At Malcolm Media’s recent Grape, Nut & Tree Fruit Expo, UCCE Viticulture Advisor Gabriel Torres provided an in-depth presentation on sour rot prevention and management. If you missed his presentation or would like a refresher, watch this brief interview as Gabriel provides of some key points growers should consider in season-long prevention/management of this crop spoiling complex.
Please thank this video’s sponsor Suterra for their industry support.
The California Superior Court in Sacramento has ruled the California Endangered Species Act (CESA) does not cover insects and that bees cannot be classified as fish. The Court issued its final ruling on Nov. 19, 2020.
The Almond Alliance of California, in collaboration with seven other agricultural groups, filed suit with California Fish and Game Commission in response to a vote to grant candidacy status to four subspecies of bumble bees under the California Endangered Species Act (CESA).
The California almond industry recognizes that pollinators are integral to many natural habitats and are crucial for the production success of our industry. The Almond Alliance of California is pleased with the ruling and reiterates that the California almond industry continues to be committed to protecting the health and well-being of bees.
Ruling in Almond Alliance of California v. California Fish and Game Commission, Judge James P. Arguelles agreed with a group of petitioners including the Almond Alliance of California. The petitioners argued that the California Fish and Game Commission (the Commission) was not authorized by the CESA to give four species of bumble bees candidate-species status because the California Legislature was clear in the CESA that insects were not protected.
The Commission and the California Department of Fish and Wildlife unsuccessfully argued that bees and other insects and invertebrates are covered under the CESA because “invertebrates” are included within the definition of “fish” in Section 45 of the Fish and Game Code (FGC).
The case follows a 2018 petition from the Xerces Society for Invertebrate Conservation, Defenders of Wildlife, and the Center for Food Safety to the Commission to add the four bumble bee species to the list of endangered species under the CESA. The four species of bumble bee were the Crotch, Franklin’s, Suckley cuckoo, and Western bumble bee. The bumble bees became candidate species, meaning “a native species or subspecies of a bird, mammal, fish, amphibian, reptile or plant that the Commission has formally noticed as being under review”, when the Commission accepted the petition in June 2019. The court’s Thursday ruling set aside the Commission’s decision.
The Almond Alliance in conjunction with our trade organization partners argued that this consideration is not justified based on the following facts:
If listed under the California Endangered Species Act (CESA), the bees would have been the first insects added. Pesticide restrictions, grazing rules, and other habitat protections could then be imposed. While the bees are “candidates” for listing, they have the same protections as species listed as threatened or endangered. This means prohibitions on killing them, which the Department of Fish and Wildlife routinely interprets to extend to harm to the bees or their habitat. That could lead to uncertainty if bumble bees are present on fields or in other areas where agriculture is happening. This type of ambiguity would be disruptive to the almond industry. For example, ripping or other soil movement could be claimed to disturb potential nesting sites. The petitioners specifically list honey bees as a threat to the bumble bees, thus a listing could regulate placement of or reduce the number of honey bee hives. Listing bumble bees as threatened or endangered is setting the stage for how other insect pollinators will be defined, regulated, and protected.The Almond Alliance thanks Nossaman, LLP for effectively representing the coalition and appreciates those in our industry who contributed to the legal fund to support this effort.
Weeds can be a significant problem in berries, tree fruits, tree nuts, and vine crops (e.g. grapes, hops, etc.) especially after transplanting and during flowering and fruit and nut set. Herbicides are a primary tool for managing weeds, even though the evolution of herbicide resistance has limited the utility of many products and off-target movement can sometimes result in damage to trunks, shoots, leaves and flowers. Many growers are transitioning to organic systems to address changes in consumer preferences or satisfy the requirements set in place to enter export markets.
Perennial cropping systems are exploring technologies such as automated harvesters and pruners, to reduce labor demands, and canopy sensing sprayers, to minimize the amounts of crop protection chemicals applied to shrubs, trees, and vines. Novel weed control tools that eliminate or reduce the need for herbicides are actively being developed for and marketed in the agriculture and horticulture industries. These new technologies could begin to play and increasingly large role in future crop production, particularly in high-value specialty crops that 1) have limited herbicide options, 2) are sensitive to herbicide injury, and 3) are heavily reliant on a labor market that is simultaneously growing more scarce and more expensive.
