- Author: Ben Faber
Current status of
Laurel Wilt: A Disease of Avocado
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Please find enclosed links to a recent on-line meeting of researchers from forestry and avocado production system perspectives on current laurel wilt research. The goal of the meeting was to briefly share information on current basic and applied research and ideas for controlling or mitigating the laurel wilt pathogen and the ambrosia beetle vectors. Below is the agenda.
https://ufl.zoom.us/rec/share/6tdrHq3spkxLRKuS2VOFGaEzRaS7X6a80SUfrqYJnkuVYiHCDKUa5wtKYTp5ucdn
https://ufl.zoom.us/rec/share/6tdrHq3spkxLRKuS2VOFGaEzRaS7X6a80SUfrqYJnkuVYiHCDKUa5wtKYTp5ucdn
Laurel wilt is a notorious example of the destructive capacity of beetle-borne fungi. Even more importantly, there is a vibrant community of researchers studying it! At this meeting we will host scientists and students that are actively solving the mysteries of this epidemic. We will hear about many topics, from glowing transgenic pathogen strains to field detection with sniffer dogs.
We hope that the laurel wilt community will also benefit from what our BBM Network has to offer. Exchanging results and experiences is important for the PIs, but perhaps even more for the students – designing and executing a laurel wilt related-project takes a long time, so it might be beneficial to get feedback earlier than at the publication stage. We see repeated mistakes that could be prevented, and old questions that would have been answered, if we talked more as a community. And how about people studying different ambrosia symbioses, beetles or pathogens? There is a lot of overlap but little information exchange with those outside of our field.
Participants
INTRODUCTION AND WELCOME
- 9:00 Jiri Hulcr: Short introduction to the Bark Beetle Mycobiome group (5 minutes)
MOLECULAR BIOLOGY
- Josh Konkol: GFP strain, colonization of the host plant by R. lauricola
- Jeff Rollins: Studying R. lauricola pathogenesis through comparative genomics and transcriptomics
- Qiang Wang: CRISPR-homologous recombination methods and deletion of genes from R. lauricola
- Ross A. Joseph: Swap of multiple GFP-labeled strains inside the vector
BIOLOGY
- Octavio Menocal Sandoval: Breeding Xyleborus, behavior of mating and symbiont swap
- Daniel Carrillo: Laurel wilt vectors in avocado
- Kirsten Stelinski: TBD
ECOLOGY,
- Denita Hadziabdic: Laurel wilt advancing North
- Robin Choudhury: LW dispatch from the Texas front
- Andrés Lira Noriega: Modelling for risk assessment of laurel wilt in Mexico
- Jason Smith: Redbay heritable resistance and rebounding populations
DETECTION
- Caterina Villari: Detection of laurel wilt pathogen in the field with LAMP
- DeEtta (Dee) Mills: Detector dogs
- Pedro Parra Giraldo: Culture-independent Laurel Wilt diagnosis in avocado groves
MANAGEMENT
- Romina Gazis: Testing “Out-Of-The-Box” Ideas to Control Laurel Wilt of Avocado
- José Luis Olivares-Romero: Synthesis of novel insecticides for the management of ambrosia beetles
- Jonathan Crane: Laurel wilt status in avocado groves and grower-initiated control
- Xavier Martini and Derrick Connover: Push-pull system to protect redbay and avocado against Laurel Wilt
- Author: Ben Faber
April, 2020 CAS/CAC/UC
Avocado Grower Meetings
The original field meeting for avocado growers was canceled this year. This was to be an opportunity for growers to get out and see, touch and interact with other growers and people experienced in the various topics that were to be covered. The meetings were to be in real groves at Cal Poly San Luis Obispo, Pine Tree Ranch in Santa Paula and Rancho Aqua Tibia in Pauma Valley. The discussion and viewing topics ranged from 1) Planting Density, 2) Pruning, 3) Root Rot Management, 4) Pest Monitoring, 5) New Scions/Rootstock and 6) the Healthy Soils Program. We had a range of speakers arranged for the different sites to show, demonstrate and spark discussion. The actual sessions were designed so that every topic got covered and everyone got to hear the highlights of the topic in a 15 minute period, before moving on to the next topic. For the Scion/Rootstock session, this would have been just a brief introduction before the more elaborate workshop of that topic which will be held in June. The enclosed outlines and references cover the topics that would have been covered at these field meetings. They are not a substitute for actually being out in the field, but hopefully they will keep you thinking about how to improve your avocado production.
Planting Density: Tim Spann of CAC
Pruning: Gary Bender, Sonia Rios of UCCE and Gabe Felipe of Mission Produce
Root Rot Management: Ben Faber of UCCE
Pest Monitoring: Enrico Ferro, Tom Roberts, Jane Delahoyde, Jim Davis
New Scions/Rootstocks: Mary Lu Arpaia, Patricia Manosalva of UC Riverside
Healthy Soils Program, Alli Fish, Esther Mosase of UCCE; Lance Andersen of Mission RCD; Jamie Whiteford of Ventura RCD; Claire Balint of Cal Poly; Mary Matava of El Corazon Compost
/span>- Author: Ben Faber
Proper pruning and tree care are important in most trees, including citrus and avocado. The question of what decay fungus is happening to a tree often comes up and a recent UC publication can help answer that question
Wood Decay and Fungi in Landscape Trees by Downer and Perry
The other question of what to do about the fungus is answered, as well. Check it out.
