produce in excess of sort of 10 aphids a day
and so it's an exponential growth in ideal conditions and that's really what hammers
plants and can cause flower abortion, reduced seed set, reduced quality, shifts in oil content
in the seed and these sorts of things.
Cabbage and turnip aphids are the culprits in terms of really causing damage to crop
and why they're important is because when they infest a crop at early flowering and
they start causing flower abortion, that automatically starts causing yield loss, particularly in
stressed plants.
so, in terms of being able to identify what aphid species you are dealing with in a particular
crop the first thing to know is aphids are very small so generally what we suggest you
use is either a hand lens, at least a 10x hands lens or what we're using a lot of these
days is actually a clip-on mobile phone lens and the reason why that is becoming increasingly
popular is you can take that photo and send it straight through one of our reporter apps,
such as the PestFax Reporter.
Send it directly to us if you're unsure or even if you think you might be sure at least
you can get a second opinion.
Being able to know what sort of threshold we have before a particular pest is going
to be economically damaging is really important for us to know.
So any sort of infestation level before that threshold we can say as a best bet threshold,
it is very likely to not be that worthwhile to spray if we're seeing those lower levels.
So through quite a lot of GRDC funded research we've conducted in the past, we've sort of
developed a best bet threshold for canola aphids for winter/spring for cabbage and turnip
aphids, that generally 20% of plants infested with aphids on the branches is the threshold
that we generally work with.
In terms of chemical control, we have two active ingredients that are registered for
aphids in canola, and that's pirimicarb and sulfoxaflor.
So we've only just in the last four weeks released a new app called Crop Scout, looking
at how they're distributed in a crop and how does that actually affect our sampling accuracy.
So every plant that you inspect can be mapped and so after you've done a number of these
surveys around a particular crop and applied that to multiple crops, later you can have
a look at the map and see exactly where aphids were above threshold, below threshold so the
idea is really so we can steer away from random, inaccurate sampling and being actually able
to visualise what’s going on at any time on a map and then see if we can target those
management activities.