A team of weed scientists from UC Davis, Oregon State University, and Cornell are asking berry, tree fruit, tree nut, and vine crop growers to take 5 to 10 minutes and answer this short and anonymous survey (link below) about your current weed management practices and your interest in novel technologies, like vision-guided sprayers and cultivators, and electric, steam, and pressurized water weeders. This will help us plan research and extension projects that will address stakeholder concerns regarding the future of weed management.
There’s always a chance that we forgot to include some amazing tools that are emerging on the horizon; please feel free to e-mail Lynn Sosnoskie at lms438@cornell.edu and let her know what you think the future of weed control will look like.
Thanks for your time. We appreciate your support of weed science research.
Survey link: https://cornell.ca1.qualtrics.com/jfe/form/SV_bEpfAijoP7puQDP
Despite the tremendous need, there are currently no preemergence herbicides that are organic-compliant. Steam injected into the soil such that the soil temperatures reach >140°F for 15-20 minutes will kill weed seed in the soil. The effect of this reduction in the seedbank viability results weed control in the treated area that persists for several weeks or months, similar to the effects of a preemergence herbicide.
Two studies were conducted at the USDA Hartnell Farm at Salinas, CA during July to September 2020. Steam was applied to raised beds using a custom-built steam injector. Prior to seeding lettuce, steam was applied in a 4-inch wide band to a depth of 3 inches deep. The steam was supplied by a SF-20 Sioux steam generator at approximately 6 to 9 PSI. Soil temperatures in the treated zone were monitored overnight with Hobo temperature monitors. Treatments tested were steam, steam plus 1% w/w peroxide, and nontreated. Treatments were replicated 4 times and arranged in a randomized complete block design. Peroxide was included as it releases heat when injected into soil, i.e., an exothermic reaction, based on the premise that it supplements the heat released by steam. Data collected were soil temperatures following steaming, weed control, hand weeding times, diseased plant counts, and lettuce yields. Trial 1 was initiated July 1 and harvested August 31, 2020. Trial 2 was initiated July 21 and harvested September 25, 2020. Soil temperature intervals >140°F in the top 4 inches of soil for steam were 88 and 67 minutes for trials 1 and 2, respectively. Similarly, soil temperatures >140°F in the steam + peroxide treatment were 76 and 80 minutes for trials 1 and 2, respectively. In trial 1 steam and steam + peroxide resulted in 90% and 92% weed control relative to the nontreated. In trial 2 steam and steam + peroxide resulted in 66% and 84% weed control, respectively. Steam alone reduced hand weeding times 22% to 35% compared to the nontreated, and steam + peroxide reduced hand weeding times 36% to 40% compared to the nontreated. There were no differences in numbers of plants with lettuce drop (Sclerotinia minor) in trial 1. Compared to the nontreated, lettuce drop incidence in trial 2 was 66% and 59% lower in steam and steam + peroxide treatments, respectively. Lettuce plant diameters in trial 1 found that lettuce grown on steamed soil was 16% larger, but there were no differences in trial 2. Lettuce plants grown on steam + peroxide treated soil were 12% and 23% larger in trials 1 and 2, respectively. There were no treatment effects on yields in either trial 1 or 2.
We are not aware of any commercial scale applicators for lettuce that apply steam in a band to the lettuce bed. However, we are working with Dr. Mark Siemens, an agricultural engineer with the University of Arizona to design a commercial scale applicator. Mark has a prototype applicator built and will be demonstrating it during the winter season in the Yuma Valley. It appears that the design for a steam applicator is not complicated and is well within the capabilities of machine shops in California to build. — By Nelly Guerra & Steven Fennimore, UC Cooperative Extension
Foundation Plant Services (FPS) has been testing grapevines in its foundation vineyards for grapevine red blotch virus (GRBV) since 2013. Red blotch infection rates have remained extremely low in the Classic Foundation Vineyard, ranging from 0% to 0.21% since 2013. None of the 4,270 vines were infected in 2020 (see table). Russell Ranch Vineyard (RRV) remained unaffected until 2017 when five of 4,132 vines, only 0.1%, were infected with GRBV. Since then, despite significant efforts to prevent the occurrence of the disease, the infection rate in the vineyard has increased to 0.5% (24 of 4,406) in 2018, 7.1% (339 of 4,761) in 2019, and 18% (788 of 4,367) in 2020 (see table).
