The whole group of plants we lump under the taxonomic classification of citrus are really changeable. It's out of this changeability that we get new varieties. Some of these can be quite fanciful, almost dream like fruit which is where the origin of the name chimera comes from. Buddha's Hand is a pretty dream-like fruit.
These changes are a genetic mutation that occurs in a branch or twig, and if that tissue survives, it can produce new shoots (called sports or chimera) with characteristics different from the those of the mother tree. These mutations can affect the color of the rind or pulp or the shape of the fruit.
Leaves on these twigs can have a different shape or size have a variegated color.
Mutations can cause the development of multiple buds, creating bunchy growth or “witches' broom.”
A chimera can produce an improved crop: some of today's cultivars were propagated from chimeras, such as the variegated pink lemon.
Usually sports are of inferior quality and should be avoided as propagation material. Prune sports that obstruct normal growth or interfere with harvest.
But some of them are so weird you just want to keep them around. This one showed up on one and only one tree branch in a lemon orchard. It looks like citrus scab, sort of, but on only one branch of one tree.
Some of the changes that you see in a tree can also be symptoms of a whole lot of other problems, like nutrients, Huanglongbing or herbicide damage. Check out some of the symptoms:http://ipm.ucanr.edu/PMG/C107/m107bpfruitdis.html
Some chimeras are yet to be found out. This image of spiral tattooing showed up for several years ago in a Meyer lemon orchard. It was erratic and inconsistent in a tree, not typical of a chimera. The orchard was finally removed because it wasn't making money. Now it just seems like a dream and will never know if it was a true chimera.
Task Force ACP-HLB update
To date, 232 residential citrus trees in Southern California have tested positive for the HLB bacterium. All have been, or are being, removed. Most were in neighborhoods in LA and Orange counties. Three of the trees were in Riverside, and although they were residential trees, the resulting 5-mile radius quarantine for HLB is affecting a few growers in Riverside and San Bernardino counties.
The latest HLB quarantine map with the running tally of HLB detections in the state can be found at the Citrus Insider website: https://citrusinsider.org/maps/. The maps are updated every week.
As HLB detections increase and spread closer to commercial citrus, it is a good time to consider removing any citrus trees that are unloved, uncared for, or not worth the time and resources required to protect them from ACP and HLB. Untreated citrus can serve as a reservoir for ACP and possibly the disease HLB, increasing the risk to other citrus in the area. The Citrus Matters ACT NOW program may be able to assist with tree removal at little or no charge to you. Find more information at: https://citrusmatters.cropscience.bayer.us/commercial-grower/act-program. Or if you need referrals for tree removal services, contact Sandra or Cressida.
ACP-HLB program meetings
The California Citrus Pest & Disease Prevention Committee (CPDPC) is made up of growers and other representatives of the citrus industry, working with the California Department of Agriculture (CDFA) and others. The CPDPC is funded in large part by grower assessments and steers the statewide effort to protect our citrus from ACP and HLB. The full committee meets every other month, with subcommittees meeting in between. All committee and subcommittee meetings are public and open to anyone to attend or listen remotely via computer or phone. Agendas for upcoming meetings and minutes from previous meetings are posted on the CDFA website: https://www.cdfa.ca.gov/citruscommittee/.
Coastal citrus representative needed for CPDPC
There is an opening for a grower representative from the coast to serve on the CPDPC. Be a part of deciding how grower funds are spent to protect our industry. Details can be found here: https://www.cdfa.ca.gov/egov/Press_Releases/Press_Release.asp?PRnum=17-069.
