- Author: Ben Faber
What about Planting Lemons in Kern County?
By Craig Kallsen, UC Cooperative Extension Advisor, Kern County
Kern County is located at the southern end of the San Joaquin Valley of California. Over the past couple of years, I, as the citrus Farm Advisor for the University of California Cooperative Extension in Kern County, have received an increasing number of enquiries about the feasibility of growing lemons here. The answer is “yes” we can grow lemons here and according to the latest Kern County Agricultural Commissioner's Report (2017) we have 4010 acres of bearing and 10 acres of non-bearing lemons in the county. Those 10 acres of non-bearing lemons indicate that fairly recently someone decided lemons were the way to go.
These inquiries as to the feasibility of growing lemons are understandable. The price and demand for lemons in the U.S. and worldwide is increasing. Depending upon where you get your statistics the retail prices of lemons was something like $1.50 per pound from 2011- 2013 to something like $2 a pound from 2015 – 2017. The statistics show 2018 was even a better year for selling lemons. Consumption of lemons in the U.S. was less than 1 million metric tons in 2011 to about 1.25 million metric tons in 2017. Worldwide consumption has increased from about 4.5 million metric tons in 2011 to 5.5 million metric tons in 2017. If you add in other factors such as a heat wave, which, for example, hit Ventura County production hard in July 2018, or extreme winter freeze events, and sometimes-erratic supplies from other lemon producing areas of the world, prices can skyrocket 40% or more in a month. Being able to sell a carton of lemons for excess of $55 can be very attractive to prospective growers. Not surprisingly, if you compare the cost and returns of growing lemons with those of oranges, a person might wonder why anybody would choose producing navels over lemons (see https://coststudies.ucdavis.edu/ ).
Planting lemons is riskier. In the San Joaquin Valley, the major consideration is the greater frost sensitivity of lemons as compared most other citrus crops. Not only do lemons freeze at a higher temperature, so do its branches. A freeze, which can spoil orange or mandarin production for a year, can devastate lemon production for three years due to increased damage to the lemon canopy and the older branches of that canopy. If your tree freezes back to the major scaffold branches, you are out of business for a while. An important question is how often does it cold enough to destroy my lemon production capacity for three years or more? Industry wide, for the last 30 years we have had three freezes where lemon leaf canopies, even in the warmer areas of Kern County, were severely damaged – December 1990- January 1991, December 1998, and January 2007. Not to be an alarmist but, in looking at these dates, it would appear that we may be overdue for an extreme freeze. We flirted with one in early December of 2013. Over the years, I have noticed that as the time interval increases from the previous frost event, citrus orchards move further and further down onto the valley floor, only to retreat to higher ground after the next severe event.
Well, what about global warming? Shouldn't Kern County be getting to be a safer place to grow lemons? In answer, predictions can be difficult, and according to baseball legend Yogi Berra, this is especially so if they are about the future. Winter air temperatures have been climbing over the past 30 years in the southern San Joaquin Valley. With our Mediterranean climate in the SJV, most of our rain falls during the fall and winter. Drought years, which means drought winters, have become more common. The higher winter temperatures are good news for citrus growers, but the droughts have been bad news in that dry air in not conducive for fog formation. Fog, historically, is our winter blanket, that holds temperatures above freezing when conditions are ripe for rapid drops in temperature associated with clear, windless nights following cold fronts that move into the valley from Alaska and other points north.
The risk in growing lemons can be mitigated. As with any real estate endeavor, the three most important factors governing the value of a prospective lemon property are location, location and location. When we are talking about cold temperatures, we are talking about nighttime low air temperatures. Daytime winter temperatures, once we get into mid-morning, usually, are more than warm enough to keep lemons from freezing. The major mitigation factor under human control is to plant lemons in the areas of Kern County that have the warmest nighttime temperatures. These areas tend to be on the lower slopes of the foothills on the eastern and southern areas of the SJV. Cold air is much heavier than warm air and runs like a river downslope. Good cold drainage is necessary. If lemons are planted too far out onto the valley floor, they end up at the bottom of a lake of cold air during late fall and winter freeze events. The area where citrus is grown, often, is referred to as a belt along the lower foothills of the SJV. Not only is this belt characterized by more fog than higher up in the foothills, but also it is close to the atmospheric inversion layer that forms in the SJV during the winter. The SJV is at the bottom of a large deep bowl formed by surrounding mountain ranges, and the depth of this bowl makes the air more difficult to disturb by wind. This still air, on cold, clear nights during the winter, allows heat radiating into the sky from the ground to warm a layer of air, usually located from 500 to 1000 feet above the valley floor. The idea of using wind machines successfully is to move this layer of warm air down to the trees on the ground. If you are down on the valley floor, on most nights the warmer air is way too high up to bring it down to the ground with wind machines. If an orchard is 500 feet above the valley floor on the side of a foothill, you might already be in the inversion layer and won't even need to start your wind machines, or at worst, the inversion layer is close enough to bring that warm air down to the trees with wind machines. Unfortunately, the amount of land winter-warm enough for growing lemons in the foothills is very limited, and, currently, is occupied by other crops, probably citrus. We cannot grow lemons too high up in the foothills, because these areas are above the inversion layer and winter temperatures there will always be too cold for lemons. Kern County, in general, appears to be colder than its neighbor Tulare County to the north, and usually suffers more in terms of fruit and tree losses during extreme frost events.
