- Author: Ben Faber
In 2018 the Ojai Valley Land Conservancy (OVLC) accepted a grant from the Resources Legacy Fund on behalf of Watershed Coalition of Ventura County (WCVC) for a study of projected climate changes in Ventura County. OVLC contracted with Drs. Nina Oakley and Ben Hatchett, climatologists with the Desert Research Institute (DRI), to evaluate historic climate variability and projected changes in Ventura County. This information is needed to “paint a picture” of future climate in the watersheds of Ventura County (Ventura River, Santa Clara River, and Calleguas Creek) to support and inform climate change-related decision-making. This study provides important information for the amendment to WCVC's Integrated Regional Water Management (IRWM) Plan
You can find a copy of the report on the DRI website at: https://wrcc.dri.edu/Climate/reports.php.
To view presentations and other information from the two WCVC Climate workshops conducted with Drs. Oakley and Hatchett in October of 2018, and April of this year please visit: http://wcvc.ventura.org/documents/climate_change.htm
Some of those most interesting findings for me, are the historical data. For example, data for the years 1896 – 2018, show a tendency toward increasing maximum temperatures over the period, especially the last 10 years (Fig 1.2). But most interesting, is the increasing minimum temperatures (Fig 1.3) as compared to the maximum temperatures. Winter where is thy sting? The 2018-19 winter was the coldest in my memory, with the heater on full time at night, but there was no general frost damage this year. I can remember 1990 and 2007.
Precipitation in the South Coast region exhibits high interannual variability over the period examined. No notable long-term trends are observed (Fig. 1.4). Since approximately 2000, the 11-year running mean decreases, associated in part with the 2012–2019 drought. It is unclear whether this trend will continue in subsequent years.
There's a lot more information in the report. READ On.
But something to keep in mind, is that we had a terrible heat wave last July, and it could easily happen again. Growers who had their trees well hydrated before the heat arrived, sustain less or no damage to the trees and much less fruit drop. Trees that were irrigated on the day it started to get hot, never had a chance to catch up with the heat. Once the atmosphere starts sucking the tree dry, water movement through the soil, roots and trunk cant keep up with the demand. Weather forecasting is pretty accurate 3 days out, and if heat is forecast, get those trees in shape. You can run water to reduce the temperature and raise the humidity in the orchard to reduce transpirational demand which helps some.
Something we learned last year. What we saw and what to expect:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27676
Map of elevational changes in Ventura County and how
- Author: Ben Faber
The So-Called “Leaf Fleck” Virus Diseases of Citrus
Robert R Krueger, USDA-ARS National Clonal Germplasm Repository for Citrus & Dates
Riverside, California
Huanglongbing has recently emerged as an existential threat to California citrus production. Although thus far it has been apparently confined to Southern California residential citrus plantings and has not yet been detected in Central or Northern California, its potential for destruction has resulted in most of the attention paid to citrus diseases (as well as most of the research funding) being focused on Huanglongbing. However, other citrus diseases have historically been deleterious to citrus production and their elimination is required in registration and certification programs. It is therefore important to remain knowledgeable regarding these diseases.
One such group of diseases is sometimes referred to as the “leaf fleck” diseases. This is a reference to the symptoms produced in indicator plants in bio-indexing. Bio-indexing was, until relatively recently, the only manner of detecting these diseases, which have quite different effects from each other in commercial orchards. Recent advances in understanding these diseases were presented at the XXI Conference of the International Organization of Citrus Virologists (IOCV) held in Riverside March 09 – 12, 2019. A brief over-view of these findings and their historical context will be presented in this communication.
The diseases to be discussed include Concave gum (CG), Cristacortis, Impietratura, and the newly described Citrus virus-A. These diseases for the most part have historically been associated with the Mediterranean area. CG has historically been present in California, apparently introduced with a varietal introduction before stringent guidelines were in place. CG, Cristacortis, and Impietratura all cause the so-called “oak leaf pattern” in young, tender spring flushes of sweet oranges and mandarins when temperatures are mild. However, other symptoms and the economic effects of these three diseases are different.
