Well, then go to that orchard and look if you see some shoots of the rootstock and get it ...

Patty is that grove ever inspected? This is where a disease could go unchecked until it is too late.

As far as I know there are hundreds of given up orchards which are never checked ...

Yes, it is checked, Laaz. I spoke with our CDFA agent this summer when we had notification that the ACP was discovered in Valley Center (about 15 miles east of me). They did confirm with me that they regularly check the orchard, but it's 147 acres, reasonably large, and they stated that their traps were all on the northeast corner of the orchard, not anywhere else. So, they were going to hang more traps throughout the orchard. Sanguinello, our CDFA (California Department of Food & Agriculture) are very good about monitoring abandoned orchards. We've got a pretty sharp group of agents keeping an eye out for HLB. However, the chances of HLB getting started most likely will not occur in a managed or unmanaged orchard, but more likely, according to all the experts I've spoken with or heard from, believe will start in someone's backyard. Here in S. California, about 75% of all homeowners have at least one citrus tree in their yard. So, trying to monitor homeowners' citrus is essentially impossible.

Patty, why the private trees should be the problem ?

They get it from certified nurseries and they keep surely an eye on their trees.
Unmonitored abondened orchrds seam much more risky to me.

Anyways you should get that 3 generations proofed sevilla orange rootstock, best on that monitored edge ...

Well, because we already has the ACP here, Sanguinello. So, all it takes is one infected ACP that can come into S. California from Mexico, with smuggled citrus, or as we saw in Los Angeles county, smuggled infected budwood that transfers HLB to an existing non-infected ACP, and there you go - the potential for disease to be spread to previously clean trees. Backyard growers for the vast majority, are not treating their trees for the ACP as commercial growers are. And, aren't being monitored by the CDFA as commercial groves and abandoned groves are. Most backyard growers would not recognize early symptoms of HLB, and have an infected tree just sit in the yard for who knows how long, which, if found by the ACP, can then start the infectious process.

So, mainly because commercial groves are being treated and monitored, abandoned groves are being monitored, and because backyard growers are not doing any of the above, and are not familiar with signs and symptoms of ACP or HLB.

Good question, this very question was asked at the last citrus seminar I conducted, by a knowledgeable backyard grower.

If that is true, then the best thing you can do is to inform the private growers about that early symptoms AND make sure they won´t get troubles when report it.
With no troubles I mean no costs and a free new tree ...

I think that would help more than any other measures then.

Yes, that's what the www.saveourcitrus.org site if for. And, the CDFA has spoken to most of the CRFG's chapters in the state to help spread the word among the community, as well as had some public service announcements in key areas. That's the best we can do when you consider we have over 8 very large metropolitan areas, with over 22 million people residing in S. California (about 60% of the total population of the entire state). Very hard to educate 75% of 22 million people.

... and a lot of illegal "invaders" from Mexico ...
I see no chance to isolate on the long term, but I wish you luck ...

You're right, Sanguinello, this is the fear of the CDFA - how on earth can we monitor and then isolate/treat all the backyard citrus here in S. California? Our commercial growers, the few we have left in S. California, have been on a preventative treatment plan for ACP for several years, now, learning from the mistakes made in Florida. But, homeowners rarely treat on a regular basis for anything here. Our citrus are fairly pest free, with few exceptions. I was told by our CDFA agent that I did not need to start a preventative treatment program because the ACP has not been found in my area. I am treating, but for CLM, since I have so many young citrus, so I made my own decision to treat twice a year with imidacloprid, because the psyllid was found so close to where I live. That means one more treatment a year for me (every 6 months). Not a fan of having to use pesticides, but for right now, this is the best and most effective treatment out there for the ACP, and I don't want to lose my entire citrus orchard, which has become extensive, and I have a significant investment in. That would be catastrophic.

Well, I think no pesticide is the better way, for natural enemies would do a better job but pesticide, which kills all.

I also do not understand why you concentrate so much on this psyllid.
Every insect which sucks or munchs on an infected tree can transport all virus, bacteries and fungy that are on one plant to hundreds others ...

Oh boy, here we go, again. There is no natural enemy that can prevent infected psyllids from passing on HLB to clean citrus. Researcher are studying this method of control, though, in hopes of reducing the numbers of ACP, infected or not. One of about 20 different research projects around ACP/HLB worldwide right now. And, I expect we'll see a combined approach eventually, for the control and eradication of HLB, including vector control.

If there was a more organic method, believe me, we'd all be using it. Why do we concentrate on this? We concentrate on this because it has decimated the commercial citrus industry in the state of Florida, cost that state's commercial citrus industry billions of dollars of lost revenues, cost the industry tens of thousands of jobs (this has put people out of work, Sanguinello, and has shut down generation's old citrus orchards, putting entire families and several generations of families and their workers who depended on that job to survive out of work). This is a big, big deal here in the United States, as we are one of if not the leading citrus producer in the world.

HLB is a very interesting disease, it kills its host, therefore, eventually kills itself. In nature, if we let nature take it's course, HLB would eventually die, if it ran out of susceptible hosts. Unfortunately, we cannot allow that to happen, and completely wipe of the world's citrus cultivars in that process. The other odd thing researchers have noted, is citrus trees have not developed resistance sports. The host plants have not been able to adapt. This, along with the inability to grow the organism in a Petri dish (Candidatus Liberibacter asiaticus, the Candidatus indicating that it cannot be grown in vitro) make it very hard to study and research, and come up with a cure or control.

I think we've had this discussion before. I think, because your area of the world (southern Europe and their respective citrus growing areas) has not yet had to deal with it, you are having a hard time understanding why this is such a serious threat to citrus. Southern Europe has not been threatened, mainly because it is protected from the spread from Africa moving northward, due to the large expanse of desert. If your area of the world DID have to deal with this, I suspect you'd have a very different opinion.

And, we're seriously diverting from this message thread, so let's get back to rooting gels, eh?

yes .. one short remark to explain:

I think it is dangerous to concentrate on the psyllids so much while a single spider mite could do the same damage ...

What!?! Spider mites do not transmit HLB. Just the ACP. True spider mites are not vectors for any citrus diseases that I am aware of.

http://manatee.ifas.ufl.edu/lawn_and_garden/master-gardener/gardening-manatee-style/c/citrus-pests-mites.pdf