Untitled
Dutch Elm Disease (DED)
 ( Ophiostoma novo-ulmi )
Dutch Elm Disease is a vascular wilt disease causing rapid decline in as few as 6 weeks after infection. American and European elms are commonly infected in two ways.  Elm bark beetles vector the disease from infected to healthy trees; the fungus may also be transmitted through root grafts.  The death of these highly valued trees has great economic impact.

 

Symptoms:
Leaves show signs of wilting (flagging), yellowing, and browning.  Brown or purplish discoloration is found in sapwood under the bark and dieback will occur shortly after symptoms are first discovered. 
PHOTOS:

A: Dutch Elm Disease symptom of flagging braches.

B: Elm Bark Beetles are the vector of the Dutch Elm Disease.

C: Discolored twigs indicating dying tissues.

Images from: forestryimages.org Photo A taken by Fred Baker, Utah State University, photo C taken by R. Scott Cameron, International Paper.

WHAT TO DO:
WHEN TO DO IT:
WHAT WILL HAPPEN:

Dutch Elm Disease must be treated pro-actively before the disease is present in the tree.  The disease spreads so quickly that treatment on diseased trees may not be effective.  Arborjet recommends a pro-active Micro-infusionTM treatment with ALAMO (contains 14.3% propiconazole).  However, if flagging symptoms are discovered, treat with ALAMO using the Tree I.V.  with the Arborplug Technology and immediately remove infected tissue.

·  Prune flagging branches immediately as the vascular wilt moves rapidly in the sapwood

·  Strip the bark from the branch with flagging symptoms

·  Inspect the sapwood for streaking  (dark staining)

·  Cut the branch 6-10 feet beyond  the discolored area to clear wood, ideally to a branch bark collar

·  Properly dispose of the infected wood or debark it completely

·  Make sure to disinfect all tools using a bleach solution

·  Trenching between infected and non-infected trees will slow the spread of the disease by root grafts

Generally, the best seasons for Micro-infusionTM are fall and spring. Uptake occurs when trees are transpiring. The environmental conditions that favor uptake are moderate temperatures, adequate soil moisture, and high humidity.  Soil temperature should be above 40 degrees for micro-infusion™.  Tree health will influence uptake time.  Generally, hot weather or dry soil conditions will result in a reduced rate of uptake.  If treating trees in the summer, micro-infuse in the morning for the quickest uptake. A dying tree is a poor candidate for treatment.  It is the responsibility of the arborist or tree custodian to assess tree health and its potential for recovery before undertaking treatment. Best treatment response occurs when trees are treated with no more than 15% of canopy affected.

Tree recovery will be dependent upon the severity of the Dutch Elm Disease infection at the time of trunk injection, and the extent of aggressive pruning.  ALAMO  should be used as a pro-active application before signs of infection are present.  Up to 60% of infected elm trees have recovered using the pruning techniques recommended above.  You may need to remove a large branch or a main leader from the tree.  This aggressive removal is still better than losing the entire tree.

A
B 
C 
PHOTOS:

Left: Healthy Elm leaves.

Right: Healthy Elm tree

Images from: forestryimages.org

right photo taken by Joseph O'Brien, USDA Forest Service.