- Author: Ben A Faber
Greening Bacterium Causes Changes in Psyllids
Recent studies, including a partnership project between Fundecitrus and the University of California, revealed that the citrus greening bacterium Candidatus Liberibacter asiaticus causes physiological changes in psyllids, posing additional challenges to management strategies. An increase in the number of eggs, more frequent dispersal flights over longer distances and greater attractiveness to the host are some of the changes observed in infected psyllids.
MORE DIFFICULT TO MANAGE
“Epidemiologically speaking, the changes we have been observing in psyllid behavior turn it into a much more problematic insect,” said Fernando Amaral, Fundecitrus agricultural engineer and post-doctoral student at the São Paulo University Luiz de Queiroz College of Agriculture.
The psyllid behavioral changes hinder the development of pheromone tools to attract the insect and improve its monitoring.
“It is becoming increasingly clear that the psyllid undergoes several changes, and this phenomenon not only poses difficulties to management, but also curbs the development of products to capture the insect,” added Fundecitrus researcher Haroldo Volpe.
Studies published between 2015 and 2024 revealed that psyllids infected with the greening bacteria can lay up to 100% more eggs than healthy insects, contributing to the growth of the psyllid population.
FREQUENT FLIERS
The studies also concluded that infected psyllids are more agitated when compared to healthy insects. In order to reach this conclusion, researchers placed adult insects from both groups on a platform. The teams noticed that infected insects flew, on average, after 50 seconds from the beginning of the observation period. The healthy subjects took around 150 seconds.
“Knowing that the insect flies more often and starts flying earlier demonstrates agitation and altered behavior, increasing its ability to spread greening,” said Volpe.
Yet another conclusion of the studies is that infected psyllids perform more frequent dispersal flights.
“Psyllids infected with the greening bacteria have a 45% higher rate of long flights when compared to healthy insects,” said Amaral.
In other words, the infected psyllid will fly longer distances and further spread the disease. Moreover, infected psyllids will also have a greater need to feed (forage) on more shoots and consequently will further disseminate the disease.
SUSCEPTIBILITY TO INSECTICIDES
On the other hand, the susceptibility of infected insects to insecticides is greater than that of healthy insects. Psyllids infected with the greening bacteria require a 20% to 313% lower concentration of insecticides to achieve the same mortality rate as healthy insects. This happens because the bacteria interferes with the psyllid metabolization of these products, which hinders their detoxication process.
CONTINUE COMBATING DISEASE
Fundecitrus General Manager Juliano Ayres emphasized the need for citrus growers to remain aware of the measures used to combat the disease in the field.
“The more diseased plants in groves without appropriate psyllid control, the more contaminated insects there will be and, consequently, the faster the disease will spread,” Ayres said. “Therefore, it is essential to continue to eliminate diseased plants from groves and keep up strict control of the insect on these plants.”
Source: Citricultor, Fundecitrus
CLas-Positive Psyllid Sample in Riverside County
July 26, 2024
An adult Asian citrus psyllid (ACP) sample from a residential property in the San Jacinto Valley area of Riverside County, California, has tested positive for Candidatus Liberibacter asiaticus (CLas), the bacterium that causes huanglongbing (HLB).
The positive sample was collected as part of the Multi-Pest Risk Survey on a residential property in Hemet. It was confirmed positive for CLas on July 17 by the Citrus Research Board's Jerry Dimitman Laboratory. Nymphs were also collected from the property and tested negative for CLas. This is the first confirmed CLas-positive adult ACP found in the San Jacinto Valley area.
An HLB quarantine zone will not be established as a result of this CLas-positive ACP detection. However, California Department of Food and Agriculture (CDFA) staff is conducting surveys and collecting samples from the property and all HLB host plants that are located within a 250-meter radius around the find, per the ACP/HLB Action Plan.
It is crucial that ACP populations continue to be controlled properly in order to stop HLB from spreading, advised California's Citrus Pest & Disease Prevention Program.