IDENTIFICATION AND BIOLOGY OF DECAY FUNGI
Many wood decay fungi can be identified by the distinctive shape, color, and texture of the fruiting bodies they form on trees. These fruiting bodies take several forms, depending upon the fungus that produces them, but most of them fit into categories commonly referred to as mushrooms, brackets or conks. They often grow near wounds in bark, including old pruning wounds, at branch scars, in proximity to the root crown, or near surface anchor roots. Some decay fungi, such as Armillaria mellea, produce fleshy mushrooms at the base of infected trees or along their roots, often after rain in fall or winter. All mushrooms and some bracket fungi are annual (i.e., appearing and disappearing seasonally), but many conks are perennial and grow by adding a new spore-bearing layer (hymenium) each year.
Decay fungi are divided into those that attack heartwood (causing heart rots) and those that attack sapwood (causing sap rots and canker rots). Further subdivision is based on the appearance of the decayed wood (i.e., white rots, brown rots, and soft rots) or location in the tree (the decay is called a butt rot if it is at the base of the trunk). Canker rots usually appear on branches or the trunk. When a fruiting body is visible on a tree, it is usually associated with advanced decay; the extent of decay may be far above or below the location of the fruiting body. Trees with extensive sap rot may show symptoms of decline, including increased deadwood and a thinning canopy with reduced density of foliage.
- Author: Ben Faber
Foliar fertilizer application is sometimes promoted as an effective means of supplying nutrients to avocado. On the market are various products being promoted as foliar nutrients for avocado, some proponents even suggest that their products do away with the need for soil applied nutrients. The nature of the avocado leaf severely limits its capacity to absorb foliar sprays.
The structure of plant leaves has evolved primarily to capture sunlight and exchange gases, roots have evolved to absorb nutrients and water and anchor the plant. Any absorption of nutrients by leaves is therefore likely to be more fortuitous than by design. In some crops passive nutrient absorption by leaves is occasionally sufficient to supplement the supply of nutrients taken up by the roots. Most often this involves trace elements, which as their name suggests are required in very small amounts (eg. copper and zinc). However if non-mobile elements or elements with limited mobility in the plant (eg. calcium, phosphorus, zinc, boron and iron) are absorbed when foliar sprayed they are not likely to make it down to the roots where they are also needed. Most nutrients will move freely in the water stream but the movement of many is restricted in the phloem, hence leaf applications don't meet the requirements of deficient trees. Occasionally major elements (such as nitrogen and potassium) are applied to make up for a temporary shortfall or provide a boost at a critical time. Citrus is an example of a crop where some benefits from foliar applied nutrients have been reported.
The ability of the leaf to absorb nutrients from its surface must depend to some degree on the permeability of its epidermis (outer layer) and the presence and density of stomates (pores for the exchange of gases). Scanning Electron Microscope studies of mature leaves and floral structures in avocado show the presence of a waxy layer on both the upper and lower surfaces of mature avocado leaves (Whiley et al, 1988). On the upper surface the wax appears as a continuous layer and there are no stomates. On the lower surface the wax layer is globular and stomates are present. Blanke and Lovatt (1993) describe the avocado leaf as having a dense outer wax cover in the form of rodlets on young leaves and dendritic (branching) crystals on old leaves including the guard cells (guard cells surround stomates). The flower petals and sepals in avocado have stomates on their lower surfaces and no wax layers on either surface, which might explain why floral sprays of boron might work.
Blanke, M.M. and Lovatt, C.J. 1993. Anatomy and transpiration of the avocado inflorescence. Annals of Botany, 71 (6): 543-547.
Whiley, A.W., Chapman, K.R. and Saranah, J.B. 1988. Water loss by floral structures of avocado (Persea americana cv. Fuerte) during flowering. Australian Journal of Agricultural Research, 39 (3): 457-467.
The avocado leaf, water beading up on the waxy cuticle.
An avocado leaf with its cuticle (white, paperlike surface) being exposed by underlying leaf fungi.
- Author: Ben Faber
NO, you didn't miss it. It's coming to you
https://californiaavocadosociety.org/seminar-presentations.html
We arranged Field Days at three locations for our Avocado Meeting co-produced by The CA Avocado Society, CA Avocado Commission and University of CA Cooperative Extension
The list of speakers and topics is below.
As well as the sponsors for the meetings
Thank you so much for the speakers agreeing to present at these sessions, but because of the current COVID crisis we have turned to the printed word to present some of the ideas intended for the meeting discussions.
Our June meeting will be zoomed. The topics will be Avocado Scions and Rootstocks, presented by Mary Lu Arpaia and Patricia Manosalva
Look for the details of that meeting in forthcoming blogs, newsletters, CAC and CAS alerts
Presented by
California Avocado Society, Inc., California Avocado Commission, and University of California Cooperative Extension