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POSITION VACANCY AP #15-27
The International Citrus Conference was just held and about 1,500 people came from all over the world to share their experiences and research in citrus. It included marketers, growers, government officials and researchers who all had citrus as their interest. It was remarkable the volume of information, everything from world production figures and marketing, new varieties, breeding technology, plant diseases and pests, water management and of course HLB and ACP, probably the two most fearsome world-wide problems.
On the whole it was most hopeful to realize how much has been accomplished in the last several years to deal with the threat of HLB. The biology of ACP is better understood in different situations, the disease progression in different citrus species is being recognized as being more or less aggressive, and how to manage the insect and disease are better understood. Unfortunately, new threats (however none as mush as HLB) are being identified, such as citrus longhorn beetle. Oh, my.
Read the Abstracts at:
Pourreza, who earned his Ph.D. at the University of Florida in 2014, worked on early detection of Huanglongbing disease of citrus. Huanglongbing, an incurable disease that is spread by Asian citrus psyllid, has seriously impacted citrus production in Florida. The disease has been found in commercial and residential sites in all counties with commercial citrus.
Early detection allows growers to remove infected trees before the disease can spread to healthy trees. Currently HLB infection is confirmed when leaves with yellowing and blotches are submitted for PCR testing, which is expensive and time consuming. However, the yellowing can be also symptomatic of other conditions, such as nutrient deficiency.
“We discovered we could see the symptoms of Huanglongbing using a camera, a set of cross-polarizers and narrow band lighting before it is visible to the human eye,” Pourreza said.
He said the yellow blotches on HLB-infected leaves are caused by starch accumulation.
“If we could detect abnormal levels of starch in the leaf, we could tell it is affected with HLB,” Pourreza said. “Starch showed the ability to rotate the polarization plane of light. We used this optical characteristic to develop the sensing methodology.”
Pourreza said the team has patented the technique and is working on developing a commercial product. He is seeking funding to continue the research in California, where, to date, HLB has only been detected in isolated Los Angeles neighborhoods. Asian citrus psyllid is found in important California commercial citrus production regions from the Mexican border to as far north as Placer County.
Pourreza is based at the UC Kearney Agricultural Research and Extension Center in Parlier.
A portion of Placer County has been placed under quarantine for Asian citrus psyllid (ACP) following the detection of multiple life stages on citrus trees within the City of Lincoln.
The quarantine zone in Placer County measures 118 square miles, bordered on the north by Riosa Road; on the south by the Roseville City Limit; on the west by Brewer Road; and on the east by Fowler Road. The quarantine map for Placer County is available online at: https://www.cdfa.ca.gov/plant/acp/regulation.html#maps. Please check this link for future quarantine expansions in this county, should they occur. Quarantines in new counties will be announced separately.
This is a case where an individual moved infested trees from a quarantine zone into a clean county and ended up moving psyllid with the trees. This is how so many of our current pests are moving around - Shot Hole Borer, 1000 Cankers of Walnut, Emerald Borer, Gold Spotted Borer. On and on, we are the culprits of our own destruction. Pretty soon every pest known to plants will be everywhere. Sorry for the rant.
Since digging for strawberry plants destined for Salinas and Watsonville started at Macdoel just a few days ago, I thought it would be judicious to have a look at how many chill hours we've accumulated so far and what it means for additions to supplemental chill, especially for our day neutral varieties.
I checked with the Lassen Canyon nursery chill accumulator here: http://lassencanyonnursery.com/cumulative-chilling-hours-and-weather-conditions/ .
Looking at the data for Oct 18 of this year and running my calculations via the Utah model (which subtracts chill hours for temperatures realized above 60oF, see previous posts), we have currently accumulated 325 units of chill. Given that last year's chill accumulation was 164 units and by most commentator's opinion a decent accumulation, 325 accumulated chill units this year is very satisfactory.
So what does this mean for adjustments on supplemental chill? Personally, I think growers may want to take the strong field chill in stride, and now look forward to what sort of winter we are going to have. Looking at the NOAA data, we are probably in for a weak “La Niña” system this year, which according to the “Color Outlook Maps” for temperature, we have something like a 40% chance of having slightly warmer than normal temperatures in November, December and January.
The question then is what sort of adjustment should or needs to be made to supplemental chill. It's actually not an easy question to answer, given the strong field chill. Then again the odds of a slightly warmer than normal winter would give me some reason to err on the side of caution and go a tad longer than customary on the supplemental chill ./span>