Akif Eskalen, R. Stouthamer, P. Rugman-Jones, G. Douhan,

M. Twizeyimana, S. Lynch, D. Wang, J. Mayorquin, A. Gonzalez,

F. Na, L. Yeung

Department of Plant Pathology and Microbiology & Department of Entomology

University of California, Riverside

Polyphagous shot hole borer and Fusarium dieback: A generalist pest/disease complex threatening

avocado and landscapes trees in California

Southern California Forest Pest Council, April 23, 2013

Polyphagous Shot hole borer (Euwallacea sp.)

Female

0.1 inch long

Male 0.05 inch long

Beetle and fungi have symbiotic relationship

Fusarium sp.

Euwallacea sp.

Mycangium

Graphium sp.

Acremonium sp.

Beetle gallery and Fungal colony on the gallery wall

Beetle eggs and larvae in the gallery

Vascular discoloration caused by fungi

Situation in Israel, Oct. 2012

Calculating colony forming units of fungal species associated with PSHB

Head Larvae Abdomen

0

200

400

600

800

1000

1200

Female Head Female Abdomen Male Head Male Abdomen Larvae

Fusarium sp.

Graphium sp.

# of Colony Forming Unit per beetle

Pathogenicity test on Hass

Fusarium sp. Graphium sp. Control

02468

101214

Fusarium sp. control

Lesi

on

le

ngh

t (c

m)

Legend&Posi+ve&finding&Fusarium&sp./Polyphagous&Shot&Hole&Borer&Nega+ve<Fusarium&sp./Polyphagous&Shot&Hole&Borer&

Known&distribu+on&of&Fusarium&&dieback/&Polyphagous&shot&hole&borer&in&southern&California&12/18/2012&

Data*source:*Eskalen*lab.,*Dept.*of*Plant*Pathology*and*Microbiology,*University*of*California,*Riverside.**www.eskalenlab.ucr.edu****

Known distribution of PSHB/FD in Southern California 2/6/2013

Determine the plant host range of the beetle/fungus complex in California

Number of tree species

observed

Number of tree species attacked by

beetle

Number of tree species colonized by

fungus

Number of tree family

attacked

Number of reproductive

host

335 213 108 58 21

Eskalen et al. 2013. Host Range of Fusarium Dieback and its Ambrosia Beetle (Coleoptera: Scolytinae) Vector in Southern California. Plant Disease. In Press.

Reproductive / Suitable Hosts

1. Box Elder (Acer negundo) 2. Castor bean (Ricinus communis) 3. Avocado (Persea americanaI) 4. English oak (Quercus robur) 5. Coast live oak (Q. agrifolia) 6. Silk tree (Albizia julibrissin) 7. California sycamore (Platanus racemosa) 8. Coral tree (Erythrina corallodendron) 9. Chenese holly (Ilex cornuta) 10.Big leaf maple (Acer macrophyllum) 11.Japanese maple (Acer palmatum) 12.Black bean (Castanospermum australe) 13.Palo verde (Parkinsonia aculeata) 14.Blue palo verde (Cercidium floridium) 15.Liquidambar (Liquidambar styraciflua)

Symptoms of PSHB/FD on avocado

Symptoms of PSHB/FD on different hosts

Red Willow (Salix laevigata)

Box Elder

Symptoms of PSHB/FD on different hosts

Coast live oak Liquidambar California Sycamore Excelsa

Coast live oak Avocado English Oak Castor bean

Quercus robur

100 years old English oak in Huntington Botanical Garden

Similar symptoms caused by other factors

Woodpeckers Bacterial canker Avocado trunk canker Phosphorous acid Injection

Symptoms of PSHB/FD on different hosts

Alice Maple (Acer pectinatum)

Detection of Fusarium sp. directly from plant material using Quantitative Real Time PCR

Lad

der

Wat

er C

on

tro

l

Fusa

riu

m s

p.

Fusa

riu

m s

p.

Fusa

riu

m s

ola

ni

Forward: ACGTGATTGACCACAAAC

Reverse: CAGCGACATACCAATGAC

188 bp

EF-1α

What to do:

•Look for a single entry hole with surrounding either white powdery exudate, staining, gumming or frass

•Scrape off the bark layer around the infected area to see the canker

•Follow the gallery to look for the beetle (may or may not be present)

•Avoid movement of infested wood out of the infested area

•Look for the other hosts (Box elder, Castor bean, Coast live oak, California sycamore

Control strategies

What to do

Control strategies of PSHB using Entomopathogen Fungi

Treatment % of beetle alive

Control 100

Metarhizium 50

Beauvaria bassiana (Mycotrol)

0

Spiral gradient dilution fungicide screening

Spiral gradient dilution fungicide screening

Control Fungicide

Active

ingredient Trade Name

EC50 for inhibition of mycelial

growth (μg/ml)a

Metconazole Quash 0.031 a

Pyraclostrobin Cabrio 0.044 a

Tebuconazole Folicur 3.6F 0.057 a

Thiabendazole Arbotect 20-S 0.193 ab

Propiconazole Alamo 0.487 ab

Triflumizole Procure 0.714 b

Fluopyram Luna Privelage 2.080 c

Myclobutanil Rally 2.432 c

Pyrimethanil Scala 4.911 d

Fluxapyroxad Xemium NIb

Trifloxystrobin Flint NI

Triadimefon Bayleton Flo NI

Azoxystrobin Abound NI

LSD0.05 - 0.64

Collaborators Tim Thibault, Huntington Botanical Garden Frank McDonogh, LA Arboretum Tim Paine, Entomology, UC Riverside Gevork Arakelian, County Ag. Commissioner in LA Tom Coleman, USDA Forest Service, Southern California Jiri Hulcr, Univ. of Florida Kerry O’Donnell, NCUR-ARS-USDA Ben Faber, Farm Advisor, Ventura County, CA Gary bender, Farm Advisor, San Diego County, CA Mary Bianchi, Farm Advisor, Santa Barbara County, CA Jim Downer, Farm Advisor, Santa Barbara County, CA Don Hodel, Farm Advisor, Los Angeles County, CA John Kabashima, Farm Advisor, Orange County, CA Reuben Hofshi, Hosfhi Foundation Mary Lu Arpaia, UC Riverside Zvi Mendel, Volcani Center, Israel Stanley Freeman, Volcani Center, Israel California Avocado Commission for funding