Those bold enough to grow lemons appear to have more choices on which lemon to grow now than in the past. Some newer seedless or lower-seeded lemon varieties are available (https://citrusvariety.ucr.edu/ ). The Lisbon lemons, of which there are several selections, is an old Kern County standby, and appears to have better frost tolerance than the Eureka, commonly grown in the central and southern coastal areas. The Improved Meyer lemon is a hybrid, apparently, with citron, mandarin and pummelo heritage, and has excellent frost tolerance. However, the fruit does not hold up well on the tree, in storage or ship very well, and few commercial groves exist. It remains a very popular and successful backyard tree for homeowners.
With the threat of the Asian Citrus Psyllid (ACP) and the Huanglongbing disease it spreads, the feasibility of growing citrus under protective screens (CUPS) is under investigation. These protective screens, in addition to keeping ACP out, would likely provide additional frost protection as well.
The other obvious concern related to the number of enquiries I have received, is that even if lemons are not widely grown in Kern County now, worldwide demand suggests that there are likely many new acres of lemons in the ground now or in advanced planning stages in other locations in California, Arizona and the world. In the past, we have seen the acreage of a number of crop commodities rise and fall with the laws of supply and demand. We have planted and then pulled lemons in Kern County before based on market conditions. At some point, even unfrozen lemons will not sell if there are too many out there.
Figure 1. Frozen mature lemon trees in photo background, after the 1998 freeze in the Edison area of Kern County. Juvenile, undamaged navel orange trees in foreground (photo by Craig Kallsen).
- Author: Ben Faber
One of the major challenges facing citrus integrated pest management (IPM) in California is the recent, sharp increase in the acreage of mandarins being planted. The current citrus IPM guidelines have been established from years of experiments and experience in oranges, with no specific guidelines for mandarins. In the absence of research into key arthropod pest effects in mandarins, the assumption that the pest management practices for oranges appropriately transfer for optimal production in mandarins has not been tested. We used a data mining or ‘ecoinformatics' approach in which we compiled and analyzed production records collected by growers and pest control advisors to gain an overview of direct pest densities and their relationships with fruit damage for 202 commercial groves, each surveyed for 1–10 yr in the main production region of California. Pest densities were different among four commonly grown species of citrus marketed as mandarins (Citrus reticulata, C. clementina, C. unshiu, and C. tangelo) compared with the standard Citrus sinensis sweet oranges, for fork-tailed bush katydids (Scudderia furcata Brunner von Wattenwyl [Orthoptera: Tettigoniidae]), and citrus thrips (Scirtothrips citri Moulton [Thysanoptera: Thripidae]). Citrus reticulata had notably low levels of fruit damage, suggesting they have natural resistance to direct pests, especially fork-tailed bush katydids. These results suggest that mandarin-specific research and recommendations would improve citrus IPM. More broadly, this is an example of how an ecoinformatics approach can serve as a complement to traditional experimental methods to raise new and unexpected hypotheses that expand our understanding of agricultural systems.
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- Author: Ben Faber
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- Author: Ben Faber
Growers of one of Florida's signature citrus crops, the grapefruit, may see more production and possibly less of the deadly citrus greening disease. Researchers have worked for four years, growing grapefruit under protective screens on a 1-acre experimental plot of trees at the University of Florida Institute of Food and Agricultural Sciences, and they're seeing encouraging results.