Santa Paula crew boss workshop
On Wednesday, Nov. 29, the Citrus Pest & Disease Prevention Program and California Citrus Mutual are hosting a free train-the-trainer workshop in Santa Paula. This Spanish-only workshop for crew bosses, ranch managers, etc., focuses on preventing human-aided spread of ACP and HLB. It has been approved by the Department of Pesticide Regulation for 2 hours of continuing education in the "other" category. For details see:
Feel free to contact your ACP-HLB grower liaisons if you have any questions or need assistance:
We are creatures of habit and when we see the effects of a treatment, we can often persist in seeing the same or similar symptoms and assuming the cause is the same. In a recent case, a newly planted ‘Pixie' orchard, planted in August had gone into an old ‘Valencia' ground. The trees went through an adjustment period, but still didn't look sprightly in the fall. The grower applied a hand application of urea on the rootball that within 10 days had caused the trees to go into a salt swoon. Meaning, they got too much fertilizer that burned them. The grower seeing the effect, immediately started the sprinklers, but the damage was done. Several months later the trees had either died or were still lingering, but hanging in there. The trees were still coming out of winter, but the trees hadn't perked up. It was a dry winter and some of the yellowing was due to underirrigation, that overall yellowing from lack of nitrogen and the leaves were curled. But the assumption was still that the trees were recovering from the salt burn from the urea.
Looking more closely at the trees, something else was odd about some of the trees that were continuing to die. The leaves suddenly wilted. Getting down on hands and knees and digging around the roots, there were few roots and ………………………….a tunnel. A gopher had been at this tree and the lack of roots were probably due to Phytophthora root rot. Looking around there were some old ‘Valencias' that had been hit by gophers and there were gophers mounds and runs all over the place.
So, young trees planted in the heat of the summer into root rot ground with gophers waiting in anticipation that had been salt burned in a year with little rainfall. A lot of causes for trees that generally weren't happy – triste, as they say in French.
So what are the lessons here? Avoid old citrus ground when planting with citrus, and if you can't make sure, don't plant in a stressful period. Phytophthora loves stressed trees and adding lack of rainfall an gophers and salt, just heightens the stress. Make sure to get the irrigation right. Don't irrigate them to the schedule of the older trees and start them off on one of the phosphite materials.
Wilted, yellow leaves from lack of water and Phytophthora
Gopher chewing on stem
Gopher run and lack of roots from Phytopthora and gopher
Gopher mounds in planting area
Older Valencias dead and dying from Phytophthora and gophers
Arpaia M.L.; Kahn T.L.; El Otmani M.; Coggins C.W.Jr; Demason D.A.; O'connell N.V.; Pehrson J.E.Jr, 1991: Pre harvest rind stain of valencia orange histochemical and developmental characterization. Scientia Horticulturae (amsterdam). 46(3-4): 261-274
Pre-harvest rindstain of California [USA] cultivar 'Valencia' orange Citrus sinensis has economic significance since fresh fruit marketability is reduced. Quantification of the incidence of rindstain as related to tree quadrant has allowed us to designate quadrants where rindstain was most likely to occur (upper outside SW) or least likely (lower inside NE) to occur. Growth and development characteristics of fruit from the two quadrants were measured throughout fruit development. Significant differences in percent weight loss between fruit from the SW and NE quadrants occurred at color break and at commercial maturity. Structural and histochemical changes in flavedo tissue of fruit from SW or NE tree quadrants were monitored over the course of fruit development and maturation. First evidence of periderm formation occurred in October, coincident with observed changes in histochemical staining for lipids. These differences were increasingly evident as the fruit approached horticultural maturity and visual symptoms of rindstain developed. The development of a pronounced periderm in affected fruit suggests that rindstain is due to a physical trauma, although we do not believe it is caused by wind.
This from Mary Lu Arpaia in response from a Central Valley problem that cropped up recently. Fruit looked on the tree, but after getting it into the packing house, it started showing these symptoms
Here is her summation of the abstract above:
1) Fruit were predisposed to this problem as early as colorbreak. We found this out by doing some elaborate fruit manipulations in the field in the fall and looking at symptoms in the spring.
2) Symptoms really started to appear about this time of year and then progressively worse
3) There was a loose correlation to presence of citrus thrips in the previous year
4) Fruit isolations did not find much of anything but weak saprophytic fungi.
5) At this point, it's not clear what a grower can do to prevent it.
Rindstain on Ruby Red Grapefruit in the Hemet area was noted in the 1990's and the observation there was possible moisture from dew or rain focusing sunlight to cause the condition. So it's not really from even a general observation./h2>