Since the discovery of red blotch in the foundation vineyards, all propagated vines related to the positive vines tested negative in every case, indicating the incidence of red blotch at RRV is due to field transmission of GRBV. In addition, material from these plants was distributed prior to the last negative test date, suggesting that material was GRBV-free at the time of distribution. In 2018, we implemented a test-to-order policy that further ensure orders being shipped were negative just prior to distribution.
One of the greatest challenges in managing red blotch has been vector-mediated transmission. The three-cornered alfalfa hopper, Spissistilus festinus, has been documented as a vector in greenhouse studies and has been found in RRV. Given this threat, we have implemented more frequent vineyard inspections and additional spray treatments specifically targeting the vector and developed a comprehensive program for control of this vector. However, it remains unknown if other vectors are involved in the transmission of red blotch. We are working closely with University of California scientists to monitor the foundation vineyards for potential vectors and track the spread of the virus.
Given the level of red blotch infection in Russell Ranch Vineyard, we feel the best course of action is to discontinue distributing material from RRV. However, grapevine material from the Classic Foundation Vineyard, which represents the majority of clonal families from RRV, will continue to be available for distribution and is tested for GRBV as dormant canes prior to shipping.
FPS is greatly committed to maintaining the highest testing standard for our foundation vineyards. We will continue to test all vines in the foundation vineyards individually on an annual basis and implement the best management strategies to safeguard foundation material. In addition, FPS has begun working
with UC Davis planners to design a 24,000 square foot ‘Emergency Greenhouse’ that will protect approximately 4,000 of FPS’ most valued Foundation grapevines. This is essential to protect the material from vectors and guarantees immediate access to the clean plant material in case of field infection. FPS is currently renting two 1,100 sq ft greenhouses in the interim from the College of Agricultural and Environmental Sciences to temporarily house the most valuable clonal selections as newly propagated virus-tested mother vines in a protected environment.
Moving forward, a collaborative approach between FPS and the grape industry is needed to protect grapevine Foundation material from exposure to viruses. Although there are major knowledge gaps about the transmission and epidemiology of grapevine red blotch virus, well-funded research teams around the country are working on elucidating the biology. In the meantime, FPS is moving forward to ensure protection of the core grape Foundation which is an essential asset to the US grape industry. — By Deborah Golino (FPS Director dagolino@ucdavis.edu) & Maher Al Rwahnih (Director of Laboratories malrwahnih@ucdavis.edu)
A total of $45 million in funding for citrus research during the 2020-21 fiscal year was awarded by the United States Department of Agriculture National Institute of Food and Agriculture (USDA-NIFA) Emergency Citrus Disease Research and Extension (ECDRE) Program. The ECDRE Program addresses priorities identified by the Citrus Disease Sub-Committee of the National Agricultural Research, Education, Extension, and Economics (NAREEE) Advisory Board by sponsoring research projects designed to provide solutions to the U.S. citrus industry. For the 2020 fiscal year, the ECDRE program selected 12 projects to receive awards.
With funding support from the Citrus Research Board (CRB), Pepsi Co and Coca-Cola, and a consortium led by the Citrus Research and Development Foundation (CRDF), NIFA awarded a $10 million grant for their on-going coordinated agricultural project with Bayer Crop Science. The project seeks to identify and develop therapeutics for HLB and the presumed HLB pathogen ‘Candidatus Liberibacter asiaticus’ (CLas). Researchers are investigating synthetic and microbial therapeutics for further characterization and optimization, intending to develop therapeutics for commercialization.
According to the CRB President, Marcy Martin, “Success with this project will help all citrus growers, not just those from a particular state. We like that CRDF and CRB were able to team up on this worthy project.”