UF/IFAS scientists and a few commercial growers have used the system, known as “CUPS,” or “Citrus Under Protective Screens,” for a few years. They're trying to keep the dangerous Asian citrus psyllid away from citrus trees. Infected psyllids can transmit the deadly greening disease to citrus. So far, so good. They're noticing higher grapefruit yields and no psyllids or greening.
Florida grapefruit production has been drastically reduced by citrus greening, also known as Huanglongbing (HLB). In Florida, grapefruit production has gone down from 40.8 million boxes in 2003-2004 to 4.9 million boxes in 2018-2019, according to the USDA.
Arnold Schumann, a UF/IFAS soil and water sciences professor, leads the “CUPS” experiment at the UF/IFAS Citrus Research and Education Center in Lake Alfred, Florida.
And right now, he sees reason for optimism. Schumann is studying how well grapefruit grows in the 1.3-acre facility at the CREC.
Four years of data show grapefruit that exhibit no signs of greening, Schumann said. Researchers planted ‘Ray Ruby' grapefruit trees in August 2014. By December 2018, the trees had produced 2,100 boxes of grapefruits per acre, Schumann said. That's 525 boxes per acre per year on average, but Schumann notes that trees are less productive in the initial two years after planting. In years 3 and 4, the CUPS grapefruit yields were 797 and 892 boxes per acre, respectively. Currently the average yield for Florida grapefruit is about 166 boxes per acre per year, according to the USDA.
“HLB reduces profits for fresh citrus producers in many ways,” Schumann said “Production costs are higher due to increased needs to use pesticides and fertilizers, and fruit production is harmed by stunted tree growth, reduced fruit set and pre-harvest fruit drop, among other factors.”
The CUPS experiment at the Citrus REC has demonstrated that nearly all those harmful effects of HLB can be addressed, Schumann said.
“During the past five years, we have learned much about optimizing horticultural practices and pest and disease management for red grapefruit grown in CUPS,” he said.
Scientists focus on producing high yields with premium grades for the fresh fruit market.
“Our understanding of fresh fruit quality has been honed by our partnership with the Dundee Citrus Growers Association, which harvested and shipped our CUPS grapefruits and tangerines for the past two seasons,” Schumann said “Most importantly, fruit grown in CUPS should all be ready to sell, and our grapefruit and tangerine harvests have achieved 100 percent pack-out. For grapefruits, the fruit size is very important because it greatly affects the selling price.”
One reason for the good yield is the grapefruit's ability to adapt to the higher daytime temperatures under the protective covers, he said.
Other reasons for the increased productions include:
- High-density planting.
- A hydroponic system with trees growing in pots, instead of soil and inducing early, large blooms.
- Drip fertigation – a combination of fertilizer and irrigation -- applied several times a day.
CUPS hydroponic grapefruit has all the important attributes for fresh fruit production: high yields of HLB-free fruit, large fruit size, consistent yields and early maturity, Schumann said.
“The experiments at the CREC focused on proving that the CUPS concept was viable,” Schumann said. “Trees were grown mostly in containers, using hydroponics and very high-planting densities.
A couple of Florida growers are using the CUPS method for grapefruit, although it's too soon to know their results, Schumann said.
Scientists are not yet recommending the intensive production system used at the CREC experiment for commercial CUPS, although one grower in Hardee County is already experimenting with hydroponics and container-grown grapefruits, tangerines and navels under cover, Schumann said.
“Our aim is to maximize fruit production and quality in commercial CUPS with trees grown in the ground at moderately high-planting densities,” he said. “We want to document the most successful methods in a CUPS production guide and to update it as we learn more.”
For more information:
Brad Buck
University of Florida
Ph: +1 (352) 294-3303
bradbuck@ufl.edu
www.ifas.ufl.edu
Photo: Honey Murcott mandarin trees grow in 7-gallon pots at 1,361 trees per acre in the Citrus Research and Education Center screen house. Photo credit: Schumann, 2017
- Author: Ben Faber
In a recent post about lemon shape being affected by high temperatures
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=29443
a grower sent an image of what I thought was a blurred view of something that was circled. I responded saying that I couldn't make it out, and a better image should be sent.
The grower resent the image, but this time it was about the long yellow thing in the background that was being asked about. The tree is planted next to a chile pepper plant and the question was whether the shape was affected by the chile proximity.
The grower had never seen anything like it before and I haven't either. But rack it up to the high temperature wave during flowering and the rapid fruit growth period and hormones gone amuck. if temperature extremes become more common, unusual fruit shapes will likely become more common.