While CDFA is not requiring mandatory treatment for area commercial growers, those who wish to take proactive steps to protect their groves or who have additional questions can contact Riverside County Grower Liaison Sandra Zwaal.
In September 2023, a CLas-positive ACP sample was collected from a residential property in California's Ventura County. That sample came from a residential citrus tree in the southwest area of Santa Paula. An HLB quarantine zone was not established as a result of that detection, either. While that first confirmation of a CLas-positive ACP in Ventura County was concerning, HLB was not detected in any Ventura County citrus trees. Learn more here.
Source: Citrus Pest & Disease Prevention Program
- Author: Ben A Faber
- Author: Hamutahl Cohen
On July 30th the Queensland Fruit Fly (Qfly) quarantine was lifted in Ventura County. Qfly is part of the Tephritidae family of flies.
The Tephritidae are one of two fly families referred to as fruit flies, the other family being the Drosophilidae. Drosophila melanogaster is the fruit fly of famous biological studies to figure out how cells and genetics work. Tephritidae contain most of the flies that cause economic damage to crops because some feed on living tissue, they go after fresh fruit. To distinguish them from the Drosophilidae, the Tephritidae are sometimes called peacock flies, in reference to their elaborate and colorful markings. The Artichoke fruit fly (Terellia fuscicornis) has a limited diet, going after artichoke and presumably other thistles, so it's impact is small unless you are an artichoke grower. Spotted-Wing Drosophila (Drosophila suzukii ) which goes after soft fruits like blueberries, raspberries and strawberries can be a major economic problem, but generally Drosophilidae feed on pollen and rotting material. They are generally nuisance flies.
Some Tephritidae have negative effects, some positive. Various species of fruit flies cause damage to fruit and other plant crops. The genus Bactrocera is of worldwide notoriety for its destructive impact on agriculture. The olive fruit fly (B. oleae), for example, feeds on only one plant: the wild or commercially cultivated olive, Olea europaea. It has the capacity to ruin 100% of an olive crop by damaging the fruit. Bactrocera dorsalis is another highly invasive pest species that damages tropical fruit, vegetable, and nut crops.Euleia heraclei is a pest of celery and parsnips. The genus Anastrepha includes several important pests, notably A. grandis, A. ludens (Mexican fruit fly), A. obliqua, and A. suspensa. Other pests are Strauzia longipennis, a pest of sunflowers and a pest of blueberries. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=60063
Another notorious agricultural pest is the Mediterranean fruit fly or Medfly, Ceratitis capitata, which is responsible for millions of dollars' worth in expenses by countries for control and eradication efforts, in addition to costs of damage to fruit crops. Similarly, the Queensland fruit fly (Bactrocera tryoni) is responsible for more than $28.5 million in damage to Australian fruit crops a year. This species lays eggs in a wide variety of unripe fruit hosts, causing them to rot prior to ripening. The Tau fruit fly (Bactrocera tau) or pumpkin fruit fly, goes after melons and other cucurbits like cucumbers and squash. The oriental fruit fly (Bactrocera dorsalis) has been seen in more than 200 kinds of fruit and nut plants.
Med, Mex, Oriental and Tau have all been in the news lately because of quarantines to contain their spread. The bulk of fruit flies, though don't pose a threat to agriculture, including all 1,500 species of Drosophilidae and the 5,000 species of Tephritidae.
Artichoke Fruit Fly - a drosophila
Tau Fruit Fly - a tephritid
- Author: Sandipa Gautam
Upcoming Citrus Extension Outreach Meetings at LREC
August 20, 2024. Register here for AAIE Organized Citrus Roundtable for SJV growers: This is an opportunity for citrus pest control advisors to get together and talk about how they manage pests. The round table will discuss Ant Control, ACP, Thrips, Red Scale, Mealybug, Weed management, current regulations and pest management problems citrus pest control advisors have had. UCANR's Dr. Sandipa Gautam, Cooperative Extension Area Citrus IPM Advisor, David Haviland, Entomology and Pest Management Farm Advisor, Jorge Antonio Angeles, Weed Management Advisor, Dr. Bodil Cass, UCR Subtropical crops Specialist, and Chris Greer Assistant Ag Commissioner, Tulare County will be presenting at this meeting.