Among this year’s awardees, three current and past CRB-funded California researchers from the University of California were awarded $12.5 million between three projects. CRB-funded researcher Chandrika Ramadugu, Ph.D., was awarded $4.7 million to lead efforts to evaluate novel citrus hybrids for tolerance/resistance to HLB in multi-state field trials in California, Texas, and Florida. Caroline Roper, Ph.D., received $6.5 million to unravel the underlying mechanisms of tree health in HLB impacted groves and develop a set of best practices for extending the life and productivity of citrus groves. Past-funded CRB researcher Yen-Wen Kuo, Ph.D., was awarded $1.41 million to explore utilizing insect-specific viruses to manipulate the Asian citrus psyllid (ACP) and its associated microbes to limit psyllid activity and disease spread potentially.
CRB-funded researchers Vivian Irish, Ph.D., from Yale University, Anne Simon, Ph.D., from the University of Maryland, and Robert Shatters, Ph.D., from the USDA Agricultural Research Service also received awards. Irish is spearheading research with a $1.5 million award to identify HLB susceptibility genes in citrus, which will assist in future breeding efforts. Simon received $1.5 million to lead efforts to develop a phloem-restricted viral vector that could be used to directly target CLas in the phloem or modulate citrus host responses. Shatters has received $9.4 million to explore the development of an in-field therapeutic screening system with accompanying delivery systems. Past-funded CRB researcher Goutam Gupta, Ph.D., was awarded $4.8 million to lead efforts in developing novel therapies for the prophylactic and curative treatment of HLB.
Additionally, researchers from the University of Florida and the University of Maryland received awards to study CLas, ACP and HLB strategies.
Click here for more information on project scope and activities can be found at. The CRB congratulates all awardees for the 2020 fiscal year cycle and looks forward to seeing the results from these studies.
About the Citrus Research Board
The CRB administers the California Citrus Research Program, the grower-funded and grower-directed program established in 1968 under the California Marketing Act as the mechanism enabling the state’s citrus producers to sponsor and support needed research. More information about the Citrus Research Board may be found at www.citrusresearch.org.
The California Department of Food and Agriculture (CDFA) is currently accepting proposals for its Request for Proposal for a contractor to serve as the Riverside County grower liaison. Proposals must be received by Nov. 18. Responsibilities may include conducting outreach directly to growers in Riverside County, providing them up-to-date information on the latest industry news or updates, staying engaged in CDFA activities, communicating voluntary or mandatory treatments Riverside County and more.
The battle to save California citrus from the Asian citrus psyllid (ACP) and Huanglongbing (HLB) is a collaborative effort that involves local, county, state and federal officials, researchers, scientists and commercial citrus growers. To help facilitate pest management and disease eradication, grower liaisons are key pieces to that puzzle and are dedicated to serving a specific region in the fight against HLB.
This position requires a fundamental knowledge of citrus production, a working knowledge of grove operations, and the relationship between growers, shippers and allied businesses that work in the area of pest and disease control. A Pest Control Advisor’s license is desirable, but not required. The contractor should be familiar with California agriculture and specifically its citrus industry. Knowledge of the ACP and HLB is desirable.
To submit a bid for the contract, you must follow these steps:
Proposals are due to CDFA by Nov. 18 at 2 p.m. The term of this contract is Dec. 1, 2020 or upon final signature, whichever is later, through Nov. 30, 2022.
For additional questions, contact Contracts Analyst Donna Weber at donna.weber@cdfa.ca.gov.
Halloween will come and go, but mummy nuts are here to stay… unless you shake them away!
To help remind growers to break the link between mummy nuts and overwintering navel orangeworm (NOW), the Almond Board of California (ABC) created a parody song that’s sure to be an “orchard smash,” just in time for the most spooky holiday of the year. It’s The Mummy Shake — listen now (lyrics here) and submit a video of your family dancing along to this “orchard smash” for a chance to win a $500 Amazon gift card!
How to Enter: Video Specifications
How to Upload Your Video
Read on below for complete contest eligibility guidelines.
Mummy Shake Video Contest – OFFICIAL RULES
NO PURCHASE NECESSARY TO ENTER OR WIN. MAKING A PURCHASE OR CONTRIBUTION WILL NOT IMPROVE CHANCE OF WINNING. VOID WHERE PROHIBITED.
