Pest Problem

[Palustris]

As some folks know I used to grow Auriculas, given up on them now because of the root aphids.
However, I did sow the last lot of seed which I had as an experiment. The plants were potted up in brand new peat free compost in brand new sterile pots and put on the concrete patio in the shade of the house, well away from any of the Auriculas which I planted out in the garden.
So how come they are all now infested with root aphids?  Where did they come from? No other plants get them and there were no other plants in any case anywhere near the seedlings.
The only thing we can think of is that the aphids come in with the compost or they may have been lurking on the seed trays.
Anybody got any suggestions as to how to get rid of them? At the moment all the plants are soaking in a vile mixture of Neem oil, Provado and Washing up liquid. Not bothered if it kills the plants as they are destined for the bin in any case.

[Tristan_He]

Hi Palustris,

Root aphids have a winged phase, so it's likely that even if you eradicated them, they recolonise this way.

In general I find that stressed plants (in primula this is most often too hot or dry) are more susceptible.

For more info there is a good article here:
https://www.planetnatural.com/pest-problem-solver/houseplant-pests/root-aphid-control/

Tristan

[Palustris]

Thanks. Still would like to know why they only seem to go on the Auriculas and nothing else. The plants were not stressed in any way that I could see though.
Bin here they come!

[David Nicholson]

When I was a Primula grower I used Methylated Spirits as drench and painted it through the root ball. Sometimes it worked, sometimes it didn’t.

[Palustris]

Tried that, it killed the plants!
Even odder is that I have just been looking through some P. siebodlii divisions. they were in a seed tray next to the Auriculas, not a single sign of root aphids on them.
The stuff recommended for controlling the blighters is £70 for 4 fluid ounces. Sheesh!

[Gail]

I've accumulated quite a few P. sieboldii and noticed how they have been very free of the pests that afflict my auriculas/other primula. Repotting auriculas can be a depressing experience with many vine weevil larvae chomping on the roots, but only once have I found a vine weevil in the sieboldii.

[Palustris]

That is good to hear.
Strangely in looking for root aphids, so far I have not found any vine weevil grubs in the pots. Perhaps they do not like the taste of aphids?

[Palustris]

Just been going through the Auriculas, again. The ones which have been soaked  for days in the insecticide do seem to be cleaner.  It looks on some of them as if the aphids have moved up to the surface of the compost so I have been spraying the base of the plants with an insecticide which claims to kill them and their eggs.
Watch this space.

[Graeme]

Hi Palustris,

Root aphids have a winged phase, so it's likely that even if you eradicated them, they recolonise this way.

In general I find that stressed plants (in primula this is most often too hot or dry) are more susceptible.

For more info there is a good article here:
https://www.planetnatural.com/pest-problem-solver/houseplant-pests/root-aphid-control/

Tristan

When I used to grow a lot of Auriculas I used to use Jeyes Fluid - and leave them in a bucket drench for an hour - it cleaned the long tom clay pots as well

I presume it's illegal now, like everything else that was any good

I did move over to cat litter and Jondo Hen grit mix with oyster shells and limestone chippings - can't remember seeing any after that

The place I used to get plants from you could guarantee they came with root aphids, so I always quarantined them as soon as I got them home

[Palustris]

Sadly despite doing everything that has been suggested, the few remaining Auriculas all had huge numbers of root aphids so I have stopped growing them altogether. Just not worth the heartache.
The ones out in the borders can stay and survive or not as they please, but the Theatre ones are gone.

[MarcR]

Palustrus,

Some horticultural supply vendors sell an insectivorous specie of nematode.

I think that is probably your best control.

[Vinny 123]

Some horticultural supply vendors sell an insectivorous specie of nematode.

Not in the UK - looking at the ones available in the US, the UK climate is almost certainly too cool for them here, especially for plants such as Primulas which prefer things cool.

I have very seldom had problems (VERY seldom grown Primulas in pots though), but a change of compost could work and keeping them well-watered (which ties in with the few problems seen here - gritty, fast-drained composts).

In pots, a drench every few days with something like cypermethrin might work - very safe (approved for use on food contact surfaces) but the most persistant pyrethroid there is on the market.

[Palustris]

Too late. All gone. Planted out in the garden and the theatre is now empty.

[lillianlambert]

Root aphids are such a pain, and it's so annoying to get rid of because there are so many of them. I've been battling with them for three months. If the roots are rotted, I recommend flushing your medium with H202 to help with it. I would do it a couple of times, then continually add it to your nutrient mix. It would be best to flush out as many as possible for the root aphids. Physical removal is key for getting aphid populations down. But to be honest, the only thing that helped me was a pest control sydney company. They used an eco-solution that killed them.

[Azkabanus]

What is the danger of root aphids ?