Greening Updates: 2018
It's been 13 years now since the start of the citrus greening crisis in the US. And there are some positive things we've learned that need to be shared.
Just what is 'Greening'?
Citrus greening aka Huanglongbing (HLB for short) is a deadly bacteria that (in America) is spread by an insect called the Asian citrus psyllid.
The bacteria becomes systemic and kills the tree by plugging its phloem and causing starvation. Phloem is to a tree much like veins and arteries are to humans.
"citrus greening" or huanglongbing (Photo by Joe Raedle/Getty Images)
fruit damaged by Greening will taste bitter, is likely undersized, will remain green at the blossom end, and could be mis-shapen
Updates on Greening: 2018
Updates on greening.
Greening is widespread in Florida and has caused considerable damage to citrus production. But of notable significance is the recent discovery of several groves of citrus growing amongst the mayhem with NO evidence of psyllids or greening --- groves that are 100% resistant to greening disease. Groves that are supplying orange juice to Uncle Matt's Organic juice company. Umm... did I say organic? yes! And the University of Florida is studying why.
Nutritional support helps a lot.
It seems that organic nutritional support keeps showing promise in the fight against the disease.
Remember the Maury Boyd story of how one brave farmer designed and tested an enhanced nutrition program using foliar spraying to combat the effects of greening and saved his groves? Many at the time were not just doubtful, but downright angry with Boyd for choosing a different path to solution, assuming it further endangered them.
Luckily Boyd prevailed. Researchers in Immokalee replicated his successes, and that study led to over 90% of growers in Florida including foliar nutrition spraying similar to Maury's in their feeding programs. Even the last two holdouts are changing their approach. Read Maury's amazing story here.
Comment from UF professor Robert Rouse who has conducted a long running study of Boyd's groves: "He's doing better with greening than he was before greening."
And from Maury's own lips:
“I worry less about the future than I used to. I’m beginning to think now that this is sustainable,” he said. And now at 69 years old, “So I’ve been wondering, kinda, ‘What am I gonna do?’ I think what I’d like to try to do is buy an orange grove or two.”
Common theme among the growers now:
Feed Your Trees regularly and consistently, including with foliar spraying.
Understand that nutritional feeding helped the sick trees to produce good fruit and appear to get on top of the disease. It is unproven whether or not the bacteria can be destroyed through nutritional support.
Available in 3 sizes: RTU quarts w/ hose end sprayer or Pro Choice concentrate quarts or gallon jug bulk refill: available here
Pro-active insect control is still essential to controlling the spread of the greening.
And 'dormant spraying' in the winter to kill psyllid populations has been found to be the best way to slow down or eliminate infestations before spring flush.
We're using our cedar oil as both a soil drench and a tree spray. While it has not been tested specifically against psyllids in particular, its overwhelming success with everything else creepy crawly suggests to us that it should be most effective in the war on psyllids.
And it doesn't hurt the bees!!!
One application of cedar oil can be as inexpensive as $50 per acre.
Thermotherapy kills HLB!
Thermotherapy is a technique research scientists have been testing on citrus since 2012 in the effort to control greening. It has been shown to kill the HLB-causing bacteria under controlled environments when trees are heated to at least 120 degrees for several minutes.
While it sounds promising, exact time and temperature for field conditions is not yet known and the science is still being discovered. You can read the latest on this therapy here and here.
In another test of thermotherapy under greenhouse conditions, researchers in Fort Pierce, FL working with the Florida Department of Agriculture and Consumer Services (FDACS) have found that heat treatments may be an effective deterrent.
For the test, researchers worked with 2.5 year old citrus plants in 1 gal plants, under fluorescent lighting, 12hrs on / 12hrs off.
Results showed that exposing citrus seedlings to a minimum of 48 hours of temperatures of 104 ̊F to 107 ̊F significantly reduced, and often eliminated, HLB infection. All of the heat treatments were equally effective, regardless of temperatures and exposure times.
The researchers continued to test the seedlings, and after 2 years of heat treatments, they have remained free of HLB.
Results were published in the journal Phytopathology.
Read more on this study here.
Breaking news:
Thermotherapy: heating the citrus trees to a minimum of 120 degrees for several minutes has been shown to kill the HLB bacteria!
In yet another field test using solar heating, Florida citrus grower David McKenzie has been encasing citrus trees in opaque, plastic PVC “tents” to heat them up for about a week, then removing the tents and trimming off the top 12" of growth that has been singed by the heat.
The results have been striking. Stunted leaves begin to flourish, and by the time the fruit is ready for harvest, its quality is noticeably improved. Read more here and here.
It works best when the HLB has not yet reached the roots. And it appears to knock back the quantity of the bacteria within the plant, though it is difficult to eliminate the bacteria in the field with just solar heat.
Working with researcher Dr. Youngping Duan, David McKenzie is tenting the trees in his grove for about a week with structures like this.
heat tunnels to cover 600' rows of mature citrus trees, raising the temperatures to 107-130 degrees to kill the HLB bacteria
In another test, grower Rex Clonts of Clermont is working on a modular tenting structure for practical field application to tent a 600 foot row (52 mature sized trees) at a time.
His design uses high tunnels of standard greenhouse materials with fans to circulate and thermometers to monitor, so that temperatures can be kept consistent enough not to burn-damage the trees. Read more here.
Another positive note to end this on:
“People who are good managers and doing everything right can still make good money on citrus,” said University of Florida economist Rodney Clouser.