1. Preliminary Information and Contest Period: The Mummy Shake Video Contest (Campaign) is open for entries starting October 26, 2020 at 12:01AM Daylight Pacific Time (PT). All entries must be submitted by the contest deadline: 11:59PM PT on November 20, 2020 (Contest deadline). Campaign is subject to all applicable federal, state and local laws. This Campaign is sponsored by the Almond Board of California (Sponsor), 1150 9th St. #1500, Modesto, CA 95354.
2. Agreement to Rules: By participating, the Contestant agrees to be fully and unconditionally bound by these Rules and decision of Sponsor, which shall be final and binding. Contestant represents and warrants that they meet the eligibility requirements. In addition, Contestant agrees to accept the decisions of Sponsor as final and binding as it relates to the content of this Campaign.
3. Eligibility: Contestant may enter to win if he or she is a legal resident of the state of California, age 18 or older at the time of entry, and is a member of the California almond industry, which includes growers, handlers, hullers/shellers and allied industry members. Contestant’s submission may include family member and/or friend of a Contestant provided that such family member or friend consents to being featured in the submission. If Contestant chooses to feature his or her children under the age of 18 in his/her submission, Contestant grants Sponsor permission to display, broadcast and/or share video for promotional purposes of this Campaign or future Campaigns. Employees, officers, directors, agents, representatives and their immediate families (parents, children, siblings, spouse and each of their respective spouses, regardless of where they live) or members of the households of the Almond Board of California/Sponsor, their parent companies, subsidiaries, agencies and anyone connected with the production and distribution of this Campaign may submit an entry for use by Sponsor solely to promote the Campaign, but are not eligible to win or be awarded a prize.
4. How to Enter: To enter, Contestants must create a video featuring themselves and/or family or friends dancing to the Almond Board of California’s “Mummy Shake” song, in an almond orchard or another setting of their choosing. Entry videos must be at least 30 seconds in length (approximately one verse and one chorus) and up to the duration of the full song. Entries will be judged based on enthusiasm, creativity, and composition. Judges will be comprised of employees of the Almond Board of California. Submit your video entry in one of two ways:
Multiple entries per person or household will be accepted and judged, but only one (1) prize will be awarded per person or household. Entries that are incomplete or that contain errors, copyrighted images or inappropriate/derogatory/defamatory images or language, dogs in the orchard, guns/firearms, nudity, violence or profanity will be automatically disqualified in Sponsor’s sole discretion. Sponsor is not responsible for lost, late, misdirected, altered or destroyed entries. The odds of winning depend on the number of eligible entries received and/or the number of contestants participating in the contest. If Contestant uses fraudulent methods or otherwise attempts to circumvent the rules, the submission may be removed from eligibility at the sole discretion of Sponsor. The Contestant may be asked to provide all appropriate clearances, permissions and releases for the submission.
All entries become the property of Sponsor and will not be returned. Proof of sending will not be deemed proof of receipt by Sponsor. Sponsor reserves the right to edit or summarize the submission or any written description or picture prior to posting to Sponsor’s website and/or social media channels.
5. Prize: The Winner of the Campaign (“Winner”) will receive a Grand Prize consisting of a $500 Amazon gift card.
The prize will be sent to Winner’s provided email address within two (2) weeks of notification. Any applicable Federal, State or Local taxes are solely the responsibility of the winner and paying any expenses associated with any prize which are not expressly included as part of the prize. Prizes are not transferable. Sponsor reserves the right to substitute a prize package with another prize of equal or greater value if advertised prize or any component thereof is not available.
6. Winner Selection and Notification: Winner will be selected under the supervision of the Sponsor. Winner will be notified by email or by direct message on Facebook within five Sponsor business (5) days following selection of Winner. Sponsor shall have no liability for Winner’s failure to receive notices due to spam, junk email, or other security settings or for Winner’s provision of incorrect or otherwise non-functioning contact information. If Winner cannot be contacted, is ineligible, fails to claim the prize within seven (7) Sponsor business days from the time award notification was sent, or fails to timely return a completed and executed declaration and release as required, the prize may be forfeited, and an alternate Winner selected. Receipt by Winner of the prize offered in this Campaign is conditioned upon compliance with any and all federal, state, and local laws and regulations. Any violation of these official rules by winner (at Sponsor’s sole discretion) will result in Winner’s disqualification as Winner of the Campaign, and all privileges as Winner will be immediately terminated.