Concave gum causes the formation of “concavities” in the trunk and larger limbs of infected trees (Fig 1). These concavities are depressions or pits that may be up to several square inches in size. In the initial stages of concavity formation, the bark cracks and exudes gum. Gum may also be present on the exterior of long-established concavities and within the trunk under the concavities. A portion of the xylem is plugged with these gummy exudates. The overall effect on the tree is generally not death but rather a general debilitation. Higher levels of concavities are associated with a larger degree of tree debilitation and decreased yield and fruit quality (Wallace, 1978).
Cristacortis (Fig 2) also results in pits on the trunks and main branches of infected trees. However, the pits are smaller, deeper, and sharper and occur in both the scion and rootstock. As with CG, the effect is a general debilitation of the tree and decreased economic performance. Impietratura (Fig 3) differs from CG and Cristacortis in that there are no vegetative symptoms. Infected trees have large numbers of small, hard fruits. Gum deposits are present on the albedo at the stem-end of the fruit and in the stem near the fruit. In some fruits, there is surface browning with gum present beneath the surface (Wallace, 1978).
What these three diseases have in common is the “oak leaf pattern” of leaf clearing seen in the leaves of sweet orange and mandarin under appropriate conditions (Fig 4). These symptoms can often be seen in the field and this led to the development of a biological index for this pattern (Roistacher, 1995). This consists of the use of ‘Dweet' tangor as an indicator, held under cool (65 – 75 ºF) temperatures in the greenhouse. ‘Dweet' proved to be a more sensitive indicator than other mandarins or sweet oranges. A problem is that the patterns in the indicator leaves are so similar that differentiation is difficult or impossible. Isolates are maintained based on the identification of the source trees in the field. Other diseases, notably psorosis, produce similar symptoms in indicators but the symptoms differ from the oak leaf pattern (Fig 4). This led to the association of these diseases and some others as part of a “psorosis complex” for many years. Since for most of these diseases, a causal agent had not been definitively established, disconnecting of the oak leaf pattern-forming presumed viruses was done based upon transmissibility, ability to cross protect, epidemiology, etc (Timmer and Beñatena, 1977; Wallace, 1978).
Recently, the di Serio group in Italy (Navarro et al, 2018a, b) and Vives in Spain (presentation at IOCV, 2019) have identified viruses associated with some of the leaf-flecking diseases and have developed laboratory assays for them. Navarro et al (2018a) identified a CG-infected tree by bio-indexing and excluded psorosis by molecular methods. Next-generation seque3ncing (NGS) identified an apparently new negatively stranded RNA virus, Citrus concave gum associated virus (CCGaV). CCGaV was originally said to be a member of the genus Phlebovirus, previously only reported in insects (Navarro et al, 2018a). However, further phylogenetic studies led to a proposal to create a new genus Coguvirus to accommodate CCGaV. A second virus from the proposed new genus Coguvirus was isolated and identified as Citrus Virus A (CiVA). A field survey in Southern Italy encompassing 71 trees showed 15 trees with CiVA present and 5 trees infected with both CCGA and CiVA. Ten of the trees were infected by CiVA and not CCGaV and were asymptomatic. CiVA did not produce symptoms in inoculated plants of ‘Dweet' tangor, ‘Madame Vinous' sweet orange, or other potential indicator plants (Navarro et al, 2018b).
At the IOCV conference, Vives reported Phlebo-like viruses associated with CG, Cristacortis, and Impietratura. A CG isolate (CG-24, originally from California) and an Impietratura isolate I-501 showed homology with CiVA, whereas Cristacrotis isolate C-601 (from Corsica) showed homology with CCGaV, based upon the sequences published by the de Serio group. At the same meeting, several other possibly-related viruses were discussed. Park from Texas presented an oak-leaf inducing virus that acted similar to a CG isolate CG-301 but grouped with CiVA was dubbed Citrus oak leaf associated virus (COLaV). Bester from South Africa described field trees that had psorosis-like trunk and limb symptoms but were negative for psorosis. Some apparent viruses were sequenced, some more like CCGaV and some more like CiVA. Cao from China described five new viruses that would also be related to CCGaV and CiVA that, converse to the South African report, produced leaf symptoms but no trunk symptoms.
