I sent a photo of a suspected Asian Physillid infestation (per advice from this column) to the Dept of Agriculture and they came out and inspected my many citrus trees. They didn't seem to think that any were resistant because they checked all the oranges, lemons, limes, mandarins and grapefruit.

The only one affected was a Valencia Orange, but the infestation on my tree was NOT carrying the disease. They took samples with them for testing, and informed me all was OK. They insisted that we use a systemic insecticide on a regular basis. We have huge commercial citrus orchards in the valley below and some of them are under quarantine. This was a couple years ago and all our citrus are doing fine.

Its not the disease but the Asian Citrus Psyllid that caries the disease. If there are citrus trees that are favored by Asian Citrus Psyllid, you can plant those as trap plants and heavily poison those to keep the Asian Citrus Psyllid off your desired trees. Being a northerner I know little about citrus or their pest and can't help on either. I do use trap plants for other things I grow with near 100% effectiveness. Perhaps fast growing and tender seedling trees are the trick. Good luck all.

Steve

You won't be able to use a particular citrus as a "trap" tree and keep infect ACP's off your other citrus trees, Steve. Just not possible, as the ACP isn't that particular. Bananafan, there are some citrus cultivars somewhat more resistant to HLB (certain grapefruit roostocks), but that is such a relative term. You may get one more year's growth out of a more resistant cultivar, but once the tree is infected, it is a death sentence, whether it is 5 years or 6 years. I would talk to the ag folks at University of Florida. They can give you more information on what cultivars seem to be able to withstand HLB a little longer than other cultivars if you're really wanting the info, but in the long run, any tree infected with HLB is doomed to a slow death at this point. Your best bet is regular systemic treatments following what your ag folks recommend for your area.

Possible Cultivar Greening Resistance

And Suzi, we do have have any reported cases of HLB, yet, in the state of California with the one exception of the grafted branch of a pummelo in Los Angeles county a couple of years ago, and that tree has been destroyed. Just the vector insect, the psyllid. And yes, using a systemic insecticide (Imidacloprid) 3 or 4 times a year will help to control the psyllid. And all orchards in your area are under quarantine. Your entire county (Riverside) is under quarantine.

CDFA - California Citrus Quarantine Information

Patty S.

While there is no known variety of citrus that is resistant to HLB, there are some that are less susceptible; and that is due to the preferences of the ACP. Thanks to the research done by one of my mentors from Texas A&M Citrus center, Dr Mamoudou Setamou, we know a lot about the habits and preferences of the ACP. If you release a group of ACP in front of a mixed citrus grove, they will first attack the lemons and limes (and unfortunately for me, the first favorite is the Meyer); next oranges; then grapefruits and pomelos; and lastly the Kaffir/Makrut "lime", which is not really a lime. The ACP just doesn't like it very much. One of my long term goals is to surround all my groves with a row or two of Makruts to "encourage" any ACP's in the area to go somewhere else.

Unfortunately, unless a HLB cure is found its only a matter of time until infection for citrus trees in the state of Florida.

Imelda, a systemic insecticide will prevent the spread. That is the cure.

It is far more likely to cure AIDS by teaching people monogamy to prevent the spread than to cure HLB by using a systemic insecticide. People can think and still don't cooperate. Trees can't think or come forward

Suzi, systemic insecticide will also makes the fruit uneatable. Suzi, shown below is a web site that shows possible or partial resistance of various citrus varieties. Hope this might answer some of your questions.

http://www.citrusresearch.org/wp-content/uploads/Stover_Ed_Is_there_useful_resistance_HLB.pdf

Suzi, using a systemic insecticide (Imidacloprid) is not a cure for HLB. It will kill any ACP's that happen to land on your tree and attempt to feed. The state of Florida would love for this to be true, but sadly, all it will do is slow down the spread of HLB, once it arrives here in California.

Imelda, using a systemic insecticide at recommended levels does not render fruit inedible. Some folks may object to the use of non-organic methods, but there simply isn't any viable organic method to control the ACP right now to enough of a degree to prevent an infected ACP from infecting your citrus trees with HLB. For right now, in dealing with and containing HLB, there simply isn't any other option. Some of the other experimental treatments Florida and other infected states are trying, such as steam heating, the use of benzbromarone to kill the bacterium, development of GMO resistant/immune cultivars, and other various vector control experiments will no doubt provide a mix of several approaches in control and eradication of the HLB organism.

