- Author: Ben Faber
UC IPM online courses:
New Fuller rose beetle course and early-bird pricing
—Cheryl Reynolds, UC Statewide IPM Program
Summer is here, and we're halfway through 2019 already! Why not get jump on finishing up your continuing education units by taking online courses from the UC Statewide IPM Program (UC IPM). If you are a license or certificate holder from the California Department of Pesticide Regulation (DPR), and your last name begins with the letters M through Z, you should be receiving your renewal packet in August.
We're excited to announce some changes.
- In January, we switched all of our online courses to a new learning system located at https://campus.extension.org/. This new system has extensive technical support, is easier to navigate, and is more stable than the old one. Note that the extension platform offers courses from all across the country, including several providers from California. Look for the UC IPM logo to be sure you are taking one of our courses.
- We are pleased to announce that a brand-new online course on the Fuller rose beetle was added to our citrus integrated pest management IPM series. Dr. Beth Grafton-Cardwell, a citrus IPM specialist and research entomologist, and Dr. Joseph Morse, emeritus professor of entomology, developed the course. The course describes the life cycle, natural enemies, and management of Fuller rose beetle and explains why it is important for countries that export citrus. Fuller Rose Beetle has been approved by (DPR) for 1 hour of credit in the Other category and by Certified Crop Advisor (CCA) for 0.5 hour of IPM credit.
- Many of our courses are now credited not only by DPR for continuing education hours, but also by the California Structural Pest Control Board (SPCB), Certified Crop Advisor (CCA), Western Chapter of the International Society of Arboriculture (WCISA), and also by Arizona Department of Agriculture.
DPR encourages license and certificate holders to avoid the end-of-the-year rush and submit renewal applications by November 1 to ensure license renewal by January 1, 2020. Submitting your renewal early avoids late fees and gives you time to address any issues that may arise such as not having enough hours to successfully renew.
Another incentive to get a jump on completing your needed continuing education units (CEUs) with UC IPM's online courses is that we are offering an early-bird price for four of our most wanted courses until November 1st.
- Proper Pesticide Use to Avoid Illegal Residues (2 hours Laws and Regulations; early bird price $40, full price $80)
- Proper Selection, Use, and Removal of Personal Protective Equipment (1.5 hours Laws and Regulations; early bird price $30, full price $60)
- Pesticide Resistance (2 hours Other; early bird price $20, full price $40)
- Pesticide Application Equipment and Calibration (1.5 hours Other; early bird price $15, full price $30)
You can find all of our twenty-one courses listed on the UC IPM website at http://ipm.ucanr.edu/training/.
- Author: Ben Faber
Canines can detect trees infected
with the bacterium
that causes huanglongbing
Research by Dr. Tim Gottwald
Article written by Tim Gottwald, Holly Deniston-Sheets and Beth Grafton-Cardwell.
Revised June 13, 2019.
What is the technique?
Canines have a highly sensitive scent detection capability that is significantly better (parts per trillion) than most laboratory instruments and they can be trained to “alert” (either sit or lay) when they detect specific ‘smells' (known as scent signatures). Most people are familiar with their ability to detect bombs, drugs, and plant material at airports. However, canines are also used to detect human pests, such as bed bugs, and agricultural pests, such as stink bugs, date palm weevils and imported fire ants.
With regard to agricultural pathogens, canines have been shown to detect with greater than 98% accuracy the fungal pathogen that causes laurel wilt disease in avocado, the bacterium that causes citrus canker disease in citrus, and plum pox virus in peach orchards.
Researchers have been training and evaluating the efficacy of canines for detecting “Candidatus Liberibacter asiaticus” (CLas), the bacterium that causes huanglongbing (HLB), for 5 years in Florida, and CLas detection efforts with canines have recently begun in California. Dogs have been trained in both the laboratory environment and in the field. Researchers have demonstrated that well-trained canines can detect CLas over 95% of the time in commercial trees and over 92% of the time in residential trees. Researchers did not observe any differences in canine performance between citrus species and varieties. The training that the canines receive is very specific to CLas. When they are taken into citrus orchards infected with citrus tristeza virus, viroids, the fungal pathogen Phytophthora, or the bacterium that causes citrus stubborn, the CLas-trained canines do not respond to these diseases.
Video of canine Maci running a row of trees in the Rio Grande Valley of Texas
The canines provide a significant opportunity to be used as an Early Detection Technology (EDT) in California. In a field study using potted citrus in Florida, dogs could detect CLas in some of the trees as early as 2 weeks after CLas-infected psyllids fed on the trees. In contrast, it can take 1-2 years for CLas to distribute itself in a mature citrus tree sufficiently for the bacterium to be present in sampled the leaves, which are then tested and shown to be infected using laboratory techniques, such as Polymerase Chain Reaction (PCR). Using canines to detect early infections could significantly help reduce disease spread in California, where HLB is currently limited to southern areas of the state and identify areas where increased psyllid control measures are needed
Who is working on the project?
