- Author: Hung Kim Doan
Sandipa Gautam
UCCE IPM Advisor
California red scale is a common pest of California citrus attacking leaves, twigs, fruit by sucking plant sap. If the scale numbers are high serious damage can occur to the trees and highly infested fruit may be downgraded in the packinghouse.
Biology and seasonal phenology of California red scale
California red scale has an interesting life cycle. CRS start out as mobile crawlers from overwintering females from a previous season (Figure 1), which only remain mobile until they find a suitable location to begin feeding. Once they start feeding, they do not move and go through development being attached to the feeding spot. Males are the only other moving stage (Figure 2). They go through active feeding stage (instars) and a dormant period (molting). Females molt twice and males molt four times and emerge as fliers. Males then find and mate with third instar female. Afterwards, gravid female starts producing crawlers, hence completing the life cycle. In the San Joaquin Valley, there are four complete generations of CRS. In years with warm winters/hot summers, fifth generation crawlers/immatures have been found.
Figure 1. CRS female (overturned) showing crawlers. Crawlers move around looking for feeding spot, settle and spend life on the same spot.
Figure 2. CRS male adult (left) and CRS males on trap card (right)
Monitoring male flights using Pheromone trap cards (Figure 2) and using degree days to predict the next life event - crawlers, male flight is a most used method for monitoring CRS seasonal activity in the San Joaquin valley. After every 550-degree day unit accumulation above the lower developmental threshold of CRS, 53°F, something important happens. My team at Lindcove Research and Extension Center has been monitoring degree days in Kern, Tulare, Fresno, and Madera counties. However, we have not had a biofix (first male flight) this year. Please visit https://lrec.ucanr.edu/Citrus_IPM/Degree_Days/ for degree day updates.
The average mean temperature in 2023 has been lower, what does this mean for CRS season?
Temperature data from CIMIS Station, Kern Co., shows that the cumulative heat units above the CRS lower developmental threshold trails lower than earlier years in 2023. To date, no male fliers have been caught in Kern Co. which is usually a week or more ahead of Fresno, Tulare, or Madera Counties. This indicates that CRS is developing, but at a slower rate than it had been in earlier years (Figure 3). Expect CRS male flights, crawler emergence to be 2-3 weeks late than normal years, at least for the first generation. If the summer temperature pattern stays similar to earlier years, we will have a delay in second and third generation too!
The effect of low temperature delaying the development, thereby affecting emergence and flights, will likely affect spray timing for CRS control in 2023 season.
Figure. 3. Cumulative degree days above the lower developmental threshold, 53°F, for CRS. Note, 2023 (purple line) trails below other years.
California red scale trial- 2022
During 2022, our group studied the impact of multiple insecticide treatments on California red scale. The trials took place at the Lindcove Research and Extension Center. The trials were conducted as single tree applications and replicated 10 times. One application was made on July 28, following the crawler emergence. We rated the twigs on 23 September and twigs and fruit on 12 October for the presence of live California red scale. We also rated fruit for infestation by CRS, 0=no red scale, 1=1-10 scale, 2= >10 scales/fruit. The insecticides applied were Movento 10 fl. oz, Sivanto 14 oz, Centaur 46 oz, Senstar 20 oz, and Esteem 16 oz. All insecticides were applied with 1% Omni 6E 415 oil. Foliar applications of insecticides were made using a 100-gal high-pressure D30 diaphragm pump sprayer with mechanical agitation with a hand wand sprayer containing D6-nozzle at 250 psi. Treatments were applied in 750 gallons of water, except for Movento which was applied in 250 GPA, and Centaur which was applied at 1,000 GPA.