7. Rights Granted by Contestant: By entering this Campaign, Contestant understands and agrees that Sponsor, anyone acting on behalf of Sponsor, and Sponsor’s licensees, successors, and assigns, shall have the right, where permitted by law, to print, publish, broadcast, distribute, and use in any media now known or hereafter developed, in perpetuity and throughout the World, without limitation, Contestant’s entry, name, portrait, picture, voice, likeness, image, statements about the Campaign, and biographical information for news, publicity, information, trade, advertising, public relations, and promotional purposes, without any further compensation, notice, review, or consent. By entering this Campaign, Contestant represents and warrants that entry is an original work of authorship and does not violate any third party’s proprietary or intellectual property rights or right of publicity. If entry infringes upon the right of any third party including, without limitation, any intellectual property right or right of publicity, Contestant will be disqualified at the sole discretion of Sponsor. If the content of the entry is claimed to constitute infringement of any proprietary or intellectual proprietary rights or right of publicity of any third party, Contestant shall, at his or her sole expense, defend or settle against such claims. Contestant shall indemnify, defend, and hold harmless Sponsor from and against any suit, proceeding, claims, liability, loss, damage, costs or expense (including attorneys’ fees), which Sponsor may incur, suffer, or be required to pay arising out of such infringement or suspected infringement of any third party’s right.
8. Terms & Conditions: Sponsor reserves the right, in its sole discretion, to cancel, terminate, modify or suspend the Campaign should virus, bug, non-authorized human intervention, fraud, or other cause beyond Sponsor’s control corrupt or affect the administration, security, fairness, or proper conduct of the Campaign. In such case, Sponsor may select the Winner from all eligible entries received prior to and/or after (if appropriate) the action taken by Sponsor. Sponsor reserves the right, in its sole discretion, to disqualify any individual who tampers or attempts to tamper with the entry process or the operation of the Campaign or website or violates these Terms & Conditions. Sponsor has the right, in its sole discretion, to maintain the integrity of the Campaign, to void entries for any reason. Any attempt by a Contestant to deliberately damage any website or undermine the legitimate operation of the Campaign may be a violation of criminal and civil laws. Should such attempt be made, Sponsor reserves the right to seek damages to the fullest extent permitted by law.
9. Limitation of Liability: By entering, Contestant agrees to release and hold harmless Sponsor and its subsidiaries, affiliates, advertising and promotion agencies, partners, representatives, agents, successors, assigns, employees, officers, and directors from any liability, illness, injury, death, loss, litigation, claim, or damage that may occur, directly or indirectly, whether caused by negligence or not, from: (i) such Contestant’s participation in the Campaign and/or his/her acceptance, possession, use, or misuse of any prize or any portion thereof; (ii) technical failures of any kind, including but not limited to the malfunction of any computer, cable, network, hardware, or software, or other mechanical equipment; (iii) the unavailability or inaccessibility of any transmissions, telephone, or Internet service; (iv) unauthorized human intervention in any part of the entry process or the Promotion; (v) electronic or human error in the administration of the Promotion or the processing of entries.
10. Disputes: This Campaign is governed by the laws of the United States of America and California, without respect to conflict of law doctrines. As a condition of participating in this Campaign, participant agrees that any and all disputes that cannot be resolved between the parties and causes of action arising out of or connected with this Campaign, shall be resolved individually, without resort to any form of class action, exclusively before a court located in California having jurisdiction. Further, in any such dispute, under no circumstances shall participant be permitted to obtain awards for, and hereby waives all rights to, punitive, incidental, or consequential damages, including reasonable attorney’s fees, other than participant’s actual out-of-pocket expenses (i.e. costs associated with entering this Campaign). Participant further waives all rights to have damages multiplied or increased.