For now, the most effective treatment in trying to keep a citrus tree HLB-free is a regular and safe systemic pesticide approach. And to make this perfectly clear: there are NO truly resistant citrus cultivars. John has mentioned that the psyllid may not prefer the Kaffir lime, but it is not resistant enough not to succumb to HLB, eventually. Same with grapefruits, until researchers can develop a truly immune cultivar.

And, researchers are looking very closely at those more resistant cultivars to try to see what makes them so, in order to develop a truly immune cultivar. Unfortunately, trying to develop immune cultivars that takes thousands and thousands and thousands of attempts just to find ONE possible immune cultivar. We have over 3,000 different citrus cultivars. There simply isn't enough time or money to make them all immune using this approach. So, the only cultivars researchers are currently focusing on (Dr. Steve Mirkov, out out Texas A & M) is pioneering these genetically modified cutlivars using spinach genes. He has has some significant success, but I believe he is only up to about 3 or 4 cultivars after several years now, and many thousands of attempts.

One of the most interesting HLB research projects is the one trying to identify the gene in citrus that makes them susceptible to HLB, and turn that gene off. If that can be found, and the gene should be in just about the same location for every citrus gene mapping, THAT would be duplicatible, and citrus researchers could then make an immune version of about every citrus cultivar out there. But then, you know there will be that group of people who will pitch a fit over a "genetically modified citrus tree". There is no easy answer to this disease, sadly.

Patty S.

I just do what the Ag's told me to do. Imacloprid. Period. I don't question. They are protecting the commercial orchards, but I am happy to comply. FYI, Imacloprid in any form will not kill you! or even hurt you! It will kill the evil bugs that spread disease. Been using it for years on our vineyard. That glassy winged sharpshooter is death to a vineyard. Yep! I'm proudly a user of Merit which is a form of Imocloprid.

I think if there is a toxicity level for bug it's there for mammals, esp. if we eat the fruits over a span of years.
http://www.ipm.ucdavis.edu/TOOLS/PNAI/pnaishow.php?id=42

Really bummed to see this nasty disease is plaguing our citrus tree industry and home-growers.

Being a chemist, my thoughts for treating HLB goes immediately to antibiotics. It looks like there is some hope in this area (see link to the article below). Some of our oldest beta-lactam antibiotics (penicillin, ampicillin, ect.) are quite effective at treating the HLB bacteria. Although at this point, to subject trees to antibiotics on large scale might have large financial implications in addition to not helping our antibiotic resistance problems. I also didn't get a sense of whether these antibiotics could be applied through a foliar spray. Seems like some work still needs to be done in this area but it could be promising.

Link: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111032

There are natural antibiotics that have been used for thousands of years to treat humans. Oregano Oil (100% grown wild in the Mediterranean) is one. Google it. You will be surprised at it's many healing properties. Being oil, not sure if it could be used as a foliar spray. Neem oil is used, but I don't think the leaves absorb it.. A lot of essential oils are known to heal disease in humans, as is natural honey.

zwoydziak, read up about the research around HLB (Candidatus Liberibacter spp., the "spp." indicating that it cannot be grown in vitro, but only in situ, which is one of the biggest issues with research - very difficult to grow and can only be researched in situ). And, read up on the research study being conducted by Claudio Gonzalez and Graciela Lorca at the University of Florida. They are examining three biochemical treatments: phloretin, hexestrol and
benzbromarone. The have had significant initial success with benzbromarone, a drug used in humans for gout. Benzbromarone appears to targets a specific protein, known as LdtR, in the bacterium. When benzbromarone binds to LdtR, it
inactivates the protein, which disrupts a cell wall remodeling process
critical for the greening bacterium’s survival inside a citrus tree. So, in this sense, it acts like an "antibiotic" as many other antibiotics act as a cell wall disrupter as well. They now want to see if this chemical alters the flavor of the fruit in any way. So, this particular study has some very significant promise, as it would be pretty easy to treat and continue to treat affected trees, which would mean a viable option for us hobbyist growers.

Another very interesting study that I cannot find any information on, is a researcher (I believe in Japan) using the Tristeza virus. They are altering it and using it as a vector, to enter the tree, enter the bacterium, and kill it. Sort of a "silver bullet" treatment.

Suzi, your treatment is sound, just want to make it clear that it is not a "cure" for HLB, but your treatment plan is designed to manage ACP infestation. If the state of Florida had taken this approach early on, when HLB was first found in their ACP population, and had been aggresive in their approach, as all commercial citrus growers in the state of California have been for that last about 10 year, they may have been able to significantly reduce the percentage of infected trees. It is estimated that at least 75% of all trees in the state are now infected, with that number rising to 100% in about 5 years, based on scientists studying HLB.

