Minnesota First Detectors Oak Wilt Deadly Pathogen.

Minnesota First Detectors

Oak Wilt

Deadly Pathogen


Oak Wilt

Impacts

Distribution, status

Biology, identification, and symptoms


Impacts

Serious disease of oaks in the Midwest, eastern US and Texas

Attacks all oak species Red oak group (northern

pin, northern red, black) is very susceptible

White oak group (bur, swamp white, white) is more tolerant


Distribution of oak wilt

Range of oak wilt in US

Range of oak wilt in Minnesota, 2006 DNR Aerial survey


Status

2011: oak wilt discovered in St. Croix State Park in Pine County

Most northern find to date Also found outside the park at a residence Want to keep it from spreading throughout the

oak resource

Range of red oak in Minnesota

St. Croix State Park


Biology of oak wilt

Fungal pathogen, Ceratocystis fagacearum

Discovered 1942 in Wisconsin Now thought to be introduced,

possibly from Central or South America or Mexico

Spreads in two ways: overland by insects and underground through grafted roots


Oak wilt spore mats

Fungus creates spore mat beneath bark of red oaks the spring after tree wilts

Pressure pads form on mats that cause bark to crack

Jenny Juzwik. Photo by Joe O’Brien, USDA Forest Service, bugwood.org


Overland spread

Spore mats have fruity odor that attracts sap beetles

Sap beetles pick up sticky fungal spores from mats

Fly to uninfected but wounded tree (e.g., from pruning or storms)

Beetles transfer fungal spores through tree wound

Sap beetle


Biology of oak wilt

90% of oak wilt is spread by root grafts of trees within 50-100 feet of each other

Fungus travels through water-carrying vessels in roots to a healthy oak

Tree tries to stop fungus by producing a gummy substance that clogs water vessels

Lack of water flow causes leaves to wilt rapidly and fall off


Symptoms

Tree “flags;” whole branches, parts of crown turn brown in July or August

Leaves drop off Fungal mats under bark the

next spring Sapwood streaking is not

sufficient to diagnose Conclusive diagnosis from

U of M Plant Disease Clinic


Identification: oak wilt v. bur oak blight

Oak Wilt Water-soaked

appearance Leaves fall off Tree wilts and dies in

same season Fungal mats produced

the following season

Bur Oak Blight Wedge-shaped lesions

between veins Leaves hang on Dark veins on underside,

tiny black bumps on petioles

Tree may live for years with symptoms


Identification: oak anthracnose

Oak wilt may be confused with oak anthracnose

Favored by cool, wet spring

Symptoms appear more in lower branches

Leaves have small to large brown areas; appear scorched

Leaves drop Tree recovers over the

season

DNR photo


Identification:two-lined chestnut borer

Adults attack oaks stressed by drought, defoliation or construction

Symptoms and signs similar to EAB (same genus)

Characteristic pattern of multi-year attack: “Dead, Red, and Green”

Red oak leaves stay on tree (unlike OW)


Oak Wilt Management

Prevent above-ground spread through firewood Mats may form on cut, bark-on firewood Debark or use firewood within 8-9 months from

wilting, or Tarp firewood carefully, covering ends of tarp with

soil, for one year after trees died

Prevent underground spread Sever root grafts with vibratory plow line Preventative treatment of high-value urban oaks

with fungicide


Other oak pest management

Bur oak blight Promote tree vigor May treat with fungicide in early summer

before leaf symptoms appear Oak anthracnose

Rake up leaves to limit overwintering fungus Increase tree vigor

Two-lined chestnut borer Prevention; promote tree vigor


Oak wilt is mainly transmitted by picnic beetles.

A. True

B. False

True

False

50%50%


The leaves of a red oak with oak wilt hang on the tree from one season to the next.

A. True

B. False

True

False

100%

0%


Oak wilt can be managed by disrupting root grafts.

A. True

B. False

True

False

0%

100%


Questions?

Minnesota First Detectors Oak Wilt Deadly Pathogen.

Documents

Transcript of Minnesota First Detectors Oak Wilt Deadly Pathogen.