11. Privacy Policy: Information submitted with an entry is subject to the Privacy Policy stated on the Sponsor’s website. To read the Privacy Policy, click here.
In California, fungal canker diseases have long been known to affect almond trees. However, they have become an increasing concern to growers in recent years as they are affecting a greater extent of young trees, eventually resulting in significant tree losses. Canker diseases can also become prevalent in mature orchards, impacting yield, the lifespan of trees, production costs and overall profitability of almond orchards. Ultimately, trunk and scaffold canker diseases constitute a major cause of tree death and branch dieback in California almond orchards.
As the University of California (UC) Assistant Cooperative Extension Specialist in Plant Pathology for fruit and nut crops when I receive calls from farm advisors, almond growers and Pest Control Advisers (PCAs) the questions they most frequently have are in relation to canker diseases, asking how can it be diagnosed, and how can it be treated.
Symptoms on affected trees are very conspicuous and often alarming to growers. Moreover, field diagnosis of canker diseases is difficult as symptom delineation among the various canker diseases is not clear. Hence, laboratory tests are usually required to obtain accurate disease diagnosis, which is essential to the implementation of appropriate management strategies.
With support from the Almond Board of California (ABC) and with the help of farm advisors, my laboratory conducted statewide surveys to characterize canker diseases in almond orchards and to get a thorough understanding of the main diseases and pathogens present. This work has provided molecular tools and a database for the accurate identification of fungi commonly isolated from almond cankers.
This article will provide an overview of the main canker diseases that impact almond trees and how they can be recognized. But first, let’s review some general concepts about canker diseases.
What is a canker?
A canker in woody plants generally refers to a lesion produced in the bark of a plant’s stem, twig, or branch, often resulting in a dead area that can block water and nutrient transport to portions of the tree, thus causing parts of the plant to die back. Most cankers are caused by fungi, which invade bark tissue and the current season’s wood. However, some fungi colonize in both bark and internal wood tissue, causing canker rot or wood cankers that persist for years.
Wood cankers typically consist of brown-to-dark brown discoloration of xylem tissues and may vary in shape from wedge-shaped to round, or irregular.
What are the main infection pathways and disease cycles of canker diseases?
In orchard systems, cankers usually originate around wounds such as pruning wounds, mechanical injuries, sunscald and sunburn lesions, as well as wounds caused by insect borers. In almonds, canker pathogens infect trees mainly through pruning wounds made for primary and secondary scaffold selection to provide the general structure of trees. Cracks in the tree crotch or on the trunk as well as shaker injuries provide other entry points for canker-causing pathogens in almonds. Canker diseases may go unnoticed during the early stages of infection, though symptoms become more visible as the trees age.
Most fungal canker pathogens produce fruiting bodies on dead wood of infected host plants. The spores produced by these fruiting bodies serve as inoculum for new infections, mostly during wet weather. The vegetation present in the vicinity of orchards, particularly trees in riparian areas or neighboring orchards of susceptible crops, may serve as inoculum sources for fungal canker pathogens affecting almonds. Once a canker disease has been established in an orchard, infected almond trees can provide additional inoculum for further infection.
Does stress play a role in the exacerbation of canker disease?
Recent outbreaks of canker diseases in perennial crops have been attributed in part to drastic changes in production practices, climate change and increased plant stress, the continuing adaptation of pathogens to new environments, and, most importantly, the global movement of plant material. Ultimately, though, trees suffering environmental stresses are more susceptible to canker diseases.
Microorganisms that usually do not cause disease in non-stressed hosts may become opportunistic pathogens of stressed plants. Increases in canker diseases are common during extended periods of drought or following sudden temperature fluctuations. Drought stress can also impair the plant’s ability to defend against fungal invasion. Conversely, excessive watering can kill roots and predispose plants to canker pathogens.
What are the main canker diseases in California almonds, and what are their symptoms?
Ceratocystis canker
Ceratocystis canker, caused by the fungal pathogen Ceratocystis destructans (formerly known as Ceratocystis fimbriata), is one of the most prevalent canker diseases in California almonds – it occurs statewide in all almond producing counties. While this disease is generally associated with shaker damage and bark injuries on trunks during harvest, C. destructans is also capable of infecting branches from fresh pruning wounds and if left untreated can kill branches, scaffolds and entire trees. Ceratocystis is spread by several species of sap-feeding beetles and fruit flies.