September 24, 2024: Register here for Citricola Scale Field Day: Citricola scale has been a problem in year 2024. This 2 hour event will focus on teaching PCAs on pest identification, monitoring, and best management practices manage citricola scale.
October 2, 2024: Register here for California red scale and its natural enemies workshop. A day dedicated to California red scale and its natural enemies is back! This hands-on workshop at Lindcove will teach PCAs how to recognize the various life stages of California red scale and their parasites with dedicated time to work with each life stage. With this knowledge PCAs can determine the level of parasitism of California red scale in their citrus orchards and make better decisions about scale control tactics. Seat is limited to 30 students.
October 9, 2024: Register here for Fall Citrus Meeting at Lindcove. Are you looking for one meeting where you can learn about various issues in citrus production? UC Researchers bring to you a Fall Citrus Meeting at Lindcove Research and Extension Center on October 9, 2024. This meeting will cover nutrient management and irrigation, insect pest, disease, weed management and regulatory pest and top issues and regulations followed by a group discussion to identify grower needs pertaining to various topics.
September 11, 2024: Register here for “Workshop on the Biology and Identification of Phytoseiid Predatory Mites in Agriculture” This workshop will teach students about the importance of predatory mites in agricultural crops and the basics of how to identify them to species level. Each student will have their own phase contrast microscope and access to a set of slide-mounted specimens to work through “The Key to Genera of Phytoseiidae Found on Crop Plants in California”. Learn from the experts – Dr. Beth Grafton-Cardwell will be leading the class with David Haviland. Seat is limited to 30 students. Full Agenda attached. This workshop will be held at Kearney REC, 9240 S. Riverbend Avenue, Exeter, CA.
Attached Files CRS Annoucement October 2 2024
Local Citrus Round Table Agenda AAIE
Workshop on the Biology and Identification of Phytoseiid Predatory Mites in Agriculture
Citricola Scale Field Day Announcement - September 24 2024
Fall Citrus Meeting at Lindcove
Photo: Wax Scale, Ceroplastes ceriferus
/span>- Author: Ben A Faber
In a recent meeting the topic of where to go for irrigation information came up. Well there's no substitute for attending a class in irrigation, such as offered at Cal Poly SLO (http://www.itrc.org/classes/iseclass.htm ,
but here's some written sources to get you started thinking.
http://ciwr.ucanr.edu/california_drought_expertise/droughttips/
http://www.salinitymanagement.org/Salinity%20Management%20Guide/ei/ei_1.html
http://www.avocadosource.com/tools/IrrigationCalculator.asp
http://lawr.ucdavis.edu/cooperative-extension/irrigation/manuals
http://lawr.ucdavis.edu/cooperative-extension/irrigation/drought-tips
http://biomet.ucdavis.edu/index.php/evapotranspiration-mainmenu-32
- Author: Ben A Faber
Farm Advisor UCCE Ventura County
Plants, therefore avocados, go through different growth stages, so called phenological stages, regular periods where they grow and differentiate from seed to various vegetative stages, flowering and finally seed production. Avocado has a preset pattern of phenology that occurs depending on variety and where it is grown, driven by light, temperature, water availability and often by different stresses, such as cold, heat, and heavy or light crop load.
