It's been a relatively mild winter here so far, but not near the end yet. A good many of the hems have retained a lot of green foliage. Now, in spite of having some cold spells, a lot are trying to to actively grow.

The freezing nights are not slowing them down very much. Mine are grown in containers and I tend to leave the old dead foliage and allow the oak leaves that collect to act as a winter mulch. Unfortunately, it also acts as a safe haven for insects and in the case of hems that generally means aphids. If you poke around in the detritus you can also find other insects including ladybugs. The upshot is that on those already infested with aphids I'm trying to decide whether to clear off the dead debris and see if I can interfere with the aphid's growing population or leave it 'til later. In terms of potential cold weather, it's earlier than I like to remove it.

I'm not sure the plants and aphids are going to allow me to wait. I have some insecticidal soap that worked pretty well on new emerging growth last year. I think it's something called Safer's, but I'd have to check the name to be sure. If I don't kill the ladybug population overwintering, they will get off to an early start and do the job later. The aphids are always a bit earlier to start. They are aggravating. I think they encourage spring sickness, but that's just a personal idea of mine which may not have any truth to it all.

I use a systemic insecticide called Acephate. Ortho and Bonide sell it as liquid. It is available in granular as Orthene 97.
I only use this in he daylilies and tall bearded iris. So far so good on no adverse reactions on pollinators. also keeps the deer out of the garden!!!

Chris, is it the granular that keeps the deer away? I'm having problems keeping up with my deer program because of the weather. I use liquids, and they constantly are being washed away or buried under snow.

They are aggravating. I think they encourage spring sickness, but that's just a personal idea of mine which may not have any truth to it all.

I get plenty of spring sickness but have not had aphids on the daylilies, so ss can occur without aphids. I suppose it is possible that aphids could contribute by damaging the plant and introducing a fungus, but spring sickness certainly can occur heavily without them.

I get plenty of spring sickness but have not had aphids on the daylilies

I am very surprised that you have not had aphids on your daylilies. Although I do not see them on the daylilies growing in the field, more or less every daylily that I have potted and brought inside during the autumn and winter has been infested with aphids. They are not obvious (visible) when I first bring them inside but their populations explode after the daylilies have grown inside for a while. I suspect that they are common on the plants in the field but are kept at low numbers by natural controls that are not present indoors.

Curiously, bulb mites are thought to be ubiquitous on daylilies but I have not found them on any daylilies I have examined, while aphids would seem to be ubiquitous here.

I guess I've just been lucky, Maurice! I have occasionally seen aphids on daylilies I've received from elsewhere in Ontario. I've seen them on daylilies in a garden nearby but I don't know what species of aphid they were (more than one can affect daylilies). But I've brought my own daylilies indoors for the winter several times for various reasons - no aphid population developed over time. Perhaps they just can't handle the winters here where it can get very cold with little protective snow cover (as was the case this year until fairly recently).

I am hoping that this winter blast we had will kill a bunch of pests!! I hate aphids!

@Sooby

But I've brought my own daylilies indoors for the winter several times for various reasons - no aphid population developed over time. Perhaps they just can't handle the winters here where it can get very cold with little protective snow cover (as was the case this year until fairly recently).

I have 38 pots inside this winter and I probably have had 25 or more pots inside each winter for a number of years. I bring some of them inside in early October, some more in mid to late October and this year I brought some inside much later at the end of November. Most are growing under lights at slightly below normal room temperature (19C). Nearly all those have developed large populations of aphids. A small group had all their leaves removed and resprouted from their crowns - they do not have any aphids. Another small group is in a deep alcove next to a north window. The warmest they get to is about 13C during the day, perhaps 10C at night. They have not had any aphids. I suspect that the aphid populations are affected by the temperatures at which the plants are grown, as well as the initial population sizes when brought inside. Presumably the later the plants are brought inside the smaller the initial aphid populations.

I would think the later the plants are brought in the fewer living leaves are left for feeding (on the phloem) so the less likely aphids will still be present on them and the more likely to have moved to their over-wintering hosts depending on aphid species.

Edited to add, the aphids I saw on daylilies nearby were not the daylily aphid, Myzus hemerocallis.

@Sooby

Edited to add, the aphids I saw on daylilies nearby were not the daylily aphid, Myzus hemerocallis.

How can I tell whether the aphids on my daylilies are Myzus hemerocallis?

It would probably be difficult but a start would be whether they are green, and according to this page kind of orangey at each end. I know the ones I saw on daylilies near here were not daylily aphids because they were black. Telling daylily aphids apart from some of the other green species that can affect daylilies would be more difficult.

http://influentialpoints.com/G...

How do aphids move around? Does some stage of them fly? All my hems are in containers, but they are kept outdoors here and thus subject to the cold temps. It's been mild this year. The coldest night here has only reached down to 22F by my thermometer and so far all daytime temps have remained above freezing. Compared to last year when it set a record by falling below zeroF. Usually winters here have some days that don't get above freezing, but not many. Not all the hems have visible infestations of aphids. Probably only about 20-30% of those where the growth is up enough to really tell. Because we had another cold front move in, I haven't done anything. However, I did pull off the old leaves and clear off the accumulated oak leaves from a couple and they are continuing to grow in spite of some more temp drops. Neither of those show any sign of aphids - yet.

This is a scan of an aphid from my daylilies. Definitely green rather than black.

Donald, yes they typically do have a stage that flies but not year round. Maurice, it's a bit too fuzzy to tell - can you scan one on a white background somehow, or look at them under a magnifying lens to see if they have black feet?

@Sooby, yes they appear to have black feet.

Is there any sign of vague darker green stripes on the backs of the nymphs? Any Prunus trees nearby?

I do not see any vague darker green stripes on the backs of the nymphs that look normal (not squashed). There are wild Prunus serotina trees on the property but they apparently have a black aphid commonly.

I was trying to see if we could differentiate between daylily aphid and green peach aphid, the latter winters on Prunus species. Potato aphids also attack daylilies and have a green stage, also with black feet. I might be able to take a shot at ID if you could send me some A better bet would be U of Guelph diagnostic lab, but they charge a fee. A really sharp close-up image of their posteriors would help.

These are very small aphids, even when they appear to be adult. I do not have a dissecting microscope so those scans are the best I can manage currently.

You guys are like true detectives