Citrus Growers Forum

David · Posted: Wed 03 Jun, 2009 8:16 pm

I am not offended by any comments to bolster a good discussion. I am sure that all of us have some ideas and opinions as to when and how the greening is spread as do the USDA and the State folks. I suppose that we shall all learn more about it as we live through it. It appears that if grafting is the only way of spreading the disease then it would be pretty easy to have it contained......by everyone using only clean budwood and such.....................David

Ned · Posted: Wed 03 Jun, 2009 9:21 pm

Good discussion, thanks all. I think we are all pretty much in agreement. I am not sure anyone knows for certain. After making my post, I found this. Bottom of page one, left column speaks to the question.

http://www.cdfa.ca.gov/PHPPS/acp/docs/usda/faq_citrus_greening.pdf

Skeeter · Posted: Wed 03 Jun, 2009 10:58 pm

Here is a very good scientific paper on the subject: http://www.doacs.state.fl.us/pi/chrp/greening/PHYTO-98-4-0387.pdf

The conclusions are particularly related to this discussion. They point out that it appears that psyllids flew (or carried by wind) across the everglades to infect a commercial grove, but the primary form of movement has been movement of plants--particularly orange jasmine.

They also mention that in a grove, the infected trees appear in concentric circles --requiring years to infect an entire grove--so their normal "natural" movement is pretty slow. However, FL DPI has a link that suggest natural spread of up to 15 miles per year. http://www.doacs.state.fl.us/pi/chrp/ArcReader/ArcReader.html

This paper also explains why they are not collecting leaves as it appears that even in infected trees not all leaves will show the disease when examined by DNA analysis.

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Skeet

morphinelover · Posted: Thu 04 Jun, 2009 9:38 am

Skeeter wrote:

Here is a very good scientific paper on the subject: http://www.doacs.state.fl.us/pi/chrp/greening/PHYTO-98-4-0387.pdf

The conclusions are particularly related to this discussion. They point out that it appears that psyllids flew (or carried by wind) across the everglades to infect a commercial grove, but the primary form of movement has been movement of plants--particularly orange jasmine.

They also mention that in a grove, the infected trees appear in concentric circles --requiring years to infect an entire grove--so their normal "natural" movement is pretty slow. However, FL DPI has a link that suggest natural spread of up to 15 miles per year. http://www.doacs.state.fl.us/pi/chrp/ArcReader/ArcReader.html

This paper also explains why they are not collecting leaves as it appears that even in infected trees not all leaves will show the disease when examined by DNA analysis.

Your right skeeter. To think that wind plays absolutely no role in the spread of the psyllid would be very silly. Your talking about a insect that is many, many times smaller than a mosquito so of course when the wind pics up they are going to get blown in the direction of the wind. Here is a little info for the ones that don't think that wind plays any role in the spread. http://www.cdc.gov/ncidod/eid/vol7no5/ritchie.htm Also, the bashing of the USDA inspector is ridiculous. Loosen up a little folks. Just because he doesn't know the difference between a Meyer lemon and a Eureka lemon doen't mean he wasn't trained well at what he came there to do which was to visually inspect the tree for abnormalities. That doesn't take a very educated person to do that sort of thing. What did ya'll expect, for them to send out a professor from a University in Florida? If they would have there would have been people complaining that they are spending too much of our tax dollars on this sort of thing.

Millet · Posted: Thu 04 Jun, 2009 12:58 pm

As far as I can read, no one in this thread, has claimed that wind has not played a roll in the spreading of greening. Wind can normally play a roll, either major or minor in many situations. In the case of greening, wind is certainly not the major factor. The vast majority of infection, of course, is caused by the ACP. BTW it was recently reported that so far, the best control of greening disease (close to eradication) has been accomplished by the people of Reunion Island. - Millet (1,325-)

morphinelover · Posted: Thu 04 Jun, 2009 1:48 pm

Some more info on controlling this disease and people supporting the idea that wind plays a very important role in the spread of the disease carrying insects. http://www.abc.net.au/rural/wa/content/2009/05/s2558522.htm

Millet · Posted: Thu 04 Jun, 2009 5:24 pm

Thanks Morphine for the article. Interesting information. Once again, I think every one has already agreed that wind can have an effect. Wind also effects many other types of problems concerning citrus. Still, with the disease greening, wind is not a major cause of its spread from tree to tree, it is the ACP. Anyway, I believe we are way past the point where the subject of wind has been beaten to death. Perhaps it is time move on. - Millet (1,325-)

Skeeter · Posted: Thu 04 Jun, 2009 6:43 pm

Millet wrote:

Ned, I would concur with you, that wind is not much of a factor in the spreading of greening. Wind becomes an important disperser primarily (or perhaps only) when one is talking about fungi that produce ascospores, such as greasy spot, melanose, black spot or alternaria, and wind blown rains in the case of canker. Greening is almost exclusively dispersed by the ACP. Ned, I did not mean to contradict the points you added, I was just saying that the main point was the lack of a valuable educated inspection. I should have phrased it better, I apologize for any unintended rudeness. Have a good day. - Millet (1,326-)

Maybe I misread this, but it seemed to say wind was not a factor.

Clearly, wind does not spread the disease--but it does spread the psyllid.

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Skeet

Millet · Posted: Thu 04 Jun, 2009 7:04 pm

OK, everyone long ago has agreed that wind certainly has the ability to move a psyllid, along with many other small items of nature. It is a given. The point never ever was that wind could not move a psyllid. The point was always, that the major factor in greening disease distribution is the ACP. However, in an effort to keep this thread interesting, and informative to our membership, it hopefully must be time to stop beating this poor dead "wind" horse to death. - Millet (1,325-)

dauben · Posted: Fri 05 Jun, 2009 1:59 am

'Don't know if anyone's attending UC Riverside's workshop on the ACP, but here's a link:
http://ccpp.ucr.edu/CA-Nurseries-WorkShop-06-11-12-2009/06-11-12-2009-CitrusNursery-WorkShop.pdf

Phillip

Patty_in_wisc · Posted: Fri 05 Jun, 2009 3:10 am

" time to stop beating this poor dead "wind" horse to death. - Millet (1,325-)"

Millet, I think you meant that you are all "beating a dead horse".

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Patty
I drink wine to make other people more interesting Wink

Skeeter · Posted: Fri 05 Jun, 2009 9:45 am

Personally, I think the information I found in this discussion is very useful information. Knowing the distance the psyllid moves or is moved by wind is useful. Finding out that DNA analysis of leaves is not reliable even in infected trees was a surprise to me. And if you read the scientific article you find that your chances of getting an infected tree when you buy one is much higher when buying from a big box store than directly from a citrus producing nursery.

What is scary, is that if one infected tree appears in Pensacola, then virtually any tree in Pensacola can be infected within a yr.

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Skeet