- Author: Ben A Faber
The recent U.S. Department of Agriculture Foreign Agricultural Service (USDA FAS) annual report on Brazilian citrus included updates on citrus greening disease, production and planted area.
CITRUS GREENING
The report noted that new chemicals and practices have been developed to fight citrus greening, a major cause of recent production declines. Those chemicals and practices include a natural repellent called caryophyllene, a non-chemical technique called kaolin and the use of vigorous rootstocks.
According to Fundecitrus data from September 2024, the average incidence of orange trees with greening in the Citrus Belt was 44.35%, or approximately 90.36 million trees. The Citrus Belt is the northwest of São Paulo and the western part of Minas Gerais, known as Triângulo Mineiro. This rate is 16.5% higher than in 2023, when incidence was estimated at 38.06%.
Fundecitrus expects the incidence of greening to rise in the short term, though likely at a slower rate compared to previous years. This is primarily attributed to a decline in the citrus greening-spreading psyllid population in 2024 compared to the previous year, as well as the establishment of new groves in peripheral regions of the Citrus Belt. The risk of the disease is lower in those peripheral areas.
PRODUCTION
Brazilian orange production is down due to drought and extremely high temperatures. In fields without a robust irrigation system, production was significantly adversely impacted, USDA FAS reported. Irrigated areas were less impacted; however, they also struggled due to a decrease in well water.
Dry weather has reduced fruit production for five consecutive seasons in the Citrus Belt.
See the latest orange production forecast from Brazil here.
PLANTINGS
USDA/FAS forecasts the area planted for oranges at 590,000 hectares, the same as the prior year.
Brazil has about 5,000 orange grove properties. Most are large producers with high productivity.
See the full USDA FAS report on Brazilian citrus here.
Source: USDA FAS
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- Author: Ben A Faber
Scientists at the University of Florida are testing a new type of citrus tree that can fight off the tiny insects responsible for citrus greening.
While the genetically edited tree has only been tested so far in the lab and the greenhouse, it is one of the most promising discoveries to date in a challenge that has plagued growers, researchers and consumers as Florida's citrus industry has plummeted over the past two decades.
The approach involves inserting a gene into a citrus tree that produces a protein that can kill baby Asian citrus psyllids, the bugs that transmit the greening disease.
That gene normally occurs in a soil-borne bacterium called Bacillus thuringiensis (Bt).
This gene provides instructions for the new citrus tree on how to make this protein. Thus, when you put the gene into the tree, the plant produces the protein that kills psyllids.
While this approach can kill baby psyllids, UF/IFAS scientists are close to finding a solution to control the adult pests.
“We are trying to deploy a biotechnological solution that is sustainable, easy for growers to deploy and replaces the need for spraying insecticides," said Lukasz Stelinski, an entomology professor at the UF/IFAS Citrus Research and Education Center. “That can't be done completely with the current Bt trees and thus it might require some additional, albeit reduced, insecticide spraying for adults, for example.”
So far, scientists have developed the modified tree in the lab and the greenhouse.
Now, they must prove this method works in the field – and they're still a few years away from perhaps reaching that conclusion, Stelinski said. They hope to begin testing the trees in about a year.
Since it was reported in Florida in 2005, greening, also known as Huanglongbing, or HLB, has damaged most of the citrus trees and the fruit they bear, around the state, leaving growers and scientists seeking answers to the disease.
UF receives funding from the U.S. Department of Agriculture for citrus greening research, which plays a key role in advancing and accelerating breakthroughs.
Through the new research, scientists have found that the tree is protected because all juvenile psyllids that feed on the tree are killed, Stelinski said.
“A citrus tree that produces its own potent defense against the Asian citrus psyllid by preventing this insect from reproducing would reduce or possibly eliminate vector populations,” he said. “In terms of stopping HLB, this approach could curtail the ability of an otherwise very effective vector from spreading the pathogen.”
Before UF/IFAS scientists started this research a few years ago, they knew that certain Bt proteins could kill other sap-sucking insects, but none were known to kill Asian citrus psyllids.