The insecticide that provided the best control in terms of reducing the percentage of fruit infested with >10 scales was Movento (Figure 4). Treatments, namely, Centaur, Senstar, Sivanto, and Movento significantly reduced the total CRS/fruit compared to control. In September, treatments did not significantly reduce CRS/twig compared to the control. In October, Centaur, Sivanto, and Movento, significantly reduced the mean number of mean live CRS on twigs (Figure ). Treatments should be applied to provide thorough coverage according to the size of the trees, except for Movento which is recommended at 250 GPA at See the UCIPM guidelines for thrips for more application details.
Figure 4. Mean live CRS per fruit on October 12 counts following insecticide treatment. All treatments were applied with 1% oil.
Figure 5. Mean live CRS/twig before and after treatments. Treatments were applied on July 28. Pretreatment count was done on July 25, and post-treatments counts were done on September 23, and October 12, respectively.
- Author: Hung Kim Doan
Invasive shothole borers (ISHB) are beetles that tunnel into trees and introduce a fungal disease (Fusarium dieback) that can cause tree death. Well established in many areas of Southern California and the Central Coast, the beetle-disease complex has killed thousands of trees. It continues to spread, threatening the integrity of California's urban and riparian forests.
Designed for land managers, arborists, and other professionals whose work includes tree health and/or pest management (as well as anyone seeking an in-depth understanding of the pest-disease complex), the 2023 Invasive Shothole Borers-Fusarium Dieback Symposium will take a deep dive into the current distribution, impacts and risks, best practices in control and management, and practical examples of successful management approaches.
Topics/Speakers include:
- Just the basics and where to learn more - Randall Oliver, Statewide ISHB Communications Coordinator, UC Statewide Integrated Pest Management Program
- Where is it now? Current distribution and potential risks - Hannah Vasilis, ISHB Survey and Trapping Coordinator, UC Statewide Integrated Pest Management Program
- New perspectives on Best Management Practices – Dr. Beatriz Nobua-Behrmann, Urban Forestry and Natural Resources Advisor, University of California Cooperative Extension (UCCE)
- Update on the search for alternative controls – Dr. Shannon Lynch, Assistant Professor of Forest Pathology, Department of Environmental Biology, SUNY College of Environmental Science and Forestry, and Dr. Akif Eskalen, Professor of Extension in Plant Pathology, University of California, Davis
- The California Invasive Species Advisory Council and its role in ISHB programs - David Pegos, Special Assistant Plant Division, California Department of Food & Agriculture
- Case study – What is possible with CAL Fire Grants? - Henry Herrera, Forester, CAL FIRE
- Case Study – Tribal response - Diego Cordero, Lead Environmental Technician, Santa Ynez Chumash Environmental Office
- A City's Perspective – City of Lakewood – Tim Hunt, Tree and Hardscape Supervisor, City of Lakewood
- Case study – Replanting & Restoration at UCI - Matt Deines, Senior Planner, Campus Physical & Environmental Planning, UC Irvine
- Case study – Restoration at Big Canyon - Alys Arenas, Restoration Manager, Newport Bay Conservancy
- Case study – Replanting at the Disneyland Resort - Rhonda Wood, Urban Forester, Disneyland Resort
Registration is required for this symposium. Register in advance at:
https://ucanr.zoom.us/webinar/register/WN_iEvMLPZyTG2DTkIGi23Hgg
After registering, you will receive a confirmation email containing information about joining the meeting.
CEUs for this symposium have been requested from WCISA and the California DPR.
Optional In-Person Field Event
An optional, 2-hour, in-person field event will follow on Friday, April 14 in Los Angeles County (Whittier Narrows area -exact location and details to be determined). Topics to be reviewed will include ISHB-related trapping, surveying, identification, sampling, and treatment/management. CEUs will be requested. This field event has a separate registration. Register at https://surveys.ucanr.edu/survey.cfm?surveynumber=40374
Click here for more information or contact Randall Oliver at rdoliver@ucanr.edu.
