- Author: Ben Faber
Citrus greening disease can infect an entire tree weeks before symptoms appear
Ashley Carlin
American Phytopathological Society
For the first time ever, scientists have been able to measure the speed of a bacterium that causes the incurable citrus greening disease. Citrus greening disease (also known as Huanglongbing) is the most devastating citrus disease in the world. Afflicted trees grow yellow leaves and low-quality fruit and eventually stop producing altogether, resulting in enormous economic losses to farmers.
Small insects carry the causal bacteria, Candidatus Liberibacter asiaticus (CLas), and inject it when they feed on a tree's sap. CLas also relies on this sap to grow and spread throughout the tree. Using a new statistical modeling analysis and measurement approach, plant pathologists were able to follow CLas on its journey through a tree.
“We found that CLas can move at average speed of 2.9 to 3.8 cm per day. At these speeds a tree that is 3 meters in height will be fully colonized by CLas in around 80 to 100 days, and this is faster than the symptoms appear, which generally takes at least 4 months,” explained Silvio A. Lopes, a plant pathologist based at Fundecitrus, research institution maintained by citrus growers of the State of Sao Paulo in Brazil.
In other words, by the time growers see the symptoms of citrus greening disease, the tree has already been infected from the roots on up, which explains why removing symptomatic branches isn't enough to cure a diseased tree.
Lopes and colleagues also studied the impact of temperature on the speed of colonization. They already knew that CLas does not multiply well in hot or cold environments—but now they have more specific numbers.
“We estimated that 25.7°C (78°F) was the best condition for CLas to move from one side to the other side of the tree,” said Lopes. This is the first time impact of temperature on plant colonization of CLas has been experimentally demonstrated. “The grower can use this information to select areas less risky for planting citrus trees.”
- Author: Ben Faber
In the citrus world there is a relative tolerance to the bacteria that causes Huanglongbing, or Citrus Greening. Grapefruit and some orange varieties are very sensitive and some mandarin varieties are much more tolerant, meaning they live longer in the presence of the bacteria. Work is being done to use mandarin juice as a substitute for the traditional glass of orange juice. A recent bulletin out from the University of Florida has this news. This does not mean that Asian Citrus Psyllid and Huanglongbing are any less of a threat to citrus at this point. Just a way of prolonging an industry until true solutions can be found.
GAINESVILLE, Fla. — Some people like to wake up and drink a glass of fresh Florida orange juice. With the greening disease ravaging Florida's citrus industry, University of Florida Institute of Food and Agricultural Sciences researchers want to make orange juice from disease-tolerant fruit.
Huanglongbing (HLB), or citrus greening as it's commonly called, has destroyed 80 percent of citrus in Florida, a state where citrus is an $8.6 billion-a-year industry, according to UF/IFAS research. About 90 percent of the state's oranges are used to make orange juice, UF/IFAS researchers say.
So it's critical that scientists find sources for orange juice upon which consumers can rely. UF/IFAS researchers have found some mandarins that are tolerant to citrus greening.
In a newly published study, UF/IFAS researchers also found that consumers sense little, if any difference in the smell and taste of certain specific mandarins, compared to oranges.
“We found out what makes orange taste like orange and mandarin taste like mandarin, even though they are very close species,” said Yu Wang, a UF/IFAS assistant professor of food science and human nutrition and lead author of the study.
“If we use greening-tolerant mandarin for orange-juice making, the first thing we need to know is the difference between them,” Wang said. “This will provide more possibilities and flexibilities for the citrus industry in particular in the HLB era.”
In the past, researchers used traditional methods such as gas chromatography-mass spectrometry to study the flavor differences in orange and mandarin, Wang said. But people's senses of taste and smell are much more sensitive than analytical equipment, so scientists integrated sniffing into the study, she said.
It's important to remember that oranges are descendants of mandarin and pummelos, said Fred Gmitter, a UF/IFAS horticultural sciences professor and co-author of the study. So there's already a lot of mandarin's genetic makeup in an orange.
The problem is that oranges are very sensitive to citrus greening, Gmitter said.
“While we find other selections in the breeding program, mostly mandarin, hold of up a lot better against greening, we are finding some of these selections produce fruit that more closely resemble orange in appearance,” Gmitter said. “But more importantly, here, that they also very closely resemble orange in flavor.”
The study is published in the Journal of Agricultural and Food Chemistry:
https://pubs.acs.org/doi/abs/10.1021/acs.jafc.7b04968?src=recsys
Brad Buck
UF|IFAS
- Author: Ben Faber
The latest National Agricultural Statistics Service (NASS) results are out for the citrus crop. These are results that are collected by the USDA to gauge production in the different growing areas of the country. From this most recent data, it is clear that citrus production is diminishing with time, most likely the effect of Huanglongbing. This is about a 60% decline from 2015.
The impact of this reduced production has reached out to not just growers, but also the juice industry they support, or are supported by. There's been a decline in the number of juice plants since 2014 which are reliant on volume to stay in business. If plants close, growers have fewer options for their juice citrus. http://www.theledger.com/news/20140705/at-least-one-juice-processor-expected-to-close
Most commercial crop production figures are collected by state and summarized on a state basis with the Agricultural Census every 10 years - https://www.agcensus.usda.gov/. The last was done in 2012.
Daily market prices for these different commodities can be seen on a wholesale basis by city, at USDA's Market News Service - https://www.marketnews.usda.gov/mnp/fv-home . This gives current prices and archived prices for products sold in different markets. It gives a general idea of what the grower will be paid for a given crop.
All of these sources are helpful for deciding where crop prices and markets are going. If you have time check them out.
- Author: Ben Faber
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:
- Author: Ben Faber
What this means is that there is different feeding behavior on different scion varieties that is unaffected by the rootstocks used in this study. This does not mean "a" rootstock can not have an effect, just that the ones used in this trial did not.
EFFECT OF DIFFERENT CITRUS SCION AND ROOTSTOCKS
COMBINATION ON FEEDING OF Diaphorina citri
Alves GA1, Beloti VH1, Carvalho SA2 & Yamamoto PT1
1Escola Superior de Agricultura ‘Luiz de Queiroz'/
Universidade de São Paulo, Piracicaba, SP, Brazil; 2Instituto
Agronômico (IAC), Centro de Citricultura, Cordeirópolis, SP,
Brazil; e-mail: gralves@usp.br
The Asian citrus psyllid (ACP) is the vector of bacteria associated to the huanglongbing and has a host range of more than 50 species of the Rutaceae family. The knowledge about the feeding behavior in different hosts can show useful aspects for future studies of plant resistance and ACP management. Therefore, was evaluated the effect of different combinations of scion and rootstock of citrus in the feeding of ACP adults. For this, we tested Valencia, Pera and Hamlin sweet orange, Ponkan mandarin and Sicilian lemon grafted on Rangpur lime and Sunki mandarin rootstocks.
The flushes were individualized with cages made of transparent plastic cup and “voile” tissue. To collect the honeydew, discs of filter paper were placed at the base of each flush. The adults fed for a period of 72 h. After this, the discs were removed and immersed on the ninhydrin solution. After 24 h, the drops area of honeydew was determined using the Quant software. The feeding was more intense on sweet orange varieties, with a highest value observed to Valencia (0.902 cm2) and the smaller area to Ponkan mandarin(0.269 cm2). Unlike observed for scion varieties, when different rootstocks for the same scion variety were tested, no difference was observed in the consumption of ACP.
Rootstocks can have a tremendous effect, but not in this case with the rootstocks used