This protein kills psyllids. It binds to specific receptors on the gut wall, causing pores to form. This disrupts the insect cells on the gut wall, ultimately killing the insect.
In their experiments, scientists at CREC inserted a gene from Bt into citrus trees. The gene yields a protein in the phloem -- the vascular part of a leaf where the psyllid feeds. Ultimately, that protein protects the tree from the psyllid and therefore, from citrus greening.
Bryony Bonning, an eminent scholar and entomology professor on the main UF campus in Gainesville, led the research to identify the bacterial proteins that kill psyllids.
In the most recently published study, UF/IFAS researchers found that the protein derived from Bt can kill the vast majority of the psyllids in their earliest stages. Additionally, no new adults can emerge on the tree, so adults laying eggs on these plants will not perpetuate the population.
Adult psyllids remain an issue that scientists hope to solve in future research. For now, they're working on controlling the baby psyllids on citrus trees.
“Given the widespread use of Bt proteins for protection of other crops against insect pests, we think we're on the right track for control of the Asian citrus psyllid,” he said. “The next step is to prove this method works in the field, so that citrus growers everywhere will no longer have to contend with the insect that transmits this deadly disease. The next stage is to grow these trees in the ground into a more mature stage under natural field conditions.”
Article Title
The sandwich feeding assay for use with first instar nymphs of the Asian citrus psyllid, Diaphorina citri confirms the high susceptibility of this life stage to bacterial pesticidal proteins
Karen Dooley
University of Florida
dooleyk@ufl.edu
Cell: 3522190567

- Author: Ben A Faber
UC Riverside excited to announce that registration is open for the 2025 Citrus Day at UCR on February 20, 2025 from 7:15 to 2:00. We are looking forward to seeing you and sharing the exciting ongoing research in citrus. In additional to a great list of speakers, Dr. Kim Bowman (Univ. Florida) and Dr. Mike Roose (UCR) will be joining us for a special presentation on the latest developments in rootstock breeding for resistance to HLB.
This will be an indoor event at the Agricultural Operations Shop. Lunch will be provided. We will send out parking instructions the week before the event.
Registration: $40
Use direct link QR code to register: https://capca.com/calendar/ucr-citrus-day-2025/
Feel free to forward this announcement to others who may be interested in this event.

Checking in at bee hotels: trap-nesting occupancy and fitness of cavity-nesting bees in an urbanised biodiversity hotspot
The design of bee hotels is critical - untreated wood, holes a range of diameters (I suggest 3-10 mm), lengths min 10 cm.
However you need to first think about what you're trying to achieve - for the author it was looking at occupancy , species composition and emergence and fitness components between two habitat types
- Are you using hotels to look at penology ? Or hole size (proxy for body size) preferences? Differences in habitat types or surrounding land use? Your metric presumably number of nests occupied . Species composition will be hard because you typically can't tell what species is using the bee hotels unless you rear them in the lab.
She has a book on bee hotels - focused on Australian species but principles still apply : https://www.honeybeesuite.com/books-for-beeple/
With urbanisation leading to loss of nesting resources, and increasing public interest in helping bees, bee hotels (trap-nests) are becoming popularised. However, their success is relatively understudied. The influence of habitat type in determining occupancy and emergence is also poorly known. Over two years across 7 bushland remnant and 7 residential garden sites, trap-nests were installed and completed nests collected monthly over spring-summer. Bees appeared to take a month to find the trap-nests, irrespective of month they were installed. A small percentage (13% and 6% in the two years) of tubes were occupied, but this was within the range of other trap-nesting studies. Smaller 4 and 7 mm diameter nests had a higher occupancy rate than 10 mm diameter tubes. An impressive number − 24 bee species – occupied the trap-nests. Representation however was dominated by five species. The species composition (species and their relative abundances) of cavity-nesting bees differed greatly between those using the trap-nests compared with those observed in the field. Bushland remnants tended to have more bee hotels occupied, and male body size of emerged bees was larger in this habitat. Unexpectedly native and total flower diversity reduced bee hotel occupancy, whereas native flower parameters tended to positively influence bee fitness. Overall installing bee hotels can provide additional nesting resources for native bees in urbanised areas, and providing high proportions of native flora in the vicinity should enhance fitness of the bees using them.
