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Why is the impact of most leaf diseases so minimal for deciduous shade trees? 

Because they usually don't drop their leafs right away. the green portion of the leaf is fully functional.....it's continuing to make carbohydrates that are stored in the stems and roots. 


When do leaf diseases attack trees?

When the leaves are soft...right after bud break.  In cool, wet conditions.


Do most fungal diseases show symptoms of wet rot or dry rot? 

Dry rot.



when a tree is infected with a fungal leaf disease....When do you usually start seeing symptoms?

It usually takes a while to see symptoms. they will get the disease at bud break in the spring...but may not show symptoms until the summer. 


When infected with a fungal leaf disease.....Once the leaves get hard and mature...does the disease continue to attack the plant? 

No. Once the weather warms up and the leaf matures, the disease stops. whats done is done. 


What does a typical fungal symptom look like?

  • Dry, usually round, paper thin.... spots, blothes or blisters with distinct, colorful borders. 


What are some ways to manage and control leaf disease in deciduous trees?

  • Try to keep the foliage dry (manage irrigation)
  • Selectively prune to open up trees to allow air to flow through the canopy
  • Remove affected plant material
  • Timely fungicide treatments on important trees

    – Treat at budbreak and repeat during wet weather at label specified rates and intervals 



How does Apple Scab affect the leaves?

It infects them, they eventually senesce and fall off.  New leaves grow, and they are infected too.  The tree will slowly suffer an get weak.  


What can you do to manage and control Apple Scab?

  • Keep Dry
  • Prune to improve air movement
  • Remove afected plant material
  • Use resistant varieties
  • Timely fungicide treatments on important trees

    – Treat at budbreak and repeat apps all year long


Needlecast disease causes what symptoms?

Yellow spots on needles that turn purple in late winter.



When infected with a needlecast disease....What happens to the spots on the needles? 

  • In late winter they erupt and fruiting bodies are ejected onto new growth.  
  • Then the needles fall off and you're left with the new growth only.


Management and control of Needlecast disease:


• Maintain plant vigor with sound cultural practice

• Avoid wet foliage
• Remove affected plant material
• Use resistant varieties

• Timely fungicide (Chlorothalonil) treatments on important trees

– Treat when some trees begin to break and repeat during wet weather (2-3 times) at label specified rates (high) and intervals (14 day) 


define Canker

  •  stem disease caused by the formation of lesions (dead areas) on the bark and/or cambium tissues. 


define branch blights

  •  stem diseases caused by pathogens that attack green shoots and twigs. 


Branch Blights are also called transitioning diseases.....why?

Because they ofter transfer from the leaf into the green stems.  


What are the two type of stem diseases called?

  • Cankers 
  • Branch Blight


describe the leaf spots that Anthracnose causes...

angular leaf lesions that are associated with the leaf veins


describe the effects of sycamore anthracnose on the leaves and stems.  What happens?

  • Can infect the buds and kill them before they open up or the tree will generate leaves put pediole is infected and leaves drop soon after they open.  
  • a second round leaf growth will happen in late summer
  • the disease can also cause a dieback of green stems


What is a key symptom of Dogwood Anthracnose?

  • completely kills the leaves...and they curl up and hang onto the plant all winter. 


What do canker diseases need to have to infect a tree?

  • a natural opening or a wound



what does the tree try to do to fight stem disease?

it grows a calice around the infected site. 


What is Nectria? 

a slow growing canker disease that keeps attacking the tree all year.


What is the biggest problem with a 'target' canker disease?

it will cause a structural problem at the infection site that can lead to the branch, or trunk to break offin wind, or heavy snow storm. 


What is the difference between Target Cankers and DIffuse Cankers?

  • Target Cankers grow slowly, they cause the tree to attempt to compartmentalize the disease by growing calus's...it slowly weakens the trees structure and it will eventually blow over or break from heavy snow/rain
  • Diffuse Cankers infect the tree fast enough to girdle the branch.  where it girdles the branch, the branch dies from that point on. 


Diffuse Cankers rarely show caluses....what are their symptoms?

They often crack and peel the bark


How can you tell ifthe tree is suffering from a canker disease or if its just a mechanical injury? 

Cut the bark away and see if the cambium is discolored.....if so, its a canker.  


management and control of canker diseases:

  • •  Prune during dry weather
  • •  Identify discolored cambium tissue
  • •  Make cuts at least 8-10 inches beyond discoloration in cambium
  • •  Make best pruning cut
  • •  Sterilize tools between cuts with 95% alcohol or 10% bleach solution