Interesting. So I have been watching the fruity one for 3 years now, and it seems to have that yellowish tinge every year. I just thought it was its natural color. It does seem to have a lighter colored leaf even in summer. Below are some pix I've taken at different times of year. (Yes, I'm obsessed with the stupid tree :-). We did have a dry late summer, maybe that contributed. But on the other hand - look at the foliage color difference between the two hollies even in summer: 2016-11-12: 2017-01-12: 2017-08-16: 2019-05-22

My sprayers have a nozzle attachment that deflects the spray upwards. Perfect for sticking in the middle of thick shrubs and getting the stuff to the underside. Hort. Oils should not be applied to broad leaf evergreens when temperatures approach freezing or above a hot weather limit on the label. I'd spray a couple of times in the spring before full flower and into the summer and fall. Oils are considered minimally toxic, but I wouldn't breathe it in or get it in my eyes. It's my habit to wear disposable gloves no matter what I'm spraying, as well as a good mask (not a respirator) . Your lungs are very sensitive organs....don't inhale stuff that can harm them. Even chemically benign horticultural oils should not be inhaled. Every product is different. Be sure to read and follow the label instructions on whatever you end up purchasing. Temperature restrictions as well as a list of sensitive plants should be reviewed each time you use it. And follow the dilution rates. More is not better! I've been using assorted oils with success and safety for many years, on evergreens such as hollies as well as a long list of deciduous trees and shrubs. Regarding the "flying insects " you mentioned. If they were the size of gnats, I'd be very tempted to guess that they might have been beneficial parasitic wasps. They pierce the scale insects in order to lay eggs; their larvae will then feed on the scale from the inside. Once they've developed, the wasps will drill a little exit hole and fly away. Parasitic wasps do a great job of controlling scale insects and other pests. I've seen swarms of them working my camellias, which often have a smattering of tea scale.

You might check with Forest Farm. I got Ilex cornuta "O'Spring" from them. (You know, you'd get more and faster responses with a less threatening user name. Just a thought.)

I find the stems of this plant to be extremely brittle and prone to breakage, you can almost snap a branch off just by lightly brushing against it. The weight of the snow did some damage the first year I had it, last year we made one of those /\ shaped things and covered it, that helped. Other than it being a bit delicate, it's a great plant, very attractive. I have ilex glabra compacta. PS: some birds/animals prefer berries after they've turned soft and old, often the next season when they're still hanging there and you think nothing is interested in them. I've seen this to be true with cedar waxwings + highbush cranberry, and chipmunks + ilex.