https://link.springer.com/article/10.1007/s11252-023-01381-5

- Author: Ben A Faber
A recent Florida TaxWatch report detailed the reasons for the decline of the Florida citrus industry. The report also described frustrations with efforts to combat citrus greening and suggested solutions for the industry's decline. Edited excerpts from that portion of the report follow:
Prominent citrus growers stated they are still optimistic about the future as many citrus entities are investing in the industry.
There have been many short-term solutions to combat citrus greening: growing trees in giant canopies to keep insects out but still allow sunlight and rain through, developing new blight-resistant citrus trees, injecting greening-resistant genes into citrus trees, and using push-pull pest management to lure pests to trap crops.
A majority of researchers believe that the only long-term solution is a new variety of citrus that is resistant to citrus greening disease. However, the use of genetic engineering in citrus production is still an ongoing debate in the citrus industry.
Most of these methods require a high investment, which many citrus growers in Florida cannot afford. The Florida citrus industry is at a critical period for survival, requiring strategic planting of citrus, scientific revitalization and increased awareness of citrus production requirements.
High investment costs present a significant hurdle for many growers. To overcome these challenges, the industry must focus on:
- Strategic replanting and infrastructure rebuilding
- Increased awareness of citrus production needs
- Continued scientific research for sustainable solutions
Preserving Florida's citrus legacy demands immediate and collaborative action to balance innovation with tradition.
Florida TaxWatch is an independent, nonpartisan, nonprofit taxpayer research institute and government watchdog. Its mission is to provide the taxpayers of Florida and public officials with high quality, independent research and analysis of issues related to state and local government taxation, expenditures, policies and programs.
Read the full Florida TaxWatch report, The Continuing Decline of Florida's Citrus Industry, here.
Source: Florida TaxWatch
And Which Way US Citrus
The U.S. Department of Agriculture National Agricultural Statistics Services (USDA/NASS) released a citrus forecast on Jan. 10.
FLORIDA
Florida orange and grapefruit production expectations were unchanged from the December citrus forecast. The Florida orange forecast remains at 12 million boxes and grapefruit at 1.2 million boxes.
Florida non-Valencia orange final fruit size is smaller than the average, requiring 327 pieces to fill a 90-pound box. Final droppage of non-Valencia oranges (excluding Navels) at 56% is above the maximum.
Florida Valencia orange current fruit size is average and is projected to be average at harvest. Current droppage is above the maximum and projected to be above the maximum at harvest.
Fruit size of Florida red grapefruit at harvest is projected to be above the maximum, and droppage is projected to be above the maximum. Projected fruit size of Florida white grapefruit at harvest is above average. White grapefruit droppage is projected to be above the maximum.
The Florida tangerine and mandarin forecast was cut by 14%. The forecast fell from 350,000 boxes in December to 300,000 boxes in January.
The Florida lemon forecast increased from 500,000 boxes to 600,000 boxes.
If the January forecast is realized, Florida's orange, grapefruit and tangerine/mandarin production will each be 33% less than the prior season's final production.
OTHER STATES
California's all-orange forecast was reduced from 47.7 million boxes in December to 47.4 million boxes. The California grapefruit forecast was reduced from 4.2 million boxes to 3.7 million boxes. The state's lemon and tangerine/mandarin forecast were unchanged.
Texas' all-orange forecast increased from 850,000 boxes in December to 900,000 boxes. The Texas grapefruit forecast jumped from 1.9 million boxes to 2.5 million boxes.
See the full January citrus forecast report from USDA NASS here. The next citrus forecast will be issued on Feb. 11.
Source: USDA NASS
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