These new developments are starting to shed some light on these previously mysterious diseases, but are also opening up new questions. Of particular interest in California is what we are calling CG isolates may in fact be CiVA isolates. This is confusing because the trees producing these isolates were those identified as CG trees based upon the field observations. Some of these trees are still maintained as field trees in Riverside. It is possible that the CG tree used by Navarro et al (2018a) to identify CCGaV had symptoms similar to our California CG trees but actually were caused by a different causal agent. However, our California CG isolates consistently produce symptoms in the ‘Dweet' indicator whereas CiVA did not (Navarro et al, 2018b). In any case, the new NGS methods have revealed interesting new insights into these interesting old diseases.
Literature Cited
Navarro B, Minutolo M, de Stradis A, Palmisano F, Alioto D, di Serio F. 2018a. The first phlebo-like virus infecting plants: a case study on the adaptation of negative-stranded RNA viruses to new hosts. Mol Plant Pathol 19:1075-1089.
Navarro B, Zicca S, Minutolo M, Saponari M, Alioto D, Di Serio F. 2018b. A negative-stranded RNA virus infecting citrus trees: the second member of a new genus within the order Bunyavirales. Front Microbiol 9:2340. doi: 10.3389/fmicb.2018.02340.
Roistacher, CN. 1995. A historical review of the major graft-transmissible diseases of citrus. FAO Regional Office for the Near East, Cairo.
Timmer, LW, and Beñatena, HN. 1977. Comparison of psorosis and other viruses causing leaf flecking in citrus. Proc Int Soc Citriculture 3:930-935.
Wallace, JM. 1978. Virus and viruslike diseases. Pp 67 – 184 in Reuther, W, et al (eds). The Citrus Industry. Rev ed. IV. Crop protection. University of California Div of Agr Sci, Berkeley, CA.
Fig 1. Concave Gum
Fig 2. Cristacortis
Fig 3. Impietratura
Fig 4. Oak Leaf Pattern
- Author: Ben Faber
- Author: Kathy Keatley Garvey
Dr. Thorp, a member of the UC Davis entomology faculty for 30 years, from 1964-1994, achieved emeritus status in 1994 but continued to engage in research, teaching and public service until a few weeks before his death.
A tireless advocate of pollinator species protection and conservation, Dr. Thorp was known for his expertise, dedication and passion in protecting native pollinators, especially bumble bees, and for his teaching, research and public service. He was an authority on pollination ecology, ecology and systematics of honey bees, bumble bees, vernal pool bees, conservation of bees, native bees and crop pollination, and bees of urban gardens and agricultural landscapes.
“Robbin's scientific achievements during his retirement rival the typical career productivity of many other academic scientists,” said Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology. “His contributions in support of understanding bee biodiversity and systematics are a true scientific legacy.”
Lynn Kimsey, director of the Bohart Museum of Entomology and UC Davis professor of entomology, said: "I've known Robbin since I was a graduate student at UC Davis. Even though he wasn't my major professor, my project was on bees and he was incredibly helpful and supportive. His enthusiasm about pollinators and bees in particular actually grew after he retired, and he continued helping students and researchers and was the backbone of so much research. His support and kindness was matched by his undemanding assistance and expertise. What a terrible loss to his family and to the research and conservation communities."
Colleague Norman Gary, UC Davis emeritus professor of entomology, commented earlier this year in a letter of support for a College of Agricultural and Environmental Sciences award: “Robbin is recognized internationally for his expertise and research on bees, especially non-Apis species, known as wild bees. I doubt that there is anyone else in the world who can compete with his expertise in the systematics of the 20,000 species of bees on this earth. He has the perfect balance of research of field research on the biology and behavior as well as laboratory research on the taxonomy of bees.” He was the go-to person to identify a bee by species.