Ceratocystis canker starts as water-soaked injuries that are darker than the surrounding healthy tissue. Symptoms of established infections include amber-colored gumballs that are produced around the margin of the canker, where the fungus is most active. The cankers are perennial, persist over several years, and are most active during the growing season. Young trees infected with Ceratocystis canker may die rapidly while infections in older trees usually progress slowly.
Band canker and other Botryosphaeriaceae cankers
Although band canker was first reported years ago as a disease in almonds, it’s appearance had been very sporadic up until the last decade, when this disease was suddenly being reported in large numbers of commercial orchards and causing severe damage.
Band canker produces unique symptoms that include oozing amber sap that forms in a ring around the circumference of the tree. Young, vigorous varieties that grow quickly from aggressive nitrogen and water inputs are especially prone to band canker. Solid sprinkler irrigation or micro-sprinklers that wet the tree trunk can create conditions favorable for infection.
Band canker is often an annual disease that occurs when trees are in their second-to-fifth leaf and usually does not necessarily reappear the following year. However, an increasing number of cases have been reported lately where cankers are being re-activated in following year. Tree death due to band canker has become more common as multiple bands can develop as the canker continues to grow from one growing season to the next.
Botryosphaeriaceae cankers are characterized also by gumming around pruning wounds made near the trunk or in main scaffold branches. Band canker and Botryosphaeriaceae cankers are particularly common in young almond orchards in the northern San Joaquin Valley and well as in the Sacramento Valley.
Infections by Botryosphaeriaceae fungi are usually associated with growth cracks or pruning wounds on the trunk and main scaffold branches. Studies have revealed there are at least 12 different Botryosphaeriaceae species in almonds, each with various levels of virulence. Among them, Neofusicoccum species, including N. parvum and N. mediterraneum, are the most common in California. Neoscytalidium dimidiatum also occurs frequently in cankers developing around pruning wounds on the trunk. This pathogen also can cause shoot blight and fruit rot in almonds.
Eutypa dieback
Eutypa dieback in almonds occurs sporadically in the Sacramento Valley and in the northern San Joachim Valley. Eutypa dieback is caused by the fungus Eutypa lata and is a common disease in apricots, sweet cherries and grapevines. Eutypa dieback in almonds is usually found in young trees.
Cankers mostly originate from pruning wounds on limbs or trunks as well as from cracks formed at the junction of scaffold branches and the trunk, extending downward toward the graft union or upwards into one or more scaffold branches. Amber-colored gum turning dark brown to reddish brown normally exudes around the cracks. Irregular-shaped to wedge-shaped, brown-colored cankers are observed from cross sections of limbs and trunks.
Limb dieback may occur several months or years after infection. The fungal fruiting bodies, i.e. the perithecia of E. lata. are rare in almond orchards, suggesting sources of inoculum for this disease most likely originate from surrounding susceptible hosts including apricot and grapevine as well as natural host plants in riparian areas such as willows.
Cytospora cankers
Cytospora species have been isolated sporadically in almond orchards in California, Cytospora canker is generally associated with pruning wounds in the branches of third-leaf trees or older. At least five species of Cytospora have been associated with cankers in California almonds. Symptoms of Cytospora canker include longitudinal cankers in branches and scaffolds often associated with pruning wounds, vascular discoloration of the wood and moderate gumming.
Cytospora species have been traditionally thought to be secondary to sunburn and other stresses or injury in stone fruits. However, their prevalence in cankers together with pathogenicity studies suggest that this group of fungi constitutes virulent pathogens. Overall, Cytospora pathogens are of increasing concern in recent years in many fruit and nut crops in California.— By Florent P. Trouillas (Through the Almond Board of California), Assistant Cooperative Extension Specialist in the Department of Plant Pathology at the University of California, Davis
Stay tuned for a follow-up article from Trouillas on how growers can manage different types of canker diseases in their orchards. Growers are also encouraged to check out the Univeristy of California IPM website for more information on various types of canker diseases.