Patty S.

Thanks Patty and Suzi for the additional thoughts. Suzi: A natural solution to the problem would be fantastic for many different reasons, but as you pointed out there are complications that can arise from those too. I wonder what people have tried. Patty: Wow! 75% is a huge number of trees. I knew this was a huge problem but didn't realize the extent of it. I'll definitely read about Gonzalez and Lorca studies as it should be interesting. I've never thought about antibiotics for plants before, but with such a large number of trees infected combined with a huge loss of revenues in the citrus industry it is worth researching. It certainly has the potential to become a reality for all of us home growers in near future, and if you live in Florida it already is.

As I understand from Zuzi post, if an Asian Citrus Psyllid lands on a Imocloprid protected tree and feeds on that tree, the psyllid will die. However, if the psyllid is already carrying the HLB bacterium when it feeds on the imocloprid tree, the citrus tree will still become infected and in a matter of time will die. If so, at this stage of HLB in Florida it would be a waste of money to treat with imocloprid.

imelda_2010, if you are referring to me as Zuzi, I never said that. You are assuming things not said. The systemic insecticide kills the critter spreading the disease, but some of the ACP don't even carry the disease. I suspected the Asian Citrus Pysllid on an unprotected tree, and the AG came out. They took samples, inspected our trees, and when the results came back they quarantined none. BUT they gave me strict instructions to use Imocloprid. NEVER did they say that if an infected ACP had dinner on the tree that the tree would get infected. They want to prevent infection. You read something wrong.

Suzi, sorry for how I worded my post. I meant to put out a scenario that a imoclopid protected would still get HLB if a HLB infected citrus Asian psyllid feed on the tree . Sorry again. I'll try to word my post more carefully

It would still get infected and if a clean ACP bit into a treated but infected tree it may have time to bite into other trees before it dies and thus spread the disease

I think all of us need to be responsible. If there is a natural cure, use it. But the AG guys commanded us to use Imocloprid. Period.

I agree. ...am using Imidaclorid 0.5g granules - get 30-40 lb bags from the local irrigation supply distributor. Now, ...if i could just permanently get rid of those ants and moles and ... and .... and ....!

Imelda, commercial orchardists in Florida (and in all citrus producing states), don't just rely on Imidacloprid. They use a series of various foliar and systemic insecticides to try to manage their orchards. The goal for commercial growers in Florida is to try to keep the trees alive a year or two longer than the average 5 year death rate. Right now, they are rotationally re-planting their orchards, and relying on several pesticides, as well as other measures (such as the one John mentioned - planting less desirable trees around the perimeter of their orchards) to try to stretch out their replacement rates due to death from HLB.

The goal for our commercial growers here in California is to kill the psyllid prior to being able to feed on the tree, or incapacitate the psyllid to such a degree, that even if it does begin to feed, there isn't enough time for a potentially infected psyllid (I use the adverb, "potentially" to indicate that we do not have any infected psyllids discovered, yet in California) to inject their infected saliva back into the tree, and thus infect the tree.And, as Steve has pointed out, most certainly would not make it to tree #2, to spread the disease. Also, imidacloprid is a neonicotinoid, and one of the useful features of neonicotinoids is that they are anti-feedants, so psyllids don’t want to feed on trees treated with them. It causes the tree to naturally repel psyllids. Commercial growers have been recommended to apply imidacloprid systemically every 6 weeks, and then use various foliar pesticide applications in between that use different modes of action.

Suzi, that is the philosophy behind integrated pest management - use the least harmful management option, first. Only resorting to more intense or toxic management options if the less harmful options are insufficient. You're doing the responsible thing. I was using Spinosad only to treat CLM, but now, I am compelled to also use Imidacloprid as well, since I have over 100 citrus trees on my property, and am adjacent to 157 acres of completely un-managed and abandoned citrus trees that are a giant magnet for all manner of pests. I don't want to use systemic pesticides, as I don't relish eating fruit with pesticide residuals, which is why I grow my own fruit. But, we are in extreme times, and as they say, "extreme times require extreme measures". I am very careful to apply only the recommended amounts and frequencies. I spray my Spinosad in the evening, after the bees have gone back to the hives, and try to spray only after blossom time is over (not always possible with my lemons, as they bloom multiple times).

Patty S.

How will Imidaclorid affect honeybees?

 Aren't some of them using chickens  And bug eating incects

  They  found a certain  extract from oak leaves  can kill the greening deiese

 Uncle molewacker  zone9b  chickens and praying mantis will eat ants and moles to a limited amount