Dr. Tim Gottwald, Research Leader and Epidemiologist at the USDA, U.S. Horticultural Research Laboratory in Fort Pierce, Florida, and additional collaborators with F1K9 laboratories, USDA, North Carolina State University, Texas A&M University and the California Department of Food and Agriculture.
What are the challenges and opportunities?
The volatile scent signature associated with CLas-infection settles from the canopy and simultaneously emanates from root infections pooling at the base of the tree. The detector dog interrogates the tree holistically by alerting in seconds on the scent signature regardless of its origin (i.e., a single leaf, root, stem or the entire tree if systemically infected). Conversely, other detection technologies, like PCR, are reliant on selecting and processing a small amount of tissue from large trees and often miss incipient infections because infected tissue is so rare in newly infected trees. Early detection via dogs is devoid of these sampling issues. Therefore, it is difficult to confirm CLas detections by dogs using currently available molecular or chemical detection methods. Dogs have been tested in hot and cold temperatures and with wind speeds up to 20 MPH with no perceptible degradation in detection.
Human scouts require several minutes per tree to visually examine it for symptoms, then they must collect tissue which must be transported to a diagnostic lab for processing and analysis, which is time consuming and labor-intensive. Whereas, in a residential environment dogs can assess all trees in even large yards in a couple of minutes. The major limitation to the number of trees a dog can assess per day is access to these residential properties and the time required to relocate from property to property. In commercial groves a team of two dogs and one handler can survey a 10 acre planting (~1500 trees) in 1-2 hours depending on the number of infected trees; each positive alert requires rewarding the dog and tagging the infected tree. Dogs usually work 30 min then rest 30 min and can work 6-8 hours a day.
Utilizing dogs, CLas can be detected early in a region, when it is in just a few trees. If these few early infected trees are removed, the establishment and spread of the disease could be greatly reduced.
Like every detection instrument, dogs need to be periodically recalibrated. This is done by resensitizing them to known CLas-positive trees or specially prepared ‘scent pads' that contain the scent signature of CLas to ensure they maintain > 98% accuracy of detection before being redeployed.
Funding source: This project is funded by the USDA Farm Bill, USDA HLB Multiagency Committee (MAC), and USDA ARS program funds.
This article originally posted on the Science for Citrus Health website.
Photo: Canine checking trees at Lindcove Research and Extension Center, Exeter, CA
- Author: Ben Faber
As you walk quickly down the nursery walkway on the way to the sales team meeting, you glance over at the 1- gallon stock that's almost ready to sell. Then you stop; something is wrong with the Chamaecyparis lawsoniana. Yikes, the older portions of the branches are browning on many plants. So you take a closer look
Left, what you might see quickly walking by. Looks pretty good!
Left, a closer look, without a hand lens. Something is wrong!
If you are like me, I've got my field hand lenses ready to pull out to take a closer look. I have got a 10 X and a 20 X (magnification) lens. The 10X is the most common magnification used in the field, and sufficient to help see and generally identify most of the common adult insect pests such as aphids, whiteflies, scales, mealybugs, fungus gnats and two-spotted spider mites.
When I see symptoms that appear to be caused by much smaller pests, such as eriophyid or broad mites, I'll pull out my 20X lens and take even a closer look. Sometimes I might see them. The 20 X lens has a very limited field of view, short depth of field, and is crazy hard to hold still. For these pests, and many other tiny immature insect life stages, it is best to take a sample back to the office or lab and use a stereo-microscope (binocular microscope), which works well at higher magnifications (20 X to 40X). But for me the 20X gives me a first look in the field, and may help pinpoint an infested sample to take back for the "scope".
You get the best view with a hand lens by holding it close to the eye. Use whatever hand and eye combination that seems comfortable. (Often right-handers use the right eye). You can keep glasses on if it works for you. Brace you lens holding hand on your cheek to stabilize it. Now with the other hand, move the specimen-- leaf, branch, stem-- to your lens until it is focused. With a 10X lens this will be about 1 inch away from the lens; with a 20X lens, about 1/2 inch away. With the subject in focus, position your body so that ambient light can illuminate the specimen. No hunching over the specimen like it is some big secret or something; let the light in.
Field hand lenses come in various forms and quality. "Hastings triplet" lenses have the best clarity, least distortion, and larger field of views than lower quality lenses. These high quality lenses are only about $35.
And back to the Chamaecyparis lawsoniana. What did the grower see associated with the necrotic branches when viewed with a field hand lens? Surprise, greenhouse thrips. Adults are black with pale wings. This slow-moving species lives in groups, unlike the solitary, fast-moving blackish predatory thrips. Larvae are white or yellow. At the tip of their abdomen they often carry a droplet of dark excrement. (Below. Adult circled in red on left image. Light colored larva and one adult on right image).
- 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.
Read on: