Threat to Avacado Trees in Florida

Tropical Research and Education Center

Jonathan H. Crane, Tropical Fruit Crop SpecialistUniversity of Florida, IFAS

Tropical Research and Education CenterHomestead, Florida


Bring attention of UF-IFAS Cooperative Extension faculty and Master Gardeners to the current or impending problem in the area.

Provide background information on the situation, insect, disease, pest spread, tree damage, and recommendations to slow the spread of this pest.

Provide recommendations on how to handle inquires from clientele and potential samples of infested material.


Photograph credits include:Michael Thomas, FDACSAlbert Mayfield III, FDACS Division of

ForestryJames Johnson, GA Forestry CommissionJonathan Crane, UF-IFAS-TRECMike Ulyshen, USDA Forest ServiceStephen Fraedrich, USDA Forest ServiceDavid Moynahan, Terrain OrganizationJason Smith, UF-IFAS School of Forestry


Ambrosia beetles (>34,000 species world-wide)Order – ColeopteraFamily – CurculionidaeSubfamilies – Scolytinae or Platypodinae

Characterized byBoring into host trees and forming galleries in the

sapwood.Carry with them a symbiotic fungus which digests

the woody conducting tissues (sapwood/xylem, phloem); disrupting the flow of water and nutrients in the tree.

The beetle adults and larvae feed on the mycelium and spore clusters of the fungus.

Typically ambrosia beetles attack trees under some type of environmental stress (e.g., drought).

These beetles may or may not be pests of specific host plant species.


Ambrosia fungi (from the Greek, meaning food of the Gods)A few dozen species of these symbiotic fungi

have been described.They rely on their symbiotic beetle vector for

transport to host trees.Spores of the fungus carried on the body of the

beetle infect the host tissue, colonize the conducting tissues, and reproduce.

The beetle larvae and adults feed on the symbiotic fungus it transports.


Redbay ambrosia beetle (RAB) (Xyleborus glabratus) was introduced through Port Wentworth in Georgia in 2002 through infested wood packing material – crates or pallets.

Origin of the insect pest includes: India, Bangladesh, Japan, Myanmar and Taiwan.

Origin of the laurel wilt pathogen (LW) (Raffaelea lauricola) is unknown.

Now found in 3 states: Georgia (2002), South Carolina (2004), and Florida (2005).


Trees in the Lauraceae (Laurel Family).Redbay (Persea borbonia)Silk bay (P. borbonia var. humilis)Swampbay (P. palustris)Avocado (P. americana)Sassafras (Sassafras albidum)Pondberry (Lindera melissifolia)Camphor (Cinnamomum camphora)Pondspice (Litesea aestivalis)California laurel (Umbellularia californica )*Other potential hosts are under investigation

* LW susceptible; RAB susceptibility undeterminedRAB-LWspread

Current spread of the RAB-LW

•Natural spread

primarily through

redbay trees and

man-made spread

by movement of

redbay wood.

•Very small (~2 mm in length), brown-

black colored, cylinder shaped.

•Female beetles - most common and

can fly; males – not common and

cannot fly.

•The RAB carries spores of the LW

pathogen (fungus) in special mouth

pouches called mycangia.

•Beetles bore into the wood just

below the bark and form galleries in

the sapwood.

Redbay ambrosia beetle (RAB) (Xyleborus glabratus)


• The adult beetles and their larvae feed on the fungus.

• Mouth pouches (mycangia) with LW spores from the head of the RAB.


Compacted frass from boringinto the tree

Holes fromboring

Galleries


Healthy redbay treesequence

Infestation of redbay trees sequence


September 2007 first report of RAB-LW attacking and killing an avocado tree – Jacksonville, Duval County.

Since that time avocado trees have been reported killed or severely damaged in Duval, Brevard, Volusia, and Indian River Counties.


Natural spread of LW by RAB flight; about 15-20 miles per year.

Natural spread through redbay and other natural hosts in natural areas and landscapes.Redbay found

throughout SE US to eastern coast of TX.

Natural spread through urban back yard avocado trees.

Manmade spread by movement of infested firewood, wood-turning wood, and wood chips.

Potential spread by:Unwitting residents Landscape servicesRight-of-way servicesIllegal dumpingLand-fills


USDAAgricultural Research

Service (ARS)Animal and Plant

Health Inspection Service (APHIS)

Forest Service (FS)Florida Department of

Agriculture and Consumer Services (FDACS)Division of ForestryDepartment of Plant

Industry (DPI)

Numerous institutions in Georgia and South Carolina.

University of Florida, Institute of Food and Agricultural SciencesTropical Research and

Education CenterSchool of Forestry

Others


Screening of avocado cultivars for resistance to LW.

Screening of native and non-native Lauraceae for susceptibility to LW.

Screening of insecticides and fungicides to control the RAB and LW pathogen.

Basic researchBiology of RAB and LW pathogenHost-RAB-LW interactionsPopulation genetics of RAB and LW pathogenIdentification of the volatiles that attract RABEconomic and environmental impact of RAB-LW


RAB appears attracted to volatiles given off by plants in the Lauraceae.

RAB does not appear to produce an aggregation pheromone which attracts more beetles.

Seasonal flight of the RAB increases from June through October (peak flight is in September).

RAB attacks all avocado cultivars (varieties) that have been exposed to the beetle so far.

LW does not appear to kill all avocado cultivars – this is preliminary because only small plants were tested.

Larger avocado trees appear more susceptible to LW than smaller trees.

RAB appears attracted to damaged (e.g., pruned) trees.


Cultivar (variety)

Susceptibility to LW

Simmonds (W) Wilted and died

Donnie (W) Wilted but recovered or died (field plot)

Monroe (GW) Wilted, mild to moderate symptoms but recovered

Brogdon (M,G,W)

Wilted, mild symptoms but recovered

Reed (G) Wilted but recovered

Catalina (W) Mild to no symptoms but infected

Hall (GW) Mild symptoms but infected, recovered

•Mayfield, A.E. et al., 2008. Ability of the redbay ambrosia beetle to bore into young avocado plants and transmit the laurel wilt pathogen. Fla. Entomologist 91:485-487.•R.C. Ploetz, unpublished data.W=West Indian; G=Guatemalan: and M=Mexican race


Cultivar (variety)

Susceptibility to LW

Miguel (GW) Wilted, moderately severe damage

Lula (GW) Wilted, moderately severe damage

Bernecker (W) Wilted, slight to moderate damage but recovered

Florida Hass (?) Wilted, slight damage, recovered

Choquette (GW) Wilted, slight to moderate, recovered

Winter Mexican (M)

No symptoms but infected

Hass (GM) No symptoms and not infected

•Mayfield, A.E. et al., 2008. Ability of the redbay ambrosia beetle to bore into young avocado plants and transmit the laurel wilt pathogen. Fla. Entomologist 91:485-487.•R.C. Ploetz, unpublished data.


A general RAB-LW infestation scenario: A few RAB locate a host tree and bore into it,

inoculating the tree with LW. The LW colonizes (grows ) the water (xylem) and

nutrient (phloem) conducting tissues inside the tree.

The tree undergoes drought stress due to blockage of the xylem.

The infested and stressed tree now becomes an attractive host for brood rearing and is attacked in mass.

The tree dies or is severely damaged. The beetle reproduces inside the tree and new

beetles emerge to infest more trees.


Where are you located?Are the wilting or dieback symptoms on an avocado

or redbay tree?Are the leaves wilted and/or brown but hanging on

the stems?Do they see any other avocado trees or redbay trees

in their area dying or showing similar symptoms?If you remove some of the bark do you see black

streaking?Do you see any pencil-sized holes in the wood?Have you notified the Department of Plant Industry

(DPI) or Division of Forestry (DOF)?


Avocado: Call or locate your local FDACS Dept. of Plant Industry inspector by calling the DPI main office in Gainesville, (352) 372- 3505 ext. 118 or go to the DPI website for closest inspection office at http://www.doacs.state.fl.us/pi/plantinsp/pi_inspectordirectory/pi_insp_map.html and ask an inspector to look at the tree.

Agents and MG may want to know the local DPI contact number in your area in preparation for this question.


Native trees: Call or locate your local FDACS Div. of Forestry forester by calling 850-488-4274 or go to the DOF website at http://www.fl-dof.com/field_operations/county_foresters/index.html and ask your local an inspector to look at the tree.

Agents and MG may want to know the local DOF contact number in your area in preparation for this question.


Initially, we recommend to people to contact DPI or DOF inspectors and if let them determine if a sample needs to be taken.

However, if the client is willing to follow specific directions –Taking a beetle sample* Collect the beetle(s) into a small jar along with a cotton ball

soaked in rubbing alcohol. Place the jar with the insect into a plastic zip-top bag. Include information on the type of plant, location, plant

symptoms, and the clients contact information. Place this in a zip-top bag.