Professor Neal Williams, who organized a symposium in Dr. Thorp's honor at the 2019 Pacific Branch, Entomological Society of America meeting in San Diego, said: ‘Through his tireless efforts in research, advocacy and education, he has inspired a new generation of bee researchers…I like many others, feel truly honored, to have received the mentoring of Robbin and to have him as a colleague.”
In his retirement, Dr. Thorp co-authored two books Bumble Bees of North America: An Identification Guide (Princeton University, 2014) and California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday, 2014). Locally, he was active in research projects and open houses at the Bohart Museum of Entomology and the Häagen-Dazs Honey Bee Haven. In his research, he monitored bees in the Häagen-Dazs Honey Bee Haven, a half-acre bee garden on Bee Biology Road operated by the UC Davis Department of Entomology and Nematology. He established a baseline in 2008 and detected more than 80 species of bees.
Born Aug. 26, 1933 in Benton Harbor, Mich., Dr. Thorp received his bachelor of science degree in zoology (1955) and his master's degree in zoology (1957) from the University of Michigan, Ann Arbor. He earned his doctorate in entomology in 1964 from UC Berkeley, the same year he joined the UC Davis entomology faculty. He taught courses from 1970 to 2006 on insect classification, general entomology, natural history of insects, field entomology, California insect diversity, and pollination ecology.
Every summer from 2002 to 2018, Dr. Thorp volunteered his time and expertise to teach at The Bee Course, an annual workshop sponsored by the American Museum of Natural History and held at the Southwestern Research Station, Portal, Ariz. The intensive 9-day workshop, considered the world's premiere native bee biology and taxonomic course, is geared for conservation biologists, pollination ecologists and other biologists.
Highly honored by his peers, Dr. Thorp was named a fellow of the California Academy of Sciences, San Francisco in 1986; recipient of the Edward A. Dickson Emeriti Professorship of UC Davis in 2010; and recipient of the UC Davis Distinguished Emeritus Award in 2015. Other honors included: member of the UC Davis Bee Team that won PBESA's Team Award in 2013. In addition, he was a past president (2010-2011) of the Davis Botanical Society, and former chair (1992-2011) of the Advisory Committee for the Jepson Prairie Reserve, UC Davis/Natural Reserve System.
Leslie Saul-Gershenz, who received her doctorate in entomology from UC Davis and is now an associate director of research with the Wild Energy Initiative, John Muir Institute of the Environment, said “I am heartbroken. I really hoped with all my heart that Robbin was going to get better and we would have more time with him, more of his sweetness, his kindness, his caring. He helped so many people over so many decades, his contributions were immense in his scientific contributions but also in his positive support of students, and colleagues alike and encouragement of public engagement. I miss him so much. “
Williams said the PBESA symposium was “perhaps the greatest honor one can receive from close colleagues--a special symposium honoring him and his contributions to the field of bee biology and pollination. We designed the symposium to honor the impact of Dr. Thorp, on the field of bee biology and conservation, but at the same time present innovative research that brings together bee and pollination biology researchers."
Richard Hatfield, a senior conservation biologist with Xerces' Endangered Species Program presented him with a framed illustration of Bombus franklini, the work of artist April Coppini of Portland, Ore. An authority on Franklin's bumble bee, Dr. Thorp began monitoring the bumble bee population in 1998 in its narrow distribution range of southern Oregon and northern California. He has not seen it since 2006 and was instrumental in placing Franklin's bumble bee on the Red List of Threatened Species of the International Union for Conservation of Nature and Natural Resources (IUCN). Long active in the North America IUCN Bumblebee Specialist Group, Dr. Thorp served as its regional co-chair, beginning in 2011.
