Laurel Wilt-Ambrosia Beetle Grower's and Advisory Panel meeting to update and discuss research and extension programs supported by the USDA research grant.
Purpose: The Univ. of Florida/IFAS created a panel consisting of local commercial avocado growers and handlers and scientists for the USDA grant on laurel wilt and ambrosia beetles. The purpose of the meeting is for researchers to update avocado growers and the advisory panel on the progress of research on this grant and to discuss future research and extension plans. This meeting is open to anyone to attend.
Date: July 23, 2020
Location: ZOOM, recording available HERE
Dr. Crane, welcome and introduction
Brief updates, plans and discussion:
1. Dr. Schaffer, Environmental Plant Physiology – Laurel wilt susceptibility of avocado scions and rootstocks in relation to physiology and stem anatomy
2. Dr. Gazis, Plant Pathology – Laurel Wilt - Plant Pathology: Research Accomplishments, Current Work, and Future Direction
3. Dr. Carrillo, Entomology – Update laurel wilt ambrosia beetle research
4. Dr. Evans and Mr. Ballen, Ag Economics - current work and work in progress and plans
5. Dr. Crane and Mr. Wasielewski – Current extension program and plans
Laurel Wilt Disease of Avocado and the relatives of avocado in the Laurel Family has devastated the the forests along the east coast from North Carolina down to Florida and along the Caribbean into Texas. It has caused significant losses to wildlands and to the Florida avocado industry.
The extent of the native tree loss is shocking and there is very little that can be done to correct the problem, other than to curb the spread of contaminated wood that is spread by humans, There has been some success in the avocado orchards. While there is no "silver bullet", there is some progress, e.g. pruning to increase light levels to suppress Ambrosia Beetle activity. In addition, research has continued for:
- Vaccinations to protect avocado trees from the LW pathogen
- Developing a faster LW diagnostic tool
- Screening scions and rootstocks for tolerance/resistance
- AB control tactics and suppression
- Molecular understanding of the pathogen
- Economics and the LW epidemic
Read the latest results in these two recent publications:
Photo: Dead avocado trees from Laurel Wilt in Florida
Update on invasive shot hole borers: Online training now available
By Sabrina Drill, Natural Resources Advisor, UCCE Ventura
Invasive shot hole borers (ISHB) are a pest and disease complex potentially affecting over 200 tree species, but posing a strong risk to box elders, sycamores, and other riparian and urban trees, as well as being a nuisance pest for avocado. The beetles have also been shown to attack a wide variety of common and less common ornamental species. For a complete host list, visit https://ucanr.edu/sites/pshb/overview/SHB_Reproductive_Hosts/. The tiny beetles burrow into the trunks and branches of trees and create galleries where they cultivate a fungus that utilizes the trees own circulatory system, harming and in some cases killing the tree. We know the beetle can reproduce in over 60 species of trees, and they have devasted natural riparian areas, though we are beginning to see recovery of some infestations. Currently, the most effective management method is to remove infested wood, sometimes entire trees, and chip what is removed to minus 1”.
ISHB are now firmly established in Ventura County, with finds throughout the Santa Clara River Valley in traps from South Mountain to Toland Park in Santa Paula, and several infested box elder and sycamores in Meiner's Oaks and Ojai. It appears not to have crossed into the county in the south, but there are still active infestations in western Los Angeles County.
Personnel from UC ANR, CDFA, the Ventura County Agricultural Commissioner, and the US Forest Service have taken lead roles in developing a statewide ISHB action plan for the California Invasive Species Advisory Committee, with an initial investment of $5 million to work on controlling the pest. Plan elements include research in the ecology and control of the pest, including work to develop biocontrol; an early detection and surveillance program; addressing green waste and other pathways of spread, and outreach and education.
In terms of education and outreach, an area where Cooperative Extension in Ventura, LA, Orange, and San Diego counties have led, we're excited to announce the release of a new on-line training course. Available through our website, https://ucanr.edu/sites/pshb/, the course is actually served by the eXtension on-line learning platform (and users will need to create a free account). The course consists of 4 chapters including history and impacts, biology, symptoms and look-alike pests, and monitoring and management. While it can't fully replace a field training, it can be a good way to familiarize new staff to the issues.
“Laurel wilt – A threat to California's avocado industry”
Presented by: California Avocado Society, Inc., California Avocado Commission, University of California Cooperative Extension, and University of Florida's Tropical Research and Education Center. Event is FREE, everyone is welcome!