Mail them by overnight mail in a sturdy cardboard box to: FDACS, DPIAttn. Redbay Ambrosia Beetle Sample1911 S.W. 34 St.Gainesville, FL 32608-1201

If possible, send digital photos of the dame to the plant to [email protected] or [email protected]

* A simplified sampling method is being developed.


Chips (1” to 2” in size) from cutting the trunk or main (symptomatic) branches should be placed in a zip-top bag.

Includes information on the type of plant, location, plant symptoms, and the clients contact information. Place the this in a zip-top bag.

Place both bags inside another plastic bag.Mail them by overnight mail in a sturdy cardboard box to:

FDACS, DPIAttn. Laurel Wilt Sample1911 S.W. 34 St.Gainesville, FL 32608-1201

If possible, send digital photos of the dame to the plant to [email protected] or [email protected]

* A simplified sampling method is being developed.


Target audiences (clientele) to informUrban and rural residentsLandscape companiesPruning companiesMulching companiesFirewood companies/BBQ smoke-wood

companiesNurseriesMunicipal waste companiesLandfill companiesWood turnersNative habitat restoration companiesFruit and native tree clubs


Report any suspicious redbay (other native tree host) and avocado trees to DPI or DOF

Voluntarily remove and destroy the tree (see following slides).

Don’t move any symptomatic host wood from a site.Don’t chip dead wood and use it as mulch around the

yard.For now, don’t purchase or obtain native Lauraceae

plants and avocado trees from an area known positive for the RAB-LW.

FDACS-DPI is working on a protocol for safely moving and selling nursery stock in infested areas.


See previous slide – don’t introduce the pest.Leaving the tree in place will increase the

RAB-LW infestations throughout your local area .

At present there is no available fungicide or insecticide legally registered that will control the insect or disease.

Controlling the beetle may be impractical in the home landscape – it only takes 1 beetle to infest and inoculate a tree with LW.


Options for dooryard avocado trees:1. Cut and burn the tree – not recommended because of

the danger of burning and the requirement for burn permits, and various ordinances of local, state and federal agencies.

2. Cut the tree down to the ground. Pile the wood or chip the wood of the tree, pile it on top of

the tree stump and tarp this pile of wood to the ground; essentially composting the infested remains of the tree in-place. (*chipping alone will not kill RAB).

Adding biosolids (e.g., manure), fertilizer, and water will speed the decomposition process.

See http://edis.ifas.ufl.edu/pdffiles/EP/EP32300.pdf and http://edis.ifas.ufl.edu/pdffiles/HE/HE02600.pdf for more information on composting.

Spray your chainsaws with Clorox™ bleach and water to disinfect it against the possibility of spreading LW fungus to other susceptible host trees.


QuestionsCan you replant an

avocado tree after losing it to RAB-LW? A – sure, the evidence so far suggests the disease is not stay in the soil but there is no guarantee at this point that the RAB won’t attack the new tree.

Does the disease attack the fruit? A – Not known but unlikely.

The situation with respect to RBA-LW will change as it spreads naturally or with the unintentional assistance by people.

Disease and insect identification will be simplified at some point.

As research results are known our approach to prevention and control will change.


Albert E. Mayfield III, Jonathan H. Crane and Jason A. Smith. 2008. Laurel Wilt: A Threat to Redbay, Avocado and Related Trees in Urban and Rural Landscapes. [http://edis.ifas.ufl.edu/HS391].

Jonathan H. Crane, Jorgé Peña, and J.L. Osborne. 2008. Redbay Ambrosia Beetle-Laurel Wilt Pathogen: A Potential Major Problem for the Florida Avocado Industry. [http://edis.ifas.ufl.edu/HS379].

Link to other publications: http://edis.ifas.ufl.edu/topic_family_lauraceae


Fla. Dept. of Plant Industry: http://www.doacs.state.fl.us/pi/index.html

FDACS-DPI Pest Alert: http://www.doacs.state.fl.us/pi/enpp/pi-pest-alert.html

USDA-Forest Service-Forest Health Protection, Southern Region: http://www.fs.fed.us/r8/foresthealth/laurelwilt/index.shtml

FDACS Div. of Forestry: http://www.fl-dof.com/Univ. of Fla.-IFAS EDIS publications:

http://edis.ifas.ufl.edu/Univ. of Fla.-IFAS Extension Solutions for your life:

http://www.solutionsforyourlife.com/Don’t Move Firewood Organization:

http://www.dontmovefirewood.org/


Any questions?

Threat to Avacado Trees in Florida

Education

Transcript of Threat to Avacado Trees in Florida