In August of 2016 a documentary crew from CNN, headed by John Sutter, followed him to a meadow where Dr. Thorp last saw Franklin's bumble bee. Sutter wrote about Dr. Thorp, then 82, in a piece he titled "The Old Man and the Bee," a spinoff of Ernest Hemingway's "The Old Man and the Sea."
“Robbin has done so much for me over the years,” Hatfield said. “I'm pleased to give back even a small fraction.” Hatfield praised him as a “a Living Legend of North American Bee Conservation” in a Xerces Society blog during Earth Week. “He has made lasting contributions to the bee conservation community in ways that might never be measured, but will certainly be felt.” https://xerces.org/2019/04/24/robbin-thorp-earth-week/.
"It was great to see Robbin interacting and enjoying the conference and the company," said Professor Gordon Frankie of UC Berkeley, one of the speakers at the Robbin Thorp Symposium. "We all have learned much from him over the years, and this was a good occasion to say thanks and acknowledge Robbin's many contributions."
Professor Diane Ullman, former chair of the UC Davis Department of Entomology, said: “Robbin was my faculty advisor when I was a student! He gave me the courage to stay in graduate school and was a wonderful supporter when I came back to Davis as a faculty member. He was an amazing and passionate scientist and an extraordinary person.”
More tributes:
Professor Claire Kremen of the University of British Columbia, formerly of UC Berkeley, praised him in her letter of support for his nomination for distinguished emeritus professor in 2014:
"I have had the privilege of working with Dr. Thorp as a close colleague since 1999. I can definitely say that without his contributions, I could never have developed as extensive and impactful a research program on pollinator conservation and pollination services. It is even more noteworthy that Dr. Thorp's contributions to this research program have all occurred since his 'retirement'– he has had a very active retirement indeed."
"Dr. Thorp has contributed in three main ways. First, he has provided expert input into the design of protocols for the research, including assays for pollinator effectiveness, developing citizen science methods, rearing experimental bumble bee colonies, monitoring bumble bee colony properties in the field, and developing pollinator survey methods. Second, he has provided expert taxonomic services, including personally identifying over 100,000 native bee specimens that we have collected during this work, and working with us to develop a bee traits database. Third, he has trained numerous field assistants and graduate students from my lab in different aspects of bee biology. He's spent long hours with many of my graduate students helping them learn to identify bees. He also helped us develop methods and information sheets for teaching field and lab teams to recognize key generic and family characters for identifying bees in the field and sorting them in the lab. He's advised many of my graduate students on different aspects of their work.
"Collectively, Dr. Thorp's contributions have impacted 35 publications that have emerged from this research program to date, with many more either submitted or nearing the submission stage. He has also been a co-author on a number of these publications. Not only has Dr. Thorp had such a significant effect on the work of my lab, but he conducts his own primary work documenting the status of rare bumble bee species like Bombus franklini and B.occidentalis and contributes at a similar level to other research labs such as with his long-time collaborators Dr. Gordon Frankie and Dr. Neal Williams. It's really quite amazing how he manages to do it all."
In another letter of support, Katharina Ullmann, director of the UC Davis Student Farm, Agricultural Sustainability Institute, and a UC Davis alumnus (doctorate in entomology) wrote:
"I met Robbin Thorp in 2007 and assumed that he was an active professor because of his continued contribution to the field of entomology, teaching activities, publishing in peer-reviewed journals and vocal support of pollinator conservation efforts. For these reasons I considered asking if I could join his lab. I remember telling someone my plan and they said 'That probably won't work. Robbin is retired.' He does so much in the field of pollination ecology that I didn't even realize he was retired.
"...The entire time that I've known Robbin I've been impressed with (1) his depth and breadth of knowledge about bees and crop pollination, (2) his willingness to share what he knows, and (3) how approachable he is. It doesn't matter if you're a MacArthur Genius or a field technician just learning about bees, Robbin always makes time to talk with you and answer your questions.