- Tuesday, July 30, 2019, 9-11 AM.,
Pala Mesa Resort, Fallbrook
- Wednesday, July 31, 2019, 9:00 a.m. to 11:00 a.m.,
UC Cooperative Extension Office Auditorium, 669 County Square Dr. Ventura, CA 93003
- Thursday, August 1, 2019, 9-11 AM.,
San Luis Obispo Farm Bureau Office
The current status of Laurel Wilt in South Florida
Laurel Wilt epidemiology and management
Laurel Wilt Vectors and Management
Vascular physiology, anatomy and susceptibility of different avocado cultivars
Economic impact of control strategies
- Author: Sonia Rios
During the first week of August, the California Avocado Society, Inc., California Avocado Commission, University of California Cooperative Extension hosted six Laurel wilt researchers from the University of Florida. The speakers were Randy Ploetz, Jonathan Crane, Bruce Schaffer, Daniel Carrillo, Jeff Wasielewski and Edward Evans. In addition to talking at all three seminar locations, San Luis Obispo, Ventura, and Fallbrook, the researchers were also able to tour the major avocado growing regions.
Laurel wilt is a deadly disease of redbay (Persea borbonia) and other tree species in the Laurel family (Lauraceae), which includes the avocado tree. The disease is caused by a fungus (Raffaelea lauricola) that is introduced into host trees by a nonnative insect, the redbay ambrosia beetle (Xyleborus glabratus). Native to Southeast Asia, the ambrosia beetle has similarities to our current ambrosia pest, Polyphagous shot hole borer and the Kuroshio Borer. That is why this visit from our fellow extension researchers from the University of Florida. However the fungus associated with Laurel Wilt is unlike the disease here in California. Laurel Wilt is a disease that that causes a reaction in the tree to restrict water flow in the tree and the tree collapses rapidly. The tree dies so fast that it doesn't even have a chance for the leaves to fall of the dead branches.
The beetle has the ability to spread the specific pathogen to other ambrosia beetle vectors which happens when they feed on infected trees. Sanitation is the most effect way to manage this problem. Scouting for wilted branches and their rapid removal has been the key to early intervention and eradication. Dr. Ploetz suggests removing the tree immediately. By the time you see frass and streaks in the wood, the tree is already infected and has been for sometime. As soon as a growers see the wilt in the branches, its time to move quickly. This disease may be mistaken for Verticillium wilt or Phytophthora. It can spread throughout the grove by root grafting.
The generation time for the beetle inside avocado trees takes about 40-50 days depending upon temperatures. Their flight activity is highest in the late afternoon and early evening. Dr. Carrillo mentioned that ambrosia beetles are notoriously difficult to control because they are inside the tree most of their life cycle versus being outside the tree. Contact herbicides will not work, because the insects are primarily inside the tree. One of the first goals to avoid infection, is to keep your trees healthy. A sick tree is more attractive
Scouting for laurel wilt in commercial avocado groves
1. Surveying for the symptoms of laurel wilt is a key component of limiting the spread of laurel wilt. Growers and their workers should survey their groves immediately and then weekly or more often if an infestation is detected in an adjacent grove. Pathogen sniffing dogs are currently being used, however there are less than half-dozen trained dogs for this purpose. Symptoms to look for might include:
i. Leaf and young stem wilting.
ii. Leaf color changing from light green to dark green, bluish-green or greenish-brown. Some leaves showing leaf mottling (dark and light green areas) and yellowing.
iii. Dead leaves curled hanging on the tree.
iv. A few stems and limbs with 2 to 4 ft of dieback or whole sections or entire limbs with dieback.
v. Inspection of the trunk and major limbs may show dried sap (white, crystalline powdery material) that indicates insect boring. In any case, on symptomatic limbs remove the bark down to the sapwood and look for dark streaking. Dark streaks in the sapwood may indicate fungal infection. Normally this sapwood should be white to yellowish with no dark staining or streaking. In addition, small, dark holes in the sapwood further indicate wood boring beetles are present.
2. If the tree shows only a few stems and limbs with 2 to 4 ft of dieback, wait for confirmation of laurel wilt before removing the tree. You can remove the dead part of the limb by cutting several feet below the dead area of the limb; burn or bury the infested limb.