The successive stages of avocado phenology are demonstrated in the photomontage below, from bud break to harvestable fruit:
Main phenological growth stages of ‘Hass' avocado according to the extended BBCH scale. From: http://avocadosource.com/journals/elsevier/scientiahort_2013_164_434-439.pdf
And, depending on where in California the avocado is growing, the latitude, or on what side of the slope (in the shade or full sun, on the top of the slope, etc.), the tree will go through these successive stages at different times of the year, offset by weeks or even months. A general plan for the California coastal region was developed from accumulated experiences and tests by a variety of groups and is shown below:
Research-based information that allows producers to anticipate the regionally appropriate times for major phenological evets is limited in California. From work conducted at South Coast Research and Extension Center in Irvine, the onset of flowering in early March extends into May, normally, and the main fruit set period is between mid-April and May. In later work from the same location, a mean beginning bloom date for “on” and “off” crop years differed between Julian date 66 (March 7) and 80 (March 21), respectively. From avocado research in Carpinteria, flower abscission (as a measure of bloom) during “on” and “off' crop years peaked on two different Julian dates, (May 4 and June 2). Mid-June has been reported as the middle of the commercial ‘Hass” season for the Irvine area. Harvest in Santa Barbara and San Luis Obispo Countries may just be staring in mid-June and continue through November in the most northern growing areas.
Difference in crop development impact the timing of cultural practices, such as fertilization, irrigation, phytophthora treatment, pollination and gibberellin sprays. For instance, nitrogen fertilization is often recommended by month of the year, rather than growth stage of the tree. Several recent efforts indicated that the timing of nitrogen fertilizer may have significant impacts on yield and that two times the fertilizer rates in April and November may result in substantial yield increase. Available information indicates the April timing might correspond to fruit set for the Irvine area compared to early bloom for Santa Barbara and San Luis. By November, Irvine's current year's crop may have been harvested three months previously. In San Luis Obispo, harvest may have just ended. So just going by date is insufficient for guiding many horticultural activities.
California's trees often have two crops maturing at the same time. It becomes especially pronounced the further north the production. The management of multiple crops on each tree becomes more important and more confusing as the length of time the fruit remains on the tree. Carrying two and even three loads of crop increases the potential for alternate bearing. Reduction in alternate bearing has been determined to be an important strategic requirement for California's growers. Understanding the impacts of cultural practices on alternate bearing is important. For example, the chart below demonstrates a stylized calendar of the avocado growth cycle for California. Rate and application timing of nitrogen as predicted by the Avocado Nitrogen Model proposed by Rosecrance et al. (2013 and Calculator) are noted for a 15,000 per acre yield outcome. The “on” year suggests nitrogen rate for the late fruit growth/harvest/summer and fall flush period is 15 lbs. This application coincides with the fruit set timing for 16 lbs of N for the “off” bloom crop during the later bloom/fruit set/spring shoot growth phase. Rates and timings to support these crops ought then be combined and represent the 2X fertilizer rate that Lovatt (2001) found to have significant effects on yields.
Calendar of avocado growth cycles with both “on” and “off” years represented when they overlap, and suggested nitrogen fertilization timings and amounts.
Taking into account the actual phenology, what is happening in your trees, then is important for assessing when to make N applications. In the winter and spring of 2023, it seems like everything was on a different cycle. Thrips delayed their appearance, flowering was erratic. Honeybees seemed to have found somewhere else to hang out, because they were not flying in the avocado trees. And then suddenly, we had some fruit set in Ventura in late June. This is a really clear example of the problem of following a cookbook to farming avocados. The point here is that just going by the calendar is not going to meet the needs of the tree. The phenological stages of the tree in your environment needs to be taken into consideration.
Notes:
Lovatt, C.J. 2001 Properly Timed Soilapplied Nitrogen Fertilizer Increases Yield and Fruit Size of ‘Hass' Avocado. J. Amer. Soc. Hort. Sci. 126(5): 555?559.
Rosecrance, R., Lovatt, C.J., 2013. Management tools for fertilization of the 'Hass' avocado. FREP final report.
Calculator: https://rrosecrance.yourweb.csuchico.edu/Model/AvoModel/Avo2NKModel.html