"Robbin is one of the few people in North America who can identify bees down to the species level,” Ullmann said. As a result he's in high demand and has identified thousands of specimens for numerous lab groups since his retirement. However, he doesn't just identify the specimens. Instead, he's willing to patiently work through dichotomous keys with you so that you can learn those skills."
Research entomologist James Cane of USDA's Agricultural Research Service, Logan, Utah, wrote in 2014 that “Dr. Robbin Thorp should be the first scientist to be cloned, so valuable and broadly integrated are his knowledge about bees and pollination. No one else I know has his combination of skills; normally several people would be needed. Thus, he is a taxonomist of several genera of bees, a competent pollination biologist studying both native bees and honey bees in both natural and agricultural realms (with research experience in several crops), and a conservation advocate for bees. Moreover, I have watched his considerable teaching skills while helping in The Bee Course over the years. There I also get to see what a model human being Robbin is: thoughtful, considerate, a great listener, playful, polite unpretentious, all traits that the students gravitate towards. I have looked to Robbin as a role model for over 30 years, listen carefully to what he has to say, and always look forward to being in his presence. UC Davis is very lucky indeed to have attracted and retained such a fabulous faculty member.”
Ron McGinley, an instructor an organizer of The Bee Course, said “Robbin Thorp converted me from bugs to bees. To say that Robbin changed my life would be a vast understatement! In retirement, Robbin continues to be one of the most highly regarded bee workers in the world. He also continues his outstanding educational/mentoring skills.”
McGinley shared several comments from The Bee Course alumni:
- It was really a pleasure to learn from one of the best "Bee Dudes” out there.
- Professors with a great deal of experience can sometimes find it difficult to teach students who are just being introduced to the material. Their command of the material is so great that it seems second nature and they can forget how to guide students through the labyrinths of taxonomic structures. Not so for Dr. Robbin Thorp. The paths laid out for students in The Bee Course were clear and the light at the end of the tunnel, although sometimes faint, was always visible.
- Robbin even bought me a Dairy Queen treat for being the first to find an active bee nest….Centris. I said ‘Robbin, you don't have to buy me this treat' and he answered ‘Yes, I do, it's tradition.'
- Robbin is fun to be with in the field and welcomes questions for which he gives very clear answers.
- I sincerely hope that I will meet and work with Robbin again in the future. He is just a joy to be with.
Dr. Thorp was known for his public service, his response to all requests for bee identifications, and his friendships.
Insect photographer Allan Jones of Davis: “I feel particularly privileged as an outsider to have drawn his friendship, attention and support. A picture is said to be worth a thousand words. But a picture with accurate text is a treasure. He has been adding depth and meaning for all of the visitors and friends he has kindly touched.”
Naturalist and bumble bee enthusiast Gary Zamzow of Davis said that “Dr. Thorp frequently helped the Wisconsin Arboretum staff and volunteers. He identified the bumble bees photographed at the Arboretum and other areas. He would confirm our identifications. A great learning experience for all of us. We could have not done it without Dr. Thorp's help.”
His wife, Joyce, 84, preceded him in death on Dec. 9, 2018. Survivors include three children, Kelly, Katie and Jeff, and stepchildren Donna Gary and Steve Gary.
Focus Area Tags: Agriculture, Environment, Natural Resources, Yard &
- Author: Ben Faber
Anthracnose, Sunblotch, and Armillaria Root Rot
Avocado Trunk Canker and Collar Rot
Avocado Branch Canker (Botryosphaeria)
- Author: Ben Faber
It seems the humble earwig that can cause so much damage in citrus orchards in some years on some small trees can be a great boon in biocontrol. Read on:
WSU scientists unmask the humble earwig as an apple-protecting predator
By Seth Truscott,
College of Agricultural, Human, and Natural Resource Sciences
https://news.wsu.edu/2019/06/05/wsu-scientists-unmask-humble-earwig-apple-protecting-predator/
Helping Northwest apple growers protect their crops, WSU scientists have found new proof that earwigs are actually valuable predators in apple orchards, rather than the creepy, crawly, apple‑damaging pests they're sometimes assumed to be.
