That brown spot is a scale bug

also those white spots might be spider mites but it's hard to tell without extreme close ups

Actually on the underside I see a small scale insect. There are probably more. Look under the leaves that are right above the sticky white stuff and I bet you'll see more.

Because that white stuff is honeydew, which is kinda like scale droppings. (or aphid, mealybug, or white fly. They all excrete honeydew.)

The scale suck the sap and make the white honeydew. You can use various methods to deal with scale. Neem oil or just regular horticultural oil works well. You may need to spray a few times a week or so apart to get any eggs that hatch later.

Scale is so sneaky. Just checked, didn't find any others. For example, here's the underside of another leaf with honeydew. Anyway I'll neem in the morning. I assume I want to get the undersides of the leaves?

@pip313 you want extreme close up?

Sorry, I meant of the white spots on the bottom of the leaf

Neem oil, or just simple and regular washing goes a long way to preventing many of these kinds of ills.

johnmerr you mean hosing it down or hand wiping the leaves?

tom1328732 God I hope not. This is smaller than psyllids I think, like fine salt

Here is a picture of ACP droppings:

http://ucanr.org/blogs/venturacountyucce/blogfiles/3262.jpg

Looks similar to yours, I think.

Well, that sucks if it's ACP. I'm going to call an arborist.

Arborist was just here. It is indeed ACP. Eff me. Thanks to tom1328732 and citrange2 for catching that.

Sorry to hear that. At least you now know and can take steps to mitigate them in the future!

-Tom

On the subject of treatment, it's not a pretty picture. The most effective treatments are pyrethroids, neonicitoids and imidacloprid for systemic and they're all unacceptable in my book. From UC Davis:

Using organic insecticides to reduce psyllid numbers and prevent the spread of the psyllid or the disease is difficult, because persistence of organic insecticides is short and they require contact with the insect body to be effective. The persistence of organic insecticides is only hours to days (not weeks like some of the conventional insecticides), therefore it is necessary to apply organic insecticides frequently (every 10–14 days) and ensure that coverage is thorough.

The infestation is in early stages so I cut off all new growth and will continue with weekly neem oil treatments and monitor. As it warms up, the population will likely grow, and if it does, I'm just going to pull the tree and replace it with some non-citrus fruit next spring.

I called LA County Ag Commission and they told me it's so widespread now in LA County residential areas they don't even bother even taking your info unless you already have greening disease

It's not a pretty picture in that area. ACP is very well-established, so there are no hopes of eradication. It's just one of things you'll have to learn to contend with. Best course of action? I don't know.

Sorry to hear of this situation shecky. It is a dire picture in LA (and coming soon to the rest of CA unfortunately) because many homeowners do not know / or even care to know how to care for their citrus trees; or worse yet, know and refuse to utilize effective treatments. Thank you shecky for planning to do the responsible thing by pulling it / destroying it - that is - if your methods do not ultimately work or the treatments are undesirable. I hope it works out for you so please do keep us updated- - - good luck!

Thanks molewacker. I'll keep the thread updated if anything happens.

Quick update: spoke to my arborist again. He spoke with the country Ag Commission as well as some people at UC Davis, and his recommendation was to alternate weeks with neem and spinosad, so I'm going to give that a go. This will give a broader spectrum that will deal with the full life cycle of the pests, according to his discussions. The good news is the arborist seems very optimistic that I can beat or at least control this.

I know someone is going to tell me that spinosad will kill bees, but according to many studies, spinosad is safe for pollinators 3 hours after application, so it's just important to apply late in the day, at night or in the early morning. I will be doing it just before sunset when the bees are all safely back home.

I live in LA County also. It's just a matter of time as reality sets in.... Very depressing! Should we be treating our trees now with imidacloprid instead of using imidacloprid closer to leaf miner season?

Should we also be doing a foliar spray of spinosad/neem oil while the imidacloprid kicks in? (I think it takes 4 weeks for imidacloprid to work?) Will the combination of the three interact and harm the trees?

After the rain this w/e in Cali I gave the trees a close exam since all the honeydew had been washed off and I saw no psyllids. Still, I kept up with the regimen and did spinosad this week.

Looked again this morning, no psyllids or honeydew. Will keep it up, but this is looking good.

PKG I really don't know about imidacloprid. This is a pretty new infestation and treatments are still being worked out (imidacloprid was only recently approved for this). In any event, the knowledge here is evolving, so I'm not sure there's even a definitive answer to your question. That being said, I'd be happy to give you my arborist's info if you'd like. He's really on top of it.

I used to have this I I just found out about in the post, it had white stuff and scale bug, I thought it was water residue but it doesn't have it anymore thankfully, but yesterday I saw this green bug and the tree for two minutes so if any were there they drowned

Update: no reappearance so far. The regimen seems to be working.

Bravo!!!!! thank you for the status update. This is encouraging.