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- Author: Hung Kim Doan
California is in a severe winter storm making conditions ideal for diseases caused by Oomycetes, also called water molds, especially Phytophthora species, which thrive in waterlogged soils and areas with standing water for periods of time. During moist conditions, large numbers of motile zoospores, which can swim in water for short distances, are produced. Zoospores are carried in irrigation or rainwater to the fruit, crown, and roots. Inoculum levels and wetness length are the most important predictors of brown rot epidemics. Unfortunately, Phytophthora species can be found on most orchards in the state. They cause trunk canker, gummosis, and crown, root, and fruit rots on citrus.
To manage Phytophthoradiseases, moisture management is foremost. Control of Phytophthora diseases are extremely difficult, even with the use of fungicides, in the wet weather conditions. In the past few years, researchers from UCR have work on a number of new fungicides, with new active ingredients, to be used in the management of Phytophthora diseases. Management of Phytophthora diseases can also be accomplished through cultural control. It is important to improve soil drainage. Adequate drainage includes both surface and subsoil drainage. Surface drainage is necessary to remove excess surface water rapidly during and after heavy rains. This is usually accomplished by
planting on bedding unless the natural topography has a slop and diverting surface water into collection ditches. Rain water that soaks into the soil and raises the water table must be removed by subsurface drainage. This can be done through the use of subsurface drains or open ditches.
- Author: Hung Kim Doan
Dimocarpus longan, commonly known as the longan and dragon's eye, is a subtropical tree species that produces edible fruit. There are numerous cultivars of longan, but only 30 to 40 are grown commercially. In the United States, longan is grown in Hawaii, Florida, and South California. In Southern California, Kohala and Diamond River are two commonly grown cultivars. Most fruits are grown in small scale operations and sold exclusively to the Asian markets in San Diego, Orange and Los Angles Counites.
Native to Asia, longan trees will grow in U.S. Department of Agriculture plant hardiness zones 9 through 11, where they prefer cool and dry winters. Young tree should be protected from extreme cold and hot weather.Young longan leaves are also sensitive to strong winds during vegetative flushing which may result in leaf dehydration, browning, and deformation. Hardened-off mature trees can acclimate and withstand temperature as low as 22 o F for short periods of time, but branches are likely injured at this temperature.
Longan may be grown from seed, however cultivars do not come true from seed and may take up to 6 years to bear fruits of inferior quality. Air layering is the most common propagation methods as tree may bear fruit 2 to 3 year after plants. Trees should be air layered from April through August, where roots will generally form within 12 weeks. Longan bear erraticallywhere in some years little to no fruit is produced. The recently introduced Diamond River cultivar is reported to fruit every year.
Longan trees should be planted in full sun with 20 feet or more spacing away from other trees. Trees are not tolerant of saline soil or water condition. In addition, longan trees thrive on various soil types (sandy loams, sand, etc) provided they are well drained as they are not tolerant of excessively wet or flooded soil conditions. With the drought in California, longan might be an option for some growers as they are tolerant of dry soil conditions.
Longan trees have few insect pests are diseases in California. Citrus Mealybugs have been observed causing problems in longan. Vertebrates pest such as birds and squirrel are a big problem in production.
- Author: Ben Faber
NEW HLB Detection Response Guide for Growers
To ensure California citrus growers are well prepared in the event of a potential commercial grove detection of Huanglongbing (HLB), the Citrus Pest and Disease Prevention Program (CPDPP) has developed the Response Guide for a Confirmed HLB Positive Detection in a Commercial Grove, which details the steps taken by CDFA and actions required of the property or grove owner, as outlined in CDFA's Action Plan and Information for Citrus Growers/Grove Managers.
Additional ACP/HLB Resources
- CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
oUC IPM recommendations for ACP insecticides
oWeb-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
oVideo on Best Practices in the Field, available in English and Spanish
oSpanish-only ACP/HLB presentation video presentation and audio-only recording.
- Research
oUC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
- Regulatory/Quarantine
oSign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
oRegulatory requirements for moving bulk citrus: Information for Citrus Growers
oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
oSanta Barbara County Ag Commissioner's Office