Apple and Pear Tree...death by fungus? #142341 - Ask Extension


Apple and Pear Tree...death by fungus? #142341

Asked July 22, 2013, 2:07 PM EDT

Requested by extension director to try out "Ask an Expert" and see how it works.- I'm a new educator with limited horticultural experience so thought I would use this opportunity to request assistance on identifying the cause of death for the apple and pear trees shown in the pictures. 
Apple and pear tree were approximately 500' apart on two separate properties. Other fruit trees in home orchard were not affected. No lesions seen on trunk or branches. No fruit set. Home owner says they appeared healthy and produced last year. Very dry spring followed by heavy rains. Would like an identification of what killed the tree.
Homeowner would also like advice on tree removal, how to avoid this in the future and suggested varieties of pear and apple that may be resistant to whatever this is.
Thanks in advance for your help. 

Washington County Idaho

Expert Response

I see that this question was sent to me form Idaho, but I will try to answer your question.

With all things being equal, I would "guess" that the trees have a sever fire blight issue:

I would suggest looking/asking for other issues such as herbicide damage or? before proceeding to be sure that it is not something abiotic too.

From the descripition of dry conditions followed by heavy rains -- this would set up a perfect environment for fire blight, and could even be predict-ed. See WSU Cougarblight model:

When conditions are hot for days before a rain event, and the fire blight bacteria (Erwinia amylovora) is present, this can set up a severe fire blight problem in susceptible hosts such as pears and less resistant apples.

In the case of what to replace the tree with, we have a great fact sheet from Montana State University with common apple diseases and a list of apples with differing resistance to certain apple diseases. I would recommend an apple that is fire blight resistant. there are very few pears that are resistant.

Sanitation is also very important. be sure to lean up all the fruit, leaves and to be sure to clean the tools with alcohol to diseinfect any tool that prunes  or digs these trees as not to infect any other hosts.

Let me know if this helps or if you need further information.



Toby Day Replied July 31, 2013, 12:37 PM EDT

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