In the May 2019 edition of the journal Biological Control, Robert Orpet, recent doctoral graduate at Washington State University's Tree Fruit Research and Extension Center, details findings from his multi‑year effort to shed light on the European earwig and its role in combating a costly orchard pest.
“Earwigs will eat just about anything, but we've found that aphid pests are high on their menu,” Orpet said. “By dining on pests and reducing growers' need to spray insecticides, earwigs are unappreciated predators that have important benefits for agriculture.”
Shy, invasive omnivore
An invader in U.S. orchards and gardens, the European earwig was first found in Seattle in 1907, spreading across the continent soon after. With their wriggly bodies and scary‑looking tail pincers, earwigs have always suffered from a bad reputation.
“Apple pickers don't like them, because they have a tendency to hide in apple clusters,” Orpet said. “Farmers often find them inside damaged fruit, and since earwigs feed mostly at night, it's hard to see what they feed on. “Some growers wonder if they cause damage themselves.”
Scientists like Orpet, however, have long suspected that earwigs are an important predator of aphid pests.
Apple trees covered in “snow”
Orpet came to the earwig through his research into the woolly apple aphid, a costly pest of Washington's $2.4 billion apple industry.
Gaining its name from their coat of cottony fibers, woolly apple aphids feed on the roots and branches of apple trees, stealing nutrients and water and causing galls, or abnormal growths. Infestations can decrease tree growth and keep fruit from developing, while the aphid's sticky honeydew secretions can bring on fungal infections.
About the size of a sesame seed, woolly apple aphids can amass in fluffy, meter‑long colonies.
“In bad years, infestations make apple trees look like they're covered in snow,” Orpet said. “That's when growers really take notice.”
Growers have difficulty managing woolly aphids with insecticides, because there are few effective insecticides, and no organic ones, currently available. Well‑known predators like ladybugs and lacewings could take a bite out of the woolly aphid population, but Orpet wanted to know if the earwig makes a difference.
Working with Jessica Goldberger, an agricultural sociologist at WSU's Department of Crop and Soil Sciences, Orpet interviewed 15 orchardists and managers in Washington state, gauging their opinions on the insect's role.
Most growers weren't sure whether earwigs make a real difference for their crops, and some thought of them as minor pests.
At the same time, Orpet was learning what earwigs are really up to in Washington orchards. Working with managers at four different commercial orchards, Orpet set about catching earwigs with cardboard traps.
Aphids: Earwigs' favorite food
Active at night, earwigs hide by day in tight spaces. Corrugated cardboard sheets are a perfect shelter, so he could easily shake them out and count them.
Sectioning off orchards, Orpet removed earwigs in some places, adding them at others. In every site, he counted woolly aphid colonies and checked for fruit damage.
“There was an obvious difference,” Orpet said. “There were fewer aphid colonies in places where I released earwigs.” He found no evidence that earwigs were causing damage themselves, but captured video footage of earwigs eating aphids and destroying their colonies.
Orpet also inspected the contents of trapped earwigs' digestive systems to see what they actually eat. He found that earwigs regularly dine on aphids, even when local aphid populations are small.
“Our results show that earwigs aren't pests, and actually improve biological control,” Orpet said. “Some farmers spray chemicals to knock down their populations, but this research shows they don't have to, and probably shouldn't.
“Growers can reduce pesticide use, save on chemicals and labor, and leave this misunderstood predator to do its beneficial work, protecting their apples from aphids,” he added.
Along with Orpet and Goldberger, co‑authors include WSU entomology professors David Crowder and Vince Jones.
Their research was funded by the Washington Tree Fruit Research Commission, USDA's National Institute of Food and Agriculture, and the Western Sustainable Agriculture Research and Education Program.
Media contact:
- Robert Orpet, doctoral graduate, Department of Entomology, 847‑337‑4480, robert.orpet@wsu.edu
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